Can a guy command the fuel rail pressure up on the duramax with efi live while at an idle like the tech 2? The mechanic ran mine up with the tech 2 at idle and saw the pressure hold so he assumes my injectors are in good shape. Wondering if I can do this test at home with efi live?

I beleive you could with Moates.

If you have suspect injectors, why not use the balance rates?

IIRC running rail pressure up at idle tests the FPRV and CP3...not the injectors. As Kappa said, injectors are generally 'tested' by balance rates.

Correct - From what i have gathered one can test the injectors via the balance rates but even if they show up good there still could be problems. When I went in and had some other work done, my mechanic ramped up the pressure and said that it not only tests the pressure regulator but also the injectors from leaking down. After all his work on the duramax's he said this was an easy way to test. Apparently at idle if it can hold the pressure the injectors and fprv are fine.

I beleive you could with Moates.Yup........):h

Yes, commanding the pressure up to the max and comparing the actual to desired will show if there is a leak on the high pressure side. Also use this to see if any fuel is showing up in the oil on an accelerated level over just letting it run/driving it.

b1012 on the LLY
if you do this i wouldnt adjust whole table
i would make it some how come on with the high rail pressue at a certain ECT
and maybee when you just touch the throttle and add a bit of fuel

how high did he go?

Yes, commanding the pressure up to the max and comparing the actual to desired will show if there is a leak on the high pressure side. Also use this to see if any fuel is showing up in the oil on an accelerated level over just letting it run/driving it.


command to 160 mPa at idle, is that correct

160 Mpa (max)


LOL....Same time on the post, but also yes at idle

interesting.... i must try it!:D

b1012 on the LLY
if you do this i wouldnt adjust whole table
i would make it some how come on with the high rail pressue at a certain ECT
and maybee when you just touch the throttle and add a bit of fuel

how high did he go?

He ramped it all the way up to 26k for a moment and pulled it back down. Basically he had the tech 2 on for my high idle "experiment". My high idle problems from adjusting parameters caused an unexplained lopy idle. After discussion with a gm engineer that wrote the "program" for the pto - they decided it was injectors. My tech proved to me otherwise that it wasnt my injectors and upon installing a new ecm, pre-programed with my stock tune (courtsey of Trippin) the lopy idle went away. When he ramped it up - it held pressure but was not a very good, smooth, or quiet idle. He was in the tech 2 and just clicked the button and it went up and then clicked it back down right away. I was curious if there was a way, not using the moates (roadrunner?) to test it like he did. Seems to me that it would be an easy test to do.

. I was curious if there was a way, not using the moates (roadrunner?) to test it like he did. Seems to me that it would be an easy test to do.


well , i was thinking you could use the manual high idle if you have one
then just change the rail pressure at the area when we are in H/I area
like that mm3 i think its 15mm3 iirc for the high idle

or you could change it in the 10mm3 area and use ECT have it come at at a certain ECT and then off when it rises above that

you would have to be ready to log and would almost want full op temps:D

It would be neat if we had bidirectional controls to turn off injectors and test the regulator:D

It would be neat if we had bidirectional controls to turn off injectors and test the regulator:D

You read my mind! ;)