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Coil pin out, how to check coil plug for power? Not getting spark

14K views 13 replies 3 participants last post by  swaid  
#1 · (Edited)
Just swapped my motor, i have a boosted setup, and went to start it. THe car has been sitting for over a year and finally finished everything and went to start it, and it only turns over. I have good fuel pressure, just no spark at the coils.

Checked the fuses behind the dash, under driver steering, and underhood, all the ing fuses look good.

I also wanted to ask how to exactly test the coil plugs. should there be a pin with constant 12v?
 
Discussion starter · #2 ·
i get 12 volts on the black white wire, but only when i disconnect the coils. If i connect one coil back(the harness plug) the voltage drops to 3v and keeps droping when i plug the rest

any ideas?


if someone could atleast confirm that it should have constant 12 at the black white, i could possible jump the wire with constant 12 and see if that starts the car
 
Discussion starter · #6 ·
Sorry. +B = Plus Battery. You correctly identified the BLK/WHT wire.

As you probably already know, if the coils are pulling +B down to 3V then one or more coil packs is shorted, or the BLK/WHT wire has too much resistance, or both. I think if one of the coil packs had shorted it would blow fuse #1 (15A) in the under-dash fuse box, so I'd make a resistance check of the wire from the coil packs to the fuse.
Ok, that makes sense.

Im going to go back out and try to see if only one coil causes the drop in voltage or if it is a consistent issue throughout the coils. Luckly i do have a spare set of coils which will help eliminate the issue faster.

As for the #1 fuse, for some reason im seeing corrosion on the bottom fuses on my inside fuse box. Its pretty weird. And i had replaced my fuse box last year(there was nothing wrong with my old one, i had thought that was the issue but it wasnt).

Now would tapping into the blk/wht wire at the coils, and feeding them another supply of 12+ have any bad side effects?
 
Discussion starter · #7 ·
ok, so i tested the coils, there are deff not the issue. Im starting to think it maybe the fuse box, because when i disconnected the #1 coil fuse, i still had power coming to the coils(when they were unplugged, because as soon as i connect all 4 the voltage goes to 0)

im thinking replacing the fuse box is worth a try, but before i waste time waiting for it to come in and install it, is there seriously any negative aspect to feeding the coils constant 12+ myself, buy cutting/splicing the wire and running a constant from the battery straight to the coils?
 
Discussion starter · #9 ·
The fuse box sounds like a likely suspect. You can run another wire to the coil packs to supply +B, but then you have a problem (and a possible fire hazard) if something shorts on the wire or the coil packs short. You really should fuse the supply wire. Also, you make things a huge pain for the next guy to troubleshoot. Much better to clean up the existing connection if that's the problem. Maybe you don't need to replace the whole box.
i would only do the wire bypass just to start the car. I just put the new motor in and havent even started it due to this stupid coil issue. but i did go ahead and ordered a new fuse box
 
Discussion starter · #12 ·
Any luck with this?

Worst case scenario to test all aspects you could supply 15a fused wire for the 12v supply on the coils straight from the battery.
if no luck then check that the ground of each coil is good.
was super bz with work, was planning on working on the car this morning, but its pouring out here -_- ill keep you updated once i install the new fuse box:fistbump:
 
Discussion starter · #13 ·
so installed the new fuse box, i checked for 12+ constant at the coils, and it seems to have fixed that issue. There power was there even after i connected all the coils. But car still didnt start -_-

i was alone, so i couldnt have someone crank it while i checked for actually spark at the coils so im going to wait till i can get a bud to turn the key while i check for the basics
 
Discussion starter · #14 ·
Its alive!!

So it started acting up again, in regards to losing power at the coils. I came to realize it would happen when I plugged this one specific coil. I disconnected it n cranked it n heard a back fire in the exhaust. So once I swapped the coil, it started right up