Fuel Pressure Regulator: Question

Onefast99gsx · 10-07-2005

Hi guys- i have a question regarding stock FPR's. I found a problem with my vacuum line disconnected last night. It created a lean spot thus got knock as a result. I put it back on took the car out and it blew off again. Put it back on one last time and of course blew off the regulator again. It wasn't until I took it home and zip tied it on that it would finally stay. Looked slightly wet around the tip of the hose too. Not much but slightly wet to the look.

Talked to a friend tonight whom is a mechanic and he said it should not be blowing off like that. He said this is a vacuum line. Is normal operation of this hose, air pressure to the regulator or suction(vacuum)? Its as though i'm getting air pressure to make the hose blow off like that. If it's a vacuum line it should be suction, correct? I have it connected to a nipple on the bottom of my Magnus manifold.

Thanks for any help.

Outlaw1 · 10-08-2005

Quote:

Originally Posted by Onefast99gsx

Hi guys- i have a question regarding stock FPR's. I found a problem with my vacuum line disconnected last night. It created a lean spot thus got knock as a result. I put it back on took the car out and it blew off again. Put it back on one last time and of course blew off the regulator again. It wasn't until I took it home and zip tied it on that it would finally stay. Looked slightly wet around the tip of the hose too. Not much but slightly wet to the look.

Talked to a friend tonight whom is a mechanic and he said it should not be blowing off like that. He said this is a vacuum line. Is normal operation of this hose, air pressure to the regulator or suction(vacuum)? Its as though i'm getting air pressure to make the hose blow off like that. If it's a vacuum line it should be suction, correct? I have it connected to a nipple on the bottom of my Magnus manifold.

Thanks for any help.

The fuel pressure regulator sees manifold pressure. If you're under vacuum, the diaphram sees vacuum and lowers the fuel pressure. If you're under boost, the diaphram sees boost and raises the fuel pressure. ALL of your vacuum lines see boost when you're under boost and vacuum when you're under vacuum. If you take the vacuum line off of your regulator and see/smell fuel in it, the diaphram in the fuel pressure regulator is bad. If the diaphram is bad, your car will run like crap.

Onefast99gsx · 10-08-2005

Thanks Super4x4. Even though finding my vacuum line off the regulator for who knows how long and putting it back on made it run somewhat better(less knock), i believe i have a failing regulator. Time for a AFPR i think. I'm mostly likely over-running the stock one anyways.

Onefast99gsx · 10-08-2005

I want to try a different regulator for the heck of it. I found an old 1g regulator that i had from a parts car. In appearance the 1g in different look than a 2g. Can someone tell me if the flanges are the same? If it would work on my 2g GSX I would like to try it.

Thanks.

Onefast99gsx · 10-08-2005

I Found this on another forum: By the sounds of it, the 1g regulator might be than my 2g one anyway. Even if my regulator isn't bad.

From dsmtuners---

Does anyone happen to know if there will be any problems running a stock 1g fpr on a 2g? I only did this cause my 2g regulator went out and was leaking fuel, so I had an extra 1g one laying around. Long story short, i got the 1g regulator on and the car runs just fine... no leaks or anything.

Correct me if im wrong, but doesnt the 1g fpr have a lower psi rating? If so, wouldnt that be better if you had a larger pump, ie 190lph?

Somebody wrote back and said:

yes it runs 38psi instead of the 2g 43psi. but thats not a whole lot of diff it wont hurt your car any as of right now. but you will want to bet a AFPR in the futrue so u can turn it back up to 43psi.