Fuel pump

[h4X6]

Hey guys

Think my fuel pump is on the way out. But was some other opinions.

At idle sometimes it sounds like "pew. Pew pew. Pew. " and my fuel ratio would go down. But at cruise and boost all is well. Perfect across the board.

My tank is just under a 1/4. Maybe the pump doesn't like low fuel?

Thoughts?




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[Skym]

Sounds like clogged o2 sensor if running rich for too long.

Depending on where fuel pump is mounted on mounting bracket, might pickup up the fumes / gasses above fuel (should vent these gasses to carbon canister next to airbox, which then filters the gasses and then what's left over gets sent to engine which is burnt off. Basically an emissions device). That would mean no fuel through fuel pump that helps to cool, lube fuel pump (fuel pump overheats and fails).

If fuel tank is low enough it might pickup the crap on bottom of fuel tank and that might block fuel filter in engine bay or sock filter in fuel tank. The stock steel fuel tank is known to rust internally.

Also sometimes it's a wiring problem to fuel pump.

To check for failing fuel pump, blocked fuel filter, check fuel pressure via fuel pressure gauge inbetween fuel filter, fuel rail. While engine is idling, should be 35.5psi with vacuum hose to FPR connected and 7.1psi higher when pull off vacuum hose to FPR (block nipple on intake plenum, so there's no intake airleak).

[Dragon Humper]

By "goes down" do you mean the AFR goes rich or lean? I'm thinking rich if you are just looking at the #s on the guage. That wouldn't be a bad pump or wiring. Like Skym said, change the O2s if they haven't been done in a while. I get a pew, pew noise too, just thought it was the check valves and other extra stuff in there that isn't normally in a tank (pumps have some sort of check valve/pressure regulator? on them too). Both my pumps do it, one has the check valve-ish looking thing, the other doesn't. Both feed through the main check valve.



Jon.

[h4X6]

Sorry by down I meant lean.

At times it would idle at 17-18.

Sock is good. Wiring is good. All checked about 3 weeks ago. Its a walboro255 is that matters any.

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[Skym]

Then fuel pressure should be higher, into low 40's with 255 Walbro, stock FPR.

Check for intake manifold airleak (blown gasket's). If there is a intake manifold airleak rpm needle usually bounces up and down (caused by o2 sensor, ECU reacting to engine running lean).

Also check for exhaust leaks (can produce a 17.0:1 A/F ratio), especially if engine has been retuned.

Does fuel pump make a strange whinning noise??? I remember seeing a videoclip of that happening when running fuel tank low with a Walbro fuel pump.

[h4X6]

No leaks.

As for sounds like I said it sounds like a pew pew pew. But it's intermittent. Doesn't do it all the time.

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[Dragon Humper]

Yup, sounds like mine. If it was going that lean at idle the engine would be pretty grumpy and stumbling a lot. Could be the low voltage at idle thing that skylines do might be dropping the flow too much with the wally, doesn't sound common though.





Jon.

[h4X6]

it cant be voltage, its hard wired to the battery. none of the stock wiring is used other then to turn the pump on and off.

[gtrjon]

It honestly could be not picking up enough fuel at idle and the pump sucking up a few air bubbles. Especially if the walbro sits higher up in the cradle. Try topping it up with gas

[Dragon Humper]

My pumps pickups are right on the tank floor and I currently have 1/3 of a tank. If it was an air suction issue it would be much worse driving around than sitting. If your pump is hotwired, it's time to start troubleshooting some electrical. Test your vacuum when it goes lean, it should drop as you go from stoich to lean on your WB, then you will know for sure if you are actually going lean.

Maybe this is a normal thing for those pumps with the little canister thingy on the top of the stock pump. Then you would only hear it below about a third of a tank. Mine is exposed right now.

Jon.