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Weird Fuel Issue...need Some Insight

Simon-S14

By Simon-S14,
in Engines & Forced Induction

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Simon-S14 Grand Master

Simon-S14

Posted
Posted

My gf just got a stock as a rock r32 with an un modded rb20det. There has been some bad hesitation issues that i pin pointed to be a failing pump. i pulled the feed line off the fuel rail and put it into a container... in 30 seconds ti had only half filled a 600ml bottle... not enough flow at all. Put the feed back off and pulled the return line off the rail and nothing came out at all... fuel was going into the rail but not coming out.... this had me stumped but i figured the pump didnt have enough pressure to push it round the rail.

So i took the pump out and its got a walbro in there, The tank however is rusting for some reason and the walbro filter was chockers full of brown crap... so cleaned the tank out best i could, chucked another fuel pump in primed the lines and what do ya know, heaps of fuel pressure in the feed line... thought i'd pull the return line off and see how much was flowing through.. and nothing! nothing coming out at all! hmmm tad weird i thought. I checked with my car (r32 w/ 25det in it) pulled the return line off and sure enough it pours out.. just as i thought it should.

so i replaced the rail in the missus car, thinking the FPR might be stuffed, replaced injectors while i was at it with some known good ones, put it all back together and it was doing the exact same thing... started it up anyway and took it for a drive and now the car drives fine... no hesitation or stumbling like it had with the dying pump.

havent pulled the return line off again.. but can anyone explain whats going on here?

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BHDave Grand Master

BHDave

Posted
Posted (edited)

It may be worth while checking the return line for blockages.

If the tank is full of rust, there's a fair chance the return line has some gunk in it too.

It's a bit odd that the reg isn't opening as that implies that the rail is only just getting about 40psi to it. check the fuel pressure i suppose. The in tank filter may be clogging up pretty quick creaking a blockage that way. I had a mate with a similar problem until he went back to a genuine nissan in tank sock.

Edited by BHDave
Omurru Veteran

Omurru

Posted
Posted

sounds like a dodgey fpr to me, take it of the end of the rail and see if fuel comes out when you prime it, don't start the car with no reg though. Although if the pump isn't flowing much fuel the regs not gonna let much fuel through in an attempt to maintain pressure. in any case if you reckon the tanks rusting on the inside time for a new tank and probably pump as well as the pumps gonna have eaten a fair bit of crap....

Simon-S14 Grand Master

Simon-S14

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in tank filter was replaced when i put a new pump in it, as was the engine bay filter, with pump out and lines off motor i blew both lines out with an air compressor, no blockages there. cant be a blockage in the fuel rail either... have swapped it over.

without testing what the fuel pressure is i cant tell you an exact figure... but theres a hell of a lot more pressure in the feed line then there was with the dying pump.

new tank coming soon, hard to find one here tho, no importers have any

abu Grand Master

abu

Posted
Posted (edited)

Similar sort of issue with my car when I got it.

Mine was pining, replaced the fuel pump with a GTR one, ran a bit better, but still pinged on boost, in the higher revs with a bit of load.

Checked all the lines, there was no leaks that I could see..

Few days later I could smell fuel fumes in the cabin, checked the line and realised that there was a slight split in the return hose, off the fuel tank side (off the cradle that the pump sits on). I left it and didnt do anything, ping slowly got worse and lower into the RPM range, and the fuel return line split and started leaking fuel.

Replaced the return fuel line and it now runs mint, no ping at all.. Cant really get my head around how a split in the return line, no leaking any fuel just pressue? can cause ping. But my theory was it wasnt holding enough pressure (air pressure) in the rail to keep it feeding enough fuel?

Anyways, I sugguest you check your fuel return lines under the car, maybe be worn and split?

Edited by abu
BHDave Grand Master

BHDave

Posted
Posted

The non genuine filters were clogging up over the course of a few days, so the car just ran worse and worse.

We pulled the tank off and cleaned it and swapped the filter and it made no difference, it died in the arse after 3 days. The next weekend he put a genuine filter on and no more problems.

abu Grand Master

abu

Posted
Posted
The non genuine filters were clogging up over the course of a few days, so the car just ran worse and worse.

We pulled the tank off and cleaned it and swapped the filter and it made no difference, it died in the arse after 3 days. The next weekend he put a genuine filter on and no more problems.

Fuel filter?

QWK32 Veteran

QWK32

Posted
Posted

when you say you take the lines off to see how much fuel comes out, are you keeping the fuel pump running by directly powering it or something? i just thought that the pumps primed for about 5 seconds and shut back off again when your switch key to on???

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