Questions about 6.2 GM diesel in C20 van

Had to replace mechanical fuel pump lower right cornor of engine. Van started than lost prime. Where are the injection pump bleeders and how do I get to them? Also where do I find engine oil pressure sending unit and is there any other oil pressure port to hook a test gauage? Any fuel filters I should replace before I bleed injector pump. Thank you for any help you can provide. Armand

You bleed at the filter housing. You have to do it by cranking the engine since the fuel pump has no hand-primer. Keep in mind that those rigs often get pin-holes in the fuel line between the fuel pump and the tank. When that happens, they draw air and the filter will never bleed out. And, since it's the suction side, when the line gets holes, it's doesn't leak fuel to warn you. I've got five 6.2 diesel trucks up in my field, and all have that problem. I.e., road-salt and New York rust. To run them, I stick an outboard-motor boat tank on the floor, and run a rubber hose to the fuel filter housing. They are parts vehicles and thus the reason why I don't fix them properly.

My '86 Chevy M-1008 Army truck lost prime also..I chased down all the fuel lines, changed that mechanical fuel pump.. Found that the fuel filter housing had a SLIGHT leak ..Not noticable from the front at all... Out of despairation I installed a spin on filter and housing.... The starting problem is no more..It doesn't have the heater , water sensor anymore , but who cares ??The total fix costed $55.00 for the filter housing , filter , 2- 3/8 street elbows ,[ a 3/8 npt to 3/8 barb fitting and a 3/8npt to 1/4 barb fitting] All from NAPA..

I had one that got a pin hole in the intake line IN the fuel tank. Took me a while to find that one! Had a RACOR filtre and bowl would slowly fill with air until engine would stall.

Yes, I've got a 1991 V10 diesel Suburban with that very problem. Drove me nuts for awhile. It was a surplus school vehicle and had been parked for two years in their lot. Ran fine when it was parked. I paid $250 for it. Put two batteries in it, cranked it over, and it fired right up. Then ran a minute, petered out, and died. I tried to bleed the filter and saw air. So . . . I figured it was a bad rear line. Got 20 feet of rubber fuel line and ran it all the way back to the pipe coming out of the top of the tank. It STILL had air and would not bleed out.

Long story short, it was the line in the tank, just as you mentioned. I got it running and on my trailer via my trusty 5 gallon outboard motor tank hooked to the filter assembly.

Something doesn't sound right. Your filter is on the pressure side of the fuel pump, not the suction side. If it had a leak, you ought to see some fuel dripping. Also, if the fuel drained back because of a small leak there, the fuel from the filter would still be air-free. Just the injection pump would get a bit air-bound. That usually results in starting problems after being shut-down for a day. Engine starts hard, but does start and runs fine once it runs a bit.

There were several Chevy and US military service bulletins about the problem. Ford-IH 6.9s had similar issues caused by a Schrader valve leaking air.

The fix was to install an updated fuel pump, along with an updated regulator/check valve on top of the injection pump. Both had enhanced check-valves to prevent overnight fuel drain-back.

Here's a copy of the bulletin:

Chevrolet bulletin # 89-329-6
Subject: 6.2L Diesel Hard starting cold
Issue date: 9-20-91

All trucks with 6.2 diesel 1982-1989 except 88/89 CK trucks with electric fuel pumps.

Even if the glow system is working properly, some 1982-89 General Motors trucks
equipped with 6.2L diesel engines may still experience cold, hard starts. GM says air leaks
in either the suction or return side of the fuel system are the source of the problem. After
the engine is shut down, air leaks can result in loss of injector pump fuel prime.

If the air leaks are on the suction side of the fuel system, GM recommends installing a new
mechanical fuel pump GM P/N 25116503 and AC Delco P/N 43254. The new pump features a new ventless check valve to prevent drainback.

If the air leaks are on the return side, a new HPCA (Housing Pressure Cold Advance)
regulator valve (P/N 10149645) must be installed. This new valve and seal configuration
superceded the old ball check regulator valve....