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78 280z fuse box hack. wires everywhere.


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Hey all

So I had an instance a while ago where the car wouldnt start, fuel pump wasn't getting power. That's when I saw the fuse box with wires in fuses. Touched a wire, heard a short, and the pump came on. Gotta check that. I replaced the injectors to fix a fuel leak and yesterday didn't start. Battery was low (being charged).

Well today I got around to looking at the fuse box and followed the cables. All of them run to the radio and an amp in the back, courtesy of the PO. I don't care for these things right now I just everything ok. There's also a cable from the battery to the amp and another may be going to the fuse box.

Would taking all these things out fix it? Let me know what you think. Don't know squat about electrical. But I guess thats gonna change

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Ok so I took out the radio and the amp. That cleared up the fuse box minus two wires that turn the pump on/off. Replaced starter and battery terminals and still wouldnt start. Got a jump and it struggled to start but eventually it did. Turned it on/off and it started up like a dream but after a couple of minutes off, dead with clicks. Jumped it again, drove around for a while, turned the car off, dead with no clicks nothing. The bat shows up around 16 volts so it should be the alternator right? Started car, unplugged the battery, and I heard the alternator make noise then the car shut off. Gonna go to AZ to get the alt checked. Or is there a short that's causing this? I can smell burnt wire smell or an acid smell coming from where the radio was. There weren't problems before it sat a couple months ago, nor when I moved it a couple of weeks ago, just fine. Very weird.

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1. Don't pull the cable off of the battery with the car running. You can kill your ECU.

2. Get a proper multimeter if you want to do electrical troubleshooting. Don't use the voltmeter in the car. If you were using a voltmeter instead of your gauge, 16 volts is too high. The voltage regulator in the alternator is gone.

3. Use the FSM for electrical diagnostics. The guidelines in the manual let you test the car without risking the components.

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Yea I saw those tests on there, don't really want to do electrical troubleshooting. Mainly cavuse I've never Hehehe. But this is probably a good time to get my feet wet. Time to buy a multimeter, gonna try it this weekend. Atleast when I get around to my 260 the electrical won't seem as bad.

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My 260 had some bad wiring mojo from the PO similar to yours. Some of connections had really pro-looking replacement wires with expensive connectors on them, I suspect a mechanic actually installed those. While some of the better connections worked it was a poor substitute for actual wiring repair.

Your harbor freight shopping list to become a wiring pro:

  1. Multimeter
  2. Soldering iron (~25w) & thin solder
  3. "Helping hands"
  4. Heat shrink tubing
  5. Spray electrical cleaner

First watch some soldering videos on YouTube then solder some wires together on your work bench. After soldering about 10 connections you will pretty much know what you're doing. After becoming a soldering pro you can diagnose and repair your connections. I pulled my fuse box out enough to work on it in the passenger foot area and worked on the whole thing. With the battery disconnected remove your fuses one at a time and inspect their seating area, use a soft wire brush on anything that looks corroded and hose down every connection with the electrical cleaner. If at all possible try and return your wiring harness to stock by removing any additional wires and replacing plastic connectors with solder/shrink. Also crack open the large plastic connectors under the dash and give them some love, mine were totally full of grime.

After the above procedure and not much money my electrical gremlins are gone and the whole electrical system is in much better condition.

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Note to self: harbor freight sells helping hands.

Thats what I plan on doing to the 260. I just need to get this 280 mechanicaly solid so I can go back to finishing the 260, don't remember that being hacked. Soldering and shrink does sound pretty pro.

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While you're at it, get yourself a cheap notebook to draw up the wiring circuits for things as you work on them, or look at the wiring diagrams so you know which wires or connectors or relays to look at before you get into the car. Things like the fuel pump circuit, headlamp circuit, horn, wipers, etc. You can make notes as to which wires get 12V or whatever. Draw up the wiring for whatever the PO did. Then you might decide what to do to correct things.

I also have a little 12V buzzer with wires & clips, so I can check power wires. It helps when you don't have a friend or don't walk to walk back & forth to check with a test light.

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Yep right there with ya. I was looking at the continuity check for the EFI and got an old notebook out. I was gonna read the diagram but drawing it sounds good. Also found a color diagram, but it doesn't pop up in adobe. Booo, I'll try later.

FSM says to use a fuse to check a relay as to not damage it. ??? When cleaning I did notice a loose one and one relay only had half of the contacts connected. So I wanna check those.

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I think Ima see if I can turn a door bell into a check, might scare me now and again. Hehehe. Maybe one of those fart machines.

My fuel gauge doesn't work. Sad face... But everything else does! So far. After checking some of the 35 pin tests and not finding anything I cleared all the sound stuff and cleared the fuse box, pulled it out, cleaned. one terminal was loose, no current. The fuse was also shot, looked intact but burnt. After that still wouldnt start. The suspects were narrowed down to the bat, alt, time, or fuel delivery. Found plug 2 & 4 were wrong. Also the red-white wire to alt was shorting from a hidden crimp mess that was loose. Still no start. Jumped...

She's aliiive!! At first it backfired then I noticed the pressure reg wasn't putting as loud. Sounded great. My pops came over and also thought it's narrowed down to bat or alt. Well AZ narrowed it down to the bat. New bat was bigger. Engine humms. Really nice.

Found 3 shop towels stashed with the air filter. Next is to see about the mixture, exhaust smells some strong. Although it's not 100%, runs 100% better.

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