Bought '96 6.5 TD in November 2003. Before I bought I had a friend who works for a GM dealer run the VIN. Here's what I know:


OPS replaced at 30k miles


Injection pump replaced at 80k miles


PMD replaced two weeks before I bought truck, truck has 125k miles.


I thought "OK, the trouble spots have beed addressed at least at some time in this trucks life"


Symptom:


Truck stalls, almost always around 5 minutes after cold startup. Only once did it stall after 10 minutes run time. Most of the time it's been on acceleration but it did recently stall while idling in the driveway at around 5 minutes from startup. Upon restart it will usually stall one or two more times then be OK for as long as I drive it. When it stalls it dies instantly, no sputtering or bucking. No check engine light


I replaced the fuel filter, still stalls. Based on what I read here it sounds like PMD. The PMD is still on the pump so heat might be an issue BUT.......It's cold here and it's only been driven 4000 easy (no towing) miles in very cold weather since that PMD was replaced and it doesn't stall after it's been running and presumably hotter than at startup. Could there be another problem that's being blamed on the PMD? Could the previous owner replaced the PMD and when it still stalled they decided to simply sell it?


I don't want to spend $300 on a PMD if it's not going to fix the problem.


Also, probably unrelated: My temp gauge intermittently shows no reading as if the engine is cold even though it's been running for a long time.


Everyone in my family is afraid to drive this truck.


Any thoughts?





Thanks in advance





Edited by: Bobt250

The majority of stalls with easy or delayed restart are PMD related. I've had guys do everything from my simple cooler setup to fan cooling etc and there is still no definite cure for this. Some will go 100k and some will go 10k. The one thing for certain is that a remote mounted unit is much easier to replace, and stands the best chance of survival.





My solution is listed here:





http://www.kennedydiesel.com/categoryresults2.cfm?Category=1&SubCategory=62

The temp gage would seem to indicate an electrical problem - supply, grounds, connectors in the wiring harnesses, inside and engine bay. I suggest going thru all these, re-seating, tightening, checking for oxidation\corrosion, cleaning. etc.


These type failures usually occur after weather has been cold\damp - Fall, Winter, early Spring.


Also, the igition switch is prone to failure in the '88-up trucks, resulting in some really inexplicable symptoms.


Also, you might try reading all the other similar posts regarding stalling, bucking, etc, for other ideas.


Open the bleed, top of fuel filter, with engine running fuel should gush out. If so, OPS and lift pump are ok.


Edited by: gmctd

Well, thanks for the quick replies.


I have been reading a lot here about it and it does seem like PMD but I just thought the specifics I gave might trigger a thought in someones mind, perhaps something obscure. It's weird to me how it always stalls within minutes of a cold start only to run well after no matter how long you run it. That makes me think of a bad connection, something that might slightly heat up after current is flowing through it making it a little better connection for the duration of the current flow.


I plan on moving the PMD to a remote cooler if only to make it easy to replace. I like the idea of carrying a spare too. I was going to crack the filter bleed while it's running to watch the lift pump. I know the pump works when the key is first turned on but I don't know after it's running. That's Saturdays job





Man I'd LOVE to know what's inside that PMD. It would probably be easy to make them (better and cheaper) if I only knew what was in there, anyone know if there's a schematic for it somewhere?





Kennedy,


Are you saying that even if I relocate FSD I have to drive around waiting for it to act up again? Makes me want to bring up the 93 mechanical pump conversion again





If I knew what was in there I could build one that wouldn't fail.Edited by: Bobt250

The fix is as simple as choosing solder-plated steel or brass shouldered fasteners and nuts over stainless steel screws and nuts, and solder-plated transistor cases over stainless cases.


Stainless steel on stainless steel is never used for electrical connection, in any good engineering design.


That, and multiple heat-cool cycles with heat-soak cause the failures.

Can I change the fasteners?

The module is potted for thermal stability, shock proofing, and sealing against the engine bay environment.


You can loosen the stainless nuts a bit, run them back down to finger-tite, then 1/4-turn more with a 1/4" nut-driver.


Any more than 1/4-turn can shatter the ceramic lead-to-case hermetic seal.


This procedure breaks the oxides which form between the cases, nuts, and screws, all of stainless steel alloy. Oxides which are of low electrical conductivity.


The nuts and screws are the sole electrical connection between the transistor Collectors and the pcb - the Fuel Solenoid is pulled up to +12v thru the paralleled Collectors.


The nuts have been found in various stages of looseness, backing off due to heat-cycle compression of potting compound. Some looseness may have been due to issues with production quality control, being found even in recently-replaced modules.


My 'fix', a replaced failure removed from another truck, has been functional since Summer of ought one, mounted back on the inj pump. (R&D project).


I keep a spare, mounted on an exact duplicate version (I call mine the 'HFE FSD Cooler', if you can ascertain my meaning) of a well-known European model, in the toolbox - affords a certain peace of mind, don't you know!


As John Kennedy stated, convenient replace-ability is a major factor when considering mounting locations.

Well, I took apart every connection under the hood, sprayed the pins with LPS 1 and reassembled. Took it for a spin, ran it HARD and no trouble. This morning on my way to work about 5 minutes down the road I hit the accelerator hard and POOF it died instantly. Restarted, it died again. Wouldn't start so I opened the bleeder on top of the filter saw fuel coming out when key turned on. It then started and seemed fine. Hit the accelerator hard again and it immediately died again. Wouldn't start again until I opened the bleeder up and ran the lift pump again. I then drove it easy all the way to work 50 miles away. It seems like some kind of fuel delivery problem because it mostly does it when you stomp on the pedal.


Problem is that when it happens I have no way of knowing if the lift pump is running at that moment. Every time I check it it's running but that doesn't mean it's always running.


I'm gonna wire up an OPS bypass relay and relocate the PMD and while I'm at it tighten those screws on the transisitors and go from there.


This is frustrating.Edited by: Bobt250

Bob that is sounding like FSD/PMD to me, IP can pull it's own fuel sufficiently to allow a restart, but can stumble while under load if lift pump isn't delivering fuel. Do you have a vac/press gauge even a cheap one from autozone etc. will do, I don't know about 96 vintage but on my 98 almost dead center front of the engine by H20 thermostat is a brass valve & rubber hose either side chrome tee handle, this is the fuel bowl drain, connect the gauge to the drain valve outlet with a long rubber hose routed to the cab.


Don't pinch the hose it will give error reading I ran mine for test purposes out back of hood under wiper blade and cracked the window.


Drive it and see what fuel lift pump ids delivering that way. If you don't have the tee fitting you can probably do something similar with the vent screw on the filter body. 4-6 psi is what you should see at idle, 2-4 at cruise speed, mine dropped to 1 psi on hard accel with heavy load but recovered to 2-4 when back at cruise speed.


But the open vent at idle is usually a good test to see if lift pump is working, I'm strongly suspicious of the FSD.


Try to retorque the transistor nuts, I salvaged my last one that way, get a GOOD inch lb torque wrench, 12 in lbs has held up so far, I also carry a spare, for my remote mount just in case.Edited by: Turbine Doc

What about all the major connectors between the fuel filter and the firewall? This is where the engine harness connects to the PCM harness.


The major bulkhead feedthru, lower driver-side firewall, to outside of steering column.


The battery cable ground connections to the block, including the major harness grounds, passenger-side head, rear.


The battery cable connections at the starter motor - there is a 10 - 8 gage wire from the starter to that terminal block upper passenger-side firewall. It supplys total electrical to vehicle.


Stalling with hard application of power seems to indicate electrical connection is failing when engine shifts against torque. Loose connection or pinched wire.


Replacment inj pump\PMD assy, then replacement PMD seemingly indicates recurring problem.


Could be the ignition switch.


Could be the PMD again - but, these suggestions should eliminate all the other known trouble spots.


Eliminate all the good stuff as not causative, what's left has to be the bad.

Thanks for the suggestions,





The battery ground at the intake manifold is good, the ground strap at the passenger side rear of the head looked nasty but when I tried to remove it I started loosing coolant BAD. I tightened it back up and ran an extra wire from there to the body. I didn't get a chance to get under the truck so I didn't look at the starter wires.





I noticed a major bundle of wires through the firewall on the passenger side, I'll have to look for one on the other side. I don't know what you mean by a major connector behind the fuel filter, There are several smaller ones right there that I worked on. It was getting late so I didn't look around as much as I could have.





I have that fuel canister drain cock at the front, I like the idea of putting a gauge on there.





Thanks again

That bundle thru the lower passenger-side firewall is the PCM harness.


Most of it joins the engine harness thru a large connector behind the fuel filter.


There is another harness bulkhead connector thru the driver-side firewall for power, ground, gages, alternator, lites, etc - it's a carry-over from pre-computer era - fastened via 10mm bolt to female half inside.


The major battery power connector block is on the upper firewall, behind the turbo


Also, the single major circuit ground for the PMD and Fuel Solenoid is that small gage black wire fastened to the top of the inj pump.


I'm taking you thru a 'new owner, pre-owned vehicle' preventive maintenance schedule here, as I'm suspecting an electrical intermittent.


One guy had an occasional intermittent for a long period, to find the lift pump harness pinched between the transmission case and the engine.


You could also let the truck idle past it's 5-minutes-to-die period, making sure it's not a temperature thing, then, while it's hot and idling , start wiggling and shaking the various harness circuits to aggravate the connections.


If nothing shows in the engine bay, do the same in the cabin, starting with the ign switch.


Still nothing, time to address the PMD. By then you should be fairly certain nothing else is causative.


If you're still willing to labor at that point, as opposed to spending, you can pull the PMD, check the connections, fasten it to a piece of aluminum heat sink, lay it on the manifold, and give it a try.


These are all the things I did to my truck, ever unwilling to admit the original PMD was failing. I already knew that PMD was cooked, tho, having fried it one hot summer day while pulling a heavily loaded trailer, elevated coolant temps, no relief in sight. Week later started the stalling with restarts.Edited by: gmctd

Thanks for the replies,


UPDATE:


As I said, it stalled twice this morning and it "seemed" to like the fuel filter canister bleed routine.


After work I started it and while I was in line to leave the parking lot at idle it died. It would not restart until I did the "open the bleed, do one cycle of the lift pump" routine. After each restart it would idle for approx 10 seconds then die then requiring the "open the bleed, cycle the lift pump" routine again. If I tried to rev it up once it started it would instantly die. After 40 minutes of this I decided to remove the fuel filter and look inside the canister. I mopped out as much fuel as I could with a roll of shop towels. I couldn't see anything wrong except a little dirt at the bottom of the canister on the outside of where the filter element would be.......basically where it should be if there is any. It then started (after bleeding the subsequent air) and got me home 57 miles down the road.


I'm starting to wonder if there is a piece of foreign material in the fuel filter canister that is "lodging and dislodging" with all this fiddling with the canister and the fuel flow within it. I DO NOT like that when changing the fuel filter any crap that's in there STAYS in there without physically removing the canister to dump it out (which doesn't look like fun). A VW diesel fuel filter takes any crap with it to the garbage can since the whole canister gets thrown away.





The truck has become basically un-drivable so my plan is to remove the intake manifold, remove the fuel filter canister and thoroughly clean it then relocate the FSD and go from there. The good news is that it's gotten so bad that I should know if it's fixed. I would kinda like to do one thing at a time so I know what it was but at this point I just want it fixed and while the manifold is off I'm doing as much as I can under there.


Any more thoughts are greatly appreciated.





P.S. I have a wealth of experience with early VW diesels, the ones that have literally ONE wire to the engine to make it run.


This isn't fun





Edited by: Bobt250

A faulty Waste Gate Solenoid will cause stalling after start-up. Does it surge when it stalls, almost like it's gasping? It's amazing how much trouble this one solenoid can cause, but remember it controls how much compresson the intake is fed. I'd say it's not the PMD/FSD due to it's usually stalling at start-up. The FSD doesn't follow much pattern when it's bad other than erratic stalling, generally heat related, like after driving for awhile.


http://www.dieselplace.com/forum/uploads/CE1_coolantsensor.jpg


The coolant tempature sensor can cause the tempature reading to read low. low readings means low voltage from the sensor. I had to splice the two wires on my dad's '96 because time and friction had made them brittle and when they where not making a good connection his RPM would jump to 1000 at idle.


http://www.dieselplace.com/forum/uploads/45D_wg-solenoid.jpg





The Turbo solenoid is GM part #01997227 and retails for $30+, but can be foud at gmpartsdirect for $16. It's a cheap application.


Edited by: quantum mechanic

Well, it's down to elbow gease and dirty words time, so good wrenching. And, don't forget to post your progress.


Also, I later edited in some further info to the previous post, if you have not seen it. Edited by: gmctd

I appreciate the replies, it's nice to feel like I'm not "all alone" in the world on this.





My family have been diesel nuts forever and are experts on the 6.2 /6.5 mechanically injected stuff. My brother knows every trick in the book on hot rodding a mechaniclly injected engine but ask him about the new electronic stuff and you get a blank stare. I've been active with VW diesels with mechanical injection and love them, drive one every day. You probably saw my post about putting a 93 pump on my 96. Oddly enough I have a degree in electronics and hate that they've put electronic controls on what should be a brutally simple diesel engine.





QM,


Runs perfect or not at all.

QM


The engine does not require boost at idle or any rpm when not loaded.


If the wastegate is allowed to open - no vacuum, bad wg solenoid, etc -the turbo engine will idle and run normally aspirated, no stalls. But, with load on the engine, the PCM will supply more fuel than available oxygen, resulting in black smoke, with less power.


This is a common complaint, and seldom results in a wg solenoid DTC.


The wastegate is held closed at idle, with 63% duty cycle, for quick spool-up when engine is loaded - resulting in excellent 'driveability'. Meaning no 'turbo lag', a common complaint with early turbos.


This is where measured vacuum at the pump is 25", but vacuum at the wastegate is only 15".


If the engine is revved, unloaded, wg duty cycle drops toward 0%, dumping turbine rpm, limiting boost to around zero.


This is where a boost gage (and EGT, and others) comes in handy - offers some definitive answers as to what is going on.


Try one - you'll like it!

There is a screen filter under the Fuel Shutoff Solenoid - top front, hex nut on top - carefully unscrew (CCW) the solenoid to check it out, noting any rust or corrosion in the inlet area of the inj pump.


Could tell you what shape the pump is in - dirty fuel, rusty fuel, watery fuel, etc.

Well, I always enjoy your posts GMCTD,


but I speak from experience on this one. The '94 EFI truck that I've posted so many pictures of on this forum was a stalling SOB when it was handed down from dear old dad. It stalled right after start-up and sometimes two and three times after start-up untill it got passed it and then would drive fine. Before I could deal with the OPS replacement and Bypass relay, I installed a new WG solenoid. OUJALA!


The stalling stopped, even with a known problem with the lift pump opperation due to inoperable OPS switch( I fixed the OPS next).


IT has not stalled again ever since. not even once.


yesterday I was using it as a tractor, in 4wd with a 30' logging chain I hooked up to a section of old moblie home at a time and pulled it down effortlessly. Screw the manual labor, I've got torque!


http://www.dieselplace.com/forum/uploads/D5F_salvage2.jpg


http://www.dieselplace.com/forum/uploads/EZC_teardown.jpg


Quantum Destruction!





http://www.dieselplace.com/forum/uploads/5BE_trailer.jpg My new trailer. She's got four axles, 60' x 12' of boxed steel frame and the neighbor threw in a second hitch as well. I will make it into farm trailers or whatever.








Edited by: quantum mechanic

GMCTD seems right to me, I fail to see how the wastegate could cause this unless maybe the solenoid was introducing electrical noise that was screwing with the other electronics. Solenoids in general often have diodes across them to suppress electrical noise and if the diode goes bad they can cause some squirrelly things to happen. Don't know about that particular solenoid or the susceptibility of the other electronics in the truck to electrical noise.





In my truck there is no surging. It just dies instantaneously like you turned the key off. Makes me think of the ignition switch except that it seems to respond ONLY to messing with the fuel filter.Edited by: Bobt250

Bobt250,


you can lead a horse to water........, maybe you should switch to a mechanical pump.


Seriously though, I'm going to stick with wg solenoid and add that A new OPS couldn't hurt, seeing as how it's all fuel related. You do know that the OPS is doomed because it's contacts are rated for 1 amp and the lift pump draws 4 amps. Only real solution is to bypass the OPS with a HD relay.Edited by: quantum mechanic

It can happen , QM, if other systems are deficient.


For instance, dirty air filter will not pass enough air, without turbo, to allow engine rpm to increase when more fuel is injected based on APP angle. Limit available oxygen, increase fuel, combustion ceases - right outta Science 101, right?


In a normally serviced, or recently serviced engine, as BobT indicated his to be, driveability would be reduced, but not dangerously so.


PCM has a backup, or limp-home, mode in case of major systems failure.


Stick a grapefruit in the intake, and limp-home is useless.


As a general rule, most problems with these Diesels are resultant because (previous) owners service them rather lack-a-daisically, just like gasser owners.


So, I do not doubt your experience, and I'm definitely not trying to rain on anyone's parade(s).


These forums are about exposing the myth, misinformation, rumor, and malicious gossip about the 6.5L Diesel.


"The 6.5 ain't nuttin' but a converted gasser!" Ha! Detroit Diesel might have a few choice words to say about that, and then some!


So, I do try to provide the most accurate information, sometimes enhancing info from other postees, giving owners further options for troubleshooting and repair.


I admire you for experimenting and R&D'ing out there in the woods, by yourself. Precisely the manner in which I learned it, beginning some 50-odd years ago, so keep at it. It's mostly fun, that way, and if something doesn't work out, you can always paint it green and hide it in the grass, right?http://dieselplace.com/forum/smileys/Wink.gif


And, yeah - great caution must be exercised when cutting grass around my place!!Edited by: gmctd

While I have the manifold off here's the plan:


OPS bypass,


Remove FSD from pump and relocate,


Remove fuel filter canister, clean it and the lines going to the pump,


Check out the screen under the fuel stop solenoid.


Install a fitting in the upper manifold for a boost gauge.


Anything else while I'm under there?

QM.


Not sure why the WG sol "cured" your stalling problem should have had no effect on that but hey it worked maybe it made one of the tron gremlins happy. My WG is fully closed at all times with the JK control or turbomaster control until sufficent pressure is made by the engine to open the WG when I set it to open. Stuck open WG at idle turbo is not boosting so it should not be a contributor in a post start stall condition, driveability/economy yes but a stall it's hard to see the correlation on a stall.


Bob


While you have the bowl off now would be a good time to put in appropriate tees for gage taps, and a filt blocked switch.


Edited by: Turbine Doc

TD,


"While you have the bowl off now would be a good time to put in appropriate tees for gage taps, and a filt blocked switch."


can you elaborate please?

Well, since you asked -


Stuff paper towels into the intake ports, immediately you remove the intake manifold. No room between piston and head for even a small stick, of which stick, or small rock, etc, can easily crack a piston.


Intake coupling tube, of silicone rubber, is RTV'ed to upper plenum and compressor outlet. Loosen the T-clamps, move them to the center. May be able to break it loose by using the plenum as a lever. If not, using a small screwdriver, or a butter knife, or similar, work the blade between the tubing and the casting, then work it around the o.d. till the RTV is separated. Careful not to split the silicone coupling tube.


Taper the i.d. in the upper plenum to around 1/16 to 1/8" at the inlet edge to smooth the flow out of the compressor. A half-round coarse file, similar to a wood rasp, works well.


Intake ports are fairly well matched, but - if you have time to play, go for it. Can't hurt.


If the plenum has the casting web where it mounts to the lower intake, remove it.


Most folks remove the intake duct, affectionately called the 'snorkle', from the fender. QM posted info and pictures on this and the 'web'.


New upper plenum gasket, has to seal up to 15psi.


Lower intake gaskets - 96 bucks for Fel-Pro at GM. Good thing I was sitting when he showed me the price. Shop around for Detroit Gaskets, and such - should be cheaper.


You did not mention 1500 series L56 with EGR, or 2500\3500 series L65 without. Leaky EGR system can cause similar symptoms. Has a tower inside the intake, seals to the upper plenum with a donut-shoulder gasket, dumps exhaust directly into the intake when blown. Egr valve with weak spring can also dump suddenly.


If EGR system, replace that donut gasket for sure. EGR is that dufus rusty thing bolted square in the middle of the upper plenum.


Last, but not least, caution with the MAP\Boost sensor and the IAT sensor, there in the upper plenum.


Further questions - you know where we are. Good wrenching, and keep us posted.Edited by: gmctd

Do you have an air compressor? I use a die grinder on the lower intake runners to remove the sand cast impressions and then polish the runners with wire wheels till they shine. I do the same for the turbo housing and upper intake, basicly resurface anything I can reach with the grinder wheel. I've had good results with this and I've even considered doing it again with a more aggressive cold seel rasp on the grinder.

QM,


I admire your fortitude and go get 'em attitude.


I have just about everything you could ask for in a personal shop including a 10,000 lb asymetrical clear floor twin post lift. (sorry if it seems like I'm bragging a bit, but not everyone has one of those). BTW it's a Manitowoc lift and I highly recommend them. NOW, the question is ..........do I have the necessary talent to use my equipment? That's another story.


To answer a previous question: K2500, no EGR but a Canadian dealer installed a catalytic converter for what reason is unknown to me as I'm from the states and don't know their rules.


UPDATE:


I bought a car that needed to be towed home. I had a choice, borrow a truck or risk using mine. I said to myself ......" DAMMIT I bought this truck to USE IT ! I figured two things, I could start it and run it around for a while, see how it goes then retrieve the car. OR try the only thing reasonable in the time available. As per GMCTD I looked into the IP intake screen filter thingy. I didn't see any way to remove the actual solenoid it has no hex nut on top (what's up with that?) but I did remove the nipple where the fuel line goes into the pump. After removing the nipple where the fuel line attaches to the pump, I saw no way of removing the nut that the nipple was screwed into. It was too close to the solenoid for a socket to work and there is no way of getting a wrench in there with the manifolds on. I couldn't see much in the hole 'cause it was full of fuel. I poked a rag down in there as best I could and still couldn't see anything so I took a can of carb cleaner with the little tube and blasted away in there. Then I took a shop vac with the crevice tool and sucked on the opening. The fuel was basically gone but I still couldn't see a screen per se'. I saw what looked like an female internal fitting with maybe some small holes around the periphery. It's hard to say, it was nearly impossible to see down in there. I hope if there was a screen there that I didn't blow it out into hyperspace. I then ran the lift pump to clear out the hose before re-connecting it.





Anyway, I put it back together and used the truck ALL day without incedent. The problem was intermittent so I'm not cashing in my chips yet but I'm cautiously optomistic. It was the first time I really "worked" this truck. I ran it HARD for about a mile up a steep hill with no problems other than it hitting about 200 degrees (by the gauge). I was wondering if that hill was longer would the temp continue to climb or would it level out somewhere? (96, pre cooling upgrade).





It looks like MAYBE Gmctd is the winner..........................MAYBE


That being said, I believe it's necessary for me to do the mods I said I was going to do, ......*IF* this truck is fixed I STILL need to do those mods for longevity, peace of mind and ease of replacement parts. I'm relying on you guys to shame me into doing those things when I become lazy because this truck is running fine.


BTW.....I love my truck, I'll posta pic soon. She's sweetEdited by: Bobt250

6.5L trucks have an oxidizing convertor - has the clay honeycomb inside, gets super hot, enough to burn the soot and ash from Diesel combustion. Usually called a 'soot trap'.


Early inj pumps had a Fuel Shutoff Solenoid with a hex allen socket in the top, rather than a hex nut.


If your truck runs, you're the winner by your labors, and that's what it's all about, in my book.http://www.dieselplace.com/forum/smileys/Clap.gif I'm glad to help.

Bob


I just got back from my son's soccer tournament in the outlet from the filter bowl put in 1 or 2 tees barb fittings on the inlet and outlet and NPT fittings for the gauge or switch, Racor sells a vac switch that will tell you if you have a blocked filter, I have one on my Racor frame mounted filter that lites a 12v LED to let me know when it's dirty, just haven't gotten to the one on engine yet, that way you will know when the filter is actually in need of changing instead of guessing or arbitrary mile/time change. the gauge will let you know if lift pump is providing adequate pressure to the IP.Edited by: Turbine Doc

TD,





I'm still a little bit unclear about the details.





Gmctd,





Two more trips today.....no problems. You MAY be the winner of the "what'swrongwithBobstruck" sweepstakes.

BOBt250,


Do you use fuel addative?


I buy 32 oz. bottles and put 8-10 oz per fill-up. I also make biodiesel and run it when I have enough grease and such to work with. It's amazing what ethyl esterfied fatty acids and Ethyl emulsified fuel oils will solvate in your fuel system. instant black fuel filter.


I noticed the '94 k3500 I've been using tows hot (200 deg. ). I drove it home empty tonight full boost pot., a/c on high and it didn't raise the tempature at all. I'm going to do what howieE always says and take the radiator out and clean it.


You must have a nice shop to house that lift. I plan to build a shop for myself as soon as I finish some of the long term projects I'm working on ( my house).


In the meantime, The shade is usually good enough for light work and I can drive down to town ( 69 miles) to use the pavement outside my dad's warehouse for stuff like pulling axles or dropping an NV4500.

If cleaning the fuel inlet is the solution to the problem, be a good idea to back flush that supply line first chance you get. Maybe even replace it. Which would also mean re-cleaning the inlet.


Necessitates intake manifold removal, but I'm still thinking this problem resulted in first a new inj pump, then PMD, replacement.


Keep us posted - I need closure.http://www.dieselplace.com/forum/smileys/Wink.gif

Bob


What I'm advocating is you add a connection point just down from the engine filter bowl outlet, use a threaded tee fitting, on the inlet & outlet use hose barb connections from the bowl and to the IP. On the third leg of the tee (the up leg of the T) either connect a gauge fitting or a nipple to a 2nd T that will allow you to connect both a gauge tap and a vac switch or vac. gauge(your preference).


Racors vac switch is set for 7" Hg to let you know when the filter is blocked. IMO this is an important piece of data as you can get a load of crappy fuel anywhere any time. Happened to me once, my truck could not pull my empty GN trailer(5500lb) without stumbling, end cause was partially dirty filter, that was "new" only had 1 road trip 5000 mi on it, my next scheduled filt change wasn't for another 5-6K mi. I thought it was still "good".


I have since mounted a primary filter on my frame pre lift pump, a Racor 660 20 mic to keep the "rocks" and water out of my 10 mic on engine filter and have instrumented the frame filt., some day not to distant will gauge the engine bay filt.


Here is Racors site a good source of all kinds of Q&A on filtration, http://www.parker.com/racor/pdf/Section01.pdf page 14 on their tech sheet is where I came up with the switch idea by accident. It's on their 325 filter sheet but hey vac. is vac., for the engine bay switch to work you will have to solder a GND wire to the tee(I used brass tees solder hard to stick to galv. tee) fitting to carry the neg leg to the truck GND plain. I connected 12+ to one side of the LED, and the 2nd leg goes to the vac. switch when dirty the switch closes and lets you know filter change is required. Maybe it's overkill since my Racor frame install 10K mi ago, I've not had the light come on yet, but I'm not guessing if my filter is clean or not either.


Another method which I found later on the Racor tech sheet is their vac. gage kit, but any would do which would allow you to trend a filters cleanliness, my LED fits on my gauge pilar via 3/16" hole vs trying to find room for yet another gauge. I also have a LED for lift pump power planned. I'll still mount a gauge for that though as I want to know when lift pump is starting to go South.Edited by: Turbine Doc

Drove it all day again, that's three days in a row all day. More than I've driven it in the previous three WEEKS. No problem whatsoever.





It's early but I'm gonna be forced to declare it fixed.





It was 82 degrees F here today, I was idling while waiting for the loader to load me with shredded bark. I lifted the hood to investigate the location I was eyeing for my remote FSD cooler. Let me digress, I was going to mount it on the inner fender behind the drivers side battery. I was also going to cut a hole in the vertical part of the inner fender, the part that has the snorkel on the opposite side. I was going to mount a cooling fan there to draw air from between the fenders and blow it on the cooler. I'm wondering about that now........man it was hot in there, all that inner fender metal was hot and the engine fan blows so hard in there that I'm not sure the little PC case fan I was going to use could overcome what is most likely a semi-pressurized environment with the hood closed. I'm thinking that Howie had the best idea.


TD,


You saying to put the vac switch BETWEEN the filter housing and the IP right? that makes sense. How much vacuum is an IP capable generating?


Thank you all so much for the ideas and encouragement. I'll keep you posted on any further developements.





P.S. I don't use any fuel additives.Edited by: Bobt250

That heat is part of the 'heat soak' problem, major destroyer of FSD modules - good idea to find a cooler location.


The engine bay does cool down soon as the vehicle starts moving forward, but those wild temperature swings also take their toll, particularly when burning the ac in summertime.


Gives a new respect for that PMD module - mostly lasting a 100k miles, or so - remembering that we only hear about the failures. Or, at least a good portion of them.

Yes between the 2, I don't think much vac across a clean filter, vac would go up against a dirty one how much vac fro IP in actual #'s I don't know, but remember there is also push from the lift pump, I'm thinking since the lift pump is internally pressure regulated you have to monitor filt outlet as a increase in pressure to the supply side won't be seen as the LiftP reg will just taper back delivered pressure in response against a blocked filter, unless total flow blockage then you should see a elevated pressure I'm guessing.


JD does the description above fit my assumption, I'm not sure some of that was parroting what I've heard others describe of Lift P operation. In the cutaway in the manual I don't see a internal pressure regulator within the pump, is LP operation only on/off function as dictated by ops/pcm?

TD,


12v pumps have internal pressure switches that switch on when the pressure is below a psi and switch off when desired psi is achived. I have a few 12v water pumps and they all work like this.

The inj pump can pull fuel from the tank, thru dead lift pump and fuel filter - haven't measured the 'draw', or vacuum.


Lift pump has feedback winding in solenoid, can sense current increase as head pressure increases, and reduce solenoid drive, accordingly.


In a simple impulse pump, outlet pressure is usually dependent on electromagnetic force on the shuttle. Edited by: gmctd

QUANTUM mechanic is right on this. anyone don;t believe it i can prove it to them. If the electrical connector at the Wg solenoid is loose or bad connection, everytime the connection makes and breaks the truck will stumble and stall, buck, jerk etc.


I have fixed so many of them with this problem it is ridiculous. new wiring pigtail and solenoid, down the road they go.


Brian Alley.

That is correct diagnosis, and applies to any intermittent electrical connection, where the device is a solenoid, or inductive. EGR trucks have three solenoids in that area.


Those connections can be damaged\broken when the fuel filter is serviced.


Broken connection is a deficient system, as is dirty filter(s), bad OPS, lift pump, etc.


But, just a failed wastegate solenoid, no vacuum (no power\black smoke) or full vacuum (Wastegate DTC78, or equiv), should not cause the engine to stall, if the other systems are functional, and ok.


The solenoid usually just sticks, rather than internal electrical failure.Edited by: gmctd

GMCTD,


I think your right in that my truck still does that surge thing, only now with all the modifications and most system working, it sounds like I'm reving my engine a couple of times. It sounds like some kind of pressure is relieveing itself ( I will now mention that this engine has about 60,000 miles now and seems to have recently developed the tendency to put out a white/grey cloud occasionally at first start-up only and has blow-bly to what so far is a tolerable degree. Your going to see pictures of my head before your know it.) but this mostly happens when shifting the 4L80E from P to R but only now and then.

I'm sorta confused - are the surging and pressure relief sounds occuring when shifting Park to Reverse?

A moment right after the shift is complete. I can feel the surge through the Hydraboost to brake pedal. It sounds like she's clearing her throat. Some times it's wild because I'm parking the truck and I start to back up, surge and I can hardly brake enough to stop it. Only lasts for a second. It reminds me of this diesel rabbit truck my dad once had. The EGR or pressure relieif or something would kick in and it would seem turbocharged( it wasn't).

Could be the Accelerator Position Potentiometer module APP. Several folks claim to have drilled a small hole in the bottom, squirted some contact cleaner\tuner cleaner inside the potentiomenter - supposed to solve the problem.


Havent tried it myself, nor would I.


Well, maybe on a stereo.


But, check your '94 inj pump for a green aluminum tag, indicating all the factory upgrades. Later pumps got a blue Stanadyne label, rather than the green tag. Original labels were black.


When the original pump was upgraded, the PCM got an upgraded prom - be ahead of the game if you have the 'green label' pump

That makes sense, The fuel pedal has had a bad spot on it for awhile. You notice it when you let your foot off at full speed. It will rev 300 RPM higher for a second as the TCC disengages, I thought APP reostats might be the problem, but the scanner shows normal volts during opperation(.46 volts, 4.46 volts, 4.04 volts, respectively) The middle reostat seemed high, but what do I know. Edited by: quantum mechanic

As the APP module wears, it gives an effect just like the controls that get 'scratchy' on your stereo, resulting in erratic voltages to the PCM.


A scanner with a data snapshot logger is needed to catch this type failure. The effect is that of a driver clearing the cylinders in a race car engine. Can be very dangerous in many scenarios.

I have a can (electronic parts cleaner) from when I was told, two years ago, that I had to replace the cell phone I'm using to this day.$10 instead of $120.