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Wiring issue-Ignition coil

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Hello, I bought a 72 521 about a month or so ago now. When I was looking at it, the owners had told me they had a shop do work on it. The shop had installed a new electric weber carb, and a new 12 volt harness. 


Well, it turns out the new 12 volt harness was half-assed. I found two wires stripped,and twisted together then wrapped with electrical tape. Not to mention, a whole mess of unneeded wiring. I mean, like AC compressor, fan, heated seats, power windows, power seats, power mirrors, etc


So, I decided to start snipping wires. Then I ended up with a hole mess of wires for about a week. Come today, I wired up basics for getting the truck started, coil, ignition, switch.


I had a wire going to the solenoid on the starter, and then a wire from the ignition port to the fuse block (3 separate blocks, ignition, accessory and constant). I Ran a wire from the ignition port on the key switch to the ignition fuse block. I then ran a fused wire (30 amp) from the block to the external resistor.  When I would try to start the truck, it would crank but not fire. I figured I had no spark. Bought in inline spark tester. Yes, no spark. I then searched for an ignition coil wire diagram. I found several showing a wire going from the switch, straight to the external resistor/coil. I hooked up the wire from the coil, straight to the key switch. I started the truck, and it started right up.


My question is, why wasn't I getting spark running the ignition coil line through a fuse block vs running the wire directly to the switch? Is there going to be any issue with running the wire un-fused to the switch?


I'm new to wiring in general, but I've been teaching myself and learning as I go. This just puzzles me though.

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Lets start with this.  This is a wiring diagram for a 521.




Power comes from the battery, and goes to the fuse box on a white wire.  A second white wire then goes to the ignition switch, and there is no fuse. Ignition power comes from the switch, to the fuse box, on a black wire, white stripe.  This wire then continues to the ballast resistor.


A stock 521 ignition switch has five terminals. 

Power in.



Ignition ballast resistor bypass



If your truck was stock, a lot of us could help you, easily.  But since the wires have been hacked, that is way more difficult.

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That's where I'm hitting the wall at. It starts with the coil wire going straight to the ignition cylinder. It does not start when the ignition wire goes through a fuse block that is hot when the ignition is on.


I know the block is hot when the key is turned to ignition, because my fuel pump is wired to the same block and it comes on when the ignition is on. 

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I will have to check on that. I don't have "start" position on my ignition cylinder though. Its battery, accessory, ignition.



Ok, I bought a new ignition cylinder last night from Oreilys (where I work). I was having issues with the starter not disengaging last night, and read that the ignition cylinder could be the cause. I replaced it this morning (after ordering in a new starter last night). That fixed my starter issue. I reattached the the ignition coil wire to the ignition fuse block and the truck started right up.



Now I am going to have to figure out how to wire the alternator. I have 2 wires coming from it. It's off an ~80s Nissan pick-up so its internally regulated. It has two wires coming from the alternator. One puts out 13+ volts, so I attached that to my battery cable but my multimeter is still not showing me more than ~12.2 volts at the battery.

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With an electric fuel pump, your 521 is definitely not stock.   That put anyone trying to help you in a position of just guessing what the previous owner did.


If your ignition switch does not have a "start" position, how do you crank the engine?


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521s will have a wire that gors from the battery to the fuse box. then the standard thick wire at the starter that goes to the fuse box.


a 72 521 should have had a elelteric wire for the carb already.


this is ez/

pull the starter wire so truck dont turn off.

put key on The blk wht wire will have 12volts.

then move key to STSART the the blk red wire at coil will have 12volt witch is the by pass wire.(this is doubler lugged like in the drawing

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