IP Mechanical advance - How far can it go.

[Splitrimz]

Having problems on a '94 with timing. I have been advised to advance the pump to the passenger side because it might be out of range to set TDC offset. I advanced it about 1/16 inch and it still will not allow me to set 0 nor TDC offset without stalling when I try. and I have a constant Code 88 that I cannot reset. I am willing to move it further but I'm apprehensive, it gets tough to move past the 1/16 mark without really putting some muscle into it. Can it be done? Without damaging fittings etc?
I made a tool, I'm not prying on any pump parts. TDC offset reads 0 right now and the truck starts, runs and really smokes until warmup, the smoke subsides a little after 180 deg is reached.

170,000 on the clock.

Thanks, Splitrimz

[JohnC]

How did you get to this point? Sounds like the timing gears have jumped a tooth or something. DTC 88 means the TDC offset is out of the normal range.

[ronniejoe]

I have been advised to advance the pump to the passenger side...

This is backwards. Moving the pump to the passenger side will retard timing. If you want to advance it, you must move to the driver side.

[JohnC]

This is backwards.


Trick question! :o

[Splitrimz]

I understand all that has been said in the previous posts. How I got here was trying to set TDC 0 with the rpm's too high. That was because the truck would stall when I first tried to 0 the TDC0 and then learn it. I have since found a service manual that states if the truck stalls when trying to set 0 or learn that the pump should be rotated to the driver's side, confirming what Ronniejoe said. It certainly could have slipped a tooth. I haven't looked at a hard mechanical fault because it starts, but being a novice maybe I should.
I'm really trying to methodically work my way back to getting the TDC set to something besides 0. As you know, setting TDC offset requires temp to be correct, rpm's to be correct, the pump within a certain window etc and no codes (ie: code 88) it seems impossible. I'm thiniking that I should

Pull front covers, check or fix misaligned timing marks.
Set pump on original mark that it has been on for the past four years (after #1)
See if code 88 still exists. If not, proceed with TDC learn and hope it sets without stalling. If code 88 still exists go to 4.
If it stalls, rotate pump a hair to driver's side. Go back to #3.
If I can't get past code 88, take it to a stealer,

Any other suggestions to get out of my dilemma? Has anyone worked out a "back to square one" scenario to resolve the TDC offset won't set issue, I can't be the first to encounter this.

Thanks

[JohnC]

You have to clear the code before atempting the TDC offset learn. Each time it trys to learn, if it is still out of range, it will (re)set the code.

Turn the pump 1/16" past the mark toward the driver's side (clockwise as viewed from the front), clear the code and try TDC offset learn again.

You don't set TDC offset. You position the pump then tell the PCM to learn the new value. It stalls because during the learn process the stepper motor goes to zero advance and in your case the timing is too far retarded to keep running.

[ronniejoe]

I would definitely attempt to do the injection timing before pulling the front covers. It just sounds like you've wandered out in the weeds on timing and need to get back in the mowed grass...so to speak.;)

I would move the pump toward the driver side, as JohnC said, clear the code and try again.

[Splitrimz]

Thanks for the encouragement. I will go back at it this weekend. I was assuming that the code 88 was setting immediately after I reset it, just before I tried to set 0. I can't monitor both the codes and the tdc set screen at the same time with my GMTD Tech.

Splitrimz

[Robyn]

If the timing chain is real sloppy this will also or can give you fits.

Be sure the chain is snug. These engines generally dont wear the sprockets out and a fresh chain will restore things to spec.

With the chain sloppy it can cause fluctuations in the setting that can possibly drive the little beast nuts while trying to set things.

If you run into a tuffy while trying to turn the IP, just crack the High pressure lines at the pump to allow things to settle and release the strain then snug back up.

Best
Robyn

[More Power]

For what it's worth, the IP needs to be rotated about as far as it can go (either retarded or advanced, depending) to get the engine to run (sort of) if the timing set is one tooth off.

Jim

[Splitrimz]

I just had to return to complete this SAGA of setting TDC offset. I finally got-r-done. One point I will make is that when you are out of the ball park. getting constant DTC 88, and it won't set I discovered that if I loosened all three pump mounting bolts, really loose and let the tension of the fuel lines relax naturally, the pump was within the setting window, way off retarded, around +2 degrees, but within the 4 degree setting window which is 0 (+/- 2 degrees).

Another thing I discovered was that on my truck it is really about 2 degrees of offset for each 1mm of rotation. From where I was at, +2 degrees, it only took about 2.3 mm of rotation towards the drivers side to get a tdc offset in the sweet spot range of -.25 to -.75. I didn't want to try for the aggressive setting of -1.9 something. 2.3mm is a very tiny movement.

The truck runs just great. Thanks for all the pointers.
I have the Engh Motors software and it worked great, once I got the timing back in the ballpark.
Splitrimz

[Warren96]

I also have the ENGH software and like it a lot, but now that you know how to do it,try bumping the off set up a hair to say -1.00 or -1.50 . A setting of -.25 or -.75 is fairly stock. When I set mine to those low settings, it dosen't sound like other 6.5's that i listen to around town. Settings of -1.00 or -1.50 also make the throtle more responsive.