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Fuel pump advice anyone?


Hughieboy
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There's a great long post on here from me that Mr B and others have kindly been helping me with regarding some issues I've been having with my newly acquired Forester XT. So far I've had it for about 2 months and it has been nothing but expense, grief and trouble. Problem is, I'm so far in now I need to carry on!

In my endless quest to sort out a slight rough running/misfire issue (after replacing secondary air valves, pump, plugs, coil packs and fitting a new MAF sensor) I decided to fit a new fuel pump and ordered a Walbro GSS342 255lph model. I have just changed said pump but all is not at all well! Firstly, after fitting and going through the ECU relearn procedure I left the car ticking over for a while. The new fuel pump makes the most horrendous intermittent whining noise, almost sounds like someone repeatedly cranking an engine over. Really loud and awful sounding! So I took it for a spin and, hallelujah, if I'm not mistaken, no misfire/lumpy running anymore, it seems smooth....... until after a few miles and I put my foot down and just when I would expect it to 'take off' at about 4000 ish rpm it just hits a flat spot so my guess is it's not getting enough fuel....!?!

Can anyone tell me whether I've done something wrong or whether it is a faulty/rubbish pump? Obviously, as you do, after fitting it I have looked and found many people complaining about Walbro problems but I'm a newbie and I'm just following the herd. I'm starting to wish I'd never bought the damn thing, it's costing me a fortune. 

I'd welcome any advice before I just go out and put the old pump back on (which, incidentally was also a Walbro so it's obviously been changed before)

Many Thanks.

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Seems like you are in exactly the same boat as me. I also have an 06 xt and have spent a lot of money fixing suspension, brakes, bushes. I've come to the conclusion that I'm also so far in it the only thing left is to push on. Although I did buy the Subaru as a cheaper, more usable car than my Audi RS6. If anything it's been more expensive! 

I've accumulated parts for a service including plugs which I was hoping would solve my misfire/stuttering, but seeing as you have now replaced everything and still have the issue has left me slightly concerned that it's going to be another expensive job. 

And to make matters worse, I went out in it last night and noticed I now only have one headlight bulb working. So either the ballast is knackered or the bulb has blown.

i will be keeping an eye on this thread with interest. If I find a fix to my misfire I will let you know!

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I'm going out this morning to pull it off and refit again in case I've made some schoolboy error but I can't think what. Yes, sounds like the same boat. I sold a 5 year old Merc C220 that I'd had for three years thinking an older cheaper car might save me a few quid on finance etc but the Merc never missed a beat once! I thought being ten years old and Japanese it would be it good bet but so far it's been an expensive pain in the butt..... I do actually really like it but it's testing my patience (and finances) trying to get working properly. I'll report back, still hoping someone who's experienced this might comment...

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Using the new parts cannon technique is expensive ... Got be super fussy buying used turbo models, Subaru of this generation are above average in reliability so you guys been unlucky with what purchased .
I wouldn't use a 255lph pump on it (assume running standard boost and map), ideally want pick up an sti or 2008-2009 wrx oem pump . We don't use walbro full stop, use denso mostly or bosch .
You want get fuel pressure checked & see FPR (fuel Pressure regulator) is standard unit and working right. If has aftermarket FPR get an oem fitted .
Ideally these faults needs diagnosis, we can run pressure guage in fuel line and also use an oscilloscope on pump power supply so can see pump operation and motor health etc . Can use oscilloscope on ignition too to rule out or pin down fault .

 


 

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Morning Mr B..... You are right and I am going to have to stop doing it! It's just too tempting when there's info on the web and parts are available easily to just have a go and hope for the best. Interesting what you say about the Walbro pump, also the one that was already fitted was a Walbro. To be honest, I bought it because it's the most commonly available, I didn't really see anything else apart from cheapo's on eBay or expensive stuff from the specialist tuners. Do you think it sounds like this pump is faulty from what I have said? If so, I'm just going to go and out the old one back on, send it back and book the car in to a Local Subaru specialist as I'm starting to lose the will to live! ;-)

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I would be inclined pick up a used oem sti/wrx pump and confirm the FPR is standard as your last attempt and tidy up before handing it to specialist . Just no need for a 255lph pump and you better off with oem match/quality .
O2 readings etc should give someone idea/clues if fueling off, being intermittent stumble/miss possibly not but hopefully good visual inspection and diagnostics can pin something down . We got well over 20K in diagnostics kit, picoscope being one of our newer ones and it super useful, can pick out faulty commutator on a fuel pump motor for example in 5 minutes, intermittent stuff can still be pain but can't see it going be too much of a problem for Subaru specialist .
 

 

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I wish I were nearer to you Mr B and I would book it in! 

Ive just taken the new Walbro off and put the old Walbro back on..... haven't been for a run yet and expect I'll have the hesitation issues still (although I have stripped and cleaned the filter) but the horrible stop/start whining is gone so the new Walbro pump was obviously a dud so I'll send it back. I have no idea if it has had any kind of remap but I would doubt it as part from having been a bit neglected in some areas it looked totally standard, no sign of 'pimping' at all.... so I guess whoever fitted the last Walbro just fitted it as a replacement, not because of any tuning. As you suggest, I will look for a used STi/WRX pump and swap them over as a final tidy up before booking it in. Will it be a straight retro fit?

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The 255lph walbro does whine a bit, was old one same flow model ? Is a lot of china pumps out there ....
The earlier sti (pre 2008) or wrx (2008-2009 wrx is same pump as earlier sti) is easy swap, we used them few times as easy find a few low mile pumps pulled purely for tuning and they cheap grade A quality pumps .
 I would imagine your issue was more than one fault, hopefully some of new parts have helped and bit of diagnosis can finish it off .

 

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Yes, I think you're right. Not sure where I'll get a good used pump from though, probably no use looking at a breakers as there's no way of knowing if their stuff is any good. I'll have a hunt around the internet I guess. Thanks for your help.

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