1995 gmc 6.5 td

[72chevk5]

the truck smokes black out of the tail pipe real bad on full throdle, and has a hard time starting in the morning. just got the truck and am new to deisels so any ideas are nice thanx

[a5150nut]

the truck smokes black out of the tail pipe real bad on full throdle, and has a hard time starting in the morning. just got the truck and am new to deisels so any ideas are nice thanx

Welcome. Now we will need a little more info to be able to help you. It's a 95, how many miles on it? Have you doen anything to it?

First off, how is the air filter?

Is the fuel boost pump working? Its under your feet inside the frame. You should hear it running when the key is first turned on and after oil presure is up.

Does the wastegate move freely with engine off?

Do you have a boost gage?


Thats a start. :D

[bbtlr3]

I'll have to go along with a5150nut it sounds like no boost at throttle, and possibly a bad lift pump or Oil Pressure Switch. My lift pump wasn't working and pulled the connector off the OPS and jumped it and the lift pump fired right up so mine was a bad OPS. $25 for an OPS and it was working like a champ again. If the pump does not turn on then check the relay for the pump. If they all check out then it's probably the pump.

On the turbo, if you don't have a boost guage, like 5150 said start it up and see if the wastegate actuator is solid. If it is solid then turn it off and see if it is still solid, if it is then you could have a frozen/stuck wastegate. If it moves freely while running then its probably not getting vaccuum. Pull the vaccuum line at the actuator and check for vaccuum it should be around 15". If no vaccuum there work back to the solenoid that is on top of the drivers side valve cover toward the rear checking the hose for leaks. If hose is good check vaccuum into solenoid it should be around 20". If no vaccuum there you probably have an issue with your vaccuum pump. Could be as simple as a belt issue or a bad pump. On these (no vaccuum= No Boost) And definitly check the air filter like 5150 said.

It's possible that I missed something in there but I think we've got you going in the right direction.

Let us know how it goes.

[72chevk5]

you were both right, waste gate was stuck open, the lift pump is new, but the truck still stumbles on acceleration sometimes. the truck is bone stock.

[Robyn]

Get the wastegate freed up and then check the vacuum at the wastegate pod. You want 26" of steady vacuum.
If the vacuum is lower than about 24" and or wiggling the gauge, replace the vacuum pump.

If this makes things better your set.

The stumble issue??? when cold or all the time???

Be sure the lift pump is working and producing pressure when the engine is running.
Do this by loosening the bleed valve on the fuel filter with the engine running, if fuel squirts out(should) your ok. If the engine craps out or runs crummy when you do this the electric pump is toast.

Also be sure the fuel filter is in good order and you dont have a bunch of crud in the lower part of the fuel filter bowl.

Check these things and let us know more

Robyn