Could This Happen? I really need help

[ryno]

For the past few months I have had nothing but problems solving the stalling issue with my 1995 2500 4x4 6.5 TD. The truck has 240K km's, a BD Power Chip and 3" exhaust. First I replaced the PDM, then the injection pump with a new PDM, then the lift pump, then added a second auxiliary fuel pump, then another injection pump and PDM. I have also changed the fuel filter and flex fuel lines to the filter and pump. Still the truck will run for about 1/2 an hour with only an occasional miss fire, then at about 2500 rpm it will begin to stall as if it is running out of fuel. Slowly the problem will creep lower in rpm's until the truck will hardly run. The check engine light will come on, it will go into a limp mode and run fine, but with VERY little power. I have checked the fuel system and it has fuel and fuel presure. I do not know what else to change.

Someone mentioned to me that it may be the injectors! As they are probably original I was told that some or all may have failed allowing air to be compressed back up the fuel lines and into the injection pump. Eventually this air over exceeds the fuel and the injection pump injects air into the cylinder and therefore the progressively the truck runs worse over time. Or as the injector begin to heat and expand they begin to fail and not open and close properly.

My question is to those of you who about diesel injection. Dose this make seems? Could this be my problem. Any other suggestions. Thanks!

[JohnC]

Long shot, but could you be developing a vacuum in the tank?

[Phil Holmen]

Have you checked the error codes... If not here is what you need to know...
http://www.thedieselpage.com/members/trblcode.htm
Please post results...

[gmctd]

First, as JohnC is suggesting, remove the fuel cap and try a test run.
Also, check the "sock" in the fuel tank(s) - a polycarbonate pre-filter on the fuel pick-up tube.
It keeps the big 'grunge' from passing thru the lift pump to the filter.

[curmudge1]

IIRC, someone, maybe Mr. Kennedy, posted or emailed (either me or the old diesel email list) that injectors' useful life is 75k-100k miles... longer than that, the injectors wear & don't have good spray patters ('****ers' & 'dribblers'). I have no interest in you spending money replacing good parts, but this is what I recall... I think I waited until 125k/135k miles to replace mine (I'm cheap). No noticeable improvement to report, but *some* peace of mind. Hmm, now at ~224k miles, I'll have to look at my maintenance log & see if it's time again.

Perhaps someone more expert can comment?

[catmandoo]

well heres my problem.i have slowly over the last 2 1/2 months been fighting my 92 n?a 6.5 started off ,as i drive down the freeway and come to my offramp i'd put it in neurtal and coast to the stop sign.and when i took off just before i could grab second it would surge and throw me back in the seat well this has slowly been getting worse and somedays it will do it just driving around town from stopsign to stopsign.if i let it set and idle for any amount of time it will surge when i take off and today i had it idling for about 10 minutes and when i took off it was about 200 ft to the stopsign let out clutch just about to grab 2nd it surges and i have good speed to make the stopsign so let off and it dies.at stopsign crank for 3 to4 seconds and nothing then do it again and acted like flooded gasser.now since i put the turbo on about 2 weeks ago it has been getting worse and the diesel shop that does pumps and inj's here says the same thing that with high miles (mine has 120,000 on inj's and pump)inj's can get weak and allow combustion pressure back thru the inj's which somewhat makes sense as the longer it sets idling the worse it seems to surge.think i'm gonna have to break down for a new set of injectors and see what happens.

[tom.mcinerney]

Ryno, you say, "I have checked the fuel system and it has fuel and fuel presure. I do not know what else to change." I'd put a fuel pressure gage on hose to a tee between filter and FI pump to monitor while miss/limp/failure occurs. Sounds like either 1.)heat-FSD , or 2.)fuel starvation. The gage would enable distinction.
Has the failure occurred when tank more than 1/2 full? Did you follow proceedures to 1.)drain dirty fuel/water and 2.) bleed air from filter chamber?
I would wait on injectors until rectify current problem. Some members have reported a miss following installation of FI pump, traceable to a union nut that loosened. Generally if air in line it's hard to start, more likely to smoothen out as runs; but not an expert. If 'crack' loose the fittings at injectors while crank/run should bleed any air. You seem to be developing air in pump input as you run, which is why above suggestions more likely than hi press injection probs.

[ryno]

Thanks All,
I have removed the fuel filler cap and gone for a test run. No diffrence. I have blead air from the fuel filter and put the presure guage on while the stall happens, still good presure. If there was air in the system would it not work it self out the longer the truck ran? As mine runs fine for a half hour and then slowly gets worse. Let it sit over night and it runs fine again the next morning for another half an hour to an hour. Codes I have read and they mostly lead back to the pump timming, short pulse, ect. Although I do not have the codes handy now. I have had GM time the pump after both pump installs. I have replaced the injection pump, lift pump and the PDM twice in less than 500km. I have not dropped the tank and checked the tank filter. Someone eles mentioned even though I have enouph fuel presure, I might not have enouph fuel volume. A plugged filter in the tank could cause this. What do you all think?

[moondoggie]

Good Day!

The only way to know what your lift pump (or anything else, for that matter) is doing is to get VALID DATA. Why guess? It's quite easy to get data that is meaningful.

If I had your symptoms & suspected my lift pump, I'd tee into the fuel line right before the IP. I think this can be done at the output of the engine compartment fuel filter. This would connect to a temporary gauge in the cab. This gauge would be in my cab until I KNEW what the lift pump was doing. I would monitor this gauge CONTINUOUSLY while driving under normal conditions. Then I don

[gmctd]

Pulse response too short means the IP is not getting enough fuel. PCM is changing advance trying to compensate
The in-tank sock, if clogged, can cause inadequate fuel supply symptoms, as can an air leak pre lift pump. Leak after lift pump would dump fuel - you would see and smell it.
Collapsed tank-to-lift pump inlet tubing gives same results. Check hoses at float\sender unit on tank.
Failing dual-tank valve can cause same problem.

Disconnect the lift pump inlet hose, put it in a see-thru container, put 3-4psi shop air on the tank filler neck, you should get a good stream of fuel. It will continue to flow after removing air pressure due to siphon effect.

[ 11-13-2003, 05:47 PM: Message edited by: gmctd ]

[patrick m.]

have you checked the exhaust for restrictions?

[ryno]

I installed a pressure gauge and went for a drive today. As usual the truck ran fine. But there was some weird pressure readings. First I have replaced the lift pump just a week or so ago. I have also added another large pump in the engine bay. With both pumps running I get tons of fuel pressure 11-12 psi. But with only the stock lift pump running I only get about 4 psi. I understand this is normal, but once I began driving the pressure dropped, real fast. In fact under really heavy load I was getting very large vacuum pressure readings. As much as 10 psi. Lay of the throttle and the pressure slowly raised back to about 4 psi. So I dropped the tank and the sock filter in the tank seems reasonably clean. I can put a flash light to it and see light through, and there in so debri that can be wiped off. Could this mean collapsed fuel lines? When both pumps are running pressure stays high, but maybe with a collapsed line it could be putting enough suction on the system to draw air?? Thoughts?

I have an engine brake on the truck with an exaust pressure gauge. With the brake off there is no back presure and with the brake on the truck still runs fine. I don't think there are any exaust resrictions?

[gmctd]

That is restricted volume symptom.
Appears as though some blockage exists in the tank-to-lift pump line.
Remove line from lift pump, remove rubber connecting hose at fuel tank, blow shop air thru the line from the fuel pump end.

Be careful with the shop air - anything in the line will be a high-speed projectile exiting the line under high pressure.

Also check thru the rubber hose and thru the fuel pick-up line.
You did not mention dual tanks, but the electric tank-switching valve can also cause those symptoms.

Also check for a crimped or kinked area of fuel line, while you're under there.

[ryno]

It would seem that I may finally solved the problem. Two injection pumps, pdm's, lift pumps and hours of trouble shooting, it would seem that I had a plugged fuel line. I dropped the tank Friday, cleaned it and the filter in the tank. Saturday I removed all fuel lines including he filter canister and forced 110psi through all. Put everything back together and I now run 7 psi with just the lift pump and no fluctuations while driving. Oh I also replaced all the small o rings on all line coupler fittings. It's been three days and no problems, figures crossed!

[BuffaloGuy]

Ain't the DP great? Worth the price of admission!