Hi all, I've had my 1991 cummins since it was new. Lately I've been fiddling with it and have tweaked the pump, adjusted the valves and straight piped it. It runs great. Starts up almost instantly even when cold but the fuel milage has been dropping consistanly for several years. I think I'm down in the 14's mpg.

I had my injector pump replaced as a recall way back about 10 years ago.
My question is: (forgive me if this has been covered, I couldn't find anything on it) How do I check and advance the timing a little if there is NO mark on the pump flange? There is a mark on the gear cover but not on the pump. Do I just scribe a mark on the pump where it is now and then advance it 1/16th to 1/8th inch from there?

Advise please. Thanks

 

"Do I just scribe a mark on the pump where it is now and then advance it 1/16th to 1/8th inch from there?"

Yup -- unless you want to take the plug off the plunger and really measure the timing . . .

 

I don't have the right tools for that kind of timing.
When this pump was replaced it was turned WAY down. For 10 years I've suffered through low power and only a few weeks ago I found out how to turn up the power. It's great but it has me wondering if the timing was set to stock when they replaced it.
How will I know if I've advanced it TOO far? Sounds, etc???

 

It will knock really loud - when it sounds like a Chevy 6.2/6.5 diesel, you've gone too far, back off. If you don't have a wrench for the bottom nut yet, read this.

 

Thanks for the link to harbor frieght! By looking at those wrenches, I think using my oxy/ace torch I could bend an old endwrench I have into the proper shape to make it work. If not, $9.99 isn't a bad price.

So, I should just scribe a mark where it is now and assume that when they did the replacement that they set it to stock advance?

BTW, I had a chevy 6.2 liter back in 1987. Bought it used from a cousin. The engine stayed in the truck exactly 7 months and I pulled it and sold it for $300 I then bought a rebuilt 350 gas engine and dropped it in. Everything fit perfectly, even the exhaust pipes to the headers I was glad but made me wonder about the diesel that was in there. The 6.2 was much bigger and heavier yet all the stuff from it fit right up to the 350.

 

Well, you are really stuck setting it by ear and by how she runs, since you have no idea what they set it to when they replaced the pump, and what method they used, either. (e.g., if they used the timing pin that locks into the cam gear, who knows if that is set right, so too many variables and too many unknowns). If you make the marks, though, you will at least have an idea of what change you have made and what the effect is.

10 years detuned!! Patience is a virtue, I guess.

 

"10 years detuned!! Patience is a virtue, I guess. "

Yeah, I know
I really didn't do much with the truck in that period. I got it in '91 because I was doing some light hauling then stopped for 10 years. Just became a commuter truck with some hauling of a little lumber, etc.

Recently, I got a travel trailer and found the 5K lb camper was HARD to pull up moderate grades as well as just starting off from a stop. This truck shouldn't even know it has THAT behind it!

So I started doing research on the web and found this place as well as others. Geno's garage site is very helpful too.

At least making a reference mark will let me go back to this setting if I don't like the advanced setting.

Thanks for all the help.