I have a 1995 gmc sierra 1500 6.5 td, it has 480000kms on it. It has recently started smoking black when i stomp on it, is this a good thing or not? thanks!

 

Black smoke is not a good thing with these trucks-it causes high exhaust heat,but can be a sign of turbo problems or just a slow spooling turbo.

Make sure the boost system is working properly,vac pump pulling 24"+?
boost solenoid working?
18"+ vacuum at wastegate actuator?
wastegate actuator diaphragm in working order?
Soot trap(cat converter) plugged?
exhaust crossover sealed and good shape?They are a double walled pipe from the factory that can collapse internally and show no outward signs-remove it and drop a golf ball through,if it comes out the other end its good if not junk.
air filter clean?

 

funny you should post this, I am having a similar issue with my 95 3500hd, when you lay into it it smokes like my dodges do with a load, I do not understand how the wastegate actuator works on these trucks somebody said it is ran off vaccum but that makes no sense

 

My 97 did this when the vacuum pump died. Like other poster said it is turbo system related. Those vacuum lines are prone to cracking also and crumbled when I removed it.

 

The vac pump creates vacuum up to the wastegate solenoid,when the solenoid is active it lets vacuum go to the wastegate actuator to hold the wastegate closed and create boost.

When the ECM senses too much boost or decides less boost is required it closes the solenoid stopping vacuum and the wastegate opens limiting boost-this all happens very fast and adjusts many times a second-duty cycle.

 

Start simple and inspect air filter first

 

everything seems to be ok. Plus i like that it smokes now, except for its just burning fuel haha. thanks everyone for the replys!

 

I had the same problem on my 98. i bought the truck with a non fuctioning or slightly functioning vac pump, it wasnt until i did some research that i realized i had an issue. installed new vac pump and new lines and haven't had an issue with it since. pretty easy fix and not too long of an install. def. difference in the power that it produces and the turbo can be heard spooling. no more black smoke =)

 

well found out that my injector at the back on the pass side might be leaking fuel so i think the injectors are going, they have 483000 kms on them and when they go bad it is suppost to smoke black so that might be the problem.

 

Bad injectors can take out pistons o get them changed ASAP-best to do the whole set,not just a few or only 1.