1983 6.2L Black smoke at low rpm and load

[Truckman4life]

I have an '83 K5 with a 6.2L diesel. Odometer says 60,048 miles which I assume are correct as this was an old grandpas truck and it has been mostly sitting for the past 15ish yrs. I've owned it for 9 and have pretty much only ran it up to temp every month to keep it in running condition. I finally got it street legal and driveable. It blows pretty good black smoke. That is the reason the PO quit driving it. If I start it and let it idle sometimes after a bit it will start running rough and blowing whiteish black smoke and even popping smoke back into the intake. I can rev it up and it goes away or if I just start it up and drive it then it won't do it. I get pretty good black smoke when flooring it up to highway speed which I know is normal since its non-turbo. I do get a lot of black smoke when it upshifts into the next gear and I'm cruising at low rpm and low load, like just on the throttle a little bit. I'm thinking I may need new injectors and possibly a pump issue but thought I'd check if I'm missing something since I haven't worked on a lot of 6.2L diesels. What about injection pump timing being off? Thanks for any advice.

 

[GWeakland620]

As most diesel posts go, I am going to be of no help. But I do like to learn. So I sit and wait, and usually tag some "helpful" people...

@campfire @AgDieseler ....and so on.

 

[Truckman4life]

As most diesel posts go, I am going to be of no help. But I do like to learn. So I sit and wait, and usually tag some "helpful" people...

@campfire @AgDieseler ....and so on.

Thanks for the help on that end. Lets tag @diesel4me also, he seems to know them pretty well.

 

[campfire]

As most diesel posts go, I am going to be of no help. But I do like to learn. So I sit and wait, and usually tag some "helpful" people...

@campfire @AgDieseler ....and so on.

I don't think I've ever been called helpful, Greg.

@Truckman4life, black smoke is normal when loaded down, to a certain extent. A bluish tint would be oil burning (fairly common in older engines, but not every engine does this). I expect a greyish color when at medium load. Sustained white would be coolant (always bad). I've never heard of backfiring smoke through the intake, but if it starts running rough after a couple minutes you are probably looking at the change between cold idle (fast) and warm idle (slow). The timing gets bumped during cold idle, and my switch trips before I consider it warmed up. I had to raise my warm idle slightly to get it running smooth during that transition, I wish it would wait a little bit longer before tripping. Your symptoms sound quite similar.

If I start it and let it idle sometimes after a bit it will start running rough and blowing whiteish black smoke and even popping smoke back into the intake. I can rev it up and it goes away or if I just start it up and drive it then it won't do it.

Try raising the idle a bit, you shouldn't hafta raise it much to overcome the rough running if my hunch is right.

Your c-code emissions engine does dump smoke into the intake in the form of EGR. This will start after it warms up. Can't recall the logic that opens the EGR valve, but it may also be running off the temp. switch.


My '83 K10 was a barn find. I bought it in 2010, and it had been sitting on and off since about 1990. Lots of time for gunk to build up, and it smoked a bunch in several non-white colors. I remember starting it up and filling small parking lots with smoke, driving through my own haze on the way out. After a couple of thousand miles it got much better. YMMV. I haven't replaced my old injectors, but doing so should help reduce the amount of black smoke (wasted, half-burnt fuel). A worn-out IP would cause inconsistent running, but shouldn't be causing smoke, IIRC. Timing can affect smoke rate, but I don't have first-hand experience here.

I'd bet that the increase in smoke while upshifting at light loading is an illusion caused by the slower exhaust flow rate (the smoke is moving away more slowly), but that's just a guess. The folks following my K10 see quite a different picture than what I see from the cab.

HTH.

 

[campfire]

Thanks for the help on that end. Lets tag @diesel4me also, he seems to know them pretty well.

Don't forget @longbedder, @kennyw, and @tRustyK5.

 

[tRustyK5]

Black smoke is partially burnt fuel. Either too much fuel, or too little air. Check the air cleaner and noise box for obstructions...especially if it sat for a while. It could have a rodent nest blocking things.

Pump timing can cause smoke issues, but once it's set it doesn't move...so having to advance the pump timing can indicate timing chain stretch issues.

 

[Truckman4life]

Yeah its been serviced and has a new air cleaner and new oil and fuel filters. At idle when running rough it is more white than black but not coolant. I may just have to run it for a while and get some miles on it. I capped off the vacuum signal going to the egr valve and it did not affect the way it runs so after the new vacuum pump last night it is back to factory. I just wasn't sure if someone in the past may have messed with the pump timing and it has been off this entire time or possibly turned the injection pump up too far.

 

[tRustyK5]

Pump timing is easy to check. There is a scribe mark on the pump housing...

This pic is looking down from the top, and this pic is with pump timing pretty advanced. It's common and OK to run the timing so the pump line is 1/16" past the line.

 

[Truckman4life]

Pump timing is easy to check. There is a scribe mark on the pump housing...

This pic is looking down from the top, and this pic is with pump timing pretty advanced. It's common and OK to run the timing so the pump line is 1/16" past the line.

Sweet! I'll go take a look at it in a little while and see where it's at.

 

[campfire]

Yeah its been serviced and has a new air cleaner and new oil and fuel filters. At idle when running rough it is more white than black but not coolant. I may just have to run it for a while and get some miles on it. I capped off the vacuum signal going to the egr valve and it did not affect the way it runs so after the new vacuum pump last night it is back to factory. I just wasn't sure if someone in the past may have messed with the pump timing and it has been off this entire time or possibly turned the injection pump up too far.

Get some miles on it before worrying too much. Sitting can cause all sorts of problems.

 

[Truckman4life]

Timing marks are lined up. I'll put a few hundred miles or so on it before I get too worried about the smoke. For now it just keeps the tail gaters away hahahaha....

 

[longbedder]

Black smoke is incomplete combustion, white smoke is raw fuel (i.e.: it didn't even try to burn). Sounds like you have both.

The timing mark are simply an assembly aid to get in the ballpark upon installation - actual fine timing is set with specialty tools. I have a tool that goes into a glow plug hole and senses the start of the burn, and trips a circuit to light up an old-school gasser timing light. That being said, all the 6.2 timing chains stretch and you almost can't get into trouble advancing the timing and going by sound/feel - try advancing it in 1/8" increments (NOT while the engine is running!).

Also get a diesel compression gauge and check compression.

Checking compression and checking and/or advancing the timing are basically free and will tell you something useful.

If advancing the timing doesn't make the smoke go away, and you have good compression all around, it's most likely the injection system dumping too much fuel.

 

[Truckman4life]

Yeah it has next to no blow-by so I'm gonna say the compression is good. I will try to advance the timing and see how that helps. I've done it with the timing lights that go on the injector lines but that was way back in tech school. I'm leaning towards an injection system issue but if the timing will clean it up a little I will leave it be til I have money to dive into it. I eventually will be building a mechanically injected 6.5 turbo engine that I've had sitting for many yrs.

 

[Truckman4life]

So when I started it to go home after it sat all afternoon it did the white smoke stumble at idle. I gave it a small amount of throttle and it clears up and it also doesn't do it once warmed up so I believe if I turn up the idle a little that might fix that issue.

 

[diesel4me]

I'd dump a bottle of Howes Lubricator or Power-Kleen in the tank with it less than half full and run it awhile before doing much of anything else..if it has sat a lot it is likely to have some nasty crap in the fuel injectors and lines..

It took my '82 a good 300 miles or more before it would idle anywhere near "smooth" and not stumble or stall at stop lights,sometimes it acted like it ran out of fuel while just cruising along about 35 or so too...
I traced that back to air getting in the fuel feed line thanks to crusty steel lines--copper I put in its place fixed that issue..

I think it might need some more fuel treatment,it has started idling a bit "lopey" at times again--I don't know what I'm getting for diesel fuel,but lately every time I floor it to pass or merge onto a highway,it smells more like burning asphalt or road tar,than diesel or kerosene like it used too,and the smoke is blacker than usual..my injectors have never been touched by me since 2003 when I got it,and by the looks of the injector lines, no one else dared touch them either..

I put my fast idle cold advance to a toggle switch about a year ago,when one day the original temp switch on the passenger side head decided to have the plastic part and the plug pop off,and land on the hot exhaust manifold--I came home right about dark one night from a 4 mile ride and saw FIRE under the hood !--right under the fuel filter and rubber fuel lines too--I wouldn't have the truck if I hadn't noticed the flames..
I think the fast idle was always "on" the entire time I had the truck till I toggle switched it too....

 

[Truckman4life]

I turned up the idle 1 full turn and I'll see how that does in the morning when it's colder. I also advanced the timing maybe 1/16" and it seems to smoke less but I haven't drove it yet.

 

[diesel4me]

Advancing the timing will boost the idle speed a hair by itself too..
As Rene said,if the timing chain is slightly loose advancing the timing helps compensate for that..

My truck sat over 2 years before I bought it --it had a blown engine and it sat all that time until someone put a salvage yard engine in it--then couldn't get it started,and "gave up" on it..like I said,after I got it to run,it ran pretty ragged for quite a while,until at least a tank or two of fuel went through it..and I replaced all the fuel feed lines & hoses and added a quart or two of diesel fuel treatment..

One day after I finally cured the bogging down and stalling issues by replacing the fuel lines and hoses,I was driving it down a highway at 55 mph or so,and it did a weird "blubbering" and it sounded like one cylinder had died--then it suddenly took off like a scared rabbit,and had more power than it ever did--I floored it a few times and saw some sparks fly out the back out of the exhaust--..

I'm guessing some chunks of carbon or soot got caught under a valve head,or one cylinder was sooted up badly and it broke free suddenly..it has run pretty good ever since.(It might have been the cylinder I cant get one glow plug out of--every cold start,I imagine that cylinder must load up with unburnt fuel at least for the first minute or so)..

 

[Truckman4life]

I really appreciate all the advice. I started it this morning and the white smoke was better at idle. I checked with a test light and I am getting power to the fast idle solenoid but I think I need to adjust it more because it pretty much does nothing to bring up the rpm. If I push the plunger on the solenoid all the way with the engine running the rpm does not come up. That might be part of my issue that the cold advance is working and the rpm was not coming up to match it? I drove it to work again and the black smoke is at least half what it was at all speeds and loads so I am happy with how it's running. Should I install a new CDR valve at some point? Does it need the CDR valve to allow the engine to suck in the crankcase vapors? What about just running the tube from the oil fill neck down below the frame like a traditional draft tube that a semi runs and deleting the valve and tubes that run to the intake? That is how I have my 6.0L powerstroke setup. Way cleaner in the intake without all that oily crap going back in there mixing with the egr fumes.

 

[diesel4me]

I never have messed with my CDR valve,its function is to ventilate the crankcase and I think it does send blow by fumes back into the intake to be burned--I'm unsure if its possible to delete it without causing any harm..I know a gas engine will sludge up and possibly force oil past gaskets and seals if you delete the PCV valve..

I also have never had to screw with an injector pump (and hope I never have too either!)--so I'm not much help there--the fast idle cold spark advance solenoid should pop out when energized, and move the throttle lever to increase the idle speed,I'm not sure how it advances the timing,I guess it moves something inside the pump ..those solenoids are pricey,like they have gold windings inside or something...

My 6.2 still has an EGR valve but nothing on it connected,the EGR solenoids vacuum hoses are simply left off--I did delete the EPR valve under the drivers side exhaust manifold last year when I had to replace the front exhaust pipe,(its a butterfly valve operated by a vacuum can,like a heat riser on a gas engine)..
I did notice a slight increase in power after getting it out of there..

I do have a "J" code intake on another 6.2 parts motor that busted the crank,but I've never been ambitious enough to install it..some guys I know say just removing the EGR valve does pretty much the same on the street as swapping intakes will,and I'd be hard pressed to notice the difference--a turbo is what really wakes up a 6.2 according to them..I just want mine to run and not s*** the bed !..

 

[Truckman4life]

Yeah I don't like all the exh fumes and oil vapors going into the intake. It makes a real mess of it. On my powerstroke I just plugged off the hole in the intake and ran the crankcase vent hose down below the axle like they do on semis to just let the crankcase vapors vent naturally and plugged off my egr. On those engines the two things mixing really muck up the turbo and intake. I would imaging it would work the same on a 6.2L. I will have to research the CDR valve some more to see if it just opens at certain times or what. It sounds like I can just unplug the vacuum to the egr like you did and it will be "deleted" that way until I remove the intake some day and change out hard parts. I did notice that when I went from a non-working vacuum pump to a working one the engine tone at idle changed. Not sure why.