Been a while since I've posted, but before I give up my 6.5L for a new vehicle, I'm hoping I can keep it running with input from here. Yes, I've searched and read various threads here on stalling. But I need some help, and any suggestions are greatly appreciated. Here are the symptoms:
* Truck starts right up when cold. Runs for about 30 secs and then stalls.
* If you crank the engine over and over, keep the revs up at about 2500 RPM, the truck will blow smoke until finally the engine "catches" and you can let it back down to idle.
* Fuel economy is down and noticeable power loss (though can still pull a 3 horse trailer)
* When cold and you open the fuel filter bleed valve, no fuel spurts out so not under any pressure
* If you prime the fuel first without starting the truck, it will start right up and not stall
Here's the truck:
* 200k miles
* '95 6.5L GM diesel (obviously)
* Never been rebuilt
* Original injectors (I think, but GM replaced )
What we've tried so far:
* New fuel injector pump (w/PMD)
* New fuel filter (not in the tank, just the replaceable up front - my wife keeps having people change it over and over thinking it's so simple . . . )
* Tested lift pump - it works and electricity seems to run to it ONLY when the engine is cranking (not when "ON"). When lift pump is running and you open the fuel filter bleed valve fuel pours out.
* Glow plugs check out (I know, it starts immediately so the glow plugs probably didn't need to be checked but we did anyway)
First, a local GM dealer says that there should always be 3 pounds pressure in the fuel lines. Obviously that is not the case when you can open the bleed valve and no fuel comes out. I've read that the Oil Pressure Switch can make the lift pump LOOK like it's not working, but it runs when cranking (think I read somewhere that the '95 model only runs when cranking, not when you turn the key to on).
Second, I've run a direct line from the ON power to the lift pump and if you let the air escape from the filter the truck will start right up (always does) and remain running without stalling. But should the lift pump always be running? Should I just wire it? I think I read somewhere that it SHOULD always run to help the fuel injector pump, but seems GM didn't design it that way.
Our thought is the problem is air leakage. There are not any large quantities of fuel leaking out of the engine or hoses. We will be replacing some fuel lines that show some signs of age (some were replaced with the fuel injection pump replacement). But I'm not sure that will fix it. One non-GM diesel mechanic is suggesting that perhaps the injectors are bad, leading air, and the potential source of the problem. Looks like we can pick up a full set of injectors for about $200, so might be worth it.
Someone else suggested the O-ring at the bottom of the fuel filter housing might be bad, but the GM dealer doesn't think that's right as fuel leaks would be obvious. Diesel mechanic disagrees, saying that you can have air leaks small enough that don't allow fuel leaks.
In any event, any words of wisdom from this crowd?
Thanks in advance.
* Truck starts right up when cold. Runs for about 30 secs and then stalls.
* If you crank the engine over and over, keep the revs up at about 2500 RPM, the truck will blow smoke until finally the engine "catches" and you can let it back down to idle.
* Fuel economy is down and noticeable power loss (though can still pull a 3 horse trailer)
* When cold and you open the fuel filter bleed valve, no fuel spurts out so not under any pressure
* If you prime the fuel first without starting the truck, it will start right up and not stall
Here's the truck:
* 200k miles
* '95 6.5L GM diesel (obviously)
* Never been rebuilt
* Original injectors (I think, but GM replaced )
What we've tried so far:
* New fuel injector pump (w/PMD)
* New fuel filter (not in the tank, just the replaceable up front - my wife keeps having people change it over and over thinking it's so simple . . . )
* Tested lift pump - it works and electricity seems to run to it ONLY when the engine is cranking (not when "ON"). When lift pump is running and you open the fuel filter bleed valve fuel pours out.
* Glow plugs check out (I know, it starts immediately so the glow plugs probably didn't need to be checked but we did anyway)
First, a local GM dealer says that there should always be 3 pounds pressure in the fuel lines. Obviously that is not the case when you can open the bleed valve and no fuel comes out. I've read that the Oil Pressure Switch can make the lift pump LOOK like it's not working, but it runs when cranking (think I read somewhere that the '95 model only runs when cranking, not when you turn the key to on).
Second, I've run a direct line from the ON power to the lift pump and if you let the air escape from the filter the truck will start right up (always does) and remain running without stalling. But should the lift pump always be running? Should I just wire it? I think I read somewhere that it SHOULD always run to help the fuel injector pump, but seems GM didn't design it that way.
Our thought is the problem is air leakage. There are not any large quantities of fuel leaking out of the engine or hoses. We will be replacing some fuel lines that show some signs of age (some were replaced with the fuel injection pump replacement). But I'm not sure that will fix it. One non-GM diesel mechanic is suggesting that perhaps the injectors are bad, leading air, and the potential source of the problem. Looks like we can pick up a full set of injectors for about $200, so might be worth it.
Someone else suggested the O-ring at the bottom of the fuel filter housing might be bad, but the GM dealer doesn't think that's right as fuel leaks would be obvious. Diesel mechanic disagrees, saying that you can have air leaks small enough that don't allow fuel leaks.
In any event, any words of wisdom from this crowd?
Thanks in advance.
Hopefully you didnt replace the IP just for this problem! Never go to the stealer (dealer) and dont trust a shop that says they have a diesel expert, because they probably just have DMax training.