720World

Little Trucks, Big World

Hi there 720 World,

My truck is not getting getting any sparked, so I went to check my coils and I realized that I have four wires just hanging out in my engine bay, with no homes. There are coming from my distributor, and they are colored black/white, blue, white, and red.

I can't find those anywhere on the wiring diagrams in the Chilton manual I have. Any help? Thanks guys.

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Hi Noah,just opened my hood and checked out them wires coming out of the distributor,I have a 85 year too,the wires leave the distributor ,then go under it into a cable then goes under and comes out in front of the coolant over flow tank,underer a little bit,you can see all the color wires,it connects into a fitting.

I just took some pics Noah,them wires go under your distributor into a cable and it travels to the front of your coolant overflow container,you can see the wires. as they go into a big connector,somehow,your's came undone under your distributor.Going to be tough reconnecting them.

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Cool man! I really appreciate the help! Thank you so much!

There were 3 and 4 wire distributors. The 4 wire distributors used a single white wire that was separate from the other three to disable the exhaust side coil when accelerating under a load. A manifold vacuum switch would connect a ground signal to this wire and the ignition module would respond by deactivating the exhaust side coil.

Here is the 4 wire distributor. Note three wires have round terminals and the fourth one has it's own plug. The three wires bundled together should go to a terminal block near the rad. Here they connect to the ignition power wire and the two coil negative wires. You can leave the forth wire disconnected if your harness never had this feature. All plugs will fire all the time.

One wire is switched 12 v from the ignition switch to power the ignition module.

One goes to the intake coil negative terminal

One goes to the exhaust negative terminal

Sorry off hand I don't know which color goes where. Seems there were different wires for different years. The B terminal below is most likely the +12 from the ignition. E and  C are the coil negative wires. The single terminal I on the far right is likely the forth wire that disables the exhaust plugs.

The ignition switch sends power to the intake coil positive terminal and also to the ignition module in the distributor.

The exhaust coil power comes from the first fuse on the left of the fuse box . I don't know why, I don't know if Nissan even knows why, but if the exhaust side stops working it's likely this fuse blown.

In operation the ignition module provides a ground signal to both coil negative terminals and power flows through them from the ignition switch through the positive terminals. When the reluctor senses a magnetic signal the module removes the ground, the magnetic field around both coil cores collapses and a high voltage spark is generated that is sent to the spark plugs in that cylinder. The module turns on the ground and the coil recharges for the next cylinder. Under certain load conditions the exhaust coil can be disabled but otherwise intake and exhaust coils fire together.

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