6.2L pours out white smoke

[iautomate]

I have a 1991 GMC 6.2L non turbo 165,000 miles, that pours out white smoke. It smokes alot when the engine is cold (somewhat normal, but its excessive), and it doesn't seem to dissapear until highway speeds. It also has little power, and poor fuel economy (about 11 mpg, city) I bought the truck used a few years ago, and its done it since I've owned it. It looks like the Injectoin pump is lined up with the timing marks.

I'm looking for suggestoins of where to start? Should I start with plugs, or injector pump, or could it be something else?

[tom yuenkel]

with that milage your timing chain is very stretched allowing the motor to be retarded, and severeretarding produces white smoke. Begin by checking the timing marks and assuming you find the timing marks on the pump case and timing cover are still lined up You could advance the pump to compensate for the chain wear. rotating the pump to the driver's side ( when standing in front of the truck) 1/16 to 1/8 should make a noticable change.

[snoman87]

I second the check timing ... mine produced large volumes of white exhaust and I found the engine was retarted.

Before
http://www3.telus.net/gmc62td/Images/timming_before.JPG

After
http://www3.telus.net/gmc62td/Images/timing_after.JPG

[iautomate]

Thanks Guys,

I've rotated the fuel pump and it is much better, but still have some white smoke even when the engine is warm. Is it possible that the timing chain is streched so much that I cant compensate for it? At this point should I change the timing chain, or could something else still be wrong.

[john8662]

Could be the injection pump itself, could also be compression.

Thanks snoman for the pics above!

A good compression test would be the best thing to check to know before repairing injection related components.

How much blow-by does the engine have? Way to check = open oil filler cap with engine running hot, how much smoke comes out, a little, no problem, but a stead thick stream (where you can't see down the tube) is real blow-by, the other symptom is usually smoke from the dipstick while running as well.

J

[Subzilla]

I would still rotate it more until you get a louder "rattle" then back off a notch. Some have said can that you activate the pump advance solenoid to hear the rattle at warm idle. Keep advancing the pump until this is heard, then you're good. It took me quite a few adjustments to dial it in. My mileage was also suffering to 15 to 16 with white smoke. Once I found the spot, it jumped back up to 18ish with not as much smoke.