Code 91

[Plowboy81]

My 95 chevy 6.5 2500 trucks been acting funny last couple of days. When you start it, it's got a miss and blows puffs of white smoke out the exhuast and you can smell diesel. Plugged in my mt2500 scanner and shows code 91 cylinder number 1 out of balance. Have replaced injector pump, new gray standyne pdm located in front bumper, and new lift pump.

[greatwhite]

Is it just on start or does it continue to blow fuel once warmed?

If its only on start, the glow plug circuit (ie: glow plug, wires, etc) is suspect.

If it continues, I would suspect the injector itself or a compression issue.

Of course, this assumes you can nail it down to one specific cylinder causing the issue.

Cheers

[john8662]

Clylinder balance faults are one cylinder not firing.

Check the injector in that cylinder, move it to another cylinder and see if the problem follows the injector.

[Plowboy81]

It is doing it from the time you start it and keeps doing it even when warm. Checked compression, it showing 400 on each cylinder. Had injectors spray tested and from what they said they are showing a good spray patterning. But that was not testing them under compression.

[john8662]

Good pattern, what about when they pop, good chatter too?

Could still be a valvetrain issue, if you have a rockerarm that's not actuating the valve correctly, due to the fact that it's been pushed off to the side.

[Plowboy81]

They never said anything about when they pop or chatter. I dont put much faith in the place we have here to test them I had to replace pump cause they wouldnt test it on there stand. Only other option is sending injectors off to test. So pulled the vavle covers last night and checked the plastic caps on the rocker arms and they are all good. Bared engine over and watched lifters and everything seems tight and working correctly. Cleaned and checked all the battery cables.

[Robyn]

Good bet that its the IP thats gone south.

An OBD1 system can not tell if the thing fired or not.
The Ballance fault code is normally associated with an internal error on the IP.
Try dumping a quart of 2 stroke oil in the tank and running it.
If this helps, then its definately the IP.

As mentioned, swap that injector with another hole and see what happens.


Missy

[Plowboy81]

The IP has been changed with a rebuilt one I ordered off line. Cause thats what the place that tested the injectors said. So its doing same thing even with this pump.

[greatwhite]

Puffs of white and strong diesel doesn't really mean too much fueling, it means it's not burning at all.

That's typically compression issues, however, your compression test seems to rule this out.

Too much fuel or a bad injector spray typically shows up as black smoke because it at least burns when it hits the compressed cyclinder. It just burns very poorly (ie: hot and smokey black). That being said, I have seen injectors go so horribly wrong in OTR engines that it just belches white out the stack. These are usually stuck wide open injectors to the point where so much fuel is injected it (for the most part) quenches the flame front.

Good compression also seems to rule out valve and valve train problems.

This is kind of a perplexing problem.

Try loosening each injector when it's running to see if you can get the white "smoke" and heavy diesel fuel smell to go away. If nothing else, this will narrow it down to a specific cylinder.

Really wrong timing could also do this, but I haven't seen it that bad without other seriously noticable driveability/running issues.

[Plowboy81]

Well dont know if this helps but it didnt start happening untill the Dtech pmd box went bad and shot the rpms up to 3800 when I was driving it. Took off fast, I pushed clutch in to stop it from running away and turned key off. Replaced the pmd with an old one I had behind the seat just to get it home. Went out start it the next day, drove it to town and it shot off and it started doing this. So thats when i started replacing what I thought was wrong and doing all the test. So far nothing I have done or replaced has worked. Have noticed a pecking sound on side where turbo is, But when pulled vavle covers everyhing looks good and like I said commprission test passed. So either sound coming from turbo or cdr vavle on valve cover. When running and oil cap off there is no blow by coming from oil fill tube. So I am lost. Unless the guys didnt test injectors right. Well try breaking lines lose tomorrow and see what that does.

[Plowboy81]

Havent got a chance to crack the lines yet weathers been bad. Could a computer problem cause this?