Yesterday im diagnosing a miss which turns out to be a burnt plug wire. In the process i lift the distributor cap and look at the rotor, i didnt unhook any wires. I set the cap back down and ever since it wont start. No spark at all.

I spent the last 3 hours tearing it apart and checking for breaks in wires and the resistance on the coil, and everything looks fine, but still no start. Its getting 12v, at the cap and at the module, the other side of the module has a about 1.5 volts. I dont know it its possible to test it myself.

I dont want to start replacing parts at random, since it seems unlikely that something just died at the exact same time i touched it.

 

What kind of condition are the cap and rotor in? You didn't say so specifically, have you pulled the cap off again?

Is the coil button intact under the coil?

Factory coils have been known to fail for no apparent reason. Trigger wheels have been known to lose magnetism.

 

Cap and rotor have about 15k km's, coil, no idea. They both look fine, no excessive wear or pitting, i cleaned all the contacts and checked for continuity. Im suspecting the coil. Coil button is present, ive removed the cap about 6 times since.

I did notice the voltage being supplied to the coil dropped to 6 when cranking. I dont know if this is supposed to happen. Im doubting this is enough to fire the module.

 

just a question here are all the wires plugged into the distributor ??

i dont mean plug wires

i mean the main wire that comes off the distributor and then up the the cap behind the power and tach wires make sure all the connections are secure

just a thought

 

yep all wires are good, and have been checked for breaks, ground, or voltage

 

turned out to be the magnetic pickup..replaced the coil and cap/rotor, wired it on the bench to a power supply and spun the shaft and nothing..

i held an electric drill near the ignition module and the field from the drill made the module fire.

gonna take the new coil and everything back tommorow and get a new pickup

 

I took the old coil out its resistance is 797 ohms. A search showed that it's within spec. I also was able to use the tach on my meter and measure 50-60rpms at the coil leads when spinning the shaft.

The coil seems to be some what responding, but the ignition module fires correctly when i hold a drill near it, i get a nice fast consistant blue spark though a spare spark plug.

So is it the coil, reluctor, or module?

This is all with my old cap/rotor/coil, they seem to work fine.

Oh and i get no spark with the distributor wired and spinning the shaft its dead.

[edit]
I disconnected the pickup coil and used a voltage to trigger pin G on the module, and the plug fired. So it seems the module is fine. On a side note i used a rather large soldering iron and was able to induce a 2" spark from the plug to ground, pretty interesting until it travelled up my arm.

 

um OUCH!!!!

 

Not unheard of for one of these - coil, pickup, or module - going bad and taking out the rest (nephew's '86 LG4, for one).

A coil can check out on the bench and fail in the car (especially when it warms up).

It's not a good idea to power the system when the secondary circuit is incomplete. The high voltage produced when the magnetic field breaks down is going to want to go somewhere, and the easiest path might be through one of those components that isn't intended for high voltage (or your arm...).

New pickup, module, and coil is a pretty good plan. I don't know of a way to test the reluctor, other than trying it with all of the other components known good.

 

i got a new pickup coil and reluctor, that fixed it. I can just spin the shaft and it works now.

[edit]

all better, running good as new