Installed an ISSPRO mechanical fuel pressure gauge last night - the one with the fuel isolator diaphragm. I filled the gauge side line with antifreeze as the instructions dictate. I tapped the banjo bolt going into the injection pump. Upon, starting I had only 10-12 psi at idle. During driving, under slight acceleration @ ~1900 rpm, it was only 20-24 tops.

These should be higher based on dodgeram.org and the service manual.

I'm fairly confident I did the gauge install correctly, but maybe not. I don't have any leaks. I bled the fuel side line as best you can. My gauge side line isn't terribly long, it should have enough fluid in it. Did I miss something?

If it is my lift pump I'm thinking about replacing the pump-filter assembly with the Air-Dog system. After installing it, can the stock pump and filter be removed out of the engine - freeing up some space? The truck has 203k miles on it, so a bad lift pump seems reasonable.

Thanks for the help.

- Craig

 

You could also have a bad overflow valve. Have someone pinch off the return while you watch the gauge, if the pressure spikes, it's your overflow valve.

 

Exactly what he said...

Rick

 

More than the likely the isolator is giving you false readings.
Replace it with a coupling.

 

Would a bad overflow valve give worse fuel mileage??

 

Low fuel pressure can cause low rpm miss/instability, white smoke, hard starting and low power.

 

I'm going to hook up another pressure gauge and pinch off the return line.

Although, I do have some low rpm miss/instability. Having driven it more, the pressure may go up to 22-24, then drop down to 15 and then go back up to 20.

I do have a little bit of flutter with the gauge: ±0.5psi. That doesn't really bother me. But, the above actions doesn't seem normal.

Thanks,

Craig