Ignition Cable Switch Failure

[NMC_EXP]

This is a carry-over from another failure to start thread.....

Does a failed "ignition cable switch" cause failure of the starter to crank or does it cause no spark at the plugs?

Thanks

Jim

 

[Pin_Head]

It could cause either or both depending on how it failed.

 

[Living in the Past]

Could someone explain what a ignition cable switch is? A ignition switch could cause either. The one time I tried to started my 73 FST the coil only had power when the switch was turn to the start position. Engine would start and die as soon as I released the switch and it moved off of start. Picked up a new switch just never got around to replacing it. Twenty years later I think I have more problems now. Tags had expired in 88 so it had already been sitting six years when I bought it.

 

[NMC_EXP]

It could cause either or both depending on how it failed.

Thank you sir.

The unit is a March 1979 FJ40. A Toyota dealer shop is working on it. The tech says things are correct at the coil but nothing coming out of the distributor. I should have taken notes on the details.

How would you troubleshoot the ignition cable switch as being the cause of no spark?

Jim

 

[Pin_Head]

How would you troubleshoot the ignition cable switch as being the cause of no spark?

Jim

1. Bypass the switch with a hot wire from the battery + to the coil+ and ignitor +. Disconnect the switch wire at the coil first. If it runs, then the switch circuit is bad.
2. If you have no spark in situation 1, then disconnect the wire at the - side of the coil and momentarily ground the - side of the coil with a jumper wire. Check for a spark at the HV center wire of the coil. If no spark, then the coil is probably bad (Unlikely as they rarely fail). If you get a spark, reconnect the stock wires at the + side of the coil and repeat. If you get a spark, the switch wire is good and the problem is in the distributor pick up or ignitor.

 

[NMC_EXP]

Thanks Pin_Head.

Electrical stuff is black magic to me.

Jim

 

[Pin_Head]

It is often useful to mentally visualize DC circuits as a hydraulic fluid, like water because most people are familiar with water hoses and valves.

http://en.wikipedia.org/wiki/Hydraulic_analogy

 

[NMC_EXP]

It is often useful to mentally visualize DC circuits as a hydraulic fluid

With DC I'm ok with pos, neg, switch and ground. Its all over for me when diodes, resistors, capacitors and the like are involved.

Thanks

Jim

 

[Pin_Head]

The fluid analogy works for those devices too.
Diodes are one way valves
Resistors are constrictions or small diameter pipe.
Capacitors are like water storage tanks.
Transistors are electrically controlled valves.