My Brief Tour of Wiring Hell
Posted: Mon Oct 27, 2008 9:43 am
While I had the motor out of the car for new headgaskets, I decided to do some items on my list; convert the crumbling old ignitors over to new WRX units, replace the O2 sensor of unknown mileage, new clutch, and clean up the engine bay.
The clutch was an easy job, once I understood how to remove the clutch fork...
The ignitors were a bit concerning for me, it seemed straightforward enough, but I found a few diferences in the wire colors Legacy vs Impreza, but muddled through it, and double checked everything from ECU to ignitors, so I was fairly confident it would work. The most time-consuming thing was cutting down the coils and ignitor body to fit into the RS-RA heads... although one side of the motor was much easier to fit than the other, for some reason. I wish there were some way of verfiying that the coil connector is actually firmly contacting the spark plug, it does not really give you a "click" like a plug wire would.
Replaced the O2 sensor w/ a generic one, had to splice it in to the old harness. Mistakenly got a 4-wire sensor, but from what I could make of the instructions, the unit has 2 wires for the heater, so I just tied them together.
Got everything back in place, hooked up & ready to go. Turned the key to on a few times to prime the fuel system, then, just as I was about to crank the motor, I got a puff of smoke from the dashboard, and the fuel pump quit working.
WTF??
Checked all the fuses under dash, all ok.
Checked the fuses under the hood, all ok.
Replaced all the relays under the dash, no help.
Plugged in another ECU, no help
So I started into the wiring... I located the main problem pretty quickly; I had miswired the O2 sensor somehow, or it was shorted internally (1st option more likely) and the red wire was starting to melt at the connector. So I undid the job and re-installed the old one, but the fuel pump was still inop.
Long story short, after chasing up and down the wire harness, including removing the dashboard to check for damage, I finally found one of the green fusible links had popped... the kicker is, IT TESTED GOOD when I had first pulled it and put a meter on it. (I tested every fuse and link on the car)
I noticed it was very slightly discolored, but the meter indicated no resistance, so back it went. After tracing the 12v wiring for the fuel pump, I ended up back at that link. It tested OK, but would not pass any current, so I made up a small jumper, put it in place of the link, said a few hail Marys, and turned the key...
PRIME!
Motor fired up the first try. A postmortem on the link revealed a cracked element, so the moral here is, if it looks the slightest bit different than the other ones, that's probably the naughty one.
Anyway, I took the opportunity to paint the dashboard while it was out, so I finally have an all-black interior
...there's the silver lining.
Never did find out where the smoke came from, I had assumed I nuked the ECU, and got another one from Matt, but the original one is running the car now, and seems to be OK.
The car is sluggish on boost, though, I have to go in and check my hose connections. Off boost it runs just like it did before, so I guess I got the timing belt correct... A couple of the HLAs collapsed, so the motor clatters now, I'm hoping they'll pump back up on their own, I may add a few ounces of ATF to the oil to encourage this.
The clutch was an easy job, once I understood how to remove the clutch fork...
The ignitors were a bit concerning for me, it seemed straightforward enough, but I found a few diferences in the wire colors Legacy vs Impreza, but muddled through it, and double checked everything from ECU to ignitors, so I was fairly confident it would work. The most time-consuming thing was cutting down the coils and ignitor body to fit into the RS-RA heads... although one side of the motor was much easier to fit than the other, for some reason. I wish there were some way of verfiying that the coil connector is actually firmly contacting the spark plug, it does not really give you a "click" like a plug wire would.
Replaced the O2 sensor w/ a generic one, had to splice it in to the old harness. Mistakenly got a 4-wire sensor, but from what I could make of the instructions, the unit has 2 wires for the heater, so I just tied them together.
Got everything back in place, hooked up & ready to go. Turned the key to on a few times to prime the fuel system, then, just as I was about to crank the motor, I got a puff of smoke from the dashboard, and the fuel pump quit working.
WTF??
Checked all the fuses under dash, all ok.
Checked the fuses under the hood, all ok.
Replaced all the relays under the dash, no help.
Plugged in another ECU, no help
So I started into the wiring... I located the main problem pretty quickly; I had miswired the O2 sensor somehow, or it was shorted internally (1st option more likely) and the red wire was starting to melt at the connector. So I undid the job and re-installed the old one, but the fuel pump was still inop.
Long story short, after chasing up and down the wire harness, including removing the dashboard to check for damage, I finally found one of the green fusible links had popped... the kicker is, IT TESTED GOOD when I had first pulled it and put a meter on it. (I tested every fuse and link on the car)
I noticed it was very slightly discolored, but the meter indicated no resistance, so back it went. After tracing the 12v wiring for the fuel pump, I ended up back at that link. It tested OK, but would not pass any current, so I made up a small jumper, put it in place of the link, said a few hail Marys, and turned the key...
PRIME!
Motor fired up the first try. A postmortem on the link revealed a cracked element, so the moral here is, if it looks the slightest bit different than the other ones, that's probably the naughty one.
Anyway, I took the opportunity to paint the dashboard while it was out, so I finally have an all-black interior
...there's the silver lining.Never did find out where the smoke came from, I had assumed I nuked the ECU, and got another one from Matt, but the original one is running the car now, and seems to be OK.
The car is sluggish on boost, though, I have to go in and check my hose connections. Off boost it runs just like it did before, so I guess I got the timing belt correct... A couple of the HLAs collapsed, so the motor clatters now, I'm hoping they'll pump back up on their own, I may add a few ounces of ATF to the oil to encourage this.
I was taking no chances, I didn't know exactly what had caused the surge, it could have been the coils, O2 sensor, or even just a random crushed wire bundle... I saw that the O2 wire was just starting to show melted insulation right at the pigtail plug, so I went on the assumption that my problem was there... I re-checked the coil wiring anyway, shot it from the ECU to the coils.