MSD pro billet dizzy 8534

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russhal

russhal

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Has anyone else had problems with an MSD dizzy? I've used MSD products for years but can't figure out why this dizzy won't work. I have an FiTech fuel injection set up on the car. Shortly before swapping from carb to efi, my car developed a miss mid range to upper rpm. Just like with a bad plug wire. Changed wires, thought I had it fixed. One week after efi swap, starts up again. Gets so bad, the efi would lose tach signal and shut off. I Chase it down to the dizzy. Put a mopar dizzy in, problem solved. I replaced the cap, rotor, and pickup on the MSD. Put it back in, problems back. Put the mopar dizzy in, problem solved. I have a $250 paper weight. Any thoughts? MSD was no help at all.
 
Seems like a distributor machine, or bench testing with 8 plugs, variable speed dril, timing light and scope would get to the bottom of the problem.
 
Try that, observe what all cylinders do. My gut feeling, it could be a rotor phase phase issue with cap terminals. I say that because you changed everthing out. As the timing advances, the rotor could be pointing between cylinders. That would generate a huge gap, resulting in EMI that could latch up the module, your loss of trigger.
 
I was looking at rotor phasing very close. When the pickup and reluctor are lined up, it's dead on. But cap on this style dizzy is pretty sorry. It doesn't lock in like it should. It has the little L shape locking tabs. With the cap in place, you can wiggle it back and forth. Not good.
 
I feel pretty dumb about the whole cap thing. It's locked down with screws. Not sure I'm ready to do the dizzy shuffle again. It's running really good with the factory dizzy. MSD suggested I use their shielded dizzy cable. It has a ground wire. Anyone using the shielded cable.
 
It seems like correct wire routing is important. The distributor trigger should be kept away from plug wires. The trigger wires should also be short as possible. Cable shield is always good, typically grounded on just one end, to avoid noise from ground loop.

A high voltage probe and scope will likely find your issue, without, just making guesses. It might have something to do with trigger levels, need for pullup.

Both MSD and FiTech seem to lack pertinent documentation. Things like MSD output drive type, FiTech input signal requirements.
 
Any time you see a schematic of a hall effect, VR pickup or magnetic pickup into a PCB, you usually see a ground sheath around the 2 wires. Like a coaxial but having 2 cores. Could you be generating enough RF interference that the ECU loses its pickup trigger signal? MS example off a Ford EDIS
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If I am generating that much rf pishta, the chrysler distributor doesn't seem to have a problem overcoming it.
 
Might have a different style pickup? Looks like both use magnetic triggers....Reluctor gap set ok, any shaft wobble? If the Mopar works...? Just sayin'.
 
I am wondering how it is wired in each case. It is not clear to me in your posts. The Mopar electronic distributor is variable reluctance, is the ECM used with that to drive coil, - lead to FiTech? The MSD seems to drive coil directly, similar. If you are using just VR to drive FiTech, that is completely different. The timing will be different vs RPM, and signal output completely different.
 
Msd is in control of all the timing as far the fuel injection goes, it just receives a tach signal from the msd box. All I'm doing is changing the trigger out going from one distributor to another. I did catch a something in an msd tech bulletin. It said it was recommended to use a shielded distributor cable with fuel injection. I'm going to try that
 
Gap is set to .018 to .030 on the msd. The mag on the msd seem to be not only larger but stronger
 
Use a scope, view the output of the distributors when turning with drill. Observe signals, check polarity. I have heard the polarity is sometimes swapped. There may be a 50% chance it is wrong. Stuff happens when things are made in China.

Check post #5 here http://www.forabodiesonly.com/mopar/showthread.php?t=217220&highlight=signal
Note signal peaks low before peaking high, if signal peaks high then low, polarity is wrong. Observe as used in connection per MSD box.

Rotation direction, offsets signal by tooth, not polarity.

A sound card could be used to check signal, but at very low RPM. The signal amplitude may easily blow the sound card, it increases with RPM.
 
The only time I've had an MSD dizzy fail me the pickup went bad. They use a ford pickup. I know you replaced yours but you could run to advanced auto and get one more to try.

If this were my car I'd order another MSD dizzy from summit and try it. If it works, return your old one. If neither work, it's a compatibility issue.
 
Check the static timing. Based on where base timing appears with timing light set crank to that, observe were reluctor is in relation to pickup. It should be on a tooth, sightly off center on the trailing side. If it is between teeth, the problem is phase incorrect at module. Pins should be swappable at connector if you know how to release them.
 
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