How the heck is this engine even running??? lol

[Fast79Chief]

I was just reading an earlier thread about Duraspark ignition problems, and after reading all of it ... I cant understand why my engine even runs!! According to the experts, it shouldn't even start, right?
Seriously ... what the H is allowing my MSD billet distributor to work with an Accel coil and a new Duraspark ignition coil??? Is this some kind of electronic magic going on here?
tgress and you other members who are very knowledgable electronically ... please chime in here and tell me what I did right or wrong, and if you think it will last or burn up.
Thanks guys.

[PossumJr]

What have you actually done? The Duraspark doesn't need much to operate and do it's job as far as external input/outputs go. Coil shouldn't matter as long as you maintain the appropriate resistance between the module and coil so you don't burn it out from excess current and the coil itself isn't drawing more current than the module is designed for. As for your distributor, I'm not familiar with the MSD ones but as long as the mag-pickup supplies a compatible output signal to the module it shouldn't matter, it's only looking for pulses. As long as you have everything hooked up right, I don't see why it wouldn't work unless there's something big I'm missing.

[Fast79Chief]

The MSD Pro Billet is a small cap, rotor style distributor with 3 wires coming out of it, one if them a ground I believe? I spliced the 3 wires to the 3 wires from the factory ignition module plug, bought a new ignition module of the correct year ... and VRRROOOM, it fired up and runs strong.
I have the aftermarket manifold and carb, no pollution crap, so I guess it's done right?

[tgreese]

What does the MSD documentation say? The MSD module can be triggered by either points ignition or a VR (variable reluctance) magnetic sensor. Both the HEI and Duraspark are VR distributors, and I'd guess the MSD Billet distributor is too. Basically you have replaced one VR-type distributor (Duraspark) with another (MSD Billet). The Duraspark module accepts the VR signal from the MSD, just like it would from the Duraspark.

The only issue might be the polarity of the distributor wires. As you guessed, the black wire is ground which splits the signal between the other two wires. There's a 50-50 chance that you connect those right, though I suspect it will still work (with the wrong phase of the magnetic signal) when wired backwards. Did you match the colors? If so, you probably have the phase right.

The coil should not matter, but the Duraspark modules expect some extra resistance in the coil wire between the ignition switch and the module that limits current to the module. Jeep uses a resistance wire between the ignition switch and the coil to add this resistance.

[Fast79Chief]

Thanks Tim, I'll have to take some pics and post them to see the wiring. I'm not near the vehicle until this weekend, but I do believe there are 3 wires up at the coil + and - ?

[tgreese]

The distributor wires go to the module, not the coil. The module switches the coil on and off, making the spark. Any wires to the coil either come from the ignition switch or go to the module. There could be other wires at the coil, such as for a radio noise condensor, or for a tach signal, but those don't have anything to do with the spark.

[Fast79Chief]

Ok ... I replaced the broken 'horseshoe' clamp at the coil terminals with a new one, and what wires were going to the coil terminals were spliced in to the new connector.
I should go have someone go over everything with a meter to make sure all components are getting proper voltage, and resistance is correct.

[PossumJr]

Ok ... I replaced the broken 'horseshoe' clamp at the coil terminals with a new one, and what wires were going to the coil terminals were spliced in to the new connector.
I should go have someone go over everything with a meter to make sure all components are getting proper voltage, and resistance is correct.

Do you own a multimeter or have $5 to buy a cheapo analog one from somewhere like Hazard Fraught? Checking voltage at the coil is easy, and if you're going to own/ be wrenching on an old Jeep, you should have a multimeter for troubleshooting anyway. Coil (+) should have a reduced voltage of 6-7V, it will vary but it won't be full battery voltage. You could try to measure the resistance, but voltage will tell you what you need to know just fine. If you measure that, the resistance wire is there and doing it's job. The coil in a stock Duraspark set-up should only see full battery voltage during cranking. Coil (-) does not connect to vehicle ground directly and is switched by the module so there's nothing to measure there and it cannot be used to measure voltage at (+).

[Fast79Chief]

Ok ... I replaced the broken 'horseshoe' clamp at the coil terminals with a new one, and what wires were going to the coil terminals were spliced in to the new connector.
I should go have someone go over everything with a meter to make sure all components are getting proper voltage, and resistance is correct.

Do you own a multimeter or have $5 to buy a cheapo analog one from somewhere like Hazard Fraught? Checking voltage at the coil is easy, and if you're going to own/ be wrenching on an old Jeep, you should have a multimeter for troubleshooting anyway. Coil (+) should have a reduced voltage of 6-7V, it will vary but it won't be full battery voltage. You could try to measure the resistance, but voltage will tell you what you need to know just fine. If you measure that, the resistance wire is there and doing it's job. The coil in a stock Duraspark set-up should only see full battery voltage during cranking. Coil (-) does not connect to vehicle ground directly and is switched by the module so there's nothing to measure there and it cannot be used to measure voltage at (+).

Could you send me the $5 ?

[PossumJr]

Best I can do is a half-eaten ham sandwich.

[Fast79Chief]

A "5 dollar muti-meter" would have about the same use as a half-eaten ham sandwich, depending on the kind of bread and if it had mustard or not. Now a 15 dollar multimeter ... we're talkin pork roast with taters!