2002 dodge ram 2500
175,000 miles
It's all stock expect I but a thoroughbred injector pump and frame mounted lift pump. The truck was idling very bad and under little load dies. I put 12volts straight to the frame mounted lift pump and it works. I check voltage from batteries to relay , good. It seems where ever the fuel pressure monitored is not telling the frame mounted fuel pump to turn on. Where is that fuel sensor and what's the correct name

 

Believe there is a relay on the firewall, not 100% sure..

 

Do the key trick and check for codes....

 

Took truck to mechanic and he thinks it will be camshaft sensor, crankshaft sensor or ECM

 

Cam shaft sensor isn't bad 60-80 dollars. would try first. was tach working? was there any codes?