97 timing issue

C

CTD5995

newb
Helping a friend here. 97 gmc 2500. Throwing timing codes idles rough with white smoke persists until 1500rpm. Then cleans up an runs perfect. Unpluged temp sensor on crossover tube and it ran fine but idles a few hundred rpms higher. Has new injection pump. Relocated pmd and just changed that coolant temp sensor. Any help would be great i know nothing about these things. Thanks


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You need to set the timing on the pump. Sounds like you have the pump set to retarded and it can't advance it enough. You'll need a scanner of some sort to be able to see what the offset is, but it is possible to initiate a self learn in case you can't get a high end scanner that can command it(you will still need a scanner to see what the tdc offset is though).
 
Im used to 12v cummins motors. Do you have to manually time it. Or is the pump keyed and controlled electronically?


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The pump is controleld lectronically, but it must have the base timing set first. The pump can only adjust for 22 degrees of timing variance, and just 1 degree off on the install of the injection pump can cost you over 10 degrees of timing adjustability in the pump. The best way is to get a scanner that can command the pump to fully retarded timing(3.5 degrees), and then manually set it to that. Then you do a TDC offset learn to see what the ECM is seeing for variation between the crank sensor and the optical sensor inside the injection pump. You want to try and get the TDC offset to -1.50 if you can, but it must be between -.5 to -1.94 in order for it to run properly. This means teh pump must be within .5MM of the correct position +/- in order for teh ECM to be able to control it. Head over to the truckstop.us and they have some pretty goods write-ups on how to set the timing.
 
Big help man thanks. Before i tear into that is there any other sensors i can check? Its just strange because the pump was done almost 2 months ago and it has been fine until a week ago when it got started one morning


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Check it for codes first, but there is a chance the stepper motor for the timing portion of teh pump is bad. Or the lift pump may not be keeping up with the pumps demand.
 
By any chance when you where crank the engine did you press down full on the throttle when the timing issue started. I have the same problem. Some where I read the Timing could be reset by Full throttle and Cranking. My 97 6.5 would not start and for the first time i depressed the throttle full. Now my is out of time for no reason.
Thanks
 
I found a chevy tech that said he will put on a computer But i need to get it to him 40 miles away. been low on Money so I didn't want surprise on parts if i needed any.
His computer he says can force time the truck.
Thanks
 
Pushing the throttle down while cranking it won't hurt anything. The procedure they are talking about is the at home TDC offset procedure. You have to run the engine until it is up to 170 degrees or hotter, then shut it off for 30 seconds, push the throttle to the floor and turn the key on, hold the pedal to the floor for 30 seconds, release and start it up. When you do this it will relearn the TDC offset so long as engine temp is still above 170, and it stays at idle. After about 30 seconds it will find the new offset and be locked in. And this procedure does not work for all OBD2 6.5's either.
 
fixed

I think I have fixed the problem
After reading numerous forums: What I found was a possible low lubrication of the pump causing the stepper and timing bump to fault.
This was what I did unplug the ECM fuse under the hood and replug the fuse back in with the key in off then bought 1 qt 2 cycle boat motor oil added to the tank started with the temp sensor off the crossover and ran to 180 and then plugged the sensor back in. All seems well now
 
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