CDI box off whilst cranking? Ideas?

[Gary71]

Trying to start the car and it would appear no power is getting to the CDi box whilst cranking.

There is only a spark when you release the key, when it briefly tried to start.

Obvious suspect is ignition switch but anything else I should be looking at?

Thanks

[MikeB]

Is the CDI box making its whistling noise when the ignition is turned on?

Usually the symptoms you describe mean the starter is drawing all the power, so give your battery a charge and check/refresh your battery terminals and connection at the starter motor.

[Gary71]

Yes, it’s whistling happily ignition on and when the engine is running, just not when cranking!

Oh and it did accidentally start on the single spark when you turn it off, so at least I know the engine runs!

[Gary71]

Voltage at central red wire drops to 0 whilst cranking.

[PeterK]

Either the ignition switch or the wire that runs to the rear fuse panel is connected to the wrong terminal in the front panel (linked to accessories, not run)

[Gary71]

Either the ignition switch or the wire that runs to the rear fuse panel is connected to the wrong terminal in the front panel (linked to accessories, not run)

I’m sure it’s something like that, there’s power on the rear panel that stays live during cranking, just not to the wire that goes to the CDi box.

I’m going to buy some new batteries as mine are toast, but I don’t think that’s this problem.

Give me a mechanical issue any day!

[impmad2000]

Did you re-wire at all ? Sounds like a wrong feed to the CDI. Make sure the feed also goes off when you turn it off too

[PeterK]

Either the ignition switch or the wire that runs to the rear fuse panel is connected to the wrong terminal in the front panel (linked to accessories, not run)

I’m sure it’s something like that, there’s power on the rear panel that stays live during cranking, just not to the wire that goes to the CDi box.)

On a ‘79, that’s not possible. Power comes from fuse 11 (live with ignition) to fuse 22 in the rear. That wire has a connection running to the CDI. Either there should be power during cranking to both, or neither.

Happy to chat if you want to bounce ideas
Peter

[Gary71]

Did you re-wire at all ? Sounds like a wrong feed to the CDI. Make sure the feed also goes off when you turn it off too

Nope. Not intentionally anyway! The rear harness and the board in the engine bay was untouched.

I did redo the fuse box, plenty of room for error there!

[impmad2000]

Same ignition switch ??

[Gary71]

Same ignition switch ??

Yup.

Just unplugged it and plugged it back in.