Inductive Timing Light Won't Fire - Help?

[tom1394racing]

Getting ready for the first drive on my '70E restoration project. The engine is in the car and has been run in for 20 minutes at 2000 RPM. Seemed to run just fine. Smooth, no funny noises or leaks. Did the first oil change and decided to check the timing using my trusty Craftsman inductive light with dial in advance settings. This light has always worked well for me on my '73 and previous cars. Hooked the negative to the coil stud ground, the positive to a terminal on the 3 pin fuse and clamped the inductive lead to the #1 spark wire. No flash on the light. I double checked for 12 V to the positive and neg leads to the light and also tried another plug wire. Still no flash on the light. I also tried powering the light with my 12V power supply. Still no flash. I also put an in line spark detector on the # 1 plug wire and it flashed as it should. It had been about 2 years since I had used the light so I fired up my '73 and connected the light as I always do and it worked like it should.

Anyone have any idea what my problem is? Are there certain types of plug wires that will not fire an inductive light? Could my spark be too weak to fire the light? I am thinking that possibly I might just have too weak a spark to trigger the inductive timing light but enough spark to run the engine. Everything in the ignition system was rebuilt except I’m using an original used Bosch black CDI coil. I checked the coil resistances both primary and secondary and they were right within spec. I guess I might try an new MSD blaster coil and see if that makes a difference.

Any other ideas??

[boyt911sc]

Tom,

I also have a Sear’s inductive timing light that is more than 30 years old. They don’t make them as good as these old products. Were you having problem getting ignition signals with the motor running? If the motor is not running, there would be no signal. It was NOT clear to me after reading your post that the no-signal was with the motor running. Thanks.

Tony

[Speedy Squirrel]

Light bulb might be burned out. Summit has replacements. Test on another vehicle?

[dannobee]

Try hooking the inductive lead up to the coil wire instead of a spark plug wire. If the timing light works, the only difference will be that it'll be brighter. If still nogo, the timing light is probably bad.

[ahh911]

The 30 year old sears timing light didn't work for me either. Opened it up and it turned out the connection from the trigger to the board was a crimp type connection and over the years had picked up resistance. I turned the wire in the crimp and voila. I used a multimeter for the whole thing. 20 min and it worked. The last time it was used before this was probably 1990.

Phil

[tom1394racing]

The engine was running and #1 was firing but no signal from the light. I tried the light on my ‘73 with MSD and it worked fine like it always had. I will see if it will fire from the coil wire. Good idea there. I might also try swapping the coil from my ‘73 into the ‘70.

[stownsen914]

Can't recall now where I read that timing lights that have the adjuster knob dont work well with some modern electronic ignition components. Might've been either MSD or the old Allison point replacement (Crane now I think)?

[tom1394racing]

An update

Yesterday I swapped the #1 plug wire from my '73 into my '70. No flash on the timing light. I then swapped in one of the MSD coils from my '73 into my '70. I then started getting an intermittent flash on the light. Not steady. I reset the inductance pickup to more firmly cover the plug wire (that I had swapped back to the original) and got enough of an intermittent flash to set the timing. I then put the original Bosch coil back in the '70 and no flash. My conclusion at this point is a bad timing light. I will try to borrow a known good one one locally to see if it works on my '70.

[safe]

I use a CoP setup and when I was doing the timing recently I put a short plug wire between the CoP and spark plug, but the timing gun would not fire.
But I discovered that if I had the clamp open, not closing it over the HT wire it would fire. It also worked if I clamped the low voltage wires to the CoP or just held the clamp on top of the CoP.

It was a normal cheep timing gun... It was almost like it wanted a weaker signal or something.

[tom1394racing]

An update. I borrowed a friend’s ancient in-line timing light. It gave a steady flash. Too dim to time with any sunlight. But works well in the dark. At any rate I have my timing set. Thanks for all the help.