13 replies to this topic

[Chadza]

Hey guys, How ironic I now have fuel leak issues after posting in another thread about their leaks! In the past week my very minor fuel leak has grown into a more major one. The car still runs fine, but whenever the car is stationary (ie no airflow going through the engine bay) the fuel smell is almost overpowering. Sure enough the leak is coming from around the fuel pressure regulator. Now the rubber hose that leads FROM the regulator to the drivers side fuel rail looks quite perished and is leaking at the clamp join, but the regulator also seems to be leaking from the brass screw where the fuel line goes INTO the regulator from the fuel tank. This is very similar to what happened last time when the subaru mechanics said the regulator had failed internally. I ended up getting a second hand regulator from a Subaru wreckers over here and it looked to be in good condition and did not leak when first installed. Now 9 months later I have a rapidly increasing leak. I have read on some wrx forums that the Walbro 255L fuel pump has a history of causing Subaru FPR's to fail due to an increase in pressure supplied. Is this plausible? Initially I was under the impression that it is just a higher flow rate pump, but to get a higher flow with the same plumbing to the engine I suppose you need to increase pressure..... So, a secondary question...if I go through all the trouble of having to take the manifold off to get to the regulator, am I better off just going an aftermarket regulator? Will the ECU need a retune to compensate or are these aftermarket regulators able to be adjusted manually?

[skillionaire]

Hi, I'm not completely sure why you'd upgrade the fuel pump without upgrading the FPR in the first place? Cheers, Nik

[alexGT]

i've had walbro on two different turbo subaru's now with stock FPR and they have been fine. unless the b4 model has issues?

[buzzda]

Havn't had any prob with mine, but (walbro) has only been there since september.

[skillionaire]

Hi, What's the point of an uprated fuel pump if you don't uprate the fpr? Cheers, Nik

[Chadza]

Nik, I think the problem with the B4's fuel system is the standard pump doesn't flow a lot, so you max out the pump before anything else. Stock is 160L/hr. This is from a Subaru guru Shane from S & J in Adelaide. I dont have a lot of experience with regulators though so if youd care to expand on why the FPR needs upgrading as well?

[skillionaire]

Hi, Well as far as I can tell, the regulator becomes the governing factor over the flow. So you could have capacity to push 500l/h if you'd like, but if the FPR isn't equipped/set to the correct flow then it wouldn't really make a difference? Just so you know, I am not a MechHead and am only going by personal logic. Cheers, Nik

[alexGT]

you don't need to increase fuel pressure, you need to maintain fuel pressure. more boost = more fuel. you want to maintain fuel pressure at those higher flows hence the need for bigger pump. increasing fuel pressure is the next step above that... my car has decent sized turbo on it running 18psi with stock rails, stock fpr and injectors. so you need to be talking pretty big power to do this.

[alexGT]

Hi,

Well as far as I can tell, the regulator becomes the governing factor over the flow. So you could have capacity to push 500l/h if you'd like, but if the FPR isn't equipped/set to the correct flow then it wouldn't really make a difference?

Just so you know, I am not a MechHead and am only going by personal logic.

Cheers,
Nik

i think the reasoning is the stock FPR can still flow a bit more fuel before it needs to be replaced... depending on whats happening with the vacuum in the motor. if the FPR is struggling to maintain pressure it will close off the return line to build it up and wait till the fuel pump catches up.

[Chadza]

Thanks for those replies so far guys, it seems like the subject of FPR's is an area where we need some more education! I just found this over on perthwrx and i realise now I had no idea how FPR's work! The regulator is almost at the end of the fuel journey, not at the start. I highly recommend everyone reads this- http://members.iinet... Regulators.pdf I know think subaru might have been giving me a bum steer before (or there was a 10% chance the regulator was actually busted) and it looks like it may just be the injector return hose that needs replacing. I should be able to gain access to this after removing the A/C compressor.

[XXB4XX]

Melpassi fuel reg = win

[B4TT]

Interesting. Anyone replace just the fuel pump and notice a difference to the way their car drove immediately?

[XXB4XX]

Interesting.

Anyone replace just the fuel pump and notice a difference to the way their car drove immediately?

I remember when Kosti put his in.. without any engine fuel mods, it kinda didn't do much apart from make noise..

without good fuel regs / injectors / rails, the difference wouldn't be that much.. as you still have the same garden hose nozzle but connected to a fire hydrant... (hence the leaks from increased pressure in the hoses..

[alexGT]

Interesting.

Anyone replace just the fuel pump and notice a difference to the way their car drove immediately?

won't notice the difference. apart from noise but my walbro i can't hear at all