Hello,

Can anyone tell me how to properly verify the operation of my Fuel Pressure Regulator (FPR)? I guess I'm looking for something like... fuel pressure at the rail should be:
- xx psi at idle
- xx psi at 2500rpm
- xx psi at idle when FPR is disconnected
- xx psi at 2500rpm when FPR disconnected... etc.

Or whatever else the proper sequence would be to confirm it's working correctly or not.

I've found a few nuggets of info in the archives, but not enough to outline the proper way to diagnose.

Thanks in advance!

Bob

 

Best place to find all the info you need and more is to download the RAVE. It is in my signature.

 

Thanks... yesterday I searched through the RAVE for every instance of "Fuel Pressure Regulator"... I didn't see any details on diagnosing it. The only info I saw was the fuel pressure data under normal operation (or was it idle?)... 2.5-2.7 bar or whatever they list. Did I miss it?

Bob

 

That's it. Unfortunately, they don't list anything except for key on, engine off values.

 

Yeah, unfortunately that's not all that helpful. I'm hoping someone will chime in here... seems like quite frequently people are suggesting the FPR as a possible cause for various issues, someone's gotta know how to tell if it's doing it's job... anyone... Bueller?

 

If you've got that specified pressure, it's doing it's job. All it does is allow fuel to dump back into the tank to keep the pressure from getting too high. The pump is going to create as much pressure as it can.

 

Ok... that helps. So if it's not doing it's job, then the pressure at the rail would be higher than the specified ~36psi of pressure. I'm guessing then that removing the vaccum hose should also result in higher pressure than spec'd (assuming the fuel pump & filter are OK)... and then re-attaching the vaccum hose brings it back to spec.

I wonder if these ever have a failure mode where they actually reduce pressure (e.g., diaphram or other internal FPR parts crap out and cause some sort of restriction)?

 

Yes, if the pressure is above OR below the specs, it can be a bad regulator. Always check your vacuum to the regulator as well.