Hi guys, just got my project up and running but I think I have a problem with my fuel system. It's a cobra tank, fore 3 pump hat with 3 GT supercar pumps. 3 -6 lines out of hat to a 3-1 Y-block. -10 out of block to a fuel lab filter then -10 to a 2-1 Y-block with 2 -8 lines to each side of fore rails with 105#injectors. Problem is I have to cycle the key a couple times to build up pressure to start. Then when I shut key off it seems that all the fuel drains back out of the lines. It seems fuel pressure drops right off to 0 psi when key is turned off. I am also to believe that this is the cause of bank 1 O2 sensor staying at .8-.9 volts and not switching like bank 2 is. Also getting P1132 and P1138 codes for bank 1. Both upstream and downstream O2's have been replaced with ford parts. Wiring is all good. MAF is good. When it's running I show at least 50psi of fuel pressure on a manual gauage tapped into the drivers side bank 2 rail. FRP sensor reads 38-40psi on scan tool when running. Why am I showing 2 different readings from FRP sensor to manual guage? Is it normal to have a pressure drop like this with a build returnless system like this? Do I need to add a fuel pressure regulator or how do I stop the fuel pressure drop when key is turned off? Trying to get car ready for racing this weekend. Thanks guys!
returnless fuel system problem
- Thread starter fastlx1
- Start date
You will see a different reading from FRP and a manual gauge. That is normal.
And the fuel pressure drop when key is off is normal. You have removed the check valve in the tank with going to an aftermarket setup. So there is nothing there to hold the fuel in the line. You can buy an aftermarket one way check valve to put in the line if you want, but I wouldn't bother. There are adjustments in the tune to make starting easier. My last terminator had a setup very similar aside from different injectors and I never had to cycle the key. Started up like factory and I had no check valve.
The fuel pumps have a check in them sounds like you have a bad pump or a fuel leak . System should hold pressure for at least 5 min after you turn it off . If you have a fuel leak in the tank you won't see it . Also make sure you run it long enough to purge the air with a returnless system the air has to go through the injectors unless you bleed it at the rails.
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Some pumps will have a built in check valve. Otherwise you'll have to add a in-line check valve as close to the tank as possible like TURBO VNM stated. I had the same issue but my tuner just made it so the pumps stayed on during "key on" forever instead of the default "prime time." I just had to wait a couple seconds after key on before cranking. At first it was awkward but after a few days it became natural and I do it now with all my vehicles out of habit.
Key on - wait for gauges to sweep - ignite. Not that big of a deal.
Key on - wait for gauges to sweep - ignite. Not that big of a deal.
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So what pumps and setup are people running returnless to handle big power?
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