6.2L Diesel ... smoke, loss of power

**kbarrett** · 10-14-2007, 06:09 AM

I am getting clouds of smoke following me on the freeway.

Not a lot of power, I need to stand on the accellerator to get it up to freeways speed.

Not a lot of smoke once it gets going, but a lot when I hit the accellerator.

Smoke is kinda dark brown, not black. Thin, but very noticable. Is there anything I should be looking at before I attack the heads/gaskets/piston rings ?

**TrailLeadr** · 10-14-2007, 08:58 AM

I'm no expert on diesel, but I'm sure our resident experts would appreciate a little more info. Like year, and mileage of your 6.2.

There may be some TSB's out there that they can help you with, but without knowing where to look.......well you get the idea.

**TomsHHR** · 10-14-2007, 09:14 AM

Past experence has been to check air filter first, and I am just a old marine diesel mechanic.

**kbarrett** · 10-14-2007, 06:15 PM

It is an '82 K10 Suburban ... I am not the first owner, so I have no clue how long ago the last rebuild was.

The air filter looks OK, although there are some soot stains inside the filter.

I ordered a diesel grade compression tester, and a glowplug hole adapter for it.

Could this be an injector pump or fuel filter issue? How would I tell?

**tbplus10** · 10-15-2007, 01:18 PM

Could be an injector pump issue. Probably not a fuel filter issue.
Older G.M. injector pumps had issues at times. The pumps were adjustable, and they often got misadjusted. Turning them up was a trick used to get more fuel pressure, but if you turned them up to far you got results similar to what your describing.
Do you have an EGT gauge? If so whats it reading when you stand on the accelerator?
Some soot in the air filter is normal. Large amounts indicate a problem (unless the filter hasent been changed in a long time).
Read the compression first, then read the EGT.
Have you checked the oil level lately? Is it burning more?
Does it have a good idle?

**kbarrett** · 10-15-2007, 01:22 PM

Idle is fine, and it is not burning oil.

I don't have an EGT.

How would you adjust the injector pump?

**tbplus10** · 10-16-2007, 01:16 AM

Mine had an adjustment set screw with a jam nut on the side of the pump. Turn it in increased fuel delivery, out decreased. It was a light duty style injector pump.

There were a few different types of pumps used on early 80's model trucks. One style was for light duty Diesels 1500 to 3500, the other style was for medium duty Diesel trucks 3500 to 6500.

There was also a non-adjustable pump used on all GM trucks. All the injector pumps were interchangeable, and even though they were designated for certain tonnage trucks any pump could be found on any Diesel truck.

I wouldnt recommend adjusting the injector pump without an EGT gauge, temps above 700deg can start destroying engine components and its easy to get those kind of temps with just a small adjustment of the injector pump. You have to watch the AFR real close to keep temps down.
To much fuel gives terrible performance, lots of greasy brown smoke, and high EGT's.
To little fuel can starve the engine and cause high EGT's.

**kbarrett** · 10-27-2007, 07:29 PM

I bought replacement glow plugs, pulled the old glow plugs and did a compression check ... 375-400 psi, all eight cylinders.

OK then ... I won the compression test lottery ... so what's wrong here?

Two things left .... pollution control crap failure, or a wonky injector pump.

Well ... the first was easy enough to test. I yanked out the vacuum lines to the EGR valve ( inside the aircleaner ), and to the EPR valve ( on the driver's side exaust manifold ) at the vacuum solenoids.

And everything just worked.

Full power, no black smoke.

All that crap ... fixable by yanking out two vacuum hoses.

**Dimsdale** · 01-07-2010, 08:48 PM

Just a thought...

Soot in the air cleaner makes me think of the EGR, which sticks up into the intake manifold area under the air cleaner. The '80 version may not have had one, but I had an EGR valve in my '87 GMC 6.2, and if it goes bad and stays open, you will get too much exhaust mixed in with the intake air. Many folks either disconnected the vacuum hose (default is closed), or removed it and make a plate to bolt over the hole. EGR did much for emissions, but nothing for performance, and added a lot of noise under the hood when open.

Similarly, you could check to see if the injector pump had slipped off its timing mark (on the flange where the pump mounts to the engine. Driver's side if I recall correctly. A really sloppy or jumped timing chain could also produce bad things, but that might be more extreme than what you are seeing.