Kevin71

440 in a 71 challenger Have a msd 6al and the msd pro billet dist. Couldn't get a spark. So I bypassed it directly to the coil. It cranked and ran. Had to do some welding on the fender support underneath. So I disconnected the battery neg. pulled the msd box and coil out. Pulled any electrical and ac lines away from the fender to make sure the heat didn't harm anything. So put it back together no fire from the coil. Coil is getting 11 volts at the positive and 11 at the neg when ignition is on. ohm meter is reading from + to - 1 on the 200 scale. from center to +or - reading .006 on 2k range. Ideas anyone

RacerHog

You have 11 volt on the ground side? (Large Black Wire)

Anyway..... Here is the test for the box.....
http://www.msdignition.com/page.aspx?id=3206

DDodger

"Bypassed directly to the coil." Have no idea what this means. Are you trying to RETAIN the factory breakerless ECU and use it to fire the MSD? Might be wiring problems. MSD NEVER has DC voltage at the coil, "that is not how they work."

Just to throw another joker in the deck, make sure you do NOT have the tach hooked up. The only wire going to the coil pos and the coil neg should be from the MSD. Do NOT connect tach or suppression condenser to the coil with MSD

Now, if you have the MSD removed, and are "back to" stock system, is this factory or a conversion unit?

Use a grounded probe at the coil tower, that is a screwdriver and clip lead to ground, to check for spark.

Turn the key to run. At coil + you should have somewhere between 6 and 11 volts. Much lower or much higher "is a problem."

At coil NEG you should have very low voltage, perhaps 1 or 2 volts.

With the key "in run" take the ECU side of the distributor connector and tap the bare prong to ground. Each time you do so should produce a spark

If so.....concentrate on the distributor as a problem.

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The ECU MUST be grounded. Higher voltage on the NEG coil lead indicates a poor ECU ground.

Wiggle and work all connectors, ESPECIALLY the distributor connector

Hook your meter on AC---that is right --low AC volts to the distributor connector. Crank the engine, the distributor should generate about 1V AC.

Inspect the cap and rotor for damage, for moisture, grease, carbon tracking. Look at the reluctor / pickup for strike damage, debri, rust Check the gap with a brass feeler for .008" (inches)

Disconnect the ballast and check each "half" for continuity. It is two resistors "the long way" in one "box."

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NOTE

You say 11V at coil NEG. Assuming everything with the Mopar system is wired right, either the ECU is NOT grounded, you have a wiring problem, or the ECU or the coil is bad. Check coil continuity. Remove the ECU, scrape around the firewall bolt holes, and the back side of the ECU flange, and remount tight using star lock washers.

The Mopar ECU system WITH the key "in run" draws coil current "just sitting". This means that "juice" is flowing from battery, through the harness, through the coil resistor, to the coil, and to ground. (Actually goes the other direction). What this results in here is a VOLTAGE DROP across the coil resistor. The resistor should have "same as battery" voltage at one end, and somewhere around 6--11V at the other. The coil NEG should have very LOW voltage, as it is "grounded" by the ECU.

Therefore your 11V reading at the coil NEG is NOT what you want to see.

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HOWEVER that 11V shows the coil is NOT drawing current, and this means you should have BATTERY voltage at the coil resistor. WHY NOT? Is the battery dead? What is the voltage at the battery? A further check with "key on" would be to measure voltage at the BLUE alternator field lead. This should be very very close to "same as battery." If it is lower than battery by more than .2---.3 volts (3 tenths of 1 volt) then you have a wiring / connection problem in the harness