i just bought an '01 2500 with a fass system on it. it will not hold a constant fuel pressure. the lowest it holds is 8lbs but somedays it will hold 28 somedays 24 it constantly changes. ive drained the water separater and replaced the filter....any ideas???? thanks for yer help

 

Sorry I'm not going to be that much help, my buddy just put on a FASS pump on my truck (the one that doesn't have the filters on it) and I haven't driven her with it yet. You can try www.dieselpp.com Diesel Performance Products they have a trouble shooting area and dealer locations where you might be able to call someone to help if their site doesn't help.

 

Ask Diesel Dan, he will help.

 

diesel dan? where would i find him?

 

Have you checked the pressure with a different gage? Sometimes "bouncy" fuel pressure is caused by a bad gage or isolator.

 

im goona try that this evening. im hoping its just the isolator...i know most people on here dont like them!! thanx

 

Charlie hit in on the nose...i think your gauge is haveing some issue....I can see where our system might be low in some situations...but 28 PSI randomly is hard for our system to do...there is too many fail safes to keep it from getting that high. Let me know what you find and we will go from there.......

 

well the extra gauge i had on standby fell through. i have heard i could use my boost gauge...is that safe? i know when the truck is idling i can tap the isolater with a small wrench and the gauge increases, so im leaning towards the isolator. do u know any good places to get an isolator that doesnt cost an arm and a leg? thanks for all the tips!!

 

There may be a large screw on the diesel side of the isolator, if so, loosen to releave any pressure. Do this with a rag or paper towel around it so you can catch anything that spills out. Keep it loose. (if there wasn't a screw, loosen the diesel line at the isolator...) Pull the isolator off wherever it was mounted, without taking the lines off. Turn the isolator so the line going to the gauge is facing straight up, then take it off. Take a pencil with a good eracer and stick it in (eracer first) and very gently press on the diaphram to ensure it is in proper position. Refil with anti-freeze, reconnect line to gauge, tighten diesel side (bleeder or line), remount isolator.

Now, turn the key on and check your gauge. It should go up. Turn the key off, gauge should go down. If it doesn't go down all the way, open the diesel side bleeder again with the system off.

The isolator has to be full to work properly. The line going from the isolator to the Gauge needs to be full too. If it isn't, fill it.

There are many ways to fill the line. I put the isolator end into a small container of antifreeze and point the gauge end out the window and hit it with an air hose pointing at the end of the line (from behind), at about a 45* angle. It sucks the air out of the line and thus sucks antifreeze in through the other end. When you are solidly full of AF, connect the hose to the gauge first, then the isolator. Bleed the diesel side for a moment then tighten.

Should be good to go. Cost $0.00 if you had some AF laying around.

 

Did you get this figured out. I have a similiar issue, but mine goes from 15-16psi down to around 9 or so and bounces back up and then zeroes out for a while until I thromp on the skinny pedal a little bit. I thought maybe the isolater, but it seems more like something with the whole pick-up. Let us know what you found.

 

Do you have a FASS or stock fuel pump? What you describe is exactly what my last stock pump was doing when it started to quit. Don't have that problem any more since I put the FASS HPFP on there.

 

Mine is doing it with the FASS. I have not had real positive experiences with it. I had one running 23psi or so and it was ok at best, then we found that a spring had ground its way into the housing, now the pump set-up is only running 15psi max if I can get it to stay there. Just replaced filters, I know that is not the cause...

 

I hate to hear that. So far, my has been flawless. Dan told me that if anything failed, it would probably be the brushes. I went ahead and bought an extra set and keep them in the truck.

 

I just installed a 30 air pressure guage along with a needle shut off valve on the diesel side of the isolator. I can keep it shut off while driving, then if I start having trouble with pressure, I just oen the needle vale up a little and compare the guages.