Hi,
i just found my dads ignition timing gun. Its pretty vintage. But im just curious how to use it. Is there any tutorial for how to use it on a cherokee? And maybe how to do the proper firing timing adjustment.
Cheers

 

You don't use it. The time is set by the computer. You can't adjust it.

 

Save the gun for your SB Chevy conversion. Your 4.0 won't need it.

 

Ok, noted. Thanks for the kind answers. Have a great day

 

Actually, I read somewhere that a dude used one of these timing lights to check his ignition wires/plugs. With the light pickup attached to a plug wire and the motor running, he shined the light on a piece of white paper and watched the strobe intensity and checked for consistant flashing. He did this with each plug wire.

It may be useful trying to chase down a misfire at idle(?).

I have a timing light left over from 'the old days'. Don't know if this works or not but I'm curious enough to see how it does.

 

I bought a nice new Matco timing light about ten years ago...used it twice. Money well spent!

 

Is that a dwell meter built into it?

 

Yup, the small separated part can be turned down. Looks like a space gun from the past.

 

I have been using a timing light a lot lately, since my 85 2.5l has adjustable timing. Experimenting with taking it up to 18degrees advance. Probably back it off a little to see if that helps the mileage on this winter blend gas though.

 

If you want to try it out, the inductive clip goes over the #1 sparkplug wire. There should be an arrow on the clip that points towards the sparkplug.
Red and black go to the battery.
Green goes to ignition coil (-) for checking dwell (back when ignitions used "points"- basically a switch to fire the coil), don't need to connect that one to use the timing light.

Pull the trigger and point the light at the harmonic balancer on the front of the motor. You should see the mark on the balancer appearing to stand still- that indicates your timing advance against a a marked tab attached to the block.


As mentioned, you can't adjust the timing- the computer does it for you. But you can look.

 

Also, might not need mentioning, but you do need to hook the red and black to the battery + and - respectively. Since it is a dwell-tach, if it were a Renix system, you could connect the green clip to a pin inserted in the #1 connection in the smallest diagnostic socket to be able to read the engine RPM while you're under the hood. The small switch below the meter would be pushed to the right and read the RPMs on the lower part of the upper scale for your six cylinder.


I don't know anything about '91 and newer, so don't know if there's anywhere you can connect for RPM on your '96.

 

I've had an intermittent misfire at idle for a long time. I'm going to try this trick to see if it's electrical or maybe a dirty fuel injector. I wonder if the pickup would sense the injectors firing if connected to their wires. Once again, thanks.