Help! 1968 mustang coupe 289 hei distributor NO SPARK - Ford Mustang Forum
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post #1 of 9 (permalink) Old 10-23-2019 Thread Starter
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Help! 1968 mustang coupe 289 hei distributor NO SPARK

I just recently got a 1968 mustang coupe. It has the 289 v8. Car was running qhen i got it. I removed the points distributor to install a hei distributor. Now i can not figure out why i have no spark. The spark plug and wires are brand new. It has a new starter solenoid new battery. Ive installed 2 different hei distributors and still have no spark. The first distributor i installed the pick up coil was bad. I installed another distributor still no change. Ive gone through and tested the ignition module and even swapped the coil to verify its not those. Please help im at a complete loss. I do have the distributor hooked up via the relay method. Any and all help would be much appreciated thank you for your time.

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post #2 of 9 (permalink) Old 10-24-2019
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Did you measure voltage at the Batt terminal on the HEI both in the crank and run key positions?


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post #3 of 9 (permalink) Old 10-24-2019
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The original wiring in the car is set up to give the points six volts from the ignition switch in the run position. It does this by a pink colored resistor wire buried in the dash harness. Study the diagram to see this detail. Wire 16 (red-green) connects to 16A (pink) to 16B (red-green).

The factory starter solenoid (relay) is actually two circuits. The fat output wire obviously goes to the starter. Wire 32 (red-blue) triggers the solenoid. Small output wire 262 (brown) backfeeds wire 16B.

Your HEI, or any other electronic distributor needs 12 volts when cranking and at run, so that should solve the mystery as to why you are not getting spark when the key is in the run position. However it does not explain why you don't get spark when cranking. My guess is that you have a fault in that part of the circuit.

Try this:

1. Make sure that you have zero ohms between your distributor case and the battery negative. If not, install a #10 wire between them to achieve that.
2. Remove the distributor wire #16 from the circuit and use a jumper wire to connect it directly to the battery 12 volts. Crank the starter. If you don't get spark then something is wrong with the distributor.

Once you get the thing running you need to bypass the pink wire in the circuit. Best way to do that is to install a new #10 wire from the ignition switch #16A directly to the distributor. Then you can abandon the small wire output #262 from the solenoid.
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post #4 of 9 (permalink) Old 10-24-2019
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Yadkin explained it all, in simple terms all you need is a solid 12v from ignition.




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post #5 of 9 (permalink) Old 10-25-2019
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Or, you can install a 30A relay and use the #16 stock original coil wire to trigger by connecting it to the relay 86 terminal, run a 10ga from the starter solenoid battery terminal to relay 30 terminal, run a 10ga from the relay 87 terminal to the HEI batt terminal, and connect a ground from the relay 85 terminal to the relay mounting screw. This ensures clean full battery voltage to the HEI and not having to worry about voltage drops through the stock wiring.
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post #6 of 9 (permalink) Old 10-25-2019
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Quote:
Originally Posted by 07redstang View Post
Or, you can install a 30A relay and use the #16 stock original coil wire to trigger by connecting it to the relay 86 terminal, run a 10ga from the starter solenoid battery terminal to relay 30 terminal, run a 10ga from the relay 87 terminal to the HEI batt terminal, and connect a ground from the relay 85 terminal to the relay mounting screw. This ensures clean full battery voltage to the HEI and not having to worry about voltage drops through the stock wiring.
This will work, but Ford kept the ignition circuit unfused and as simple as possible for a reason. They also over-sized the wire.
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post #7 of 9 (permalink) Old 10-25-2019
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I agree, but ford didn't use an HEI back then either. I suggested a non fused 10ga to power the distributor.

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post #8 of 9 (permalink) Old 10-25-2019
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Quote:
Originally Posted by 07redstang View Post
I suggested a non fused 10ga to power the distributor.
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Quote:
Originally Posted by Yadkin View Post
...install a new #10 wire from the ignition switch #16A directly to the distributor. ..

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post #9 of 9 (permalink) Old 10-26-2019
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You still lose voltage from running through all the original wiring. Most HEI module failures are from low voltage.

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