1990 Nissan 240sx, Ignition System Not Working

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Jonathon594
Posts: 3
Joined: Tue Mar 31, 2015 10:48 am
Car: 1990 Nissan 240sx XE SOCH

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I'll explain what happened from the beginning, Basically I changed my timing components, and after I finished I didn't install my electric cooling fan yet. Somehow by a freak accident, my hot wire from my fan came undone from the relay and decided to ground itself out, instantly melting itself. Afterwards I had been having very strange electrical issues like my dash going crazy and basically every electrical component on the car loosing voltage. I figured I still had a small short somewhere. Months ago, my clutch fan decided to chew up my front wiring harness (hence the electric fan now). And I re wired everything it messed up, and everything work fine. I assumed my short may have been in these wires that I redid, so I decided to undo them and just rewire them. Well I did, And now my car wont start at all. I have been researching how the ignition system works as well as perusing wiring diagrams. I still dont know whats wrong. It appears as though the coil is NOT firing. It has voltage to it (Black-Red Wire) and its ground is good (Green-Black Wire). I know the ground runs through the PTU. and Im guessing that is where my problem is. I do not think the PTU is working propperly. But I don't know how to check it. It's Green-Black wire has continuity with the Coil. The black wire has continuity with ground. But strangely enough the White wire also has continuity with ground, Is this normal? I don't think it is, But I dont know anything about the PTU so I can't say. I havent checked its continuity with ECU because I don't even know which white wire it is at the ECU. Is this wire supposed to have ground conductivity? The only codes my ECU is throwing is 41 for air temp sensor which is normal because its been cut off before I bought the car. I beleive my crank angle sensor is working normal but I cant say that with any certainty. If anyone has any help they can give I appreciate it. I am willing to go and test anything needed to find the answer. I just dont want to go buying parts if I dont need them.


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PapaSmurf2k3
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Posts: 18997
Joined: Thu Nov 21, 2002 3:20 pm
Car: 2017 Corvette, 2018 Focus ST, 1993 240sx truck KA Turbo.
Location: Merrimack, NH

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I thought there was some fuse that often blew in the event of something major shorting out. I want to say the fuse is called "electronics" or something.
Do you know anyone with a spare coil you can try if you can't find that fuse? Its possible to overload the coil, and have it short out internally.


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