altitude and idle speed question

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Dec 3, 2005
Coquitlam B.C.
this weekend i drove non stop from vancouver to williams lake ( 3084 feet ) above sea level , when i got to my dads my idle speed was about 1250 , i thought it might be from the 6 hour drive ? , the next morning after my truck warmed up it idled back to about 1250 again and continued to all weekend , when i came back to vancouver on sunday after another almost non stop drive the idle speed came back to where it usualy is around 800 rpm ?

whats up ?

and it can not be the diaprahm as it was just changed two weeks ago when i had it serviced , and its a 3b .

could it be the high altiude compensator out of adjustment and how do i adjust it ?
Last edited:
There is no high altitude compensator, at least not on my truck. I get that too but not that much variation. I'll idle at 600 or so in Vancouver and at high altitudes it will go up to maybe 1000 or so.
come on diesel guru's , some one out there must know somthing about how to correct this ?
Reviving this thread because I'm messing around with this on mine...

I don't think Canadian BJ60s had HACs (high altitude compensators) on them, but if yours does, it's probably a silver cylinder on your injector pump. Look at the arm the EDIC motor moves to open and close the fuel rack, and you'll see the HAC there, limiting how far back that arm can get pulled.

To adjust the HAC, turn it farther in (clockwise) for higher altitude to restrict the amount of fuel the injector pump can have, and farther out (counter-clockwise) for more fuel at lower altitude. 1/4 turn at a time!

As far as I can tell, my HAC is not working at all. I'll do the test in the FSM this weekend and confirm that, but is this a standard part that I can get at a diesel shop? All of them around here do Dodge/Cummins, it seems...

Users who are viewing this thread

Top Bottom