6.2 white smoke

[Marknsteph@hotpop.com]

Got a tough one, late 88 6.2 diesel with a white smoke and a little rough. steady white smoke with clouds when the throttle is revved. I have spent a lot of money so far and don't want to spend more in the wind without testing and confirming the problem. I have done a compression test and all cylinders test fine with 425-450 psi. I replaced the return line with a clear hose and no bubbles. I ran the return line into a bucket to test for excessive housing pressure and no difference. I depressed the advance mechanism and the engine did run rough. I advanced the pump by 1mm and the motor sound changed but the smoke did not. I advanced the pump after I tried to jumper the cold advance like the manual said to test for timing and it did nothing to the sound. On my other truck it does. I figured the cold advance was bad. I changed the pump with one bought off ebay but it has the exact same problem to the same degree but didn't idle as well and had less power so I swapped the origional one back in. I also cracked the injectors one by one and the sound changed apropriatly but the smoke remained. I am not loosing any coolant and there is no abnormal amount of pressure in the coolant. No oil in the coolant or vise-versa. I had the injectors pop tested and all tested from 1500 to 1600 psi and he said 2 were spraying a bad pattern but replacing them made no difference in how it runs. I put a fresh tank of fuel with fuel conditioner but no difference. I pumped 4 gallons out an put it in my other truck to test fuel and no problem. I have an 82 6.2 that runs ok that I am considering swapping the injector pump from it since it is a known good pump but I have a feeling I am wasting my time. I would swap injectors but the 88 uses the short fine thread and the 82 uses the long course thread. I can't tell what the smoke smells like so I had 2 big rig mechaniks smell and they both said it's definitly fuel. Ideas? More tests I can do?

[john8662]

Do you know any shop around that can check your injection pump timing? If you do, then the timing check will reveal some really off numbers in relation to the pump position. How is the power on the rig when you drive it? If its really low, meaning it won't run over 45 with your foot to the floor it could have the timing way off. By way off I mean, the timing chain could be excessively worn or when an injection pump R&R the injection pump drive gear could have moved one tooth, and is going to be out of time physically.

Thats a tough one, I had one do this on a 91 blazer, it would Eventually warm up and quit smoking, after about 30 minutes of driving. It would also back fire sometimes when starting. I never got to finish troubleshooting that one, never made it home with it (long story). But I suspect it was out of time, it didn't have any blow-by, or bubbles in the coolant or coolant in the oil either, but ran really bad.

[britannic]

Mark, how did you advance the pump? Is it hard to start when warm?

[BobND]

Have you replaced the fuel filter, and verified the operation of the lift pump?

Any restriction in the fuel supply system, from a collapsed sock in the fuel tank, to a dirty filter that restricts fuel flow may cause low pressure in the injection pump, and cause the timing advance not to work properly.

[Marknsteph@hotpop.com]

The book says to energize the cold start advance when warm to see if there is a difference in smoke. The advance made no difference in the sound of the engine and no difference in smoke so to make sure just in case the advance wasn't working I manually loosened the pump and turned the top of the pump to the drivers side by 1mm which acording to the manual should have advanced the timing by a few degrees. That did add a little to the clatter but no difference in smoke. This all started when trying to diagnose a nasty knock that's had this rig down for about 6 months. In trying to fix that problem I replaced the timing chain and bearings just to find out that the flex plate had cracked all the way around the bolts. BAD. I don't remember it running this poorly before working on it but it may have been. I was carefull to line up the marks on the timing gears and the chain. The retired diesel mechanic That saw the truck said it's running too good to be off a tooth, but at this point I have considered tearing it all apart to check. It doesn't sound that bad idleing and seems to be abou 80-85 percent on power. I tried to make sure the injector lines didn't get mixed up and checked again as best as I could with the intake manifold on and everything looks ok. The retired mechanic said he thought it was the injectors but I'm not spending 250 bucks just to try it when cracking the injectors one by one doesn't reduce the smoke and they all suposedly pop tested ok. My next thought was to take the injector pump off my 82 that is a known good pump and put it of the 88 just in case I replaced a bad pump with another pump with the exact same problem but thats a lot of work and unlikly. Personally I would rather buy a used timing meter for $200 off ebay than pay one of the local yahoos $150 to check it.

[Marknsteph@hotpop.com]

Also its when the throttle is snaped fast that it really smokes. Otherwise it smoked a little a steady. Strangly on a long drive with my wife in another vehicle she said it stoped smokeing for about a mile a couple of times which I noticed it running better and then as soon as the throttle changed the smoke returned. Maybe a fluke, but that's what prompted me to think it may be worth trying the known good pump. It start harder than it used to cold. It used to start within a second or two of cranking and now takes 5-10. When hot it's still just a tap of the key.

[dieselbegreat]

You've done all the right things. I'd still bet your IP timing is retarded one tooth. Advancing 1mm is nothing if it's a whole tooth off. You should be able to advance it enough so the injectors get real noisy, and with black smoke when you accelerate from a stop. Seems to me you need to have your timing verified or it's just a guess, but that costs money too.

[Marknsteph@hotpop.com]

So my thinking here is that if I got the thing off a tooth I should be able to make a difference in the smoke by advanceing it further. What would the symptoms be if I got the cam off?

[john8662]

I'm thinking you have the timing chain timing correct or something would possibly hit. The tolerance in these engines is very tight, so I I would think that if it were off on the timing chain it would be worse than it is. I think the problem could lie in the injection pump gear to the cam gear. For that you wouldn't have to remove the whole timing cover but just the waterpump and waterpump plate.

[Marknsteph@hotpop.com]

Ok before tore into the front of the motor. Again... I went ahead and adjusted the pump to cover timing a little at a time until it reached the end of adjustment (about 5mm) and it still smoked, but would initially smoke black when the throttle is goosed. My thinking is that as long as turning the top of the pump to the drivers side (clockwise acording to the service manual) it should sound like it's coming apart at this adjustment and as carefull as I thought I was I need to check those gears, correct?

[Peter J. Bierman]

If you adjusted it that far it should sound like a powerstroke with a heart condition :D
I think you are right and you should check on the gears or have a timingmeter on it to be sure.

Good luck, Peter

[Marknsteph@hotpop.com]

Well, I tore apart the front of the motor and looked at the gears and I was right that I was carefull to line up the marks. After talking to my dad I may have installed the timing chain incorectly and gotten it off, but I'll tear the rest of it off tommorow. What I did was put the gears in the new chain and pull them apart and line up the marks. What he said is you have to account for one side having tension and the other not. On a side note I bought the more expensive chain and got it on just to find out that it has a little slack, same amount as the old set. (doh!) Aparently there is supposed to be some slack. I like things nice and tight. Someone mentioned that their gears came right off, and mine took a puller. Is that normal? or a sign of something getting hot? Anyone ever get the timing chain off a link?

[jonflies]

Mark,I'm going to post a new topic under the title "unable to set timing" which has some of the same symptoms your engine is displaying. Maybe, between the two threads, we can figure out what the problems are.

[Marknsteph@hotpop.com]

It just didn't make sence that the injectors tested good and the injector pump smoked the same as the last. The marks on the crank, cam, and pump all lined up. When I got the intake manifold off to try a known good (3rd) pump I looked at the lines again and noticed 5 and 6 were reversed. I had the injector lines off the first time I removed the pump for a knock problem to go ahead and replace leaking rocker arm covers. Swapped the lines and now it runs great. Thought I checked the lines several times but aparently not enough.