quick mileage blooper

[T.winegar]

ok, now i had my pump rebuilt and turned way up power wise. he never gave me the exact number hp, but it is turned way up. not crazy, but pretty powerful.

now, ever since the rebuild my mileage has gone to hell in a hand basket! i was getting 18-19 before, and now if i'm lucky i make 16mpg!

so, i was thinking it is probably my injectors. they are still stock, and with the pump turned up that much, they are probably not doing as well. i dunno really, i'm just guessing.

suggestions?? i am looking for new injectors though, so if anyone has some for sale pm me or something.

[Richie O]

Do you have winter blend fuel? also try to nurse it one tank. No smoke bombs. You only get the same or better milage with turning up pump and other mods if you don't rod the snot out of it. My milage went from 16.5 mpg in my 89 to 13 or 14 because I push the hell out of it now. If I go easy I can get my old mpg. Who's gonna do that? Not I.

[gear jammer 91"]

Another thing you can check is where he set your smoke screw and your star wheel. With the smoke screw turned in it will help your truck fuel in the low rpm's, but it will also cause you to burn more fuel just cruising around than you would have before. Turning the star wheel down will cause the same thing.
That being said, with my stock lift pump and my injection pump turned up, the stock lift pump couldn't keep up and my fuel mileage suffered. When I installed a low pressure piston lift pump I gained approximately two mpg when I could keep my foot out of it.

[T.winegar]

i tried nursing it and just taking it easy for one tank, but it barely got 16. i even loaded it up with lucas injector cleaner additive for the last 3 tanks.

about the smoke screw and star wheel. all i know is he is pump rebuilding and tuning shop. he knows whats going on, but maybe he did something i didn't want him too. maybe i'll give him a call and see what he says about those two things and what he did...

[burnt_servo]

have you played with the timing yet ?

[KTA]

I was going to say your timing could be too advanced. If that is the case it will run great when you are in it good, but just cruising boost will be down and you will lose some low end response. That can also hurt mileage.

[dpuckett]

KTA- what would you recommend for timing to maximize MPGs?

[KTA]

About 12 deg static.

[dpuckett]

Which converts to what in MM lift? Near stock? I know I could probably look it up somewhere, though......

DP

[KTA]

Yes that is pretty close to or slightly advanced from stock, as the ic motors run a bit less timing than the non ic factory. I use a dynamic timing light that indicates start of injection to determine the base timing at idle. There are several factors that can influence your actual timing because of the variable timing in the injection pump. Diffrent springs, diffrent fuel pressures, and diffrent nozzles can all play into the equation so determining your timing when running can be pretty tricky without special tools.