weird ignition problem

[JDMSTYLE]

ok so ive been trying to solve my problem with my ignition lately on my 90' coupe. the 30a ignition fuse (in the engine bay next to the battery) keeps blowing every time i turn the key to the "on" position. i checked most of the wiring and took off my alarm and sound setup but the fuse still blows. The first time i was able to get the car to start after cleaning my battery connections (which were completely covered in acid) and replacing the battery with a new one. well after letting my car sit for 2 weeks it is having the same problem, but this time when i tried to turned it on the battery was dead. so i charged it and was able to get the car to start and run for about 5 mins then the ignition fuse blew again (while the car was running). Now i cant even start the car and it is doing the same thing as the first time but the battery terminals are not corroded and the battery is only a couple weeks old. damn that was a lot to type hopefully someone can help me troubleshoot. i want to drive my 240 so badly!!!!

[reinvent]

ok so ive been trying to solve my problem with my ignition lately on my 90' coupe. the 30a ignition fuse (in the engine bay next to the battery) keeps blowing every time i turn the key to the "on" position. i checked most of the wiring and took off my alarm and sound setup but the fuse still blows. The first time i was able to get the car to start after cleaning my battery connections (which were completely covered in acid) and replacing the battery with a new one. well after letting my car sit for 2 weeks it is having the same problem, but this time when i tried to turned it on the battery was dead. so i charged it and was able to get the car to start and run for about 5 mins then the ignition fuse blew again (while the car was running). Now i cant even start the car and it is doing the same thing as the first time but the battery terminals are not corroded and the battery is only a couple weeks old. damn that was a lot to type hopefully someone can help me troubleshoot. i want to drive my 240 so badly!!!!

search , it happens alot. disconnect the ignition switch to see if it still blows. you probably nicked a wire on purpose or by mistake. inspect the on wire leaving the ignition switch. you will find that all the selfish little piggies never got back to explain where they found the short.

[JDMSTYLE]

well i found 2 wires that were cut but i have no idea what it is for... heres some pictures, it is the red yellow and black wire. http://i36.photobucket.com/albums/e35/machgtr/01102009245.jpg http://i36.photobucket.com/albums/e35/machgtr/01102009246.jpg http://i36.photobucket.com/albums/e35/machgtr/01102009247.jpg http://i36.photobucket.com/albums/e35/machgtr/01102009249.jpg

[reinvent]

I assume that plug is not plugged in? tape up those wire so they cant short . not sure what that plug is. anyone who would leave bear wires like that is retarded.

I would focus on the "on" wire from the ignition switch.

this is what the ignition switch looks like. the aluminum part plugs into the cylinder lock. not sure of wire colour on your car.

the aluminum part is the switch.

http://i36.photobucket.com/albums/e25/vancouverbc_2008/star001.jpg
http://i36.photobucket.com/albums/e25/vancouverbc_2008/star002.jpg
http://i36.photobucket.com/albums/e25/vancouverbc_2008/star003.jpg

[reinvent]

these are the wire colours for the ignition switch i showe the pic of. the wire colours change at the white plug but you can just follow it . check if someone has cut into it. or nicked it.

white with red stripe- is power coming in
blue- accessory
black with green stripe-"on" position
black with yellow-start-goes to fuse
black with white-start goes to interlock relay and then starter(it changes to black/yellow as it leaves interlock relay to go to starter)

[JDMSTYLE]

well i will have to take a look at the black green wire. any way to actually test the switch?

[reinvent]

well i will have to take a look at the black green wire. any way to actually test the switch?

you could test the switch with a multimeter.

i would check any places where the previous owner did any wiring.

there could be a short in other places than the "on" wire because when you turn to on you are increasing amps which could be triggering a short in the power wiring coming from relay box.

[reinvent]

you can see ignition switch in this picture.
in this pic can be removed from ignition lock assembly by removing the small screw.

[JDMSTYLE]

you could test the switch with a multimeter.

i would check any places where the previous owner did any wiring.

there could be a short in other places than the "on" wire because when you turn to on you are increasing amps which could be triggering a short in the power wiring coming from relay box.

hmm that sounds about right. well this is a really strange problem because it was running fine earlier it just started occurring after the battery got drained.

[reinvent]

Does your car start now if you have a good ignition fuse in place?

[JDMSTYLE]

no unfortunately it just blows the fuse. ive blew 10 ignition fuses trying to see where the problem is occurring T_T. could the alternator or starter also cause this problem or do i just need to trickle charge the battery back to life. ahh a whole day spent and no progress.

[reinvent]

no unfortunately it just blows the fuse. ive blew 10 ignition fuses trying to see where the problem is occurring T_T. could the alternator or starter also cause this problem or do i just need to trickle charge the battery back to life. ahh a whole day spent and no progress.

I wonder why your new battery is drained if you have not driven car?

You can take the alternator out of the question by pulling the 75 amp fuse. Your car will still start and run still. overcharging alternators can blow fuses and ruin batteries but lots of possibilities.

[reinvent]

pretty sure they have testers so you dont have to keep blowing fuses. resetable fuse thing. looked but never found.

[JDMSTYLE]

ahh yea ive been trying to find those too.. well i think the battery was draining from my sound setup i had in there. dont know exactly where its draining but thats where i figure it would drain.

[reinvent]

I checked at 12volt.com and two people have said use a light bulb as described below. I have not studied this in years so can't verify/disqualify with confidence:


Grind the plastic off of one of the already blown fuses and solder a 12 volt light bulb across the 2 terminals of the blown fuse. Use enough wire to reach the area that you think the short is in. Or use a 12 volt buzzer. With a bulb you do not need to check for polarity. If you use the buzzer you may have to figure out which terminal of the fuse is hot and which is ground. As long as the short is present the bulb will burn brightly or the buzzer will buzz loudly.

[JDMSTYLE]

wow haha i guess ill have to bust out my soldering equipment. i think ill have enough fuses to solder haha. or ill use alligator clips =)

[JDMSTYLE]

hmmm having some slight problems determining where the short is.

[JDMSTYLE]

need to get this thing rolling!
haha thanks for the help so far reinvent just the dang car doesnt want to cooperate...

[reinvent]

pull the 75 amp alt fuse which take the alternator out of the circuit. this will tell you if you have an alternator problem.

you really need a multimeter to test resistance. you can get a good one for 20 bucks. the needle ones are no good. you want digital.

it could be a loose solder connection right in the relay box.

wiggling wires to try to trigger the short is always worthwhile

[reinvent]

these are a couple comments about finding shorts from people on net.

Divide and conquer.
Thats really all you can do.
It's also important to identify exactly when the problem is occuring, especially if there are several components on one fuse.
For instance, if you keep blowing a headlight fuse when you turn your headlights on check to see if the fuse blows when you only turn the parking lights on (if they are on the same fuse, which most are not, but its the only example I could think of).
Also, as said above, unplug as many things as possible and keep testing with a meter (I don't recomend using small fuses to test as they are somewhat costly, especially if you use 25 of them!) If you know you have a short to ground you can measure the fuse holder output side to ground and determine when the short has been fixed.

I'll give my take as well since I basically spend my entire life chasing down shorts.
First off there really is no particular place where shorts occur most..basically they can occur anywhere..any time..for many reasons. In my industry it is common to see wires pinched under seats..or wires hanging against exhaust manifolds. Sometimes a screw is put through a wire as well.
Some devices can internally short...motors..speakers and a host of other components. By simply disconnecting the suspect component..then checking the wires for a short with a meter can quickly tell you which one is the culprit.
As far as voltage drop vs.resistance.. Voltage drop is a sympton of resistance...that about sums up the relationship for this topic. A dead short to ground (zero resistance)causes blown fuses..and in the worst case burned up stuff and/ or wires.

[JDMSTYLE]

i have a multimeter and thats been helping somewhat. hopefully ill be able to find the short. a friend told me the best way would be to connect a buzzer directly to the ignition fuse terminals and when the buzzer turns off that is where the short is.

[JDMSTYLE]

blahhhh day 5 no progress i guess ill be pulling all the wires out and doing continuity checks...

[JDMSTYLE]

hmm well i was trying to find out the source where the battery was draining and it seems to be the alternator 75a (drawing about 12.7 volts) fuse and the engine control fuse 25a (drawing about 8 volts)?
any clues on where this might lead.

[JDMSTYLE]

turns out it was a short in the harness....screw from headlight motor...