nickmears

own a wrx import 94. recently had trouble with it non starting . the noise from the fuel pump could not be heard . so checked relay and fuses, all ok , checked voltage at the end of the connector and that was 12v, fine. so thought it may be pump, wired it straight to battery, and was working fine. then i thought it may be the plastic connection the harness cable connects to outside the tank and the pump and sender are connected to inside the tank (situated in the cover) so connected battery up to top of this connection where it would connect to wiring harness and the whole assembly worked fine . so if im getting 12v for 2 seconds when relay switches on from the battery which is what i would expect ,and from where it is connects to onwards seems to be working then by rights it should all work when i connect the harness up. but NO!!!! it wont pump. is there some kind of ground that could be faulty???? help would be much appreciated asap. thanks

mart360

fuel pump dosent run until engine starts!!!

if i recall it works like this...

ignition on,

fuel pump initialises (2 secs whine) this pressurises the pump ready for action

ecu interrogates,

alarm / immobiliser

crank sensor

cam sensor

and various other inhibit sensors

then and only then will the ecu trigger the +12v for the ignition circuit

when the ecu detects returns from the sensors, the fuel pump then energises and starts pumping.

check ignitor pack & coils

if i recall there is a check you can do, that if the engine turns over and the injectors click its not the fuel circuit, its the ignition side, but i,d need to dig out the article to confirm

Mart

nickmears

the spark plugs havent long been changed so cant be them could be coil packs though is suppose someones gonna have a look tommorow as im lost
thanks and ill hopefully find out what the problem is tomorrow!!

nickmears

the spark plugs havent long been changed so cant be them could be coil packs though i suppose someones gonna have a look tommorow as im lost
thanks and ill hopefully find out what the problem is tomorrow!!

raysubgrt

hello there i had the same problem on my legacy it was the socket under the back seats causing problems then on my impreza found that under the steering wheel on the inside footwell there are 3 no relays and i beleave one is for the fuel pump hope this helps ray

nickmears

the socket seems to be working as i have tested both ends of it and relay is clicking on and off and iam getting 12v through the other end of the connection for a couple of seconds while the relay switches on to prime the fuel pump, then goes to 0v when relay clicks off as it should do. its a weird one!!!

esp ltd

iTrader: (1)

I had this problem on a Type R Impreza a few months ago, it turned out to be a damaged wire case under the rear passenger seat base. What happens is that the white plastic clip that links the loom to the fuel pump can come unstuck from the floor (should be taped down flat) when the seat is removed for the fitting of foglight wires or stereo cables. If it isn't put back properly it can become damaged when people sit on the seat and the wires can actually short out causing power failiure or reduced power so it'll show voltage at the pump but not enough to actually spin it........defo worth a look!!
Dave.

David_Wallis

if the fuel pump is running for a couple of secs, then the relay is fine and the wiring and the pump is fine.

David

nickmears

recently had me rear shocks done so wires could have got trapped when back seat re-installed. ill have a look tonight. as for the pump switching on for 2 seconds (dave), it doesnt when plugged in to connection, but does if i connect whole assembly straight to battery!!!!!!

MickWrx

I had this intermitent problem with my 94 WRX, pump suddenly stopped working, the last time it did, it cost me £100 to get the car towed home.

I did all the test on the circuit in and out of the plug (under the rear seat) and no power ? pulled the hose off from the fuel filter to visually see if i was getting any fuel feed and nothing.

The very next day, turned on the ignition and low and behold fuel pouring out of the tube, put it all back together,and no problems, however, 6 weeks later same thing again, but never fixed itself.

Local Subaru Garage told me it is a fault with the ECU and although normally reset themselves, but once its started to fail, will intermitently on a regular basis.

I can only speak from my own experiance on this, having spent days under the bonnet and seats chasing wires down the side of the car only find they change colour in and out of the different plugs right to the ecu, I eventually put my own fix in place to cure this once and for all.

David_Wallis

when you connect a positive and negative to the fuel pump it only runs for 2 secs, or when you connect a new 12v feed??

If when its just a 12v feed, its either immobiliser or fuse as the ECU switches the ground wire

David

Shark Man

Remember you can see 12volts on a wire with no load, but if it's a bad connection with a high resistance, it can still show 12volts with no load across it, but as soon as you connect a load it will drop to zero.

Worth bearing in mind when prodding about with the multimeter

And btw, it should be 13ish volts...charge up your battery or your immobilser will start to throw hissy fits

nickmears

problem solved!!!!!! turned out to be a faulty wire under back seat!!!
someone had put a junction box in for some unknown reason and i was getting power though one side but not the other (under load showing nothing) cut wire going though connection and soldered it together and that solved it!!! happy days

esp ltd

iTrader: (1)

Does that mean i was correct??
Dave.

nickmears

yes mate. thanx for the tip!!! at first the mechanic tried tellin me it was the relay!! it was only when i showed him what you had suggested that we found the problem!!! thanks again and i think ill have to come on here more often if my car starts playin up again!!! cheers dave

esp ltd

iTrader: (1)

No worries matey.......and i'm a Jap car dealer so we aint all that bad eh . Glad she's running well without spending too much!!
Dave.