Cranking on after ignition switched off

So my car has been in a garage for around the last 14 years. Its an 81 manual, weber carbed 1500. Its now been released. A PO had added a relay mod(53) for the starter. When it first arrived you could notice it cranking slightly over once it had fired. I can now turn it on and fire it but if I turn the key off the starter is  still going. Do I suspect a bad starter or ignition switch or has the mod failed. I've have recently cleaned all the earths and battery terminals.

Car in Neutral or Park, E-Brake fully on.


Disconnect the relay prior to starting, or use a DVOM to see if the relay kicks out after starting by measuring the voltage at the relay.

Test it prior to start take the Solenoid wire off the relay that goes to the starter solenoid.

Turn the key on and see if there is 12V on the Solenoid wire, then turn the car off.  Yes/no?  Yes then you have a stuck relay or bad ignition switch.

Turn the key on and then to start is there 12V there on the solenoid wire?  yes/no yes good.  Turn the key off is there still 12V on the wire, yes/no . Yes Bad relay, no, good relay. Your relay and ignition switch is good so suspect a faulty starter.

You can also measure the relay with power off for resistance of static voltage across the Terminals, if there is 12V on both sides Faulty relay.  

If there isn't voltage then Jumper the Relays pick (ignition in from the switch) to 12V, does the relay click and the starter spin?  now, disconnect it… Does it stop the starter spinning?  Yes/No.  Yes then it is good, and so is the starter, if it doesn't then look at a bad starter as the starter solenoid is sticky… If all works that way as it should then suspect the ignition switch.

I think I'd immediately go for the starter sticking over anything else.

They do wear out and especially with it having a bit of a history of being sticky.

Perhaps try removing it and giving it a degrease and re grease might help. You can also bench test it to check if it sticks. If so and re freshing it doesn't help you can then replace it.

If it woks find on the bench then try hot wiring it directly from the battery and see what it does in situ.

The you can try the other stuff.

Ian

borednow said

I think I'd immediately go for the starter sticking over anything else.

They do wear out and especially with it having a bit of a history of being sticky.

Perhaps try removing it and giving it a degrease and re grease might help. You can also bench test it to check if it sticks. If so and re freshing it doesn't help you can then replace it.

If it woks find on the bench then try hot wiring it directly from the battery and see what it does in situ.

The you can try the other stuff.

Ian

Automatics require jacking the car and removing the Starter, manual not so much.

I used a Ford Starter Relay on my Autos (higher amperage rated) than a standards 40amp Bosch relay 53.

Removing the Relay and Jumpering the contact terminals together will allow the starter to engage without removing it from the car, the engine will spin
if the starter remains engaged when you disconnect the wire, bad starter solenoid, then removing it and Repair or replacing is needed…

I would rather rule it out without having to remove it from the car first.

You can also take the Starter Solenoid wire post and tie that straight to the battery. The starter should spin, and if the Starter stays on after the jumper is removed, bad starter solenoid…  

Testing things a wee bit is better than removing things, then finding out that it is good and having to back up a bit further…

Those 53 Bosch relays are susceptible to water migration and rusting if not shielded from spray.  The classic sign of the later Cabriolets 53 relay mounted in front of the battery to control the radiator fans.

I think I started writing it before you replied me old mucker.

I knew you'd be along with your expert elektrikery advice  

Ian