My 6.2L's smoking...time for injectors?

[arveetek]

My 6.2L TD is smoking more than it used to. It's the white/blue unburned diesel fuel smoke, the kind that you see at cold startup. It used to just puff a few small clouds of smoke for a few seconds, and then clear up when first started. Now, it puffs a huge, billowing cloud of smoke that is quite large and embarrasing.

That wouldn't bother me so much, except that it keeps on smoking even after the engine is warmed up completely. I just got back from towing a trailer about 20 miles, and even after working the engine really hard, it's still smoking at idle. Not a huge, billowing cloud, but just a continuous stream of acrid smoke that burns your eyes. It's enough smoke that I have to shut the engine off if people are standing around, because it starts to smoke us out.

It's not glow plugs, because it smokes when engine is fully warmed. I'm not losing oil or coolant, so it's definitely diesel fuel. I've got about 120,000 miles on the injectors and injection pump. I'm thinking they're just getting worn out.

I did turn the fuel metering adjustment up some more a while back. I'm about a 1/2 turn from stock. After the last adjustment, I had to adjust the idle speed back down because the engine was running too fast. Could this be the problem? Am I dumping too much fuel now, even at idle?

Probably just time for injectors, eh?

Any comments will be greatly appreciated.

Casey

[tom yuenkel]

You make no mention of the condition of your timing chain. I just pulled mine in the past few days and there was more than 1 inch play. As I learned here this means timing is off 4 to 6 degrees retarded which contributes to smoking. My engine has 220000 miles on it and all the parts were original. For me the smoking increased suddenly and the the engine began to stumble but only until it warmed up. I began by replacing my injectors and this had no effect what so ever. I had preveuosly replaced the mechanical lift pump and hose so i assumed it was time to rebuild the injector pump and chain set. I can't give you the results because im still in the process.

[G. Gearloose]

consider giving the timing a bump more advance, even if just for 'diagnostic' purposes to eliminmate that.

[Rob C]

Check your compression. Mine went from good (all over 400 psi) to bad (none over 380 psi) fairly quickly. I had the same symptoms, even when fully warmed up on a hot summer's day, I could actually see the white smoke floating past the hood (if the wind was blowing the right way) when I was stopped at lights.

Rob

[arveetek]

Timing chain has approx. 120,000 miles on it as well. The engine was overhauled then, with new rings and bearings. Bore was good on all cylinders. Original pistons, etc. I have no idea how many miles were on the engine before I got it (salvage yard special).

I did advance the timing quite a long time ago. Maybe it's time to bump it up again.

I've never checked the compression, but it starts good when cold and runs great, just smokes.

Thanks for the replies, ya'll, and keep 'em coming!

Casey

[TimK]

Definitly check your compression. If it's unburnt fuel your smelling, then there is some reason why your cylinder(s) are not getting up to temperature to burn the fuel. Do you still have seperate dual exhaust and are you noticing more white smoke out of one side then the other? Pull the oil filler cap off when idling. Does there appear to be excessive blow by such that your seeing puffs when the oil cap is removed? You may have a one or two cracked piston crowns. This is a common failure point for the 6.2L. When the combustion temps get too high, the timing gets too far advanced, the timing chain gets too worn or weeping injector creates a hot spot, the crowns can crack. Eventually the crack will get large enough to allow combustion gasses through the crown and therefore decrease combustion pressure and temperature.

Let us know what you find out.

TimK

[arveetek]

I'm running a 4" single exhaust, so I can't tell if one bank is worse than the other or not. Idling with oil cap removed reveals slight puffs of smoke...just enough to be seen. But that's on a cold engine. I'll try again later after it's warmed up. If I have time, I'm going to play around with the timing tonight.

Casey

[Vaughn MacKenzie]

My old Blazer has so much blowby it's a huge volcano out the hose, so much I had to disconnect the blowby system and run it straight out. But doesn't smoke much during normal driving (mostly gray/black on acceleration, no blue).

Why would compression suddenly take a dive on a 6.2?

I was fighting a blue smoke problem on my Dodge Cummins and tried 2 sets of injectors to get rid of it. It had a slight miss too. My buddies kept telling me the motor was tiring from high miles and the .010" over gasket I installed this summer lowered compression too much (to about 16:1). I did a test and replaced the injectors yet again. Wallah, smoke gone, miss gone. All cylinders were 520 lbs except #1 was 500.

Vaughn

[arveetek]

Okay, now that it's gotten colder (35 degrees in the day, teens at night), it's smoking even worse. About 19 degrees this morning, and on startup (not plugged in), it smoked so bad the truck almost disappeared in the fog! Quickly cleared up to just a much lesser stream of smoke, but now it's smoking so bad I can't let it idle in parking lots, because the smoke just drifts out and all over the other cars and people nearby. I don't want them to get annoyed or choked. Plus, I can sit at stop lights and see the smoke drifting by. When I open the door with the engine running, the acrid diesel fumes are overwhelming.

I just came in from playing with the timing. I can't advance it any more than it is right now. It's fully advanced, there's no more adjustment left in the injection pump slots. I can't get it to rotate any further to the driver's side than it already is, I'm out of adjustment. There's about a 1/4" between the factory timing lines on the pump and engine block, with the pump line closer to the driver's side.

I hooked a jumper wire up to the HPCA switch to advance the timing that way, and that does cut the smoke down, but doesn't elminate it. And the engine does run much smoother at idle with the HPCA engaged, has a slight stumble at idle when disconnected. So I'm thinking it's time to replace the timing chain.

Any other ideas? Anybody have a compression tester they'd like to loan/rent to me?

Thanks,

Casey

[arveetek]

I can buy a new timing chain kit for $89.00. A new dual idler timing gear kit is $324.00. Is the dual idler kit really worth the extra $235.00? That's a pretty good chunk of change for something that might be a marginal improvement.

Casey

[More Power]

The gears are a good choice for those who plan to keep the same engine/truck for a few more years. However, a chain can get you through another good while.

I once played with the injection timing on a well-worn 6.2 to get it to stop smoking. Like you, I could advance the timing all I wanted, but it still didn't rattle like what I expected it would with a big pump rotation. The problem turned out to be a worn out timing chain. Not only does a sloppy chain retard injection timing, it also retards cam timing.

MP

[arveetek]

Thanks, Jim.

I have never thought this truck has made enough of the usual "diesel rattle." I've had the timing checked at a diesel shop, and they said it was spot on. That was before I joined TDP, though, and I don't know what the actual timing is.

I just got back from another run, and with the engine fully warmed, flipping on the HPCA cuts the smoke in half, nearly making it invisible to see. I'm betting I have a pretty worn chain.

Casey

[john8662]

I vote for the timing chain being gone too. I once dealt with a 91 blazer with a 6.2 that smoked badly when cold, but would finally clear up when up to full operating temp. The engine had 190k miles on it, I think it jumped time.

I've just got the gears installed on my 86 6.2, I'll be starting the truck later this week, I'll report back on my findings, the chain had quite a lot of play for 145K miles.