Help Losing Fuel Pressure - Subaru WRX Forum
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post #1 of 19 Old 02-12-2009, 05:32 AM Thread Starter
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Exclamation Help Losing Fuel Pressure

I have an 2002 wrx with 94k miles..the problem started when it was bone stock around 83k..I am losing Fuel pressure under a load..at idle im getting 45-48..but when its under a load it drops to 17-20..i have replaced the fuel pump,fuel filter(Every8-10kmiles),switched out the fuel controller with another wrx of the same year,checked the fuel pressure regulator and its fine..im not leaking gas..just have the usual winter gas smell when i first start it .i have talked to several subie dealers,and several independent mechanics,and i have 2 out of 2.5 in the auto tech program,and i have had some of the instructors opinions..and i cannot find any answers.. Please help its driving me crazy.
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post #2 of 19 Old 02-12-2009, 10:00 AM
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wow...ive never heard of something like this...does it gradually drop off or just all of the sudden as soon as you put it under load

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post #3 of 19 Old 02-12-2009, 04:01 PM Thread Starter
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its not an instant drop off but it goes from 45ish to 17ish in about a second..maybe less..the thing thats throwing me loops is it only does this for a while then it will go away for a month or more then it comes back..idk..i have cleaned the screen going to the fuel pump twice now..and i have looked at everything i could possibly think of..even little things that really doesn't have that much to do with fuel pressure..and when it loses FP of course its going to retard the timing a little bit..so its not burning all the fuel and its puffin black smoke from the unburned fuel and sometimes the black smoke turns into beautiful flames..lol.last night i was going down the road and it started doing it and i just happened to look in my driver side mirror and it was shooting flames so big it was flashing and lighting darkness behind my car.it first started when i got gas at a cheaper gas station, and i thought it was water in the gas or bad gas..so i drained it out..that didn't work so i took it to hickory and put $40 worth of 100 octaine it it..it was like 7 or 8 $'s a gallon.still didnt fix it.. i went and talked to one of my automotive instructors today and he told me that my car was a "Rolling Mind####"..lol. because it f's with your mind so much..lol.if anybody has any clue's as to what it is or what it could be-please let me know
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post #4 of 19 Old 02-12-2009, 09:50 PM
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have you checked the fuel pump...or the circuitry...it sounds like the pump may be wearing out...or some thing is causing the pump to not be able to flow enough fuel

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post #5 of 19 Old 02-13-2009, 12:39 AM Thread Starter
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i replaced the stock one with another stock one..and it still done it..so i have a spare one for sale..it only has 1000-1500 miles on it..now i have a walbro 255..and its still doing it..with the stock one the car sounds like it cuts off..but with the walbro it just bucks/backfires/burns rich..i used an ohm meter and my friend road in the back and checked the connector while i was going down the road and its getting good steady voltage..and its got good grounds..plus like i said before i switched out the fuel controller and it still done it..thats where the pump gets the power and what tells it what to do..so F if i know..
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post #6 of 19 Old 02-13-2009, 12:50 AM
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maybe you should change your injectors. is your car stock now??
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post #7 of 19 Old 02-13-2009, 10:49 AM
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Quote:
Originally Posted by dubrex2002 View Post
I have an 2002 wrx with 94k miles..the problem started when it was bone stock around 83k..I am losing Fuel pressure under a load..at idle im getting 45-48.
At idle you should see only around 38 psi with the vacuum line on and 43.5 psi with the vacuum line off.Check the vacuum line for the FPR.It may need to be replaced if it is hard and not sealing.Under boost the manifold has positive pressure so any bad lines can get blown off or leak.For every 1psi boost the fuel pressure should raise 1 psi to compensate for manifold pressure.At boost thresh hold (0 vacuum/0boost) you will have 43.5 psi so if you have 10psi boost pressure your fuel presure should be 53.5psi.If you have access to a Tactrix cable you can datalog the car for better info

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post #8 of 19 Old 02-13-2009, 02:22 PM
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here's a curveball.......

well how about a tune? dont you have to tune after fuel pump upgrade? or is it just the fuel injectors?

although you said it was doing it while stock

rollin on 17's now and they're dirty
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post #9 of 19 Old 02-13-2009, 04:37 PM
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Originally Posted by baller_v24 View Post
here's a curveball.......

well how about a tune? dont you have to tune after fuel pump upgrade? or is it just the fuel injectors?

although you said it was doing it while stock
You do not have to tune for a fuel pump.Fuel injectors control the amount of fuel,not the fuel pump.

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post #10 of 19 Old 02-15-2009, 01:43 AM Thread Starter
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i will check on that line asap..but at idle im getting 45psi..
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post #11 of 19 Old 02-15-2009, 09:17 AM
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Sounds like the FP is failing to me.

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post #12 of 19 Old 02-15-2009, 02:59 PM Thread Starter
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but its had 2 stock fuel pumps..and now it has a walboro 255,and i have switched the fuel controller with another car that runs fine..
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post #13 of 19 Old 02-15-2009, 07:27 PM
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does your car do this no matter what level your fuel tank is at? what does the sock look like in your fuel tank? just some ideas for ya
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post #14 of 19 Old 02-16-2009, 03:38 AM Thread Starter
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it does it at all levels..ive taken it out and cleaned it several times with throttle body cleaner..and when its not backfiring and losing a shitload of fuel pressure it just feels like its leaning out..but when it feels like that its only losing 5-10 psi of fp..and i put another hose on the FPR to the intakemanifold today..and its still doing it..the stock one was getting a little hard..it was also hard to pull it off of the FPR..but came off the intake manifold really easy..i might just try to switch my FPR with another 02wrx and see what happens..i mean it couldn't hurt to try it.
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post #15 of 19 Old 02-16-2009, 01:13 PM
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didnt you alredy try another FPR?
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