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Old 02-23-2011, 09:08 PM   #1
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Default Engine harness short?

I know the answer to this may seem obvious, but before I tear the entire engine harness out I figured I'd ask.

I've been doing a lot of wiring in the car lately with the new ignition system. Well, when I went to test, I was unable to start the car. My battery was drained. So I charged it and tried again, still nothing.

In an attempt to diagnose, I disconnected the megasquirt ECM and removed the battery. Then I checked continuity between the two battery terminals. I have continuity. I checked resistance, 55k ohms.

Is this a good indication of a short in the harness somewhere?
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Old 02-23-2011, 09:46 PM   #2
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Little update, with key on I go from 55,000 ohms resistance to 4 ohms resistance.

So my short is definitely somewhere that receives power at key on. I've eliminated the alterenator, starter and ecm power and ignition power lines.

Still hunting...
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Old 02-23-2011, 09:58 PM   #3
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3 fuses under the hood have shorts run through them. I'm trying to figure out what these fuses are for but they are not labeled. :(
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Old 02-23-2011, 11:46 PM   #4
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Oh I found it! I pulled the C100 firewall harness off. I found ground on a large yellow wire. Yellow is switched 12V ignition. I traced it back to the transmission for the neutral safety switch and disconnected it there. No more ground at the C100 so I kept going. Also on the NSS the purple wire had ground. Took the purple wire off of the NSS runs to the starter signal. So I checked it at the starter and sure enough, ground. So just to make sure, I pulled the start wire off of the solenoid and... you guessed it ground at the solenoid.

I just bought this FU#@%NG starter last year and it has maybe 100 starts on it because I took the car off the road for the engine swap and then it sat all winter.

Im going to raise some hell, as soon as I remember where I bought the starter.
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Old 02-24-2011, 12:39 AM   #5
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Wow, sounds like you had a fun day. Very rewarding when you track down a electrical problem. Sorry I wasn't around to help out.
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Old 02-24-2011, 02:32 AM   #6
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Quote:
Originally Posted by Danthurs View Post
Wow, sounds like you had a fun day. Very rewarding when you track down a electrical problem. Sorry I wasn't around to help out.
You know, I thought for a minute when I started that maybe it could be the starter. Then I thought, nah, I just bought that thing
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Old 02-24-2011, 08:23 AM   #7
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You sure there'* a short? maybe it'* just an uncompleted circuit? That'* along the same lines as testing a light bulb that doens't work and saying.. it'* got a short. The filament is supposed to short.
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Old 02-24-2011, 09:03 AM   #8
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When I measured across the battery terminals (with the battery removed), I had continuity. So yea I'm sure it was a short. The resistance across the terminals went from 55k ohms (still a short) with key off to 4 ohms (very bad short) at key on. That lead me to the C100 firewall connector where I found that the switched 12V line had ground on it.
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Old 02-24-2011, 09:09 AM   #9
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Some times you need to go with your gutt.
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