1982 Chevy 6.2 Diesel problems!

[dchough]

Hey Guys,

Some of you have heard this story before,but the problem still isn't fixed.

I bought a 1982 Chevy 6.2 C10 and drove it home from New Jersey. After about 4 hours of running on the highway, I came to a tollbooth. As I proceeded to pull away from the booth, the truck was about to shift into second (revs really high, because the TV Cable needs to be adjusted) and then all of a sudden the truck shut off, and wouldn't start (truck cranks perfect, but won't start).

I got it towed to a shop, and the mechanic ran a fuel pressure test and they said there was no pressure at the rail. He replaced the fuel filter, still wouldn't start. He then cleaned up the mechanical pump and finally got it started and idling. However, when he went to drive it, it stalled out again.

He has since primed the system and got the truck to start and idle for another 4 times, however, every single time he goes for a test drive, as the truck gets into high RPM (remember the 700r4 tranny shifts VERY late, 1-2 shift at about 25-30 MPH) the truck stalls out.

He has given up and believes its an electrical issue.

He says mechanically he believes everything is working. He checked out the fuel filter, mechanical pump, IP and LP, and even the pink wire to the fuel shutoff solenoid on the IP. Although he is is hesitant to completely write off the lift pump and injector pump as the problem.

Anyone have any ideas? Does this sound like an electrical problem? Will solving the late shifting fix this problem? Could the shutoff solenoid on the IP not be receiving a constant 12v as the truck goes to shift? Bad grounds? Bad lift pump or injector pump?

Any help would be much appreciated. This one really has me stumped.

[lindstromjd]

You're over on DieselPlace, aren't you? I remember this story.

I'm going to have to say it's your lift pump. It's the only thing that makes any sense with your issues. It's got enough to prime the system and get it idleing, but as soon as you're asking for more fuel (i.e. driving it) then it can't keep up with the engine's demands for fuel. I don't know who in their right mind would "clean up" a lift pump when they only cost $30 to replace with a brand new one. I didn't like the sound of your mechanic anyway when he called your engine a converted gasser.

I don't see how you could possibly have an electrical problem.

Oh, and get your TV cable adjusted properly. You don't want to have that thing fry itself here in the near future. It's super simple, and will only take you about 5 minutes to do.

[78customdeluxe]

There could be a possibility that the elastic ring inside the pump too is comming apart and partly blocking the return valve on the pump. It might be letting enough flow though to let it run some, but when the engine speeds up it cant let enough flow that it puts too much pressure in the pump and shuts it off. what you can do to test that theory is to TEMPORARILY put an 1/8 inch pipe to 1/4 inch barb fitting in it to see if it runs better. If so you'll have to get the pump rebuilt. You might also check to make sure the lines are not pinched anywhere. When I first bought my 82 i was having a similar problem and the supply line was alright, but the return was getting pinched between the cab and crossmember, didnt find that till i went and dropped the tank to see what was in it there.

[dchough]

Hey lindstromjd,

Yeah I'm over on Dieselplace, haha still got the same problem. So listening to you and 78customdeluxe, you guys agree its the lift pump huh? The truck is still 100 miles north of me, so I think i am going to get it towed back home and work on it myself. I guess i'll replace the lift pump and check out the fuel lines.

And would a lift pump just die like that? All of a sudden, or would it go out gradually? The more I think about it, it seems like a bad lift pump would make sense. Injector pump can draw enough fuel to start and idle, but when the truck really needs the fuel, the injector pump alone isn't going to cut it. Is there a test i can have this mechanic perform to test if the lift pump is bad? Also, I which pump would you guys recommend? I've read online about some brand of pumps being better than others.

Thanks a lot guys. Hopefully this saves me some money and gets me back to work.

[lindstromjd]

If you're at all worried about parts quality, then dealership parts are best. It's a GM... you should be able to walk in and order one and have it in hand a few days later. I just got a new one from O'Reilly's because I didn't trust the one I had on my engine. It wasn't technically bad, but I just figured preventative maintenance is best. But, I did have it in hand the next day.

Lift pumps can do strange things when they die. Sometimes they'll work fine for 2-300 miles, and then they'll die, and then work again a little, and then die again. Or they could just fail completely and not pump a single drop. It depends on the type of failure it's having. I'm going to assume yours is either a) original equipment, or b) very old and not up to the task. Either way, replace it.

I wouldn't have that mechanic touch my engine if he told me half the things he's told you. But he did in fact say that there was no fuel pressure up on the rails, right? That means he figured it out on his own, but was too ignorant to understand how to fix the problem he uncovered. Bad fuel pressure = bad lift pump. Granted, it could be other things, but if it was running fine and then died, that's the most likely culprit.

I'd tow it back to your house (either with a friend's truck and trailer, or something else you can figure out) and replace your own lift pump. Bleed out the system, and see what happens.

[dchough]

Sounds great! I still have a few more AAA tows, so I'll get that arranged first thing tomorrow and I'll report back when I get the lift pump replaced.

Thanks again

[dchough]

I should add, that once the truck stalls, it will crank, but won't start. The system has to be primed to get it to start again. He said when we took off the filter, it was bone dry. This would leave me to believe its a lift pump problem or perhaps there is some blockage in the line?

It still puzzles me, because the mechanic says the pump look relatively new and he believes it is functioning. Perhaps air is getting into the line?

[hatzie]

Originally Posted by dchough

I should add, that once the truck stalls, it will crank, but won't start. The system has to be primed to get it to start again. He said when we took off the filter, it was bone dry. This would leave me to believe its a lift pump problem or perhaps there is some blockage in the line?

It still puzzles me, because the mechanic says the pump look relatively new and he believes it is functioning. Perhaps air is getting into the line?

I'd start with a lift pump. A sudden failure like you describe is what they do. They're cheap and easy to put in.
Check your oil before you drive it. If it's even slightly over-full or smells of fuel change the oil and filter along with the fuel pump. The mechanical fuel pumps have a nasty failure mode that allows them to pump fuel into the oil pan. I saw this years ago on my fathers' 350 G20 van and on one of our 6.2 diesel farm trucks.

If the fuel pump doesn't fix the problem you could be sucking air through a pinhole in rusted fuel lines.

[DetroitDan]

If I heard the words converted gasser I would push the truck out of his shop. Obviously he knows nothing about nothing. The Olds 350 was a converted gasser. 6.2 was designed specifically as a light-duty pickup diesel, period.
Definitely sounds to me like you have one of two possible problems, based on the dry filter. Your lift pump may have failed, but I'm leaning toward a plugged pickup. Most trucks had a what's called a sock on the pickup in the tank, they get plugged up with snot from either bad fuel, or just grossness from 20 years of age and buildup in the tank. Some fuels have more bio in it, plus bio stuff can grow in the tank over time, especially with moisture. Sometimes this stuff is clear and doesn't even show up on the sock. Quick check is to pull the line off the back of the LP, and blow it out into the tank, to see if you can detect a blockage. Don't blow a ton of pressure into the tank or you'll blow the sock right off. Which will then allow all the crap into the system.
LPs are cheap. I read somewhere that 93s had the best LP, so that's what I used on mine. I don't know that it would be interchangeable with your year. But change that first with a quality one, lots of the cheapy parts store ones only last a year. Even if it's not bad it won't hurt you to replace it. You should empty the tank, clean it out, clean or replace the pickup, and you're in business.

[jltait]

I would pull apart the fuel line under the hood, bypass the filter and all the lines and run it directly from a container of fuel. A gear lube bottle should work ok. Make sure the Pickup hose and return that you rig up in the bottle are completely submersed in the fuel, bleed the injection system, and I bet it will fire right up. These trucks have a tendancy of getting a blockage at the sock in the tank, and or air leaks in the pickup/return lines which will create problems. The OEM filter housing can develope leakes in the O rings too. And yes, even a return line air leak will allow the injection system to become air locked, experience talking here. Verify the lift pump is working correctly as well when you pull everything apart to bypass fuel system. I also beleive 6.2's will wear the fuel pump pushrod to the point where it will not actuate the pump, so definitely verify operation whil cranking the motor with the inlet/outlet into a container, or better yet pressure gauge it.
JLT

[rare86]

I agree with jltait, its sounds like its getting air in the system between the tank and the pump.

[ElGracho]

I've had a few "suction side" fuel problems with 6.2 diesels that took me a while to find but were simple fixes. They weren't exactly like what you are seeing, but sort of similar.

1. The fuel filter housing was leaking from the differential pressure sensor. I got a later model filter housing from the wrecking yard that didn't even have the d/p sensor. The sensor leak was such a common problem that Stanadyne/GM eliminated it in the later years.

2. Vibrations wore a tiny hole in my fuel line right under the engine mount. It leaked so slowly and my engine had enough general grime on it that it was very hard to track down. I cut the hard line and replaced it to solve the problem.

For both of these issues, I suspected the lift pump. It was never the problem. They both had symptoms of hard starting / air locked fuel system. The fuel line leak finally got bad enough it kinda acted like a clogged fuel filter.