I am at a loss

[jcrouse.com]

I thought I had solved my problem with a fuel filter change.

Then I changed another (less than 100 miles) and another, and another and. . . etc.

The truck often won't start in the mornings (not glow plug related - they are cycling) half the time (or better). I am living in Florida where the ambient temprature is often in the upper 60's to low 70's in the mornings when I leave.

It will eventually start after cranking on it forever. I have even resorted to using starting fluids. When it does finally start it runs a bit rough until I rev it to about 2000+ and hold it for a few seconds.

I then get the wonderful "limp mode" which is a joy to try and drive in traffic with - being it has basically no power and not enough tourque / HP to let the TC lock up at 55 so I end up running in 3rd gear.

Anyway - randomly it will start just fine. When it does start fine - it seems to be okay for the rest of the day. Then it starts the whole process all over again. It seems to start anew each day. Generally it is in the mornings when it starts this hard start crap and after a few starts through the day it may or may not clear itself up. It almost appears as though it is not getting enough fuel to start.

I have recently changed out the starter (two days ago) since cranking it so much finally burned up the OEM one, so I know that's not an issue ($250) and I just put two new batteries ($180) as the old ones were dying.

I want to dump this truck, but am unable to do so if it won't start - kind of hard to get any money out of a vehicle that won't start. I am just so frustrated with these constant fuel / IP / PMD related problems and I don't know how to fix it.

I recently had a new PMD installed by a very reputable local diesel shop - they remote mounted it ($465) and that fixed my random stall / no start problems.

When the truck is actually running correctly (rare as of late) it does seem to blow more black smoke that I previously remember seeing, which is indicative I know of unburnt fuel.

Can this be injectors? I have spent $500 in just the last two weeks on this truck and I really don't have a pile of cash to throw at random parts.

At this point, I just want to make this truck go away. I am so sorry I took another chance on another GM diesel. What a perfect example of bass ackwards GM engineering.

Any ideas that won't cost me another $500? Remember - I just changed a fuel filter yesterday and it didn't seem to make a difference, although after fighting with it half the day, it started just fine, and started just fine for the rest of the evening, only to start hard again this morning. I don't think it is a fuel filter at this point.

Thanks in advance for any ideas you can provide.

[BobND]

Is your fuel lift pump operating AND pumping?

[JohnC]

Your sig says "84 6.2" yet you talk of PMD's and such....

Check for DTC codes. Sounds like you've been shooting in the dark.

[HowieE]

What was the reason for changing fuel filters every 100 miles. If they are clogged in that short a time what are they clogged with?

First thing I would do is a fuel flow test. Open the pit cock and place the hose in a clear plastic bottle and have someone put the ignition switch in the run position. While the glow plug cycle is running you should see fuel coming out of the hose in a strong stream. If you do not have fuel do the test directly after the fuel pump and see if the pump itself is working.

If you have fuel flow did you vent the fuel filter completely when you changed it? You should have had fuel coming out of the top of the fuel filter at the vent before you attempted to start the truck after the filter change.

[jcrouse.com]

Sorry it's been so long - but I've been busy doing things like changing out the starter because I have wore the old one out cranking the truck. :confused:

Anyway - I had not previously updated my signature in answer to one of the questions. I have a 1995 Z-71 6.5 4l80e with 256k mi.

My lift pump works. I think I stated that, but I *know* it works, because I have literally pulled the fuel line in front of the line as the pump was on. Additionally I have opened the T-valve and got good flow.

Why had I changed the fuel filter so frequently? It seemed to work!:)

I *think* I have narrowed it down to a fuel issue. I have found if I get fuel at a "known good fuel" source, I seem to have troubles. It is a large truck stop and I know several other diesel truck owners who get fuel at the same stop with no problems.

Maybe my truck is just allergic. :)

I am going to research a bit more and I'll keep you posted.

Thanks for all the help.

--jcrouse

[john8662]

Any codes? If you've got an injection pump issue this will surely show up with some sort of code eventually. For PMD problems, you won't have codes, but you've been there done that recently.

I'd also recommend actually checking the glow plugs to verify they are functioning. The varying starting in the morning could simply be due to ambient temperature, etc. The easiest way to test plugs is going to be with a test light, you'll verify that the plug at least has continuity, and is not completly burned out (open circuit).

[HowieE]

Are you saying the truck runs for a short period of time after each fuel filter change and then shows problem in about 100 miles?
What do the filters look like when your remove them? Are you draining the fillter bowl by pulling a vacuum on the drain line before you remove the filter?