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 Post subject: Re: Fuel pump causing ignition issues
PostPosted: Mon Jun 19, 2017 12:49 am 
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I Say: Car mods are like OddBodz, you got to collect them all! -------------------------------------
Vehicle: MY05 STi swapped sled

Posts: 17762
Location: Spearwood Perth WA
One thing that would be good to look at is the connectors at the fuel pump circuit. The one into the tank lid. And the one in the cabin before it where goes through the floor.

Its not uncommon for these to get a bad connection over time in older subarus. That causes the terminals to overheat and melt the plug. Usually on the earth side of the fuel pump. If thats the case then the pump wont work. And it could also cause the power to the pump to look for an earth via a shared circuit like maybe the fuel guage circuit/instrument cluster. ( you mentioned something about swapping fuel level sender over in the conversion or something) The backfeed causing the dash lights to illuminate dim and making the temp guage move aswell. It would probs also cause the fuel guage to move aswell, but this might not be apparent because usually fuel guages are made to move very slow so you dont get inconsistencies with sloshing fuel.

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 Post subject: Re: Fuel pump causing ignition issues
PostPosted: Mon Jun 19, 2017 10:07 am 
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I Say: Car mods are like OddBodz, you got to collect them all! -------------------------------------
Vehicle: MY05 STi swapped sled

Posts: 17762
Location: Spearwood Perth WA
Another thing to check would be if there is an aftermarket alarm/immobiliser. If so try and locate the circuits cut for immobilisation and check they are closing properly when dis-arming. And also check for any shorts/rub-thrus/pinched wiring etc with the install. It is quite common to cut the fuel pump relay trigger circuit and/or main ignition switch circuits for immobilisation.

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 Post subject: Re: Fuel pump causing ignition issues
PostPosted: Mon Jun 19, 2017 11:23 am 
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I Say: wouldja listen to them ball bearings!
Vehicle: 98 Ver.5 STi-swapped SF5

Posts: 1585
Location: Sunshine, Vic or Sale, Vic
Thanks for the replies guys!

Just to clarify though, i completed the conversion over a year ago, and everything worked perfectly, loom was laid in the factory position, with all the firewall connecters etc. I had the engine out in January to do the clutch, and had no electrical problems in the weeks after I was using the car.

I decided to pull the car off the road due to the engine not seeming so healthy, and in that time the only electrical thing I've changed is the in tank fuel gauge, which I did by unplugging the old one from the intank assembly, and plugging the gt one in, which fixed the fuel gauge issue, which I'd had from when i first did the conversion, but wasn't too worried about. I'm fairly sure i drove the car briefly which confirmed the fix worked, at the very least i had the ignition on, and the fuel pump issue didn't come up then, but it did a few days later

Before making the post I've already checked the plugs to the tank and under the rear seat, and checked the ground from the pump, which was fine up to the connecter to the main loom, but I should probably double check from connecter to the actual ground point, and the ground point near the driver's side taillight. Looks like I'll probably hafta take the dash out though, and have a good look around.

No immoboliser (aftermarket or OEM), as JDM ecu, no dodgy modifications save for 4 solder and heatshrink joins near the keyless entry module, which seemed fine but i haven't checked with a multimeter, and the keyless entry is working fine as ever. Anything else I've done to the loom has been by repinning the plugs

I guess from here it's dash out, and check connections and relays, I did swap out my fuel pump relat for a mate's the other day, to no result, but it seems more likely to be the ignition relay or something

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 Post subject: Re: Fuel pump causing ignition issues
PostPosted: Sat Jul 01, 2017 5:20 pm 
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I Say: wouldja listen to them ball bearings!
Vehicle: 98 Ver.5 STi-swapped SF5

Posts: 1585
Location: Sunshine, Vic or Sale, Vic
FOUND IT!!!

After doing more testing, I narrowed the problem down to the #11 fuse, which isn't just for the fuel pump, but also provides 12V to the ECU, coilpack and immobiliser. I removed the corrosponding pin from the ecu plug, but nothing, ignition lights stayed on. Went to the coilpack, unplugged it and tried to find the right wire (using an 00+ service manual). While I was looking at that I saw the problem...

...the ground for that part of the loom was not at all tightly bolted to the manifold, like, AT ALL. This was likely to be the issue, as I think it was on a bolt that had a TMIC bracket also on it, and the last thing I was doing was installing a FMIC, so the TMIC brackets came off!! Looks like I just put the bolt in a few threads so the wire would get lost.

Tightened the little f*cker up, plugged all the sh*t I'd unplugged back in, turned the key, and it primed, and started!!! :D :D :D

Cheers Bram and Phrewfuf for your input!

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 Post subject: Re: Fuel pump causing ignition issues
PostPosted: Sat Jul 01, 2017 10:24 pm 
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I Say: Car mods are like OddBodz, you got to collect them all! -------------------------------------
Vehicle: MY05 STi swapped sled

Posts: 17762
Location: Spearwood Perth WA
Bram wrote:
Those symptoms could also be indicative of a bad connection. High resistance connection. Perhaps a loose plug. Or loose earth bolt eyelet.


Good to hear you got to the bottom of it. Told you it could be a bad/loose earth.

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