Help with fuel pressure question. 2003 V6 - Toyota 4Runner Forum

CarlosV · 06-27-2022, 11:57 PM

I am trying to figure out why recently I get occasional longer cranking times.

The fuel pressure goes to “0” inmediatly after turning off the engine. (Running is at 40-41psi.) Is this definitely abnormal? No obvious leak…

Thanks

4r-4ever · 06-28-2022, 09:37 AM

looks like your fuel pump is on it's way out. fuel pressure should slowly decrease.

Quote:

Originally Posted by CarlosV

I am trying to figure out why recently I get occasional longer cranking times.

The fuel pressure goes to “0” inmediatly after turning off the engine. (Running is at 40-41psi.) Is this definitely abnormal? No obvious leak…

Thanks

BlackWorksInc · 06-28-2022, 11:31 AM

You likely have a bad fuel pressure regulator allowing pressure to just blow out the return line (or a faulty pump doing the same).

The pressure regulator should be easy to test, just block off the return line and do a fuel pressure test, if it's still dropping to zero then it's probably back feeding through the fuel pump.

CarlosV · 06-28-2022, 08:40 PM

Quote:

Originally Posted by 4r-4ever

looks like your fuel pump is on it's way out. fuel pressure should slowly decrease.

Thanks 4r. What in the pump will not hold pressure, when the car&pump is off?

CarlosV · 06-28-2022, 08:44 PM

Quote:

Originally Posted by BlackWorksInc

You likely have a bad fuel pressure regulator allowing pressure to just blow out the return line (or a faulty pump doing the same).

The pressure regulator should be easy to test, just block off the return line and do a fuel pressure test, if it's still dropping to zero then it's probably back feeding through the fuel pump.

Thanks BWInc. Will check pressure regulator.
Back feeding thru the pump back into the tank?

CarlosV · 09-22-2022, 10:13 PM

Quote:

Originally Posted by BlackWorksInc

You likely have a bad fuel pressure regulator allowing pressure to just blow out the return line (or a faulty pump doing the same).

The pressure regulator should be easy to test, just block off the return line and do a fuel pressure test, if it's still dropping to zero then it's probably back feeding through the fuel pump.

Thanks a lot BlackWorksInc. You were right. Changed the new Denso pump (it may well be a fake Denso even it looks very well constructed, like OEM) back to my original OEM pump after putting a new pump motor on it and that was the end of immediate zero pressure after turn off and no more occasional long cranks.

Question: problem in the pump allowing return into the tank is more likely localize at the junction of the pump and the plastic carcass where fuel line takes off? O-ring?
Thanks again.

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