Engine/Transmission (1998.5 - 2002) Helped Friend replace VP44, now poor mileage

[Sean Flanagan]

I recently helped a friend replace is Injector pump (VP44) and now his fuel economy dropped from about 18mpg to 15mpg. Other than that, the truck runs just fine. Anybody out there have an idea of what could be wrong?



- We also replaced the lift pump, which is why the injector pump failed.

- The key on the pump shaft was definitely put in the correct orientation.

- The truck is a little quieter at idle than it was before (Different timing?)



Is it possible that the gear could be off a tooth? Would it even run that way? The "check engine" light is not on.



Thanks for your help...

 

[TPlasek]

FYI...



Not that will help your problem, but when I changed my Vp44 I went from consistent mid to upper 16's mpg to low to consistent low 15's after I changed my pump. Not sure why this happened and the truck seems to run the same.

 

[Sean Flanagan]

ttt

 

[Pkelly]

same way with mine. before lift pump and injection pump replacement i was getting 18 mpg, after replacement 14-15 mpg. my truck also runs the same.

 

[Sean Flanagan]

That is disappointing



Did it ever get any better over time? Is there some sort of break in period?



Thanks.

 

[pcarlson]

My understanding is, draw yourself a bell curve. Now the VP has a tolerance level anywhere inside your bell curve and its not that tight of a curve either. The top of your curve represents performance and mileage and then as you slip down either side of your curve they drop off. You have one that is probably at a lower tolerance than the one you had. T

 

[ISBPilot]

ditto..................

Just replaced my VP and LP, same mileage problem. Was hoping it would improve.



Todd

 

[OffroadK9]

Seems that this is a common problem. Mine did the same thing 18s to 14s after both pumps. I installed a Raptor 150 w/big hose kit. Plenty of power, just mileage headed south.

 

[Chief USA]

Have you cleaned or replaced the IAT sensor?



IAT sensor - Ram Diesel Problems and repair



SmokinDiesel.com Home



MAP sensor can effect fuel economy as well.



Bear in mind that it does take a bit of time for the ECM to adjust/calibrate/learn to the new IP.



My fuel mileage went back up to original mileage after my IP was replaced.