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Mike, Mechanic
Category: Subaru
Satisfied Customers: 39198
Experience:  Hi, I have been a Car/vehicle mechanic 34 years. 29of -running my own repair/diagnostic business.
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I'm having a problem with my 2008 sti w/ walbro 255, fuel

Customer Question

hi I'm having a problem with my 2008 sti w/ walbro 255, fuel pump will not prime . car will not start. the fuel pump fuse blew, not the sbf no. 5 one that everyone talks about, the mini 15 amp, they are both located in the engine bay fuse box .
*installed gauges night prior and zip tied wires to be neat under dash. during install of the gauges i had a grounding issue / confirmed bad solder, connected with butt connectors / gauges worked and i drove the car home / following morning i had my father start the car , roughly 3 seconds later the car died , tried to start it again and i did not hear the pump prime and car would not start
- heres what I've done
* replaced mini 15 amp fuse / fuse will not blow again / pump still unresponsive
*replaced Fuel pump control unit with used FPC(maby try a brand new FPC unit?) / pump still unresponsive
*switched the fuel pump relay with a good relay / pump still unresponsive
*inspected wires on o2's / appear undamaged
*inspected wires on maf
Submitted: 1 year ago.
Category: Subaru
Expert:  Mike replied 1 year ago.

Hello and Welcome...

My name is ***** ***** Im glad to help.

Having read all through what you have outlined, the first thing to check is that you don't have an immobilser issue...for whatever reason.

If the car "starts" everytime - but cuts after the 3 secs - and you have indication of security system issue - then thats what it is... in which case, try a different key fob case its that.

If it is that - but not the fob, you have disturbed something with the wiring that will need checking through..

If you rule that out as above.. then the fuel relay is activated by the Ecu - computer... you will need best to check to see if the pump though is getting powered or not.. if it is.. you have a pump fault..which can have just happened out the does happen. If the pump is not being powered - back to the relay to check... ( Im not sure if your version has a fuel cut of switch - if so, check that )

Let me know how you go..and / or let me know if you need anything further on this..

~>>~~>>~ Meanwhile now - Please do click on the "Exc / Ok rating" for me at this time.. "Thank you" in advance for that .

.. Note that you can get back to me anytime at all after doing the rating - it doesn't close you out --

Best Rgds, MIKE

Customer: replied 1 year ago.
hi thanks for the reply.its not an immobilizer issue as the car will not start at all and fuel pump will not prime.
a. do you have a pin out for the fuel pump plug?
b. how do i test the fuel pump without removing it?
c. could it be the ecu relay its-self?The big hint here is that my mini 15 amp blew and now it will not blow again but the pump still does not work. So doesnt this mean i should be able to narrow it down to just a few things.
Expert:  Mike replied 1 year ago.

Hi again - thank you for your reply / message -

Im not so sure the "big hint" is the 15 amp fuse you refer too - what is that fuse for / which one is it -? you haven't stated.

You could have blown any fuse with the wiring as you had it --

Going back to testing for power to the pump you don't need a wire diagram for that - you have two thicker wires and either one or two thinner.. the thin are for the gauge so you are looking to power on one of the two thicker ones.. one is an earth / ground, one is power.. so check both - looking for power. If you have power on either one, you know the circuit is there - if on test you don't find power at all .. then you are back to the relay - ecu / circuit.

-- If as you say the fuel pump is not priming then yes as you say, that narrows it down to that circuit.

If you do not have power to the pump - AND you dont have power at the relay then you need to check the connections to the relay - and back to the "main relay"... and then , ECU.. the relay is actuated from the Ecu. Power comes from the main relay to the fuel pump control unit and then to the pump.

Let me know how you go -- but please I do click on the OK / Exc ratings for me at this point- Thank you..

Rgds, MIKE.

-- Again - you can come back to me anytime as you may need after. Thank you.