Starter stays engaged

Hey Ya'll, Hope everyone in the Southeast is enjoying the dry weather and able to get out and start making some.

I've got a Cat It24 F Serial 4NN00391

The starter stays engaged after startup. If I cut the electric off at the master switch then the starter disengages and the diesel motor continues to run. I can then shut the motor off at the fuel solenoid. I tried disconnecting the key switch and then replaced the starter relay with no fix on either. Have electric diagram thanks to the wonderful Nige from a previous issue. Thank you Nige.

Just not sure where to go next .

Wastepro said:

Hey Ya'll, Hope everyone in the Southeast is enjoying the dry weather and able to get out and start making some.

I've got a Cat It24 F Serial 4NN00391

The starter stays engaged after startup. If I cut the electric off at the master switch then the starter disengages and the diesel motor continues to run. I can then shut the motor off at the fuel solenoid. I tried disconnecting the key switch and then replaced the starter relay with no fix on either. Have electric diagram thanks to the wonderful Nige from a previous issue. Thank you Nige.

Just not sure where to go next .

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If it were mine i would try unhooking the small wire from the starter and start it with a remote start button to eliminate the machine wiring keeping power on it . This would isolate it to the starter solenoid itself , if starter is fine doing it this way it sounds like you may have changed wrong relay or there is a second one sonewhere latching closed.

Two random thoughts come to mind for me. Both from past experience. I had a drill that would not shut off with the key. It turned out to be a rat chewed harness allowing wires to touch therefore bypassing key switch as far as shutting off fuel.

Second is a long shot. On our race cars we have to run a battery cutoff with a third post that cuts the alternator off as well. If you don’t do that even cutting the battery off won’t kill the engine as the alternator isn’t eliminated and will continuing providing juice. My thinking with this idea is perhaps it explains why battery cutoff won’t kill it but could also be indicative of another potential wiring gremlin. I’ve also had faulty diodes create weird issues like this as well.

Just don’t let the gremlins near water!! Haha

Check the solenoid that sits on top of the starter... there is a plate inside that when energized it comes in contact with the copper studs that come out of the end. Over time from use, the plate becomes burned and then will weld itself to the studs allowing power to pass through at all times.

Hey thanks to everyone suggestions. One small update to reply, I disconnected the small wire to the starter which comes from the starter relay. This made no change. The starter immediately tries to start the machine and stays engaged when the master electrical is cut on.

So far I have tried
1. Disconnecting the key switch
2. Replacing the starter relay with a Caterpillar new one
3. Disconnecting the small wire from starter


My guess now is that the starter Solenoid is stuck as Grandpa has suggested. This seems slightly out of place considering the starter is only 4 years old and was purchased new from napa auto. But could be?

I usually try to stay away from napa rebuilt starters and alternators. I have had more problems with them compared to other brands. just my personal opinion

Low battery conditions cause premature starter failures. All starters wear out, but low voltage brings it on sooner. So does extended cranking.

Contact plate failures in the solenoids is Not uncommon no matter how much time on one. Take the solenoid off and apart, you will find the culprit, may even take the starter off and validate the bendix is not stuck extended.

heymccall said:

Low battery conditions cause premature starter failures. All starters wear out, but low voltage brings it on sooner. So does extended cranking.

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This^^^^

Starters will draw the same amount of watts. If voltage is low, its going to pull more amps. Amps = heat. Amps also = bigger electrical arc between studs and contact plate.

Tapped the solenoid real good with a hammer too see if would disengage. No luck so After that we pulled the starter and the bendex was stuck extended. Bad news since we had to give my left arm for a starter from Cat at $549.99.

Just fired it up and everything is good to go. Thanks everyone for replies.

-Wastepro

Glad you got it going. On the bright side you still have your right arm..... unless your left handed!!!

Well if you gave your left arm then guess you will be "all right" from now on!

Only thing worse than spending that $550. would be spending it and then still have the same problem!