# 1997 GM 6.5 trouble running



## jhook (Jan 24, 2004)

1997 GM 6.5 Turbo diesel. Problem with fuel system. When you turn on ignition, lift pump charges the system. Truck starts and runs until fuel is used up out of filter. Lift pump and filter have just been changed (because of problem). Then truck quits. 

When I open the bleeder on the top of the fuel filter, air comes out (under pressure), I can close it and restart the truck, no problem. If I open the bleeder a bit while the truck is running, it will spray out some air and then fuel and keep running. I can keep the truck running by doing this (in my shop). Not sure what is causing the air pressure buildup in the filter in the first place.


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## dheavychevy38 (Nov 19, 2008)

Try removing the fuel cap ? There will be some vaccum but try to get it running with the cap removed. Try to start the truck with bleeder valve open.


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## jhook (Jan 24, 2004)

Ya, I had the cap off actually. When I first brought it in to my shop from outside and left it to warm up overnight, the tank was actually pressurized so when I took the cap off, it was not under vacuum, it was under pressure (I tried starting it first).


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## dheavychevy38 (Nov 19, 2008)

If I remember right that motor should run with that valve open. Does the lift pump stay running when the truck dies ? Have some one crawl under there and hold on to it. When the truck dies what is you oil preasure the switch could be the culprt. Cause when you first try to start the truck it is in bypass mode but when it goes to switch if the oil preasure switch is bad it will stop pumping fuel and die.


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## jhook (Jan 24, 2004)

when the truck dies the pump is not still running. The oil switch was also brought up by a friend however it doesn't make sense to me because when the truck dies it sounds starved - not turned off. Also, there is a pressure build up in the fuel filter. Also, as long as I "vent" the fuel filter, it will keep running - and pumping fuel up. It does not necessarily shut off after a certain amount of time or engine temp - just after a couple of minutes if I leave it alone. But it will keep running if I let the air out.


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## augerandblade (Jan 17, 2009)

Could it be that by venting the fuel filter you are causing the lift pump to keep on operating and supply fuel to the injector. Theinjector pumpon its own will keep the truck running as it will lift fuel but your engine performance will suffer. And I would think that you must have a hole in your supply line somewhere in order to get the air in the system. Just my .02 s


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## augerandblade (Jan 17, 2009)

Another thing that works well with my 6.5s is after changing the fuel filter I will bleed it when the engine is cold, You probably know that the lift pump comes on when you turn on the key. And could it be that you still have a lot of air in the system from the job y a did on it. If I got the age of the truck right you may be due for new lines. Anyway hello from Renfrew here (down the line) and I see ya still got the back hoe I delivered. I ll be keeping a eye on this thread to see /find out your solution cuz it might happen to one of the three that I got.


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## dheavychevy38 (Nov 19, 2008)

How many miles since last injection pump ? How old is the truck ? Will the truck stay running if you crack the bleeder ? If you try to give the truck throttle does it stay running or doesn't matter.


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## dheavychevy38 (Nov 19, 2008)

http://www.dieselplace.com/forum/showthread.php?t=42248 This is where I found this and have used it many times hope it helps.

The Diagnostic Checklist:

Please fill out to best of your knowledge.

1. Describe the problem you are having in detail:

2. Year of truck/engine.
3. Odometer reading (indicate miles or kilometers).
4. Indicate the model number on the Injection pump (starts DS4 or DB2......).
5. Indicate if you know if it's a 1500, 2500, 2500HD, 3500, 3500HD.
6. Do you have an EGR on the engine? (An F or an S engine code 8th VIN digit)
7. Air Filter condition (visual check).
8. Fuel filter condition (freshly changed, mileage since changed).
9. Location of PMD/FSD? (ex. on pump/remote over intake, behind bumper).
9a. If remote mounted, describe wiring harness (homemade or purchased from which vendor).
9b. Indicate the location and condition of the FSD/IP grounding wire.
10. Outside Temperature (C or F). _____ °

11. Service Engine Light while running?- on/off/intermittent
11a. Service Engine light does glow during start/cranking/bulb check: Yes/No
12.Have you scanned for engine codes? Yes/No
12a. List exact results on engine codes.

13. Condition of Battery terminals (removed, cleaned and tightened).
14. Known condition and age of Batteries.
14a. Are batteries a matched set of same age?
15. Condition of Major Grounds (removed, cleaned and tightened)

16. Does engine crank, or "turn over"?
16a. Does engine start and run?
17. If engine does not start- Crack injector line: do you have fuel? Yes/No
18. Does your Wait To Start light come on?
18a.Number of seconds WTS light is lit.
19. Engine Cranking speed (if you have an accurate tachometer).

20. Are you experiencing Stalling?
20a. Describe the event (upon startup only, down the road, hit a bump, etc...)
20b. Do you notice loss of dash or instruments?
21. Check turbo inlet and air filter for obstructions.
22. In a no-hot start, pour a bottle of room-temp water on the injection pump. Does it start now?
23. Lift pump test - Describe results.

24. Upon cold start, does the radiator hose get hard quickly? Yes/No
25. Upon cold start, do you have excessive white smoke? Yes/No
26. Do you have excessive cranking time before the engine starts? Yes/No
27. Have you used the block heater? Does it affect engine starting? (only try for starting problems).
28. Are all glow plugs in proper working order?

29. During hard acceleration, do you have excessive black smoke? Yes/No
30. Do you have any unusual exhaust smoke issues?
31. Turbo check out - Pass/Fail
32. Indicate fuel that you are using: Bio-Diesel, #2 Diesel, SVO/WVO, other
32a. If running Veggie Oil fuel setup, indicate details of your conversion (homemade or packaged system).
33. Are you using any fuel additives? If so, please list.
34. Upon unscrewing fuel cap, do you have a large vacuum formed in the tank? Yes/No
35. Do you have any service history available that might pertain to the problem you are having?
36. Please indicate any modifications to the vehicle that might help us diagnose better.
__________________


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## jhook (Jan 24, 2004)

augerandblade;983717 said:


> Another thing that works well with my 6.5s is after changing the fuel filter I will bleed it when the engine is cold, You probably know that the lift pump comes on when you turn on the key. And could it be that you still have a lot of air in the system from the job y a did on it. If I got the age of the truck right you may be due for new lines. Anyway hello from Renfrew here (down the line) and I see ya still got the back hoe I delivered. I ll be keeping a eye on this thread to see /find out your solution cuz it might happen to one of the three that I got.


Hey, great to hear from you again. That hoe is still pushing snow (what little we have had this year) 

I had sent the truck over to a shop to get the filter changed and it was because we were already having trouble with the truck.

My main concern now is the air in the line. I have to find out how it is getting there. I think if I can fix that I will have it beat. There should not be air at the fuel filter. It will stay running if I crack open the bleeder. It must be drawing air before the lift pump somehow. The fuel tank on that truck isn't that old but you never know...


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## jhook (Jan 24, 2004)

dheavychevy38;983786 said:


> How many miles since last injection pump ? How old is the truck ? Will the truck stay running if you crack the bleeder ? If you try to give the truck throttle does it stay running or doesn't matter.


Don't know on the injection pump. Truck has 330,000 kms on it (about 190,000 miles?) I have only put the last 30,000 kms on it in 3 years. I have not touched the injection pump. truck revs up fine when there is fuel but it will die out. Then when I crack the bleeder again, air pushes out as though it were under pressure, if I leave it cracked, it will stay running. Truck is 1997.


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## Dewey (Feb 1, 2010)

I have a 99 GMC with the same motor I have had it since it had 25,000 miles . It has 1000,000 on it now I've replaced the injector pump 4 times...... WTF anyideas to get more life out of them ????


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## pmorrissette (Sep 15, 2008)

Your injection pump is sucking air. check / change the rubber hose between the lift pump and the filter bowl. Sometimes the fitting at the bowl leaks. Check the steel elbows under the cab that connect to the lift pump, rust can cause them to allow air in, but no fuel out. The LP doesn't generate much vacuum wheras the IP does. Possibly drawing from further back, but relatively easy to inspect the hose there. You may have to drop the tank to inspect connections on top of the tank.

When you remove the filler cap, is there vacuum? There shouldn't be. If there is, start by changing the filler cap.

Good Luck.

DEWEY: add 1 quart straight 30W non detergent motor oil to the fuel every other time you fill up. If you buy your rebuilds off Ebay, that's another reason. I've got 260000 kms on mine and still running strong...


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## jhook (Jan 24, 2004)

Ya, I was going to take a closer look at the lines next. I am guessing it would have to be leaking between the tank and the LP, even if there was a leak further up that did not let the fuel out, air wouldn't come in because the fuel is under pressure there. I am guessing the LP is drawing it in someplace. I may have to drop the tank to find it. I'll try that in the morning and report back.


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## jhook (Jan 24, 2004)

I always use a fuel additive/lubricant - every fill up.


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## BigLou80 (Feb 25, 2008)

FWIW my cousin has a 96 chevy 350 gas, really hard to start becasue it was getting air in the system. Still in the process of resolving it but it appears that venturi effect is drawing air in to the system instead of letting fuel out. Some of the fuel lines and fuel tank are badly corroded should know if replacing them fixes the problem tomorrow


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## dheavychevy38 (Nov 19, 2008)

Defenitly check the line before the lift pump for rust and holes.


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## damian (Jan 29, 2009)

suction side leak(before lift pump)get to work.


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## jhook (Jan 24, 2004)

How to find a leak in your fuel line...

Well, I had to find out where my lines were leaking so here is how I did it:

1. Put truck outside where it is cold, loosen fuel cap
2. Leave it for a couple of hours
3. Tighten fuel cap
4. Move truck in to heated shop
5. Go sit in hot tub for approx 60 minutes
6. As the fuel warms up and expands to build pressure, it will start to spray out of the leak.
7. Replace faulty lines.

In my case there is a rusted line coming out of the tank. I am off to get a new sending unit for the tank, hopefully that fixes the engine problem by preventing air from entering the line.


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## Torque454 (Feb 4, 2010)

Its probably the oil pressure sensor or a leak in a fuel line somewhere. Check out dieselplace.com in the 6.5 section. Me and the gang will get you fixed up.


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## jhook (Jan 24, 2004)

Truck running fine. 

I replaced the sending unit. The lines were corroded just out the top of the tank and must have been drawing air through that. Truck is out plowing now payup


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## pmorrissette (Sep 15, 2008)

Good Job


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## towpro570 (Jul 23, 2009)

on my truck i have rubber lines after lift pump to filter and same at tank . get fuel cap drill hole in it big enough to put air fitting in feed it 8psi you will find leak and if the pump came from a place like advance or auto zone get it replaced pump my be defective had it already


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