My Isspro Performax Fuel Pressure Gauge started showing 40 psi anytime the key is on.(pegged all the way) I have unplugged it and plugged it back in, turned the truck off and back on, and it will not change. Truck and AD150 run fine and sound fine. What gives? I had an issue with it last week dropping to zero and going back to 18 psi everytime I came to a stop.

 

Just sounds like a bad gauge to me.

 

Check your connections from start to finish on the gauge. Try cleaning them.

Do you read pressure directly from the fuel, or is it electronic? Is there an isolator?

I had a problem with my FP one time, I took an air hose, set it to 20 psi, and blew air into the FP line (unhooked from the fuel line) to make sure my gauge was not bad. I have also had an isolator that was crap, now I just run fuel straight into the cab.

 

No Smoking in Madhat's truck!

 

The Performax has a sensor that you thread into a banjo bolt. Then the harness from the processor plugs into the sensor. No isolator or fuel lines into the cab