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Old 06-01-2012, 11:24 PM   #1 (permalink)
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Default Does 2003 Outback H6 fuel pump prime when key os turned on?

!!!traveling out of town with limited tools and resources and my 03 OB Sedan won't start.

on older subarus the fuel pump turns on for a second when the key is turned on (key on but not starting engine).

is this the case of newer ones too?

my daily driver quit and i believe its the fuel pump. when key is turned on there is no gas, when attempting to start some gas comes out....not sure if its enough but looks like not enough.
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Old 06-01-2012, 11:53 PM   #2 (permalink)
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No distinction between priming & pumping actions in a self-priming pump. The electric motor powering it just runs based on A) ignition power on and B) duty cycle dictated by ECU. I *think* the ECU just runs it for a few seconds at power-up no matter what. I can't back that up with documentation but by observation of many Subarus I'm confident in that understanding.

Since the overall fuel pressure is always regulated by a spring valve, any fuel beyond what is required is just sent back to the tank via return line.

Read another way: The Subaru fuel pump does not stop automatically when there is enough fuel pressure- it always overshoots the goal. The autopilot is blind and guesses how much it should run the pump by dead reckoning. Applied to a diagnostic, that thing ought to be blasting gas out for a few seconds and then powering down for a bit. "some gas comes out" doesn't sound like the right description.
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Old 06-02-2012, 12:21 AM   #3 (permalink)
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maybe this;

Symptoms of fuel pump O-ring problem?
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Old 06-02-2012, 12:48 AM   #4 (permalink)
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I understand how the fuel system works, not interested in anything but answering *one* question, I'm traveling out of state.

please ignore my use of the word "prime", that is semantics.

on Subarus of the past few decades, when the key is turned ON (without starting the engine) - the fuel pump runs for a second. many call it "priming", but i don't care what you call it my question is:

**** Is my 2003 Outback Sedan H6 is the same as other Subaru's of prior years in this regard. I assume it is...as it sounds like you surmise - But i'm at the point where I need to know for sure. ***
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Old 06-02-2012, 01:13 AM   #5 (permalink)
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Originally Posted by grossgary View Post
I understand how the fuel system works, not interested in anything but answering *one* question, I'm traveling out of state.

please ignore my use of the word "prime", that is semantics.

on Subarus of the past few decades, when the key is turned ON (without starting the engine) - the fuel pump runs for a second. many call it "priming", but i don't care what you call it my question is:

**** Is my 2003 Outback Sedan H6 is the same as other Subaru's of prior years in this regard. I assume it is...as it sounds like you surmise - But i'm at the point where I need to know for sure. ***
all i can tell you is, I know of no reason it wouldn't be 'the same' as other FI soobs, or similar vehicles. I will go in the garage and try to listen for my pump. (I have never heard it - but I never had a reason to listen for it.)

As for what's wrong, a 'little' fuel coming out seems to indicate the fuse/relay/pump are working at some level. So, either the pump is receiving less power, has a rstriction or is leaking fuel (internally in the tank - like the o-ring or externally such that you only see a little fuel.)
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Old 06-02-2012, 01:18 AM   #6 (permalink)
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OK - I can hear it hum/buzz for approx. 2 to 2.5 seconds each time I cycle from acc to 'on'. It was easier to hear with the pass rear window down. I suspect it might be easier if I had lifted the rear seat, like preparing to fold the rear seats flat.

I assume the sedan has the same fuel set-up as our wagon.

hope this helps.
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Old 06-02-2012, 02:03 AM   #7 (permalink)
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OK - I can hear it hum/buzz for approx. 2 to 2.5 seconds each time I cycle from acc to 'on'.
great, thanks for verifying that, big help!

i pulled the fuel pump and like you said - it's that oring and the cap that's the problem.

finding that oring tomorrow morning, that should prove interesting.

thanks again - i'm traveling and have limited resources, tools, etc....not too mention i want to get back on the road tomorrow morning.
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Old 06-02-2012, 02:12 AM   #8 (permalink)
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great, thanks for verifying that, big help!

i pulled the fuel pump and like you said - it's that oring and the cap that's the problem.

finding that oring tomorrow morning, that should prove interesting.

thanks again - i'm traveling and have limited resources, tools, etc....not too mention i want to get back on the road tomorrow morning.
dammit - this happening way too often.

be VERY careful replacing that cap - some of them (as you've probably read) have a cracked tab. There's a some thought that the cap fails, allowing the old o-ring to poke out - not a failed o-ring.

maybe post your present location in case some helpful member here lives nearby, or knows of helpful mechanics - location of junkyards, etc.

good luck buddy!
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Old 06-02-2012, 02:32 AM   #9 (permalink)
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indeed one of the tabs is cracked, not all the way and it still installs tight. i'll reuse the cap for now with a new oring, get home and then source another pump assembly to pilfer a cap from (well, a couple since i'll be doing this preventatively to our other H6 OB.

the NAPA site suggests they don't have it in stock...but advance auto parts says they do...though they're oring computer supplies aren't usually accurate - it's a poke around and see kind of thing. so - i'm not sure how parts will shake out tomorrow.

i'm between westminster, MD and Hanover, PA.
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Old 06-02-2012, 03:03 AM   #10 (permalink)
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Originally Posted by grossgary View Post
indeed one of the tabs is cracked, not all the way and it still installs tight. i'll reuse the cap for now with a new oring, get home and then source another pump assembly to pilfer a cap from (well, a couple since i'll be doing this preventatively to our other H6 OB.

the NAPA site suggests they don't have it in stock...but advance auto parts says they do...though they're oring computer supplies aren't usually accurate - it's a poke around and see kind of thing. so - i'm not sure how parts will shake out tomorrow.

i'm between westminster, MD and Hanover, PA.

Ace hardware might be a source. Dunno how long their o-ring will last in gasoline, but the metric o-ring I got from them for my power steering air leak is still holding. just fyi
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