I have a 95 gmc 6.5 turbo 2500 series runs and starts pretty good but it is starting to miss, kind of like a bucking action under a load passing etc. I replaced fuel filter didnt help.Can anybody help me is there anything I could do myself to check for problems? also it has 150,000 miles

HAVE YOU CHECKED YOUR LIFT PUMP?? TRUCK WILL RUN FINE EVEN IF ITS NOT WORKING. BUT WILL BUCK AT YOU FROM FUEL STARVATION. TO TEST IT OPEN BLEEDER VALVE ON FRONT OF ENGINE WHILE ITS RUNNING, IT SHOULD HAVE STEADY STREAM OF FUEL IF ITS WORKING PROPORLY. BUT IF ITS NOT WORKING, THERE WILL BE NO FUEL AND ENGINE WILL DIE AFTER A SEVERAL SECONDS. IF IT DIES LIFT PUMP IS NOT WORKING. WHEN YOU ARE DONE AND IT DIES IT WILL BE HARD TO START,DONT WORRY JUST CLOSE VALVE AND KEEP CRANKING ON IT, IP WILL SLOWLY PRIME ITS SELF AND START. HOPE THIS HELPS OUThttp://www.dieselplace.com/forum/smileys/Approve.gif

ditto on the lift pump. Likely cause is oil pressure switch as the pump is powered throught the o/p switch, its also cheaper then the lift pump. You may choose to wire the pump up using a relay that the oil pressure switch closes to take the load of the switch.

Buggy69,


I feel your pain. I am having the "exact" same problem with mine. I have actually been through the warranty replacement pump (60,000 ago), a new PMD (20,000 ago) and a new rail pump (2 weeks ago).


Your description is very accurate. It seems to run fine until it warms up........Then it will start bucking and skipping? The condition over the past couple days has been much worse in my case and the truck now is almost impossible to drive once it warms up. It starts jerking like a gasser V8 running on 4 cylinders up to a point....... Then it throws a code or something, the check engine light comes on and it seems to run much better but with reduced power. Today it actually cut off on me while travelling 75 on the interstate (un safe!).





I'm guessing the PMD has died again or the oil pressure switch is messing up?





Any help on this topic is greatly appreciated!





AJ

Pinehead, what year is your truck? '92-'95 will give a code with a wire between A and B Terminals on the ALDL link located under the dash next to the hood release.


http://www.dieselplace.com/forum/uploads/E58_aldl.jpg


'96 up OBDII and you have to have a scantool to read the DTC's (Diagnostic Trouble Codes). Your right to think fuel delivery but on the '94 and newer EFI 6.5L There's sensors that control injection timing and delivery, as well as a timing advance piston that's known for failing due to scoring of its' aluminum housing. Without an enhanced perameter scantool proper diagnosis would be guesswork. It's not a bad Idea to have an extra FSD (Fuel Solenoid Driver). Do you have it remotely mounted? It sure makes it easy to change.Edited by: quantum mechanic

Quantum,


Hello....... Thanks.......





The truck is a 95 Chevy 2500. King Cab, long bed 2 wheel drive with 174,000 miles. It is actually my fathers truck (company truck). The thing really is great when it runs right........ When it does'nt...... It is a nightmare that no local diesel shop can figure out. The dealers are a joke. So we have taken it upon ourselves to try to do so.





Unfortunately I took off the battery terminals to clean them. I have been told that this clears the codes? Are you saying it is possible to read the codes without the scan tool? I also changed the fuel filter and re-oiled the air filter. All were really dirty and it seemed to make a difference. The truck has to be driven a little over 1 hour before it really starts to act up. It seems the hotter it gets...... The more it acts up. I put some pretty serious hours on it every day so I'll see how it does tomorrow.





No........ I do not have the remote mounted PMD. I have already planned to order the remote cooler with the long harness so I can mount it on the firewall. I was looking at that PDC/PMD cooler. I was going to get it tonight....... But I want to be sure before I order it. Of course I want to get the kit anyway. If anything..... Just because it is easier to change and swap it out.





I also plan to rip that snorkel restriction out of the fender tomorrow. Good pics of that on the other thread!





Thanks!





AJ

Yes,


With the '95 you can read the codes. key turned to on, ignition off, put a wire between A and B. The check engine light will flash, and you must count the pulses. They will come in sets of numbers. Three flashes and then five flashes would be 35, the code for injection response too short. www.kennedydiesel.com (http://www.kennedydiesel.com) has all the DTC's listed under the 6.2/6.5 tech tips. Also on the '95 you might have the cast web in the upper intake.


http://www.dieselplace.com/forum/uploads/815_96intake2.jpg This is what it looks like with no cast web. If you see an aluminum veil,remove it as best you can, as it's a restriction.


I made my own wiring harness remote mount and cooler for about $15 and it's worked excellent. The post with pic's is here on the diesel place.

Hey Quantum;


May I steel your photo of the scanner plug?


http://www.dieselplace.com/forum/smileys/Geek.gif


hope so ; thanks.

Quantum,





WOW.......... I think the air filter was the problem. It was toatally plugged with dirt and crud. The fuel filter was not too bad. It looked the same as it always does. I removed the restrictive snorkel before I left today......... I drove it all day long.......... Problem resolved!! I cant believe it was that simple (clogged air filter). There is no telling how long it has been like that.


I am still ordering the remote PMD cooler and harness. I also want to check for and or remove the webbing you are talking about. Did you use a Dremel tool or some other to remove? Was it easy?





Thanks again!





AJ

16gasxs,


Steal away.


Pinehead,


I'd keep an eye out, as most problems are compound complex problems(you mentioned a code). I have a cut off tool(air powered) that I score a line around the inside and outside of the cast web, then I gently tap it with a ballpeen hammer to crack it out. I score the whole thing and then break it out a small piece at a time.


I've heard of using a short jigsaw or sawzall blade to cut it. You could drill holes along a breakline and then use the hammer.


I would ask you to consider a 3" downpipe and straight exhaust and make a boost controller. These two things will give you more power than most mods, and if you make your own boost controler you might feel up to making your own wiring harness remote locator and cooler.


http://www.dieselplace.com/forum/uploads/DZ1_exhaust.jpg


http://www.dieselplace.com/forum/uploads/BF8_96dashswitch.jpg


This gives you the choice of 6psi, 10 psi at half pot. and 15 at full pot. but do the exhaust or your just turning up the back pressure.

Hey QM,





Where would I get that 3" downpipe? Mine also has a catalytic converter. It was added by a dealer in Canada, I guess it's the rules up there. Anyway, would I obtain a pipe for that from the same place?

Bob;


Down Pipes can be had from a number of sources. BD, Banks, Jardine (that's what I have) Heath Diesel, Kennedy Diesel. Most have the just the down pipes or complete systems.

Wycliff diesel has the '93 6.5L downpipe $155. It's a bullydog pipe though.


http://www.dieselplace.com/forum/uploads/659_downpipes.jpg


Next, I buy a joint of 3" stock and have it expanded at one end and 15 deg. bend at the other.


http://www.dieselplace.com/forum/uploads/FC7_exhausts.jpg


The result is more power, less back pressure, and a pleasent BB sound. Step on the reostat to hard and it throws your head back.


without actually having had it dynoed, I'd guess 350hp and near 500Tq. I'm going to do a HD friction plate rebuid myself and maybe take the heads off for new valve guides( I see smoke when I start two of the trucks.).





Edited by: quantum mechanic

clean all your ground wires ,my 98 has a ground wire on the passenger top side rear of the head 'very important even if they look clean take them loose and clean them

I have a 95 gmc 6.5 turbo 2500 series runs and starts pretty good but it is starting to miss, kind of like a bucking action under a load passing etc. I replaced fuel filter didnt help.Can anybody help me is there anything*I could do myself to check for problems? also it has 150,000 miles Edited by: ken smith

I have a 95 gmc 6.5 turbo 2500 series runs and starts pretty good but it is starting to miss, kind of like a bucking action under a load passing etc. I replaced fuel filter didnt help.Can anybody help me is there anything*I could do myself to check for problems? also it has 150,000 miles

HAVE YOU CHECKED YOUR LIFT PUMP?? TRUCK WILL RUN FINE EVEN IF ITS NOT WORKING. BUT WILL BUCK AT YOU FROM FUEL STARVATION. TO TEST IT OPEN BLEEDER VALVE ON FRONT OF ENGINE WHILE ITS RUNNING, IT SHOULD HAVE STEADY STREAM OF FUEL IF ITS WORKING PROPORLY. BUT IF ITS NOT WORKING, THERE WILL BE NO FUEL AND ENGINE WILL DIE AFTER A SEVERAL SECONDS. IF IT DIES LIFT PUMP IS NOT WORKING. WHEN YOU ARE DONE AND IT DIES IT WILL BE HARD TO START,DONT WORRY JUST CLOSE VALVE AND KEEP CRANKING ON IT, IP WILL SLOWLY PRIME ITS SELF AND START. HOPE THIS HELPS OUThttp://www.dieselplace.com/forum/smileys/Approve.gif


*

HAVE YOU CHECKED YOUR LIFT PUMP?? TRUCK WILL RUN FINE EVEN IF ITS NOT WORKING. BUT WILL BUCK AT YOU FROM FUEL STARVATION. TO TEST IT OPEN BLEEDER VALVE ON FRONT OF ENGINE WHILE ITS RUNNING, IT SHOULD HAVE STEADY STREAM OF FUEL IF ITS WORKING PROPORLY. BUT IF ITS NOT WORKING, THERE WILL BE NO FUEL AND ENGINE WILL DIE AFTER A SEVERAL SECONDS. IF IT DIES LIFT PUMP IS NOT WORKING. WHEN YOU ARE DONE AND IT DIES IT WILL BE HARD TO START,DONT WORRY JUST CLOSE VALVE AND KEEP CRANKING ON IT, IP WILL SLOWLY PRIME ITS SELF AND START. HOPE THIS HELPS OUThttp://www.dieselplace.com/forum/smileys/Approve.gif


*

HAVE YOU CHECKED YOUR LIFT PUMP?? TRUCK WILL RUN FINE EVEN IF ITS NOT WORKING. BUT WILL BUCK AT YOU FROM FUEL STARVATION. TO TEST IT OPEN BLEEDER VALVE ON FRONT OF ENGINE WHILE ITS RUNNING, IT SHOULD HAVE STEADY STREAM OF FUEL IF ITS WORKING PROPORLY. BUT IF ITS NOT WORKING, THERE WILL BE NO FUEL AND ENGINE WILL DIE AFTER A SEVERAL SECONDS. IF IT DIES LIFT PUMP IS NOT WORKING. WHEN YOU ARE DONE AND IT DIES IT WILL BE HARD TO START,DONT WORRY JUST CLOSE VALVE AND KEEP CRANKING ON IT, IP WILL SLOWLY PRIME ITS SELF AND START. HOPE THIS HELPS OUThttp://www.dieselplace.com/forum/smileys/Approve.gif


* very very importantto clean all ground wires ,main one is on top of passenger head .i spent $1500.00 to find this out

I have a 95 gmc 6.5 turbo 2500 series runs and starts pretty good but it is starting to miss, kind of like a bucking action under a load passing etc. I replaced fuel filter didnt help.Can anybody help me is there anything*I could do myself to check for problems? also it has 150,000 miles

Quantum,





You were right............ The truck still runs awesome most of the time (99% now). It had 3 bucks today.





I loaded 2,400 lbs. of concrete scrap in the back last night to haul to the dump. Today I had to do some errands before I could go to the dump. Along the way (and going up a bridge) the truck skipped (bucked) once. Then when I got to the dump (about 30 minutes later) I had the rough idle associated with all the bad bucking and skipping before I cleaned the air filter and changed the fuel filter....... I also noticed that under load (hauling the concrete) and under hard acceleration in a top gear that there is a bunch of black smoke is coming out of the tail pipe? Still not enough air flow and too much fuel? Right?.......... A wastegate problem?





After I left the dump........... I had a couple of intermittent "bucks" and the rest of the day all was well? I was actually trying to duplicate the problem....... But to no avail..........





So like you said........... A complex problem with multiple issues. 2 are fixed and I will have the PMD relocated to a different location next week........ So 3 issues down......... But this still does not explain the unburnt fuel.......





By the way, pulling that snorkel out........... It made a difference..... The down pipe is next........ What is that twisted thing? Is that on my truck?


Geeeeeezzzzzzzzzzzz!





AJ

Pinehead,


The EFI 6.5 uses a vacuum pump to close the wastegate via the ECM's openning of the waste gate solenoid.


http://www.dieselplace.com/forum/uploads/B36_wgarm.jpgThe canister in front of the arm has a vacuum port. With the engine on,


http://www.dieselplace.com/forum/uploads/C44_wg-solenoid.jpg


unplug the line from the vacuum port on the WG arm and check for vacuuum. It should be 15" Hg, which is strong enough to feel, if you put your finger over the end of the vacuum line.


If you don't have any vacuum, you don't close the wastegate and you burn extra fuel trying to haul a load. It smokes like you're one of those old steam locomotives.


If there's a vacuum, disconnect the wire connector on the WG solenoid and check again. Now, there should be no vacuum. Vacuum would indicate a non-functioning WG solenoid.


Or, if there's no vacuum, pull the vacuum line to the WG solenoid from the vacuum pump. It should pull a strong vacuum, 22"-25" Hg. If not the vacuum pump has lost it's diaphram and should be replaced.Edited by: quantum mechanic

Dedicated ground,


Ken good point on GND, here is one trick I learned on my 90 GM gasser GM ground plane is crappy by design, that wussily strap they use as a GND is hidden from view and will break after a while; what I did was take a #4 double ring battery cable 1 end to the truck frame and ut the other end to the lower alternator mount bolt stud, this way I have a excellent ground plus it's in the open where I can see if it's broken or contact point needs cleaning.


Pine(AJ)


QM has some good advice there for checking for vac. how did you make out on that front, also take a minute to update your sig line the info there can help us try to sort a better course of action in troubleshooting, for instance if you are a L56 config truck, there is a little more to your vac system than WG vac loss that could be causing problems.

Hello Everyone


I have been reading the board for a couple of weeks, and joined last week, now I need help.


I have a 96 3500 6.5 with 140,000 miles and today after driving about 8 miles and a 30 minute shutdown, it restarted and quit after about 15 sec. First I checked that I had fuel from the drain, it did then I poured water over the injector pump/FSD as best I could and it started right up, I drove about 3 miles, it quit, more water and it restarts. I did this all the way home. Run time got shorter each time.


Is it safe to assume the FSD/PMD is going on vacation?





John G

http://www.dieselplace.com/forum/uploads/4FE_96l65.jpgFSD mounted on cooler at top right corner. total cost $15.


Take this opportunity to mount the fuel driver on a heatsink away from the block. Personally, I would splice in the six wires needed and find an appropriate aluminum sink and tap it for the driver mount and screw it to the body with self tapping screws. The other way is to get a package deal that comes with the driver, heatsink and wireharness for $500 or so.


Yes, I'm assuming that pineheads truck is L65, but it is.Edited by: quantum mechanic

Hello Everyone


I have been reading the board for a couple of weeks, and joined last week, now I need help.


I have a 96 3500 6.5 with 140,000 miles and today after driving about 8 miles and a 30 minute shutdown, it restarted and quit after about 15 sec. First I checked that I had fuel from the drain, it did then I poured water over the injector pump/FSD as best I could and it started right up, I drove about 3 miles, it quit, more water and it restarts. I did this all the way home. Run time got shorter each time.


Is it safe to assume the FSD/PMD is going on vacation?





John G





My 95 was doing that when my injector pump went out, so, yes, that is probably what the problem is. You did better than I did as far as mileage before it started going out. Mine only had 120k something on it when mine went. The injector pump is the only thing major so far that I have had to replace on mine besides the windsheild wiper module for the pulse wiper.


As far as the jumping & bucking problem that I have seen posted in this thread, that sounds like the PMD. Edited by: GMC Cowboy Cadilliac

Cowboy


Thanks for the reply. I think I read somewhere that GM is replacing the wiper pulse board as a recall or service bulletin, if you have receipts, you might want to check.

Quantum,





Thanks for your posts and Pics.......!! They have helped me tremedously. I pulled the top of the intake manifold off today so I could get a dental mirror in there to see which resistor is in the PMD. In the process I found that the 2 bolts in the center of the upper intake manifold (plenum) were stripped out and there was an obvious leak there. The shop that worked on it last forgot to mention this (morons). You cant really trust anyone when it comes to this stuff. So I tapped those and went one size over........ No problems. The webbing you were talking about is not in there. So I assume it is the newer one? I also remotely mounted the PMD to the firewall next to the master cylinder. I cannot believe how hot that thing gets!!





I followed your procedure for checking the waste gate..... After step one there is no vacume. But the morons that stripped the bolts (and did not tell me) replaced most of the vacume line too! So is it possible that they swapped the lines that go to the solenoid? If so........ Which side of the solenoid shold have the vacume all the time?





Also, I already tried swapping them just to see what would happen.... There was always vacume over at the wastegate diaphram after I swapped them. Even with the solenoid unplugged?





Thanks,





AJ

Cowboy


Thanks for the reply. I think I read somewhere that GM is replacing the wiper pulse board as a recall or service bulletin, if you have receipts, you might want to check.








Ha!!!!!





Been there done that......... Got it fixed at the dealer and it is worse than before. Consider how badly you need or want it. Now I have to wait a couple of minutes for the wipers to quit working after I turn them off. Or re-start the truck.





AJ

Cowboy


Thanks for the reply. I think I read somewhere that GM is replacing the wiper pulse board as a recall or service bulletin, if you have receipts, you might want to check.





Already taken care of. I got a recall letter from the dealership where my dad works and we replaced it....http://www.dieselplace.com/forum/smileys/Approve.gif

pinehead,


The emissions diagram for L65 non-EGR models shows the line form the vacuum pump to the WG solenoid on the front port and the line to the WG arm coming off the rear port.http://www.dieselplace.com/forum/uploads/631_emissions.jpg sorry it's blurry.


The valve is GM part# 01997227 and lists for $30+ but it's $16 @ www.gmpartsdirect.com. If I don't want to wait for shipping, I tell the dealership parts guy I want a discount and it came to $26 with tax.

I would like to THANK ALL of those involved in helping with ideas and troubleshooting my truck. It has run perfectly for over 2 days now. The longest it has run correctly in over a year! I still am amazed at how simple all of the problems were.


The real test will be when I haul a car up to Nashville this weekend for a car show. I will be pulling around 6,000 pounds of car, trailer and gear. If I make it round trip with no problems I guess I will officially call it fixed and work on other things.......... Like the exhaust.





THANK YOU!!!http://www.dieselplace.com/forum/smileys/Approve.gif





AJ

Generally -


If the upper intake plenum has the raised EGR boss in the center, it will also have the casting webbing.


The plenum with no raised boss does not.


All EGR plenums have the webbing.


Easy to check for.Edited by: gmctd

Mine had the raised boss (circle chunk) but no webbing. I was contemplating cutting out the thing....... But it looked as if it smoothed the airflow as it enters the plenum......... So I just left it.





AJ

About removing the air cleaner snorkel,


Are you guys saying that the connection from the air cleaner housing to the fender be removed?


Wouldn't that cause the engine to breath hot under hood air?

http://www.dieselplace.com/forum/uploads/E6B_restrict.jpg


The black thing sometimes has a cone in it, but other than that it goes back in place. The fenderwell air restrictor runs from the airbox to another air duct behind the battery.


Removing the restictor opens the flow, but you still draw it along the same path. if you look, the air duct behind the battery opens up behind the grill, making it a cold air induction of sorts.Edited by: quantum mechanic

Ok.......





More Frustration.............





The thing has been running perfect (like never before) and today as I pull in to pick up the trailer for my trip.......... Buck, skip, and hicup at idle. Just a couple chug, chugs. But enough to tell me the problem is still there. Under acceleration and hauling the trailer all seemed to be well. Of course....... I havent had it up on the interstate yet.....http://www.dieselplace.com/forum/smileys/Cry.gif





Any ideas? I am thinking now the oil pressure switch is intermittent causing the rail pump to come on and off? It is about the only part I have not replaced........ Except for the injection pump. The pump dosent have that many miles since the last install (new). New PMD (remote to firewall) and new rail pump too........


Where exactly is the oil pressure switch and is there a way to test it?





By the way Quantum.......... Thank you for the above diagram. The vacume lines going to the soleniod were backwards.





AJ

pinehead,


The OPS is behind the fuel filter to the drivers side. You have to have a OPS wrench to get it off. You can fix it for good by bypassing the OPS to lift pump operation. To do this you need to install a new OPS. Then obtain a 30amp (or what ever) relay that can be mounted to the firewall. There are three wires coming from the OPS connector. The grey wire feeds the lift pump and the orange is the common. cut the grey wire, and connect the end from the OPS connector to the coil of the relay, ground the other side of the coil. The other end of the grey wire you connect to the post on the relay that will be powered when the OPS is switched and powering the coil on the relay. The orange common you have to splice into, it still has to power the OPS, and now it has to power the common on the relay. Leave the yellow wire alone, it sends signal to the Oil Pressure Guage on the dash.





http://www.dieselplace.com/forum/uploads/A51_opswires.jpg


If this is confusing to you, I will explain more.Edited by: quantum mechanic

Engine idling, open the air bleed, top of fuel filter - lift pump will push fuel out in a steady stream. Idling is lowest oil pressure, should test system at worst condition, where OPS cuts out at lower presssures.


You can put a clear hose on the bleed to lessen the fuel spill mess.

Well..........





I had a major failure on the way to Nashville last week. The truck is up there now at A&M Turbo in Macon GA.


I was Pulling a car on a trailer. About 5,300 lbs. combined weight. It seemed to pull it very easy. I noticed some black smoke (on and off) all the way up to the point where it died. I pulled off at rest areas several times and diagnosed the wastegate solenoid as sticking. I pulled the line off at the wastegate (diaphram)........ No vacume. Then I would tap on the solenoid..... Then there was vacume. Intermitent problem. So I kept going. I noticed the truck working a little harder on the hills in GA. But not too bad. We pulled off to have lunch............. When we came out to start the truck....... Click...... Like a dead battery or weak starter (all just replaced and working perfectly along with alternator). When I finally got it started (it just started out of the blue) there was a large puff of white smoke out the tailpipe. As we pulled back on to the interstate I noticed reduced power with no black smoke. On hard acceleration there seemed to be some blue smoke? But not too bad.......... No hint of anything getting hot here either. All gauges were indicating normal operation. So........... I pulled off again in Perry GA. I walk in the store to get a drink and come back outside................. Whoaaaaaa!!!! There was lots of white smoke coming out of the tailpipe.......... Like a steam engine? Once again all gauges indicating normal operation. The truck never got hot once. Right up to where I finally turned it off and had it towed to a dealer.





Anyway.......... The dealer in Perry wanted to install a new engine (go figure!) at the bargain price of $8,900.00. So with some help from the folks at home (Florida) we found what seemed to be a pretty good diesel shop in Macon. The current diagnosis from this shop is a faulty starter..... and a blown head gasket. At this shops recommendation I am having him remove the heads to check the pistons, rings and cylinder walls for damage as well as any possible damage to the heads. They say if the bottom end looks good and the heads are not cracked....... All that is required is a pressure test on the heads to prove they are worthy of going back on and new gaskets.





I am curious as to what the people of this forum think about all of this. Any input is GREATLY APPRECIATED.





AJ

Rip-off mechanic shops should have to wear a patch over one eye. Head gasket sounds right to me, I was thinking it before I read it. 6.5 heads crack between the valves and the water passage.