Engine/Transmission (1994 - 1998) Needle Valve & Snubber ?????

[JPETE]

I AM ON MY SECOND GUAGE, FIRST ONE NOT LIQUID FILLED PULSATION BEAT IT YO DEATH, NEEDLE FELL OFF. INSTALLED LIQUID FILLED GUAGE,IT IS TAKING A BEATING ,I WILL INSTALL A NEEDLE VALVE AND CHOKE IT DOWN . I HAD SOME 1/8 SNUBBERS BUT I CANT FIND THEM ,I GOT TO MUCH STUFF AND NO TIME TO LOOK THRU IT

 

[P Madrid]

Fuel press readings in park:



Idle: 18-24 psi

high idle: 28-34



Dyno run, WOT, engine lugged/loaded to 1800 rpms: 26-30 psi.



At work I do this all the time for low power and hard start issues. I use a Fluke PV 350 transducer (Pressure-Vacuum, 350 psi range) and Cummins quick CK connectors. I have use these readings for the past four years to condemn a over flow valve.



Some over flow valves will CK OK when engine and fuel are cold, but once you get them hot they will drop pressure, heat affects the over flow valve spring. It usually takes a 5-10 minute dyno run to see this and you start to loose power right away. I have had new valves to be under spec and swap them out with another new one to get the readings higher.



A quick way to ck lift pump out-put press is to pinch the return line for a few seconds at idle, pressure should jump to 50+ psi and if you CK it at high idle it will go way past 75 psi, I release the return line pinch at that point. This will tell you if the pump is working within its range.



High mileage and older engines usually need the over flow valve, newer ones with little road time need the filter/s, algy build up or dirty fuel. Very few bad mechanical lift pumps. I hope this helps.



Pablo

 

[Joe G.]

Thanks for that Pablo. I was getting kind of worried that my fuel pressure was too high. It gets over 30 sometimes, especially if I'm running empty on a highway like I5 and slow down. It will jump up to 35 doing that. I have seen 40 but not very often. Most of the time it runs somewhere between 25 and 30. Idles about 22 or so.