pump alignment?

[clem_acc]

On my 95' chevy TD there are 2 alignment marks on the mount for the pump, and 1 mark on the pump itself, which mark should the pump line up to. It is currently on the right hand mark looking from the front of the truck.

[john8662]

95?

Is this electronic? It should be.

If it's the DS4, sometimes there are multiple timing marks, pay no attention to any of them, they are rough scribe marks usually drawn by the GM tech that worked on it.

[clem_acc]

Yeah it is a DS4, i just wanted to make sure there wasn't any mechanical adjustment on that pump. The dealer is telling me there is some mechanical work to set the pump timing and that it will take several hrs. to do. I am leary of this after reading that this adjustment is all computer oriented. I am having a tough time finding a reputable service tech. near me. i am going to order the pc software today and just wanted to confirm that there was no mechanical adjustment.

Thanks again,

SS

[Bnave95]

There is a Adj. Mech. for the BTDC that will show up on his OBD scanner.
Than he set the TDCO learn with a push of a button.
Should take 30 min. and not 2 hrs. Unless 2hrs rate is what they are wanting to charge.
BTW BTDC=Before top dead center 3.5deg.
TDCO=Top dead center offset -1.95 or less.
Would ask how many 6.5 diesel has he/they timed?

[john8662]

With the DS4 you have to get it mechanically in a range where the computer can compensate and run.

There is a procedure to set the timing in the computer, which will need to be performed, but if the value is off or a code is set.

As mentioned, the marks were likely reference marks by a tech while setting the timing before.

On an MFI 6.2 or 6.5 the mark is a precise mark generated by a tool, and is a more accurate mark to go by.