Starter keeps cranking after startup...and Won't stop?
 

86 turbo, sequence goes like this...
turn key to crank position, car starts, but starter continues cranking along with the running engine

Key then switched to off, but engine and starter continue to run, and the only way to get it to stop is to pull the battery cable off.

What's going on here?

Bad starter solenoid or starter.

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also, check your ignition switch and starter harness.

with the switch unplugged and battery disconnected, see what the resistance is between the battery cable and the starter trigger (terminal 50 in vw land).

The wiring and insulation near the starter is often a concern too.

Sorry, not sure i follow you, are you saying that I should get an ohm reading between pin 50 of the unplugged starter switch connector and the positive battery cable? What should the value be and what does it mean?

first pull the negative lead off the battery. remove the battery positive terminal and remove the smaller wires from the female lead terminal. (wear gloves or wash the lead off your hands afterwards.)

get the car raised up to access the starter.

the starter should have two wires on the large terminal. one coming from the battery and another from the alternator. there will also be a smaller gauge wire coming from the ignition switch on the steering column.

remove these three wires and fan them out. if they are fuzzy and green, polish them up with 400 grit and vinegar.

with the key removed from the switch and doors closed, use a volt ohm meter to check the resistance between the battery cable and the other two wires. it should show open line on a digital meter or infinity on an analog meter. (you might pick up the clock or radio memory if the fuse panel lead is fused into the battery's positive lead.)

now check between the alternators lead and the keys starter wire. this is the prime suspect. when a lead acid battery ages, they start gassing off when the voltage is below 12.4. that why the tray rusts out. the alternator will start throwing massive amounts of current to try to charge the weak battery which will create enough heat to start melting the insulation.

if both tests show open or infinite, and the starter performs well on the bench, it will be time to look at the ignition switch.

do you have a pre 85 or after? the early cars are simple. a wire from the battery or B+(30). a wire for the lights(X). a run wire (15). and a start wire(50). there are some standing lamp terminals but they don't matter for your issue.

in the states, lead acid batteries are made south of the border because of smelting rules. the lead isn't too pure so there is no value. load test what you have and replace it if the standby reading is low. interstate still makes a good battery and, on the other side of the pond, exide or sonnenschein.

Thank you, that is very helpful. I will get the car up on stands and let you know what I see. Really appreciate it

right on. let me know if you have more wires on the big starter lead/post. a starter going south can pull a couple hundred amps so its always cheaper to find the root cause of the issue.