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Ignition issue (main fuse always blows)


StrokedEJ

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Hi so ive had a problem with my gc8 for a few years now as it keeps burning then blows the main fuse over time. Im unsure whats causeing it but now i think its starting to affect the cars performances as my car just came off dyno with some misfiring at high rpm under full load. We thought it maybe the loom as it was fine till we touched the loom then it started burnig again then we moved loom then it stopped but it still gets real hot which i know it shouldnt be that hot. Just wanna know if anyones had this issue before. Cheers

 

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Not in subaru's but if the holder clips are loose any vibrations can cause miniature arcing and that heats things up.

The same will happen if the wiring loom isn't crimped into the clip underneath as well.

 

has the loom been out before and are you missing and grounding cables?

 

 

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Not sure what the main engine fuse runs further down, but grab a wiring diagram and look at the next level of fuses downstream.

have you upgraded any electrical component that run off those i.e. fuel pump, coils, injectors, Ecu etc.

  • guess at the least the voltage has been checked and are ok from alternator? Won't always show on digital multimeter but good start.
  • when you replaced the fuse did you just get the same value or check the manual and confirm cover to make sure it was the correct one to start with? Could be lucky and just have a fuse that's to small.
  • is the rest of your loom tidy? No shorts from unterminated or poorly joined cables.

other free things to consider is anything electrical cable or component running closer to heat sources as the more you heat them the less efficient they run, which can increase current draw.

 

Disclaimer: I know nothing about anything, ever.

Edited by Gripless
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Not sure what the main engine fuse runs further down, but grab a wiring diagram and look at the next level of fuses downstream.
have you upgraded any electrical component that run off those i.e. fuel pump, coils, injectors, Ecu etc.
  • guess at the least the voltage has been checked and are ok from alternator? Won't always show on digital multimeter but good start.
  • when you replaced the fuse did you just get the same value or check the manual and confirm cover to make sure it was the correct one to start with? Could be lucky and just have a fuse that's to small.
  • is the rest of your loom tidy? No shorts from unterminated or poorly joined cables.
other free things to consider is anything electrical cable or component running closer to heat sources as the more you heat them the less efficient they run, which can increase current draw.
 
Disclaimer: I know nothing about anything, ever.
Cheers thanks for the help. Voltage check 12v under load. So just purchased a alternator to replace. I have replaced the fuel pump and injectors loom seems tidy as i havnt touched it

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Not in subaru's but if the holder clips are loose any vibrations can cause miniature arcing and that heats things up.
The same will happen if the wiring loom isn't crimped into the clip underneath as well.
 
has the loom been out before and are you missing and grounding cables?
 
 
No loom hasnt been touched. Appreciate your help

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If you're replacing alternator then that maybe the only fault, can't see half of what's wrong with them without an oscilloscope.

 

Check the current draw specs on the fuel pump at higher pressures if they list them and injector impedance is same as stock. 

 

If the engine has ever been out I'd still check around the main connection points, never know when someone forgot to unplug something or it got caught up during removal. Beers and late nights make for strange electrical faults.

 

otherwise fingers crossed it was alternator.

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If you're replacing alternator then that maybe the only fault, can't see half of what's wrong with them without an oscilloscope.
 
Check the current draw specs on the fuel pump at higher pressures if they list them and injector impedance is same as stock. 
 
If the engine has ever been out I'd still check around the main connection points, never know when someone forgot to unplug something or it got caught up during removal. Beers and late nights make for strange electrical faults.
 
otherwise fingers crossed it was alternator.
Injectrs ar high imp

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Is this coil over plug or common coil?  Could be coil drawing too much, a broken lead wouldn't increase draw I don't think just have failed spark.

Not sure how to test that other than swap it out. Got any Subaru mates that could lend you a coil.

 

Maybe use IR temp gun on a known good car vs yours. Even that may not show enough difference due to their location. Unless you tested the temp without running the car. Could still draw a bit more current even without firing. Could wait until you have two cars cold and just turn key to on and not start and see if coil heats up a little more on your one. But now I'm really guessing or making S*** up.

 

if it's coil over plug then one spark plug could look different. Black art of reading plugs, need an old school v8 guy for that.

 

is the impedance the same as stock injectors.

 

See still know nothing about Subarus... Yet.

 

 

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Is this coil over plug or common coil?  Could be coil drawing too much, a broken lead wouldn't increase draw I don't think just have failed spark.
Not sure how to test that other than swap it out. Got any Subaru mates that could lend you a coil.
 
Maybe use IR temp gun on a known good car vs yours. Even that may not show enough difference due to their location. Unless you tested the temp without running the car. Could still draw a bit more current even without firing. Could wait until you have two cars cold and just turn key to on and not start and see if coil heats up a little more on your one. But now I'm really guessing or making S*** up.
 
if it's coil over plug then one spark plug could look different. Black art of reading plugs, need an old school v8 guy for that.
 
is the impedance the same as stock injectors.
 
See still know nothing about Subarus... Yet.
 
 
Its a wasted spark system. Yes next thing ill do tommorrw is change all the coils to new ones to then eliminate that and maybe spark plugs too. Also car idles at 2500 once this issue occured. Injectors yes they are

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F*** you must have a spare parts bin... 

Depends how sick of the issue you are but if you swap one coil at a time you'll know which is the problem.

mark the plugs with which cylinder they came out of. Masking tape and a vivid works so you don't mix them up for later inspection. Or easy for smart people to see in photo if you post one.

 

thats a high idle! Not sure what caused that... Does your car have an idle control valve? Did the idle start hunting or was it rough when the issue started? Idle stepper motor maybe shorted. Again not familiar with Subaru just guessing from other cars.

 

2500 is the cold idle temp isn't it (think that's what my one does)? What's the Ecu think the water temp is? That would alter fueling a could fowl plugs etc. again some of the smart people on here maybe able to tell you more about the Ecu side.

 

only time I've had idle that high was throttle not sealing when I ran a bored out throttle, but could be throttle position not reading correctly. Should be able to see it if you have a cable, even a cheap one can read to OBDII which may have TPS.

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F*** you must have a spare parts bin... 
Depends how sick of the issue you are but if you swap one coil at a time you'll know which is the problem.
mark the plugs with which cylinder they came out of. Masking tape and a vivid works so you don't mix them up for later inspection. Or easy for smart people to see in photo if you post one.
 
thats a high idle! Not sure what caused that... Does your car have an idle control valve? Did the idle start hunting or was it rough when the issue started? Idle stepper motor maybe shorted. Again not familiar with Subaru just guessing from other cars.
 
2500 is the cold idle temp isn't it (think that's what my one does)? What's the Ecu think the water temp is? That would alter fueling a could fowl plugs etc. again some of the smart people on here maybe able to tell you more about the Ecu side.
 
only time I've had idle that high was throttle not sealing when I ran a bored out throttle, but could be throttle position not reading correctly. Should be able to see it if you have a cable, even a cheap one can read to OBDII which may have TPS.
Hahaha nah no spares bin just a budget ive put aside for the car which is near the bottom of the barrell haha. Ecu link g4+

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I feel like a dick but a vacuum hose off the fuel reg came off and i didnt see it off till i inspected it all properly and didnt think twice about checking it yesterday and what do you know took it for a boost an no misfiring. The culprit was that blue hose at back going to reg

 

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So many $ sunk into the engine/turbo setup and yet the rest of the bay is a disaster.

 

Not hating on the car man but I wouldn't go near a dyno with it like that. One issue and the tuner is just gonna say "go sort out your engine bay"

Things like the vac line coming off the fuel reg, that happened to a member here on track and it almost instantly melted his motor, it immediately went full lean.

 

Is that the boost control solenoid just ziptied to the breather hose on the left side? Also battery appears to just be chilling out in the engine bay, no clamp....

 

The alarm siren is surely taking the piss, what's even the point of having it there? Also the stereo fuse holder in the middle of the firewall with a whole lot of wire between it and the battery waiting to catch fire over by the passenger suspension pillar.

 

Fixing the vac line to the FPR isn't going to have fixed your wiring issue. You have something drawing too much current. Gripless trying to help but clearly no auto-sparky - what you need is a clamp ammeter, clamp it around the entire loom and see how much current you're pulling, then remove single wires from the clamp until it drops hugely, then you know which wire is your culprit. Follow it or look it up in the car's wiring diagram.

For now my money is going on it being the fuel pump wiring, the wiring is barely enough to run the stock pump let alone a way bigger one.

 

 

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So many $ sunk into the engine/turbo setup and yet the rest of the bay is a disaster.
 
Not hating on the car man but I wouldn't go near a dyno with it like that. One issue and the tuner is just gonna say "go sort out your engine bay"
Things like the vac line coming off the fuel reg, that happened to a member here on track and it almost instantly melted his motor, it immediately went full lean.
 
Is that the boost control solenoid just ziptied to the breather hose on the left side? Also battery appears to just be chilling out in the engine bay, no clamp....
 
The alarm siren is surely taking the piss, what's even the point of having it there? Also the stereo fuse holder in the middle of the firewall with a whole lot of wire between it and the battery waiting to catch fire over by the passenger suspension pillar.
 
Fixing the vac line to the FPR isn't going to have fixed your wiring issue. You have something drawing too much current. Gripless trying to help but clearly no auto-sparky - what you need is a clamp ammeter, clamp it around the entire loom and see how much current you're pulling, then remove single wires from the clamp until it drops hugely, then you know which wire is your culprit. Follow it or look it up in the car's wiring diagram.
For now my money is going on it being the fuel pump wiring, the wiring is barely enough to run the stock pump let alone a way bigger one.
 
 
Cars been off the road for a while tidying it up an paintjob is next on list. Just tryna get it working the teeth out any issues then hit test an tune next week.

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20 minutes ago, StrokedEJ said:

Cars been off the road for a while tidying it up an paintjob is next on list. Just tryna get it working the teeth out any issues then hit test an tune next week.

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Is it getting the engine bay painted, so no point sorting all that stuff yet?

 

Honestly all the teething stuff is probably due to that giant crap-storm under the bonnet....

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Is it getting the engine bay painted, so no point sorting all that stuff yet?
 
Honestly all the teething stuff is probably due to that giant crap-storm under the bonnet....
Yeah atm main fuse hasnt burnt or blown . So fingers crossed alternator fixed it. 13.5volts now

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