Manual IP timing adjustment

[AndyL]

At a local shop my truck timed @-1.06. I am looking for -1.5 or -1.6. What does a 1/16 or ?? measure out to in terms of degrees?

[MTTwister]

Do a deep serach - I ran across it somewhere, and think it was in the order of 2 degrees!( for that 1/16") Not a lot of room for variation of the scribe marks if you ask me....

[cruzer]

IIRC in a past post 1mm=2*. Moving pump towards driverside =advance.

[AndyL]

After I adjust the pump manually will the ECM see that and adjust it back with the advance servo? How does the offset learn effect this idea?

[ucdavis]

According to JohnC, on TDC Pump Timing in a previous post:
"TDC offset is the difference in degrees between crankshaft TDC and the pump's internal "TDC" which is a reference point in the pump's rotating mechanism. A negative value means the pump reaches TDC before the crankshaft, or is advanced relative to the crank. TDC offset learn is the process by which the PCM learns that value. The pump has a wheel inside with index marks on it that the optical sensor reads so the PCM knows where the pump is relative to this reference point.
The value is stored in the PCM and that value is not affected by changing the pump or even the engine, although the value will have little to do with the actual engine parameters after any such changes.
Once the value is learned, moving the pump (or timing component wear) will not affect injection timing, as long as the change is within the range the timing stepper motor can compenstate.
During the TDC offset learn process the pump cycles through the timing stepper motor range and also the value fluctuates from timing component slop. True, you can force the PCM to learn a value as it passes by on the scanner, but that value may or may not be an accurate reflection of the nominal value.
I recall that the factory setting range is around -0.25 to -0.75. Diesel Page lore suggests (strongly) that performance is improved by setting the pump position such that the value learned is toward the negative end of the scale, i.e. -1.94. (-1.94 is the most negative value the ODB 1 PCM will accept without setting an error code.) I suspect it is possible to further fool the system by choosing the reading closest to the positive end for a given position, causing the PCM to think the pump is less advanced than it really is. I have no emperical proof other than that when I set it this way my mileage seemed to improve noticably. I further hypothisize that the optimal setting would be the most advanced pump setting that still permits grabbing an in-spec TDC offset value, -1.94."

[eracers999]

UCdavis;
Excellent post.
Kent

[david]

I think the main thing is YOU can't do it your self. You can move the pump all you want and it won't change a thing with out a tec 2.
Isn't the government great????? tongue.gif tongue.gif

[gmctd]

OBD-I PCM will learn new offset value over period of starts - could be up to 50 cycles, per the manuals.

I bought a 6.5L TD engine from a K1500\4L80E.

The 1500 series EGR engines are Factory set at -1.5deg TDC Offset and +8.5deg desired inj pump timing.

TDC Offset is the value learned during the TDC Learn procedure, involving setting the injection pump, and is direct reflection of Desired IP Timing in degrees advanced (+) or retarded (-).
Greater the IP advance, the more negative TDC Offset becomes.

I bought a PCM from a K3500 6.5LTD with manual shift, as I was using a T400 and did not want to fight the 4L80E DTCs. :cool:

The 3500 engines are Factory set at -0.5deg TDC Offset and +3.5deg desired ip timing.

Needless to say, the clatter was amazing for a while, but over the month or so r&d and first month I was driving it, the engine settled into it's normal routine.

Called several dealers to do the timing setup, but they would not touch it, being a 'hybrid'.
One Pontiac\GMC service manager flatly hung up on hearing my request. :mad:

Later I had it checked, at a Stanadyne shop, to find -1.5deg TDC Offset and +8.5deg desired ip timing.
We left it there for further r&d, altho it is too far advanced for the truck's weight.

I recently checked it again to find same K1500 timing values, including +18deg Desired and Actual at 2500rpm.

Manuals describe a procedure for doing the OBD-IIs, but a Tech XX is needed to indicate from where you are starting in either series.

Catch-22, ain't it? ;)

[ 03-10-2004, 08:46 PM: Message edited by: gmctd ]

[AndyL]

Too bad AutoZone doesn't Loan-a-tool a Tech II. The only local shop that will time mine won't let me in the shop, I don't trust them.

[ 03-11-2004, 07:41 AM: Message edited by: AndyL ]

[Turbine Doc]

Andy if you know a shop or somebody with a Snap On MT2500 much more common to find than a T2, you can use that to to the reading of offset, if you were in MS we could do it with mine. Using a key on/key off process as described in the manual the TDC learn can be done on OBD II without T2, I've set both a 98 & 99 PCM this way.