93 mechanical 6.5L stalling issues

[Dennydiesel]

So I have a 93 Chevy 2500 with the mechanical injection pump 6.5L turbo diesel
I have checked with a clear hose on the return line for air intrusion, I found none. I replaced the coolant sensor, oil pressure switch, fixed all coolant leaks and yet it still stalls. When it does stall (usually in the middle of traffic) it sounds like its starving for fuel. I can pop the hood and crack the filter manger bleeder and I either hear air sucking in or escaping. Then open the fuel drain and crank it until fuel pours out, shut it and pump the heck out of the accelerator pedal while cranking and it will sometimes start. When cold it always runs perfect, once it reaches operating temp it's anybody's guess when its going to stall. Usually about 30 minutes of running from cold. Now my starter is burnt up, it was smoking hot and the truck has no electrical power, so I'm thinking fusible link on that.
Any help would be appreciated. I'm a gas engine mechanic, so I know my way around a vehicle. But this diesel is about to meet the scrap yard! It runs awesome cold. I'm stumped. Thank you.

[CedarGrove]

Relevant thread here. Post #11. http://www.thedieselpageforums.com/tdpforum/showthread.php?t=41892&highlight=tank+sock&page=2

I would try to plumb in a line between the tank and the lift pump and run the truck off of a 5 gallon jug like that fellow did. If it runs great you can drop and inspect the tank. Been down that road.

[trbankii]

Prior to going that far, I'd check to make sure that the lift pump is running since that was one item you didn't mention.

[Dennydiesel]

That's the part I suspect of shutting off but, I flow tested through the drain on the front of the motor and I get fuel out of it. When cold and running the filter manager is full of fuel, when it warms the manager has air. I think I will do what both of the replies said to do. It can't hurt. Also one hint is I popped the hood this morning and both radiator hoses were sucked flat? I loosened the cap and they went to normal. Replaced the radiator cap since.

[CedarGrove]

I might also just leave the fuel cap loose. It may be developing a vacuum.

[Dennydiesel]

I tried that already. With no luck. I drilled a small hole in the fuel cap.

[Dennydiesel]

One question on the lift pump. When I just turn the key to the on position should the lift pump be running? Mine is not. I get fuel out of the line during cranking only. I assume the lift pump is grounded as soon as it sees oil pressure. Am I right so far? I do have power and ground at the connector when the key is turned on.

[trbankii]

The LP won't run with the key just to the "on" position. Honestly, I'm not sure if it runs at the "start" position? I can't hear it over the engine noise and don't have anyone else to start it while I see when it comes on. But it definitely runs at the "on" position with oil pressure.

[Dennydiesel]

Thanks. That's what I thought.

[Dennydiesel]

So I finally got around to dropping the tank, I found all kinds of debris in the tank (rust scale). The sock looked clean, don't know if its the right sock or not? Ive heard stories of other people buying a new sock at the auto parts store for their specific vehicle, and it collapses which slows fuel flow. Has anyone else heard that? And how can you tell?
Also I pulled vacuum on the pressure line before the lift pump and after. The gauge held steady @ 15psi.
I guess it's time to pull the top of the injection pump off and see if that scale made its way up there. How would it get past the filter manager though? It should stop most if not all of it I would think. I'm starting to think that the fuel system is plugged.
Any other ideas to check? Besides running the engine off a fuel can. I will do that tomorrow after work.

[CedarGrove]

I think I would just deal with the crap in the tank and see if that doesn't do the trick. I had a similar issue and replaced the tank and sending unit. I noticed when I installed the new tank that it had a thin film of coating on the inside. A few months down the road I noticed my fuel filter was clogged with a gray paste. I dropped the tank and noticed globs of white gooey stuff floating around. I believe the diesel was breaking down the coating. Anyway, I returned the tank and they gave me a different brand that was not coated. I ripped the tank sock off and threw it away. No problems since. Putting some sort of course filter between the tank and the lift pump is on my list.

I believe the rust is plugging the sock after you run it for 30 minutes or so. Once you shut it down for a bit, the rust settles off of the sock and you can reprime and go again. Just my opinion. I wouldn't worry about disecting the pump until after the fuel tank situation is handled. That may be your only problem. At any rate, that has to be handled.

[Dennydiesel]

So I put a new tank in and replaced all fuel lines and clamps. Yet I'm still getting air in the fuel system. I put a clear hose from the injection pump to the return system and an visually see air bubbles once in awhile at idle? Also a lot of air bubbles when I rev the engine up? I don't believe this should be normal. Any help would be helpful.

[sctrailrider]

You should not have bubbles, recheck all lines back to the tank, then give it some time to clear the air out..

[Dennydiesel]

Ok I will recheck the lines. I only ran it for 10 minutes. Probably not long enough to bleed all the air out of the system. I want to drive it down the road, but last time it would die every 500ft or so, took an act of congress for me to get it back to my shop. Needless to say I thought of adjusting it with my 10lb sledge hammer. I'll post my findings when done. Thanks

[Inspector]

You have one of the best resources on these engines as a neighbor. Robin lives right there in Newburg. I'm surprised that she hasn't piped in on this.
Denny

[Dennydiesel]

I rechecked all lines and no external leaks. I ran the engine for two hours and it ran great even though it still shows air bubbles in the clear hose. Not at idle anymore only under acceleration. I'm thinking the return hoses on the injectors leaking still? I see wetness on the ends at the injectors. It does blow a tad of greyish smoke off idle. Must be due to air entry.
Yeah some local help would be great. I'm great with gas engines and am new to diesels, although I know my way around one.

[rustyk]

I had a similar issue with my Ford 6.9L - the return lines can cause many odd issues...they're relatively easy to replace, so I suggest doing it.

[CedarGrove]

http://www.thedieselpageforums.com/tdpforum/showthread.php?t=23040

May help find the air. I would put a bit of pressure on the system and look for wet lines between the tank and the lift pump.

[Dennydiesel]

In conclusion to this mess I wired my lift pump to a separate relay and my ignition switch. It seems to work well. Somehow my lift pump was not running when it should. Runs everytime the key is on now. Been driving the truck all week and hasn't stalled once. I still have some air on return side but minimal. I left all wiring intact except disconnecting the lift pump to wire in my relay.

Thank you all for your help and I'll repost on this in a little while. It has to convince me for awhile because it stalled so many times.

[twaddle]

I had a problem similer to your troubles a while back with my 96 Suburban. Any time I checked the voltage to the lift pump it would always show 12 + volts. Then I wondered if it was reading ok in volts but perhaps not getting enough amps/watts. I did the same as you and wired it up from another source with an inline fuse from the battery and it ran ok.

I also had a 84 ex army K30 (M1008) that would intermittantly run rough then run ok. It turned out to be a suction hose from the tank to lift pump line that had rubbed through on the chassis and sometimes let air into the suction hose then close up enough not to let much air leak into the line and would run OK. That one took a bit of finding as the hose looked ok as the damaged area was in against the chassis.

Good luck, I hope you have found the problem.

Jim

[Dennydiesel]

Well the truck is still running well after 400 plus miles. Still has a slight surging problem under load. Might be a weak lift pump? Still getting some air in the fuel system? Planning on replacing the fuel suction line from the tank to the lift pump. Saw a damaged o ring land where the line threads into the lift pump.

[Dennydiesel]

Had to finally replace the tank and sending unit with new ones. Rust got me again. Plugged the sock. Runs good after, but I have a miss at idle. Planning on putting new injectors in it, luckily their mechanical. Cheaper is good. My turbo also has an excessive amount of side play. It touches the housing, won't last too much longer. What are some better turbo's and injectors too get more power? Any help would be appreciated.