Why does my FP gauge sometimes read 50psi?
06-30-2003, 02:50 PM
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Why does my FP gauge sometimes read 50psi? I finally got the damn adapter to hook up my Autometer FP gauge. Most times it reads around 61psi, but on the highway yesterday, it would sometimes drop and stay around 51psi. The A/F guage still read normally and the car acted exactly the same. Is this an electrical glitch or something that the LS1s actually do?
06-30-2003, 05:09 PM
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Re: Why does my FP gauge sometimes read 50psi? Just cruising... Just kind of looked at it after a while and saw that it was at 50psi. I thought I was going crazy because I could have sworn that it was at 60psi. Sure enough, after I stopped at a rest stop, it was back to 60psi again. It happened one last time before the end of the 400mile trip too.
06-30-2003, 05:43 PM
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Re: Why does my FP gauge sometimes read 50psi? My stock FB would read 60 at idle but at WOT, I'd see it drop to around 55 and stay there. Just installed a larger FP and I still see the same thing??
Common for a returnless fuel system?
Mark
Common for a returnless fuel system?
Mark
06-30-2003, 10:33 PM
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Re: Why does my FP gauge sometimes read 50psi? I would say no....thats not normal even for a returnless....
at WOT....the fuel pressure should drop at first (sudden load increase). But after a second or so, the pressure regulator should realize "hey...they are pulling more fuel (low pressure)" and lock down. The fuel flow will stabalize (5000RPM take "X" amount of fuel) and the pressure should return to 60.
Either the fuel lines are too restrictive (hard to believe) or the pump is not providing enough flow. If you have a stock pump, there is your problem. If you have a Walbro (or other aftermarket), did you change the power wire to something larger? The factory wire is undersized for the required current flow.
at WOT....the fuel pressure should drop at first (sudden load increase). But after a second or so, the pressure regulator should realize "hey...they are pulling more fuel (low pressure)" and lock down. The fuel flow will stabalize (5000RPM take "X" amount of fuel) and the pressure should return to 60.
Either the fuel lines are too restrictive (hard to believe) or the pump is not providing enough flow. If you have a stock pump, there is your problem. If you have a Walbro (or other aftermarket), did you change the power wire to something larger? The factory wire is undersized for the required current flow.
07-01-2003, 06:45 AM
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Re: Why does my FP gauge sometimes read 50psi? How far back should you change the factory wire? I have a heavy gauge wire tapped directly off my battery that runs to the back just near the stock fuel Relay Box. I have a Bosch Relay there and have my Walbro's stock wiring connected to the relay. When I turn the key on to my car the old Gray FP Power wire energizes the relay and allows current from that heavy gauge wire to flow thru the Relay and to the walbro. I had considered replacing the smaller gauge wire from the relay to the top of the pump but figured it would be silly to stop there when inside the wiring is still small gauge. I figure just running the dedicated Line to the Bosch relay has got to be worth something though.. At least it's not being routed thru fifteen different wiring harnesses and factory relays.. It's a straight shot.
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07-01-2003, 10:30 AM
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Re: Why does my FP gauge sometimes read 50psi? Stalker.....I would think your setup is fine. A little section of "small" wire should not cause any problem. The problem comes from having that really long length small power wire running all the way from the factory relay back to the tank.
Sparky.....what Stalker did is the generally accepted way to rewire the fuel systems power.
Sparky.....what Stalker did is the generally accepted way to rewire the fuel systems power.
07-01-2003, 09:10 PM
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Re: Why does my FP gauge sometimes read 50psi? Stalker, opps, sorry, got confused with who posted what. Are you not seeing the fuel pressure drop on your gauge as described?
Mark
Mark
07-06-2003, 08:14 PM
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Re: Why does my FP gauge sometimes read 50psi? OK, yesterday it started to go nuts for a while. I'm thinking it is an electrical issue because it would go from 60 to 0 back to 60 to 0, etc. until I shut it off and back on. Then it acted normally. 
07-07-2003, 10:33 PM
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Re: Why does my FP gauge sometimes read 50psi? It could be water/moisture in the the electrical sending unit box. Water on the circuit board will cause erratic readings....
07-08-2003, 08:00 AM
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Re: Why does my FP gauge sometimes read 50psi?
It could be water/moisture in the the electrical sending unit box. Water on the circuit board will cause erratic readings....
