Electrical Starter Question

[1990fredi]

I purchased a 1990 K1500 Sierra, test drove it a few times, everything seemed good, got home and sat over the day, later that afternoon I needed to jump it to get it in the driveway. after that I tried to put the charger on it and it was erroring out so I tried to jump it again and every time I hooked any amount of power to the truck the Starter motor just runs, constantly. now for the part I don't understand. the positive line that goes to the starter, makes the starter run, but also the positive line that goes to the alternator and then to the fuse box which should go through the ignition, that also makes the start motor run.

how can that be and what do I need to do to fix it? I thought the ignition might be bad but when I remove the wire out of the ignition, it still runs, so I am going to try to replace the starter but not sure what else to try.

where do I start, it was just fine, then the day I buy the truck, this happens.

 

[Scooterwrench]

I purchased a 1990 K1500 Sierra, test drove it a few times, everything seemed good, got home and sat over the day, later that afternoon I needed to jump it to get it in the driveway. after that I tried to put the charger on it and it was erroring out so I tried to jump it again and every time I hooked any amount of power to the truck the Starter motor just runs, constantly. now for the part I don't understand. the positive line that goes to the starter, makes the starter run, but also the positive line that goes to the alternator and then to the fuse box which should go through the ignition, that also makes the start motor run.

how can that be and what do I need to do to fix it? I thought the ignition might be bad but when I remove the wire out of the ignition, it still runs, so I am going to try to replace the starter but not sure what else to try.

where do I start, it was just fine, then the day I buy the truck, this happens.

Sounds like the starter solenoid is bad. There is a disc in there that connects the battery to the starter motor,I think yours has come loose from the plunger rod and maybe welded to the battery/motor contacts.
New starter should fix it.

 

[1990fredi]

sounds good, I'll try that.

 

[evilunclegrimace]

OR the starter main lug is twisted around and is touching the the solenoid stud that the iginition controls.

 

[Scooterwrench]

OR the starter main lug is twisted around and is touching the the solenoid stud that the iginition controls.

Wouldn't that energize the solenoid winding and pull the drive out and engage the starter to the flywheel?

 

[SEEDSOWER]

I purchased a 1990 K1500 Sierra, test drove it a few times, everything seemed good, got home and sat over the day, later that afternoon I needed to jump it to get it in the driveway. after that I tried to put the charger on it and it was erroring out so I tried to jump it again and every time I hooked any amount of power to the truck the Starter motor just runs, constantly. now for the part I don't understand. the positive line that goes to the starter, makes the starter run, but also the positive line that goes to the alternator and then to the fuse box which should go through the ignition, that also makes the start motor run.

how can that be and what do I need to do to fix it? I thought the ignition might be bad but when I remove the wire out of the ignition, it still runs, so I am going to try to replace the starter but not sure what else to try.

where do I start, it was just fine, then the day I buy the truck, this happens.

THE STARTER RELAY UNDER THE HOOD CAN STICK KEEPING THE STARTER RUNNING. I THINK THE HORN RELAYS ARE THE SAME, SWAMP THEM TO SEE IF THE STICKING CHANGES.