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REPU Ignition Issues

Old 05-04-18, 12:34 AM
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because race car.
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REPU Ignition Issues

Good lord, my first time on this forum in over FOUR YEARS. Good to be back!
So, here's the deal: I just bought a 1974 REPU and am having a little trouble getting it to start. Got good spark while cranking on the leading plug wires, but the trailing wires have nothing. After a bunch of troubleshooting, here's what I found:
With the key ON I get around 9-10V on the (+) side of each coil. With the key in START, however, power remains good on the leading coil but drops significantly (almost to nothing) on the trailing coil ONLY. I've checked some simple schematics (my REPU shop manual doesn't have a full wiring diagram for some reason) and believe it to be a faulty ignition relay. Does this sound right to yall, and if so, where on earth do I buy one?
Is there anything else I should be checking? Any advice would be greatly appreciated.
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Old 05-07-18, 10:41 AM
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Lapping = Fapping
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It might be the ballast resistors. Are you keeping the points?
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Old 05-08-18, 10:18 AM
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because race car.
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I do still have points, yeah. I checked the ballast resisters, though, and they are both outputting 9-10V to each coil, and its my understanding that with the key in START the circuit actually bypasses them, and that's where I'm getting my loss of power.
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Old 05-08-18, 07:44 PM
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The REPU has two wires to provide power. One is in the key START position while the other is in the key ON position. This is obviously to provide two different voltages to the coils depending on key position. As you are aware, START is full battery voltage because it bypasses the ballast resistors. This is necessary as cranking the engine drags the voltage down a bit, sometimes to 10 volts or less seeing as the battery is located under the bed and the cable is only aluminum and subject to corrosion over time leading to a slow starter speed.

I upgraded my REPU to electronic ignition and later to DLIDFIS. I connected both the START and ON wires together and this worked but it sounds like yours possibly has a fault in the key switch itself. Consider disassembling it and cleaning the contacts. Then grease 'em and check for continuity.

Well, good luck. I happen to like electrical unlike most people haha. Hope it works out in the end.
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Old 06-02-18, 11:24 AM
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Power Harness

I had a similar issue with my REPU so I replaced the power side harness after checking all components were in good working order. Problem solved...Bad terminals.


1977 Mazda REPU
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