# Timing Light Mystery



## Mike O’Neill (Feb 5, 2019)

Got a new Innova 5568 Pro Timing Light. Tried it on my 67 GTO with the clamp close to number 1 plug and the arrow pointed toward the plug. Found the timing exactly where I left it with my old timing light. I then tried the Advance feature of the timing light, expecting to see it move the indicated degrees on the damper. No effect at all - it still pointed the same as with advance set to zero. Then tried it on my 1963 CJ5 Jeep - it worked as expected. Pressing the advance up/down buttons on the light would move the indicated degrees on the damper.

I called Innova - the guy was stumped but said he would discuss with the other techs and call me back. He hasn't in over a week.

I was about ready to sent the light back, but on a hunch I tried clamping to the plug wire far back, about even with the back on engine block. It worked correctly there. I then tried it about midway between the plug and back of block, and saw a double flash. One would show the expected advance, and one without. This seems really odd. The plug wires are much closer together near the back, where cross feed would be expected.

The GTO has what looks like an HEI distributor from a late '70s GM vehicle, installed by previous owner. But the light is supposed to work with HEI. Any ideas what causes this weird behavior?


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## Mine'sa66 (Oct 30, 2019)

Just spitballing. Not too much it could really be. The inductive clamp has an issue or there's something weird with your plug wire. Maybe something strange with the spark plug itself. Maybe it has one of those HEI modules that multiple fires the plug and the light is having trouble with that?
Clamp on the pickup not closing correctly?
Can you switch out the plug wire on the GTO?


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## Lemans guy (Oct 14, 2014)

Could be a bad plug wire, try hooking it to the number 6 plug and reading the advance....you can time off number six as well.....also try switching the plug wire with another one. To see if that works,...if so then replace the plug wire. If the number 6 wire works then switch it with number one...if it will reach, because you know that one is good...


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## Mike O’Neill (Feb 5, 2019)

Thanks for replies. I tried it on plug wire 6 and it acts the same way, maybe a little worse. Maybe there is something flaky about my plug wires, although the car idles and runs OK.


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## Mine'sa66 (Oct 30, 2019)

Mike O’Neill said:


> Thanks for replies. I tried it on plug wire 6 and it acts the same way, maybe a little worse. Maybe there is something flaky about my plug wires, although the car idles and runs OK.


Sure sounds like it. What are they? Maybe the insulation is something unusual. Are they heat shielded in some way?


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## LATECH (Jul 18, 2018)

Voltage drop down line on the wire. Wires have X amount of resistance per foot. The farther from the coil the higher the resistance, the lower the voltage. Higher voltage increases the possible amount inductance, which is the type of pick up the timing light uses.


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## Lemans guy (Oct 14, 2014)

Agre with mines and Latech....two bad plug wires #1 and #6.....you need new plug wires


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