After recently suspecting my ignition coil was failing on my '78 20R, I went searching for "good" coils specs so I could test my coil with a volt/ohm meter. After much legwork I was finally able to locate a complete source for the ignition coil specs, so I decided to post them up here for reference. These charts cover coil specs for the 8RC, 18RC, 20R, 22R, 22RE, 22RE-T, 3VZ-E, F and 2F, and the 3F-E. Years covered are 1968 to 1988. I put 1975 to 1988 in the title as I know that's what most people will be looking for.

Here's the spec charts, plus diagrams on how to test both Primary Resistance and Secondary Resistance:

Primary Resistance Specs
Primary Resistance Testing, + & - terminals on coil, ohm meter range 200.
Secondary Resistance Specs
Secondary Resistance Testing, - & center port terminals on coil, ohm meter range 20,000.

 

I have an 86 2WD SR5 X-cab 22RE and about 25 years ago I upgraded my still working stock coil to a MSD Master Blaster 2. It provided ~45,000 volts vs ~15,000 stock. It has not had one issue and still in use. It did allow me open the spark plug to 0.40 for a bit bigger spark kernel. Not any huge power increase, but I feel a more instant throttle response and the engine doesn't seem to die above 5000 RPM. Fit perfectly in place of the stock coil. I paid ~ $45 and it's now ~$75. I highly recommend one.

 

I've got a 22R-E in a 1988 4x4 pickup and the coil tests out to the 1988 specifications in the list but the ignition is breaking down under load. Don't know if that means bad igniter. wires, cap and rotor not too old. But this is classic, idles perfectly, revs up at park but as soon as I go to move the truck it completely dogs out. there are tons of videos of folks monitoring ignition wave forms on oscilloscopes with the car parked and idling or revved without load. Is there any way to monitor this while actually operating so I might get some hint at what is actually going on?

thanks,

brian

 

Engines under load require more fuel compared to just revving it without load, so this could be a fuel issue. First thing I'd suspect is the Idle Air Control Valve. They can get carboned up just like EGR valves, so maybe taking it off & giving it a good internal cleaning wouldn't hurt any.

If you still think it's an ignition problem, test out the coil after you've run the engine at idle up to full operating temp. Make sure that coil gets all the "normal" heat it usually gets, then test the resistances again. A weak or failing ignition coil is going to show a noticeably higher resistance reading hot over cold. And usually on the Secondary side. When ignition coil get weak, the resistance goes up with heat, and they can't pass as much current as an in-spec coil. It may not be producing enough current to totally fire off the increased air/fuel mixture under load. So, bog & sputter happens, as your mixture is basically too rich, as it's not getting completely burned.