Schibrew

Hey everyone I have a stock 99 and I'm have a defuel issue around 2000 rpm it has a fass lift pump which always stays above 13psi I've already tried tps,map,vp44,and ecm any other ideas?

cougar

Not enough information to guess what's going on.
Please define your defueling issue.
And what is your fuel pressure range? Best fuel pressure range is 15 to 20 PSI for the health of the VP44.
Have you checked the regulator in the return line banjo bolt on the the Injection pump?

jrs_dodge_diesel

13 PSI is perfectly fine as far as lift pump pressure. And the lift pump pressure has absolutely nothing to do with defueling as far as engine performance. In fact, our engines will make full power with lift pump pressure all the way down to 5 PSI, assuming everything else is working normal, so lift pump pressure can be easily and quickly ruled out.

Defueling is done by way of the ECM and VP44 in response to sensor readings. Your description of your problem is a bit vague though. What are you noticing above 2000 RPM? Stuttering? No power? Falls on its face?

What transmission do you have? Is this problem in any gear, or at certain gears? Or is it at certain speeds?

What exactly have you done to try and fix this?

The more details you can provide, the better we can help pinpoint your problem