Engine/Transmission (1994 - 1998) Lots of smoke on takeoff

[#crnxr]

Having a problem lately. I have a #10 plate and housing 1/2 way forward, 3K GSK, and PDR-40/16. Had a shop install the springs and I installed the plate. Every once in a while on takeoff (empty around town starting in 2nd gear) I'll get a huge plume of unburned fuel smoke even though I'm easy on the go-pedal. Then it goes away instantly. Power seems down a bit lately too. I've been told it could be the GSK are too tight. What about timing? Full boost still reaches about 35lbs at WOT. EGT's have been normal (250* idling, 800* accelerating empty, 1000-1100* towing 5000lbs. uphill). Any thoughts? Thanks.



-Kyle

 

[JGheen]

Sounds like you could back off on the AFC star wheel a bit and see how that clears it up. I get the same thing once in a while as well. It just depends on how much throttle you give it before boost comes up. The AFC star wheel will tune your pre-boost amount of fuel.

Pull the 8mm allen plug off the top of the AFC housing and if you cannot turn the wheel anymore towards the engine then the spring is backed all the way off. If so, try turning it away from the engine about 10-20 clicks and test drive. Kind of a PITA to do adjust then drive, adjust then drive..... but I think you can also see how much pre-boost fuel there is by idleing the engine and pin the throttle wide open for a quick 2-3 seconds(blip the throttle, so to speak).

I don't think it has anything to do with the governor springs as if they were too tight your idle would be high. The governor springs just limit the amount of fuel you will be feeding the engine at high revs.

 

[EBottema]

Smoke is good :-laf

 

[Forrest Nearing]

black smoke is good... white/blue smoke is not...



sounds like you might need to adjust the lever arm.



Forrest

 

[Howard Durand]

When I installed my #5, I followed instructions and set the housing full forward with the plate in stock position.

I was getting a lot of black smoke.

Reset the housing to stock position and adjusted the governor arm to touch just above the nose on the plate.

I get better low end response now and very little black smoke.

 

[#crnxr]

I agree that some black smoke is good. I've talked to the shop that installed the gsk and he recommended moving the housing back to control the preboost fueling and see if that helps. If not then I might go with the AFC spring kit and start adjusting the starwheel.



-Kyle

 

[JGheen]

I agree that some black smoke is good. I've talked to the shop that installed the gsk and he recommended moving the housing back to control the preboost fueling and see if that helps. If not then I might go with the AFC spring kit and start adjusting the starwheel.



-Kyle

Don't know if the AFC spring kit would help your issue, as I was told by Piers that they are typically used for those who are running A LOT of fuel and need more adjustment. Not sure what he refers to as A LOT of fuel, I am thinking maybe someone who would be running 370 injectors or bigger??

Double check your star wheel as it is now and see how far turned out it is, sounds like it is backed all the way off as I had a similar issue until I tightened it up some.

 

[Forrest Nearing]

Kyle,



it really sounds to me like the lever arm needs adjusting... when I had a #6 plate, I would get white/blue smoke and stumbling if I gave it lots of throttle at the wrong RPM/load conditions...



ended up being a lever arm issue.



I now have a #0 plate full forward, AFC and starwheel full forward, and 370 injectors, and there's no more unburnt fuel... just LOTS of black smoke!



the only time I've experienced a stumble is up in the mountains in the 9000+ range. with my slow spooling turbo, if I lay into it at the wrong rpm/load conditions, I think the lack of oxygen is allowing the fuel to try to put out the fire. it's happened a couple times since I got up here, but back at home, no problems.



Forrest

 

[JGheen]

Every once in a while on takeoff (empty around town starting in 2nd gear) I'll get a huge plume of unburned fuel smoke even though I'm easy on the go-pedal.



-Kyle

He said he gets a "plume of unburned fuel smoke", which tells me it is black smoke and the AFC needs adjustment. Not argueing, just going by what he said.

 

[Forrest Nearing]

ahh, interesting... maybe it is black smoke...



when I think "unburnt fuel" I think blue/white smoke... to me, black smoke is burnt (just not completely burnt!! )



Forrest

 

[1dslram]

I have the same problem when the truck is cold and the A/C is on. I am on the brink of overfueling and when cold with the A/C on it is just enough to make a lot of extra black smoke and create extra lag on take off. I know I could backoff the star wheel some more but this is the only time it is really black at takeoff unless I push too hard on the loud pedal.

Bruce