AHarada

iTrader: (2)

I'm using a Vette filter/fpr to regulate my fuel rail pressure. I have my fuel pressure sender in the rail. With the key on engine off fuel lines primed, my gauge reads about 60psi. With the engine on, it always reads about 68psi. From my understanding, the Vette FPR is supposed to always regulate pressure to 58psi? I tried 2 brand new filter/fprs, so unless I got 2 bad ones, the fpr itself is not the problem. I've checked my plumbing and my lines are on correctly. I need to get this issue fixed before I take my car in for tuning. Has anyone ever experienced this?

salemetro

iTrader: (5)

Have you verified fuel pressure with another gauge?

John McGraw

60 PSI is not too high. It does not make sense that the fuel pressure would be higher running than engine off, key on. If it is 60 engine off, it should be no higher engine on. The ECM will automatically compensate for slightly higher or lower fuel pressure. If it runs well at idle, it will probably not be a problem at the tuner. If the fuel trim can adjust low enough at idle, it will have no problem at higher engine speeds or load.

Regards, John McGraw

flame

iTrader: (13)

Make sure you don't have a restriciton in the return line to the tank

AHarada

iTrader: (2)

You're right John, it really doesn't make sense to me either, but that is what my gauge reads.

I have not verified with another gauge, that will be my next step.

I don't believe there is any restriction in my return line. With the engine running, my gauge reads 68psi regardless of load. Idle, WOT, etc. it's all a consistent reading.

Rick Speed

iTrader: (55)

Yeah fuel guage could be a pos. Restriction in return line possible. OR a crap set of filters.. I would make sure to get a wix filter because some of the others are junk.

LS1MCSS

iTrader: (18)

Sounds like a return restriction. Give us more info on the setup, things what like car, fuel tank, fuel pump, and line size.

flame

iTrader: (13)

What gauge are you using? I got one of the autometer electric senders and the underhood temp causes it to read high after heat soak.

Old Geezer

iTrader: (3)

It's possible that the line voltage to the pump is lower due to batt drain w/ KOEO, vs engine running and alt output being introduced.
Check the volts at the pump, batt, and with the engine running, check for alt output.
Volt drop tests are the correct way to do this. [Done on the + and - side.]

Also, if the gauge is one of the "silver dollar" sized gauges...That's where I'd start.

hoopty

I'm using a corvette fuel filter with built in regulator and mine reads around 68 psi all the time also. My engine runs fine. The engine is a 1999 LS1 installed into a 1991 mustang gt. The engine is bone stock. I ran a 3/8 steel line from the out put side of the filter to the engine. I would not worry about your a little higher than normal pressure. I also own a 2000 corvette and it has about the same pressure. It could be the difference is in the pressure gauge.

rao

iTrader: (18)

I have used the Corvette FPR (different brands) on several swaps and my fuel pressure was and is always 58 psi key on and 68 engine running.

John McGraw

I think the mis-understanding comes from the term key-on. The pump only runs for 3 seconds when the key is turned on, unless the engine rotates, so the pressure will drop a little after it turns off. There is no logical reason that the pressure will be less with the pump running and the engine not running. The pump does not know whether the engine is running or not. All it knows is whether it is powered, and if it is, the pressure should be the same whether the engine is running or not, if the pump is actually running. If you flick the switch off and back on, the pressure will come right back up for as long as the pump is running.


Regards, John McGraw

rao

iTrader: (18)

I think I have a pretty good idea of what it means to have the key on but I could be confused given the complexity of the key and the whole turning it part.

On my car when you turn the key on and the fuel pump primes, the fuel pressure at the rail is 58 psi, when the car is running the fuel pressure at the rail is 68 psi.

LS14fever

iTrader: (5)

Sorry to bring this back from the grave.
I have same exact problem prime at 58 psi & 66-67 psi Idle. My first regulator put me at 72!
Did u ever fix the problem mechanically?
Or did u tune it regardless?
One reason is my filter might too far from tank causing restrictions. (located firewall)

Project GatTagO

iTrader: (7)

Interesting. My car primes at 58 psi and doesn't move when the car starts. I monitor the fuel pressure with a auto meter gauge and an electronic sender. I am using an AC Delco filter/regulator.

Andrew

gagliano7

Everytime I checked mine it is always 58 when running.

garys 68

iTrader: (1)

No issues with mine either.
There's a cut up view of the vette regulator on one of the GTO forums. It's just a filter with spring on the return to control max pressure.
I guess it would be possible for a pump to overwhelm the capacity, but I think more likely it's a restriction in the return line. The bypass spring would just measure the pressure differential on each side. So a few lbs of restriction in the return somewhere will add that to the fuel rail.

LS14fever

iTrader: (5)

Yea pump might be overwhelming the regulator.
Don't know for sure tho.
Seems like a hit or miss.
Another possibility is I Might have hurt the internal
Regulator in the pump when I mixed the
Return and feed line causing
It to be stuck open.
Pump was also sitting to long.

Going to pull return line and prime fuel
See if I get 58psi when I get home in few days
Get to bottom of this.

Project GatTagO

iTrader: (7)

I am using a Walbro 255 pump. If you mixed up the inlet and return, that could have potentially hurt the part. I'd swap it out for a new AC Delco part and see what happens. They are cheap.

Andrew

LS14fever

iTrader: (5)

I did. Switch out for a wix.
I was talking about the
Internal regulator in the Walbro.