Need an ignition guru

[Brian in Illinois]

I have a 1953 MM UB set up for negative ground. I put a brand new battery in it. It turns over easy, but won"t fire. Checked the coil and distributor with a light tester. I found that the distributer has constant power running to it, when the ignition is turned on. I also found constant power on both positive and negative sides of the coil. Is the coil bad or are the points and condensor bad? Or both? Or am I looking at a different monster all together?

 

[Molineone]

Remember - don't run both a positive AND a negative to your ignition coil. One wire from your ignition switch to the coil, and the other terminal on the coil to your distributor terminal. Take one plug out of the engine and ground it to the case as you turn the engine over. You should see a spark. You might feel it if you are holding on to the spark plug, don't do this because it will hurt! (It's high voltage - it won't kill you, because the current is to low) Even with kinda bad points, you should get a little lightning. Good luck!

 

[rvirgil_KS]

Sounds like your points are not closing. Could be bad points or just need to take a business card or dollar bill and polish the point contacts.

Here"s a link to some electric diagrams. click "Miscellaneous Diagrams" on left side under Albums and find the one on "Ignition Circuit Test Voltages".

You can ground the wire from coil to distributor to simulate closed points.

Bob
Wiring Diagrams

 

[brian(MN)]

Here is a timesaver tip:

When I need to check for spark, instead of removing the plug and trying to hold it against metal somewhere, what I did was weld a large allegator clamp to a spark plug. Now when spark is in question, all I do is clamp that plug to a bolt somewhere and attach one of the spark plug wires to it.
Brian(MN)

 

[440roadrunner]

(quoted from post at 20:51:30 04/26/09) I have a 1953 MM UB set up for negative ground. I put a brand new battery in it. It turns over easy, but won"t fire. Checked the coil and distributor with a light tester. I found that the distributer has constant power running to it, when the ignition is turned on. I also found constant power on both positive and negative sides of the coil. Is the coil bad or are the points and condensor bad? Or both? Or am I looking at a different monster all together?

It is not clear to me if you did this test with the engine stopped or cranking. If the engine is stopped-----

the coil will show power on both sides of the coil IF the points are open OR if the the points are closed and are corroded

the coil will show power one one side only IF the points are closed AND if they are conducting, that is, not dirty or corroded

Also remember that if the condenser (capacitor) in the distributor is bad you will get very little and possibly no visible spark.

Here's how I check "no spark"

Use a 12V test light and verify power to the coil

Put the lamp on the coil points side, and crank the engine. You should get a blinking indication as the engine cranks

If no spark at the high tension coil lead at this point, you either have a bad coil or condenser, or possibly a bad coil wire