You know who you are,


Sadly my 96 has returned to it's unreliable ways and is stalling badly. It always restarts if you wait a while but On Saturday I had to leave it along the roadside as it refused to restart. Came back on Sunday and it fired up and ran home but continues to stall even in the driveway. I was watching fuel coming out of the top of the filter housing when it stalled once so I'm sure it's not the lift pump. It's time to pull the intake manifold and extend the PMD harness and relocate another FSD. That mod seems necessary to me if only to make troubleshooting easier. I remember a post a while ago about bypassing the OPS which I would like to do while I'm in there. What color wires do I cut/splice etc.? I don't remember.


Another thing, I remember someone saying that some nuts could be carefully tightened on the backside of the transistors of the FSD. The one I have doesn't have the transistors exposed, how do I get at them?


Thanks,


Bob

Could be the FSD/PMD. Do you see any fuel in the smoke when it's cranking and won't start?

Put a flat head screw driver between the transistor cover and the body and with just the slightest twist they will fall off. I think the retourquing might make it sorta work for a little while but if your driver is failing it needs to be replaced.


There's several ways to hot wire the lift pump, I simply ran a single wire from the fuse box that was hot with key on directly to the + side of the lift pump, runs whenever the key is in the run position.

Check out this members site for OPS bypass and PMD mounting.


http://mysite.verizon.net/vze54tx9/index.html


I have use the information and am quite pleased with the results. If you have a 96 it might be worth replacing the OPS switch (small cost) but need a special socket to remove/replace and by all means do the relay bypass with a new OPS. If the OPS is old it may be on its last legs and the bypass may not solve the problem. I have read that you can test the OPS with an LED light attached to the Gray wire coming from the OPS - lead the LED to the cab and if you see any flickering then the OPS switch is cutting in and out, but I found it easier to just start with a fresh OPS.


If you have not changed the lift pump before and have over 100K, you may want to do this too, because it is just a matter of time until you have to do this anyways. What I have done is made these 3 changes (PMD, OPS and LIFT Pump) when I first noticed a lift pump problem (148K) and added a pre-pump filter to help with the fuel cleanliness. I am diligent in keeping fuel clean, but it just seems to be a problem you can never completely remove without additional filtering.


I am happy with how things worked out and plan on keeping the 6.5 for at least another 250K. The $1000 CDN investment in parts to prempt common problems will pay for itself with no breakdowns on the road where I would have to get someone else to fix it and pay way more, plus the inconvience and hotel bill while I wait.


The old adage you can pay me now or later is true. There is not escaping problems where vehicles are involved. It is only a matter of time.

MDhorban recently posted about relaying the ignition load off of the ignition switch and anything you can do to improve your stock battery connectors is well worth it.

MDhorban recently posted about relaying the ignition load off of the ignition switch and anything you can do to improve your stock battery connectors is well worth it.


QM, where might this be found @

Stainless steel is not a good conductor of heat or electricity.


Stainless property is achieved when oxides of chromium form on the surfaces of the metal.


Problem with the FSD\PMD is - stainless transistor cases were spec'ed for the drivers, which were then fastened with stainless nuts with captive stainless star washers thru stainless screws to the pcb.


Did I mention that stainless steel does not conduct electricity well due to the formation of chromium oxides on the surfaces?


Also, because of the oxides, stainless does not solder well.


Guess where your high-current path from the Fuel Solenoid to +12v power is?


Thru Pin B on the pcb thru four stainless screws thru four stainless nuts thru four stainless star washers to two stainless transistor cases (Collector) thru the Emitter pin soldered to the pcb, thru two 100watt laser-trimmed steel bar resistors, back to the pcb, thru a switching-duty diode on the pcb to +12v via Pin D.


With a knick-knack-paddy-whack, give a.... but that's a story for the kiddies, so never mind that.http://www.dieselplace.com/forum/smileys/Wink.gif


Now - you wanna know a good fix for some of the intermittent-stall problems?


Not only is the stainless connection a problem, but seems as tho many FSD\PMD modules left the factory with looser than necessary fasteners, and most of the fasteners then loosen more from the continual heat\cool cycles as we drive our trucks.


Loose electrical connection interrupts circuit continuity.


Loose electrical connection generates heat.


Loose high-current electrical connection generates high heat


Loose electrical device on a heat-sink reduces thermal transfer to the heat-sink.


Anyone want to hazard a guess as to why the FSD\PMD is a problem?


Btw, it is the Fuel Solenoid Driver FSD if you're holding it in your hand - it becomes the Pump Mounted Driver PMD when attached to the injection pump.


FSD\PMD - same device, different locale.


So - the fix........


Very simple - back all four nuts off, finger-tighten each one down on the case, then 1/4 turn more with a nut-driver.


And for all those who think "if 1/4 turn is good 4 turns should be better, 'cause 'at sucker ain't never gonna loosen now!" - wrong! ! ! ! ! !


You will be clamping a stainless steel case with two hermetically sealed (thru ceramic) leads, which are soldered to a printed circuit board inside the potted module - pcb ain't moving, no matter how much torque is applied to the nuts.


When you hear the distinct sound of breaking glass, it's all over but the wailing - a new module is around 275 to 375 bucks, and those transistors with the broken seals, if they function at all, will not survive many rainy days.


Breaking the glass also pretty much guarantees that the welded circit connection(s) from the lead(s) to the die has been ripped loose.


Now - how have so many tens of thousands of modules survived for so many hundreds of thousands of miles on the injection pump?


The answer is simple - engine heating\cooling cycles effect a properly torqued connection to continually burnish the stainless-to-stainless interfaces, allowing electrical connection, with correct thermal transfer.


So.... give it a try - may still be some life in that old module.


My 'rework' has lasted since late Summer of ought one - on the injection pump, where it belongs.


'Course, ya don't make 63yrs without learning a few things, so I do have a spare FSD on a BETA FSD Cooler heatsink copy (called the HFE FSD Cooler) with an extension harness safely tucked away in the truck.<IMG onMouseOver="thi

gmctd,


If a basic schematic of the driver were available here, someone would try and make there own, we've heard a few who said they had thought about it. That and a thoery of how to make it better to help the production and we'd see new, homemade FSD's come to be. probably cost less too.

Like come on here Stanadyne. . . If Kenwood can make an amp that rattles the license plate off that teenager's car, can't you make a little piece of circuitry that melt down like a candy bar in a car on a 100°F day?


Does anyone have the information about the leads going into the PMD and what their functions are? Maybe instead of reverse engineering the PMD, just design a circuit from scratch, or is that just pie in the sky? How about this idea guys . . . instead of running the power to the injection pump off of those failure prone PMD transitors, can you re-route the power to another amplifer circuit? Know what I mean? Kinda like powering your lift pump off a relay/OPS instead directly off the OPS? Keep your PMD to give the singal, just power the pump off of another circuit that would take the brunt of it . . . like a Kenwood amp?http://www.dieselplace.com/forum/smileys/Geek.gif

This is the holy grail of info, it might be out ther but ain't nobody sharing the info, besides it might be a case of patent infringement that many fear to tread, Stanadyne has got a lot of them hi powered lawyers out there looking to burn some enterprising individual trying to go it alone.

Therein lies the problem, kn - the FSD module IS the Kenwood amp, out there in hell doing the dirty work for the PCM.


And at much greater temps than 100deg.


The FSD works just fine - too many thousands of them out there working prove that.


If a steel shoulder stud had been used to secure the transistor to the pcb, to establish a reliable circuit path and a set clamping tension for thermal transfer, loss of circuit continuity would not be problematical.


If the potting compound had been removed from the holes used for fastening the module to the inj pump, such that the torx screws could be torqued to a holding setting against the module heatsink, the inj pump could efficiently remove operating heat from the module.


As it is, the potting compound settles with heat cycles, clamping force is reduced, with resultant loss of thermal transfer to the inj pump.


And, internally, loss of circuit continuity.


Some modules are destroyed by thermal runaway - those die and never recover.


If a module is 'addressed' at the first signs of problems - stall with restart - it can usually be recovered.


Problem is, it is such a hassle to R&amp;R the module on the pump, that most folks do not want to take the chance.


With remote mounting, meaning not on the pump, it becomes a simple matter to replace and try.


And there is a too significant number of Stanadyne modules running remotely with no failure for many years, collectively, to outright condemn the module and\or the design.


Anyone with training and experience to redesign the module already has the basics, and can see the basics for what is required from the signals and devices connected to the module.


BETA Maskin, of BETA FSD Cooler fame, has done so, but, last I heard, is still held up for a suitable (read: economical) connector to be 'plug and play' compliant.


I think most designers feel it is not worth the trouble, since the 6.5 is obsolete, and the PCM system is primitive.


Pilot injection with injection pressures of 20kpsi is the future, and the technology is here, now.


But not for the 6.5.


So, in my opinion - pipe dream? - yeah.....


edited for politically correct contenthttp://www.dieselplace.com/forum/smileys/Wink.gifEdited by: gmctd

The 6.5 is obsolete, that's why no matter what year you have and what you've done to it, it's a project. The never ending project unless you tackle it upfront the way gmctd did.


And there's no money chasing the 6.5 aftermarket based on the lack of new products. It's the time of the enthusiast. You have to want to drive this diesel and it's relatively low price is attractive. those two things alone sets the stage for do it yourselfers to find their own way. The Driver is only a complilation of circuitry, start putting your own together and patents fall by the wayside. The new won't resemble the old.


Bow MDhorban's post was called "Stalling and stalling solved" only a few days old.Edited by: quantum mechanic

Thanks for the info:


I read with interest the post by MdHorban about his ignition switch. I've been thinking it could be something else since my PMD has only 5k miles on it. It was replaced by the previous owner just before I bought the truck. Seems to me like it was replaced to solve a problem that doesn't seem to be fixed. I suppose the PMD could be bad but I think the first thing I'll do is look at the ignition switch.


On the backside of the FSD I see a metal plate with two recesses that have the transistors in them but they are covered by a black plastic substance. Did you mean pry just those covers off or that whole metal bottom?


I need a schematic and I'll build myself a FSD for about $10. Electronic components are way cheap. Heck, I'll build one for anyone if I can just get my hands on a schematic or an explanation of what the FSD actually does.

Also forgot to say that my temp gauge was intermittently not reading any temp but now never works. I doubt it has anything to do with my stalling but thought I should mention it anyway.





Is the temp sensor the one on the front drivers side of the head?

Repair or replace the coolant temp sensor, truck runs rich without it.


only pry the plastic off the FSD.

QM is referng to the Engine Coolant Sensor - PCM uses it for fuel delivery adjustments.


Gage input is from the sensor in the head.


Sounds like you may have connection\grounding issues.


Open sender or wiring - gage reads pegged full scale


This includes faulty connection thru firewall bulkhead, harness to cluster and inside instrument cluster


Shorted sender or wiring - gage reads pegged zero scale


Gage not moving indicates no meter connection to inst cluster circuitsEdited by: gmctd

The gauge just never moves from it's cold "rest" position.


I have bad connection issues for sure. I have headlights that are intermittent due to green corroded connectors. I also have an intermittent low coolant light even though it's not low. I have taken apart all the wiring harness connector in and around the engine the last time it had fits of stalling but they all looked good.


Is the temp sensor the one all the way on the front drivers side of the engine? the one with the single wire?


I could swear that with that connector "off" that the gauge needle still doesn't move.

That location is the usual one for the gage sending unit


Try grounding the wire to the block, see what the gage does.


Appears more like the gage has no power to it


Also try dipping the headlite, and other, connectors in CLR, then rinse with clear water.


Corrosion density will determine soak time.


Then, vaseline, or GM sells a connector lube\seal, used in Corvettes and other hi-end vehicles.


It's about same color, consistency, and odor as EP Chassis Lube.Edited by: gmctd

Stupid question #1,


What's CLR ?





The transistor covers pop right off. (I'm playing with a spare FSD that I have laying around). Once I get my working unit off the pump I'll check those nuts.


Stupid question #2,


That pad that goes between the PMD and the IP. I'm sure it's supposed to transfer heat but I'm also sure that I have better heat sink compound (arctic silver). Is THAT pad necessary, like does it provide electrical insulation? If I use a compound without that pad will it short something out?

CLR is limeaway, probably has caustic sodas of rare earth metals (sodium,magnesium, ect.)


Heat transferpad is for IP mounting, I don't use it on my homemade cooler.

No stupid questions, here, please.......http://www.dieselplace.com/forum/smileys/Wink.gif


CLR - Calcium Lime Rust - an acidic cleaner sold in Walmart and various other drug stores and such. Think it has citric, phosphorus and other mild acids


Can also use hydrochloric acid based toilet bowl cleaner - rinse with clear water, use anti-oxidant grease.


Use the pad - it is a heat activated adhesive, supposed to maintain contact if screws loosen.


Alternate thermal compounds can be used in the transistor cavities, in conjunction with the pad.


How loose were the nuts on the module?Edited by: gmctd

I have a friend/neighbor who is a mechanic at a Chevy dealer. A 98 6.5 came in running badly and like they always do they installed a new IP/PMD combo. It did not fix the problem, turned out to be a bad injector (I think that's what he said, can't remember). They are supposed to send them back to GM but it layed around long enough to "disappear" to my place. Nobody ever asked about it. Anyway....I'm assuming I have good spare parts since it didn't fix the problem. That's the FSD I'm playing around with and NO I didn't try the nuts yet but I will just to see.

Good find - what's the five digit number printed on the module cover?


Or the eight\nine digit GM part number, below the scan label?


After the tighten-up routine, unplug yours, substitute that one, crank it up and see how the engine runs.


Functioning modules are transparent to the PCM, so it's an easy test.


And, of course, post your findings for the database.


Please......http://www.dieselplace.com/forum/smileys/Cool.gifEdited by: gmctd

34583


When I got it home Sunday it wouldn't run more than 2 minutes without stalling. I was thinking "yeah, I can be sure if I fix it right this time!"


Since Sunday it's returned to running fine without stalling and I haven't done anything to it yet..


Still haven't tried messing with the transistor nuts.


I'm GOING NUTS though.

Took it for a ride, it stalled three times within a mile from home.


I'll be digging in this weekend

I have a stalling story.





My dad's 96 was stalling/hesitating with a slow cranking speed. My dad bought two new batteries and had me put them in. His connectors were badly corroded and I asked him to get new ones. When he was driving the next morning it stalled a few times and restarted but as long as he didn't run the A/C it seemed better. It turns out his crossover cable between batteries was being eaten by the clutch for the A/C. It had a 1/4" gouge in it. I repositioned his cable and put on top post connectors, no more stalling.

I think I'll keep my obsolete mechanical 6.5, anything obsolete thats electonic seems to be a


huge pain in the http://smileys.smileycentral.com/cat/10/10_6_2.gif Edited by: dslhead

GMCTD,


I didn't get a chance to work on my truck yet, I live in an area declared a federal disaster area due to flooding from the remnants of hurricane Ivan. Although my place didn't flood many around me did and I've been busy helping others.


I just wanted to tell you that I put a nut driver on the nuts of my spare FSD and they were pretty loose. Too loose in my estimation. If they are all like that I can see what you mean.


I'll be gettin' to it soon.

The procedure is specificlly important - ir burnishes the interface contact areas to re-establish electrical continuity.


Back the nuts off, finger-tighten to the case(s), then 1/4 turn with the nut-driver, or wrench.


Any tighter may shatter the hermetic seals.


Take care in your efforts in the cleanup, there.........