Tank rusted out & contaminated fuel system. Replaced tank,cleaned sender and fuel lines.
Replace pump & rebuild fuel-bowl. Install pressure gauge and at pump prime pressure is 35-40lbs. Start truck at idle 48-50lbs shut truck down pressure drops to under 20lbs.
Truck starts and idles no problem with minimum smoke. when under load sounds like spark-knock & vibration. apply 100% to accelerator truck gets up and goes. Am i looking at an injector issue??

 

did you clean or remove the mixing valve filters in the fuel tank?

 

No replaced and cleaned sender. I now see there is a screen in assembly. Also thought there was a screen on the side that is missing. I removed tank tonight. Whats this modification i hear about to sending unit? Does it make a difference? I run truck today at idle i had just under 50PSI. In transit if you go 75% on accelerator pressure drops to almost 40PSI and needle bouncing back&forth about 5PSI. This is a service truck and has good PM record. Replaced FPR&IPR had techs at work put on scanner and performed buzz test they say it was good but Fuel Pressure was erratic. They work on big trucks and do not know much about the 7.3

 

open the mixing valve and remove the 2 screens, then put an inline filter pre pump

 

Ya a little late on screen removal. I pulled chamber apart cleaned screens and reinstall tank. Pressures stayed the same. Tried putting my stock pump back in pressure is around 48psi and drops on accel. Have not test drove yet will try in morning. Also when i replaces return regulator International told me to use my old spring. Whats your thought on that?

 

if the screens were clogged more than likely the pump inlet is clogged also!

 

Thanks i will look into pump. I bought after market at Hastings dont recall the name. What do you think about FPR spring if i install new one? Its a bit longer. What should PSI be at idle?

 

30-70 psi is spec, usually see 53-65