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Discussion Starter #1
I started having problems with my Malory MSD distributor 6 weeks ago. One morning I went to start and the car, it just cranked, would not start. I found no fire to the distributor. Had it tested to find it was bad and bought a remanufactured MSD, stuck it in and could not get the car running. It would try to start but just misfire, backfire and would not stay running long enough to adjust the timing. I have tried to advance the distributor one tooth forward and then back to no avail. Finally, I stuck the brand new points distributor that has never been fired from my project vert and she fired right up. Drove it for a day or two and tried to put the MSD distributor back in with the same negative results. Tried another rebuilt MSD with the same results.

This is on my 1970 green standard w/ 351 C. I have 12V going from my starter switch to the cylinoid. 12V going from cylinoid to the positive on coil, a brand new stage 3 coil, and 12V going into and out of distributor. All of my grounds have been redone and cleaned.

She runs fine with the points distributor but won't even start with the new MSD.

Any suggestions? I have to leave in a few minutes but am looking forward to what you have to say. Sal
 

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12v going into and out of the distributor? Isn't that the problem right there? Shouldn't that be like 50,000V or whatever? Not gonna get any spark out of a 12v signal.
 

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Okay, looks like 12,000 to 40,000 is a more realistic range, from 30 seconds on Google. But 12V at the distributor means the ignition coil isn't doing anything. It should be stepping that 12V way way up, to a voltage high enough to create a spark.
 

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What distributor do you have? Is it a Mallory or a MSD? If you are running a msd box 6AL or Digital 6 or the likes. There should be two wires in one connector that go to the distributor one is violet the other is green I think. Unplug that connector turn the ignition on and get a paper clip or piece of wire and just touch the box side of the harness together very briefly (Tap test) repeatedly the coil should fire. That will test the box if you have one.
 

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Discussion Starter #6
I have the MSD distributor that has a built in module inside, so I don't have a box. I have a new harness and have spark from the coil to the distributor. I have not tested how much Volt the coil is putting out, but I have a spark tester and am getting spark to the plugs. I have 12 volts going to the distributor through the harness and spark to each contact inside the distributor cap. Sal
 

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OK. So you have spark at the plugs what color is the spark? If it is orange then the spark is weak. The spark should be blue.
 

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Discussion Starter #9
Will check whether orange or blue and meter coil voltage tomorrow. Thanks The coil is new. What could cause a week spark other than the coil? Sal
 

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Discussion Starter #10
All of the grounds have been checked and cleaned. I have the ground from the battery to the block. The distributor is grounded to the manifold through a new harness and I put a new braided wire ground from the fire wall to the block.
I even grounded the distributor straight to the battery and there was no change.
Sal
 

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What's the health of the battery? A full 12.5 volts needed for msd. Try charging up the battery.
Kevin
According to what I have read, the MSD systems will work to full potential with as little as 9 volts. The only other things that can cause weak spark is high resistance in the plug/coil wires, or reversed polarity of the wires on the coil. I have seen cases of the rotor button burning through and grounding to the distributor shaft, but that usually causes a no spark issue at the spark plugs. Make sure you have the coil wired up correctly. Also look for carbon tracking under the dist. cap. It will look black and will be very tough to remove (if you can at all) if there are signs of carbon tracking or a faulty rotor, look for bad plugs, wires, or even loose or bad grounds.
 

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Discussion Starter #13
The cap and wire are not new but do not have any signs of fatigue. The red wire is positive and the orange wire is negative. I have pulled plugs and cleaned them for fear of cylinders loading up with gas vapors and having vapor lock. I'll try to replace the coil wire and see if that helps. Thanks

The battery has had a work out but is kept on a charger the whole time that I'm working on it and test at 12V.
 

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Discussion Starter #16
That is the distributor, and the plugs are as old as the cap and wires. I have owned the car for 2 years. It would be a cheap fix to change out plugs.
 

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Discussion Starter #17
Woodsnake, thanks for site links. Will buy a set of high performance plugs and see if that solves the problem.
 

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Discussion Starter #18
Replaced coil wire and installed a set of NGK's and still will not start. The car ran fine with the old MSD distributor and will run all day long with the points distributor. What am I missing?
 

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Just went to MSD website. I want to verify that you have an 8350 dist. The diagram shows red to Pos side of coil. Orange to neg side of coil. Black to ground. Just to be sure why not take a jumper wire and jumper the black wire to neg side of battery. If you have verified that the pickup coil is within specs cold and hot then the only other thing it could be is the Ignition module in the distributor. Does this module look like a GM style module? If so you should be able to disconnect the pickup coil from the module. leave the wires connected to the ignition coil plugged in. Get a test light, connect it to the POSITIVE side of the battery. Turn your key to the run position. Take the test light and scratch terminal P on the module repeatedly. The coil should fire repeatedly. This simulates the pickup coil spinning in the dist. If you don't have spark after this test you have a bad module.
 
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