Installed a new injection pump on one of our M1009's, pretty easy job. I advanced the injection pump 2 timing marks widths and it pours a liitle more black smoke out! I can feel a slight difference in power. The agencys that get these trucks are usually around 10,000 feet or more in elevation, should give em a little more power!

Anyone mess around with this advancment?

Hmmm...perhaps you should have ordered a pump with altitude compensation. Gets rid of some of the black smoke and still gives you full power.

High altitude compensation??? I am curious about this because the engine sticker under my hood (84 Blazer) says it is the "high altitude" model and I just assumed it was a different pump, or pump setting. Is there some senso involved...or is it all internal to the pump?

Sorry to hi-jack your thread...