Timing Light

I bought an inexpensive HEI distributor for my '70 cj5.


The engine started and ran. I turned the distributor a bit until the engine ran well. Then I hooked up a timing light. I bought the timing light new in the late 1980's.


I couldn't get the timing light to work. I checked the connections. I even took the light apart and inspected the xenon bulb. I figured it must be burned out. I bought a new timing light from Harbor Freight and it didn't work either.


No way could two timing lights be bad. I tested both timing lights on a '53 jeep that has a '76 odd-fire 231 and HEI. Both lights worked fine. What could the problem be? Ah ha, I forgot to short out the resistor when installing the new HEI. Perhaps the lower voltage to the distributor didn't generate a sparky enough spark to trigger the timing light? I jumpered the resistor. Did the timing light now work? Nope.

When I installed the HEI, I had to install new plug wires too, because the distributor connectors are different between the stock distributor and the HEI. Could the shielding on the new plug wires be so good the timing light pickup can't register the high voltage pulse?


Got any theories?

 

Yeah, both timing light pickups have a little sparkplug symbol and an arrow. I've checked and checked the arrow is pointing toward the sparkplug.

 

Did you try a differet wire? Could be dead on one try number two just to see if the light works.

 

Bad connection at the battery? Your HEI needs 12 volts, not the 9.8 or whatever the OEM uses.

 

Yes, I tried the pickup on other wires with no good result. I just tried replacing the new number one wire with the old wire and finagling the mismatched connector to work on the distributor. The timing light worked fine on the old wire. The new wires must have some sort of super shielding or something.

 

That's a new on on me. That's some good shielding!

 

I suspect that the timing light power supply is reversed polarized. In the above picture appears that the timing lights red/positive power cord clamp is attached to the black/negative terminal. The red clamp is somewhat visible just behind the battery disconnects "red key." The "red keyed" disconnect switch looks to be installed on the black/negative terminal.

 

Agree..........Bigger pic , Please.

 

It's interesting, I never gave this any thought before. I have two Snap-on lights with no markings on the pickup but my smog-machine pickup is so-marked.