weird smoke problem with 6.2

[dually man]

OK, it cold here now and my 1984 gmc with 6.2 starts after 17 seconds of manual glow plug time. starts fine but misses. the truck has true dual exhaust and out the pass side it puffs LOTS of blue smoke, but not out drivers side. The engine also sounds like it is backfiring into the intake with loud random pops for about 45 seconds. At 1 minute and 30 seconds the exhaust on both banks is clear, the engine runs perfect, smooth, lots of power.
History:
10000 miles on gm goodwrench rebuild, uses no coolant. No oil usage after 3000 miles, no leaks. always used power service lube with fuel. NEW fuel filters, electric lift pump, timing set on the mark, no timing chain slop, very little black smoke under HEAVY load 7000 lbs trailer. injection pump is set to stock fuel rate. truck is a 3/4 ton 4x4 wih turbo 400 auto and 4.11 gears, it gets 19.5 mpg, like I say it runs AWSOME, it just smokes out theat one side like crazy oncold start. Cold start after like 6 hours of sitting makes very little smoke, but I do have to use my glow plugs for about 10 seconds. outside temp is 25-35 degress F. Thanks for any help

 

[ak diesel driver]

sounds like a sticking inj to me

 

[dually man]

thats kinda what I was thinking, but did not wanna here, Im broke and this is my only "get to work rig" right now ARGGGGG

 

[iamdave0887]

Blue smoke is either oil or unburned diesel.

Smoking from one side and not the other would tell me it could be a compression related issue that goes away once the motor gets enough compression strokes and heat into the cylinder. typical low comp sign.

I'd remove all 8 glowplugs and do a compression test. Start with the side that never smokes blue, and then move to the other side and when finished post and compare the numbers.

Usually when an IP goes bad it'll smoke from both sides of the exhaust. Mine was bad when i bought the truck, and it ran like trash with lots of blue unburnt diesel smelling(burns your eyes) smoke at all times.

A sticking injector would be accompanied by a "knock" or a loud tick and individual puffs of white-ish blue smoke when that cylinder fires.

If you've got popping back through the intake then you've got valvetrain issues of some sort.

Could possibly be two separate issues that look like one issue.

 

[littleboy]

Sounds like a lifter is not bleeding off correctly an is holding a valve open ever so slightly.

 

[dually man]

if you watch the exhaust and listen to the intake popping, they are in sync, you get a pop, then a big puff of blue.

 

[dually man]

It has only started after it got cold, I use rotella t6 synthetic 5w40 oil every 3000

 

[dually man]

to the post above, "it has only started popping and smoking after it got cold"

 

[WarWagon]

You have checked the glow plug wires, checked for voltage at each glow plug, and ohm tested each glow plug?

Don't forget, and this may or may not apply to you as a 3/4 ton, the driver's side exhaust has an EPR valve on it. This valve closes off the driver's side exhaust forcing it through the intake to heat it up and may provide some EGR pressure. So the driver's side can smoke but blow it out the passenger side. Bypass the EPR for testing banks for smoke - disconnect the vac line...

You can also get air in the system from the fuel filter box. Air from a sticking injector or air leak in the fuel system will smoke blue and be very hard to start.

 

[dually man]

what ohm reading do I need to see at each glow plug?

 

[dually man]

There are no epr valves on this truck LOL

 

[dually man]

It starts good if I use excessive glow plug time like 22 to 25 seconds, I dont like running glow plugs that long.

 

[dually man]

fiul filter box has been deleted, in it place are the two round filter from an 82 chev.

 

[NVW]

The glows should ohm out to 1-2ohms. They can test good but still take too long to heat up. The best way to check them is removal, put 12v to them and see how long it takes to heat. It should be 5 seconds or less for a good glow plug.

 

[dually man]

tested all the glow plugs they were at 0.7 ohms. Just started the truck and now it isn't smoking out that side very bad, it's equal amount of smoke out both sides, it was still backfiring for like 10 seconds though.

 

[dually man]

and it started real fast this time, its 38 degrees F out now.

 

[3500GMC]

With a gasser, (the infamous late 70's early 80's 305 SBC with their camshaft wiped lobe problem) would pop through the intake or exhaust when the cam was on the way out...

Your engine has roller lifters, so if this is indeed a cam/lifter problem you would see serious metal shrapnel in the oil.

So I guess the next question, how's the oil look?

 

[dually man]

I got 1200 miles on this oil and it is still not black, pulled the injector lines and valve covers then put the lines back on to check for sticking valves, everything looks good while running, equal amount of lift in all the rockers, and oil squrten out of them. Ifit was mechanical it seems like the engine would run crappy all the time, when hot itis the best running 6.2 I have ever seen.

 

[Missy Good Wench]

Popping in the intake is due to a lifter bleeding down.

The miss and blue smoke can be a bad injector.

On a cold engine, an injector that Peeing a stream will not fire until there is some heat in the engine.

If your pop pressure on the injectors has fallen off too far it will cause issues.


Missy

 

[dually man]

Engine no longer pops out of intake, but it still smokes like crazy on pass bank cylinders and has an intermittant sound in the exhaust, I can hear this very well cause Im running dual 2" straight pipes!!!. If I run the glowplugs (afterglow) for 5 seconds after cold start the smoke goes away and runs great for the rest of the day.
WIERD PART:
sitting 4 hours: light blue for a few seconds out both pipes, 10 seconds of glow
sitting 8 hours: light blue for 15 seconds out both pipes, 15 seconds of glow
sitting 10 hours, same as above.
sitting 14 hours: heavy blue out pass bank, light blue from drivers bank, 18 seconds of glow, easy to start.
Start conditions: 24 degrees F up to 32 degrees F, rotella T6 5w-40 oil, power service winter blend additive.
New CDR valve. NO blowby at idle when below 150 collant temp. When collant temp is 190 I get a very slight amount of blowby, a steady stream not puffing. ANY IDEAS???