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Discussion Starter #1
I just recently replaced my IP using the advice presented in http://www.dieselplace.com/forum/showthread.php?t=279750
I was very careful to make sure the index pin in the gear hub and the actual position of the new IP was in the same position as the old IP. Everything went smoothly and the truck started up w/out any problems. It sounded pretty smooth.

I then hooked up GMTDScan (Basic) to check the IP timing. The notes provided with the IP stated that IP timing must be set to 3.5degrees. I've also seen that value mentioned in IP timing threads. The values I received with GMTDScan were:
Actual Injection Pump Timing (fluctuates around 31-32 degrees)
Desired Injection Timing (9.9)
Measured Injection Timing (8.9)
TDC Offset (-0.79)
(The engine operating temp was only about 90 degrees when I measured these.)

Questions
1) What is the difference between "Actual Injection Pump Timing" and "Measured Injection Timing" ?
2) Which one relates to the 3.5 degree IP timing mentioned in the notes and posts?
3) The way I understand things, the TDCO is changed by rotating the IP. How do I change the IP timing to meet the 3.5 degree specification? (which I think is supposed to be set before adjusting the TDCO)

I ran into a few threads that mention timing values similar to the ones I have,
(http://www.dieselplace.com/forum/showthread.php?t=245150)
(http://www.dieselplace.com/forum/showthread.php?t=213374)
but they didn't clarify anything for me.

I've spent many hours searching and trying to find relevant information, but I can't seem to figure this out (maybe I'm not finding the right threads???).
Can someone help?
 

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you need GMTD scantech....payed 1...to set your time the PCM has to learn where the timin' is....just replaced my IP on the burb Wednesday....engine must be above 180f before time can be set... i have mine set at TDC Offset -1.94....little loud at startup but she runs great after warm...
 

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Discussion Starter #3
If I understand what you are saying, it is GMTDScan Tech that sets the IP timing to 3.5 degrees. Is the procedure for doing this well documented with the software?

What is the difference between "Actual Injection Pump Timing" and "Measured Injection Timing" ? If the pump needs to be timed at 3.5 degrees and my IP shows "Actual Injection Pump Timing" at ~32 degrees why does the truck run so well?
 

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here is what you do....

* Start GMTDScan Tech.
* Connect to your truck.
* Go into the dashboard view and verify that the engine coolant temp is at, or above, 180 °F. If not, wait before proceeding.
* Go into the DTC view and verify that no trouble codes are present.
* Go into the TDC view.
* Take note of the current DES/ACT/TDCO values. OEM is +3.5°/+3.5°/-0.5°. For both DES and ACT 7-9 degrees is more normal and acceptable.
* Click the TDC Time Set ON button. DES should now read 0° and ACT should read +3.5° on average.
* Click the TDC Time Set OFF button to go back to normal operating mode.
* Click the TDC Learn ON button. The TDCO value will now fluctuate for about 20-30 seconds before setting itself. You can end the sequense prematurely by clicking the TDC Learn OFF button. The current TDCO value will then be set in the PCM.
* If you are not happy with the TDCO you get you must turn the injection pump. Towards the drivers side is "-" and towards the passenger side is "+". A 1mm move equals 2° so take it very easy and do not attempt to turn the injection pump while the engine is running!
* Repeat the TDC Learn procedure until the TDCO you want is attained.
 

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Truck needs to be up to operating temp to set timing. Timing will be advanced when cold. Your desired is what PCM is requesting and the measured I would assume is what it is. Haven't used that software but on scanner the actual is well what it actually is. But if it's running good why mess with a good thing.
 

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I'm to slow.what he said
 

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Discussion Starter #7
I've read the GMTDScan Tech FAQ "what steps do I need to take to set TDCO" before, but didn't (and still don't) really understand the IP Timing to TDCO relationship. I think I do understand however that the software (or scanner) enables the IP timing (and I assume it is relational to the crank position - hence the offset in degrees to TDC for each cylinder injection event).

Nevertheless, I still don't understand the difference between "Actual Injection Pump Timing" and "Measured Injection Timing" - and why there is such a difference in values measured by the GMTDScan Basic software (32 to 9).

One other thing I'm not clear with GMTDScan Basic and IP Timing. If I was to move the IP 1/4mm (right now, before I set the IP timing to 3.5 degrees) towards the drivers side, theoretically, that should decrease my TDCO to about -1.45. Is that what the GMTDScan Basic software would show, or are all changes to TDCO before IP timing irrelevant?
 

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good god,i dont understand any of this,i was told make sure i put the pump in the same place as the old one,which i did,i was told to pour water on pump,i did,and it cranked,so thats why i change the pump.i dont know the tdco,i cant do this till i get the truck to run,i have done everything that i was told to do on here,and now i have a dead truck,that i cant get to run,truck was running fine,just would cut off after driveing a while,and would not crank back till it sit for a while,so thinks alot guys
i have spent a fortune for no reason.i am going to junk the dam thing
 

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#1) Im not sure you should really be blaming anyone on this forum for your truck not running.

#2) We need to know the whole story. Did you buy a new injection pump? Where did you buy it from? Did you bleed the lines after getting it back together? Does your lift pump run? Is the PMD good, etc...

These trucks aren't terribly complicated, so with standard hand tools and the know-how this forum has to offer, you should be able to get it running. If the new injection pump is a good one, and all you did was swap the pump, im guessing you either have air in the system or a bad connection somewhere, or possibly a dead lift pump... Give us some info and we will try to help.
 
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