Help me diagnose my DVA readings! I think it's my distributor...

Hey all,

Below, I have a pic showing what the voltage outcomes should be on my switch box (1974 Merc 500 50hp.) using my DVA adapter as well as the voltage results I got from my DVA adapter (IN RED). Clearly, the voltage is low coming in from my Lightning Energizer distributor (red especially); so, the output of the switch box is low as well. This was done at idle. Soooo.... The problem is in the distributor, right? I mean, if the voltage was right going in, it would probably be right going out... or not? Please weigh in!

Looking at my Thunderbolt ignition analyzer book the ohm spec for low speed coil(red) are: Rx100 scale and 350-450 ohms. This is tested between white and red wire disconnected from switchbox. There also should be no continuity between red wire and ground and any of the white wires and ground.
And if its low going in it will be low coming out....

faztbullet said:

Looking at my Thunderbolt ignition analyzer book the ohm spec for low speed coil(red) are: Rx100 scale and 350-450 ohms. This is tested between white and red wire disconnected from switchbox. There also should be no continuity between red wire and ground and any of the white wires and ground.
And if its low going in it will be low coming out....

Click to expand...

Yep. When I put my digital multimeter on "diode" and check the resistance of those wires disconnected from the switch box, all the numbers check out great. (On a rather weird note, when I use my analog multimeter, the readings are actually opposite of what they should be. Go figure THAT out).

Anyone? The readings (see above) coming in to the switchbox were pretty low from the Lightning Energizer distributor (this motor isn't alternator or stator driven) and too low on the switchbox output. Does this mean the distributor is dying or is the switchbox also possibly dying?

Thoughts? Guesses?

Had the high speed coil on one of those die on me. Motor would start just fine, but break up massively on throttle up.

Jeff

PS: Got a few of those for sale, cheap. Interested?

fastjeff said:

Had the high speed coil on one of those die on me. Motor would start just fine, but break up massively on throttle up.

Jeff

PS: Got a few of those for sale, cheap. Interested?

Click to expand...

Thanks, Jeff. Might take you up on that. One question, though: while you're dead right about the motor completely bogging and stalling out upon any acceleration, it's also got weak spark and is missing some when idling. But the red coil is the one testing way too low (as well as the switchbox output, I assume because of the low input) and that's the low speed coil. Could it be that both coils are bad?

Thanks!

I doubt it would run with both of them bad.

Jeff

If it runs ok on top end it not the switchbox or high speed coil....