Please ID This Fuse - No Start

[Doc Hawk]

I have a 240Z that was running last week, and was shut down normally last time I drove it. I went to start it today, and got no start. I found that my white (small, positive) lead to my starter was extremely hot to the touch, and I took that as a cue that it was finally time to redo the crappy twist-and-tape wiring that the PO had done, as something had probably come loose and was causing high resistance.

 

I soldered about a dozen connections throughout the car today, most of which had to do with the ignition, main positive lead, or the starting circuit. I also did some various other housekeeping, but I didn't make any changes to the wiring, just made the existing bad connections permanent.

 

After what I thought was a job well done, I still had no start. At least the white lead to the starter is no longer getting hot, but I hooked up a timing light and got no flash on #1 nor on the coil wire.

 

I dug into the stock rat's nest under the dash, and found an inline fuse had blown, shown below:

 

 

It was located in the center console, behind the main fuse panel, and the unplugged connector seen at the lower right plugs into the “choke” light on the fuse panel bezel. There was a smoked 20A in there. I replaced it with a 25A because that was all I had on hand, and when I tried to start the car it smoked that immediately, too.

 

Two questions, then:

1) What is that line?

 

2) What might be popping that sucker?

 

All help appreciated. I'm trying to shake this car down for my first autoX of the season, which will be next weekend.

 

Additional info:

MSD 6A, MSD Blaster 2 Coil, electronic ignition, fresh Yellow Top battery with 875 CA.

 

Thanks,

David

[Doc Hawk]

I still need help on this please; I'm dead in the water until I can figure out this electrical issue. I have quadruple checked the wiring that I redid, and I have not found any routing that I changed.

 

Major piece of new news is that my multimeter shows 3.1A flowing with the car off, key out, and all fuses removed from the main panel. I disconnected the negative battery terminal and bridged the cable to battery gap with the multimeter. Nothing was on at the time, and the doors were closed. That looks like a dead short somewhere.

 

In case I didn't mention it, the starter cranks the motor and everything, just no start and not even a hint that it "wants to fire." I am pretty sure I have no spark whatsoever.

 

My suspicion right now is that I may have had a short all along (battery has been known to go dead after a couple weeks sitting), and by improving the wiring I actually turned an intermittent short into a full short.

 

Any help on any of these angles truly appreciated, guys.

[Doc Hawk]

Well, since I couldn't find the direct culprit, I did some deductive reasoning and solved the problem myself. Since I really, truly didn't change any wiring (just solidified what was there), and it was running last week, I decided that something I improved must have actually made a bad connection more solid.

 

Sure enough, I found that the white wire to my MSD ignition was grounded, which puts it in anti-theft mode (no spark). It was previously on a very poorly grounded screw, so in the course of my wiring fixes I moved that wire to a better ground. I never bothered to find out what it was before upgrading the ground, since it was grounded in the first place and I figured it was in need of improvement like all the other crap hack jobs throughout my car (from the PO, I promise).

 

The car is running and driving. I still have a 3.1A draw at the battery that I need to track down, and there is something seriously wrong with the blue wire in the photo (I bridged the fuse to see what lit up, and a bunch of magic smoke came out of the wire loom it was attached to).

 

Well, she's running!