1981 Chevy Silverado Rebuilt starter will not stay engaged.

Tim,
Sorry for the delay. I agree with the use of the spring in the solenoid after I thought about it because that is the only spring in the starter.

When the gear releases from the flywheel, the starter motor keeps running so I do not think it is an ignition switch problem and I believe that the wire remain hot as long as the ignition switch is held in the start position. By the way, the ignition switch is new. I also cleaned the contacts on the actual switch mounted on the steering column.

I can understand a starter drive going bad as it did on my old starter but wouldn't it be unusual to have the starter drive go bad on a quality rebuilt. How can I check the starter drive or is there a way to tweak it to stay engaged longer? My understanding is that when the starter drive gear starts going faster than the starter, it moves inward releasing itself from the flywheel gear. So why doesn't the gear move back out while the starter is still running and the engine is not?

Yes, two different AC Delco rebuilt starters. That is why I replaced the other starter but I have not gotten the truck started with this new rebuilt starter. It was under warantee. These starters on the diesel are different than the regular Chevy V-8 starters as they are longer and a lot heavier so they can turn over the high compression engine. I bought this truck new in '81 and have replaced the starter only twice before. However, this is the second starter in the past three months. The main case is AC Delco as stamped into the housing and I think they were the only ones who made them. I don't think anyone else make these big cases so as far as I know, there are no other replacements or brands, only rebuilts.
As you know, sometime I believe in the '80s they went with gear reduction drives to use a smaller motor and still provide the torque needed to turn over a diesel. This a a rebuilt from PEP Boys in California.

I should probably state this over again. Three months ago my starter went bad and I installed a new rebuilt. It worked fine until one morning I tried to start and the starter would not stay engaged. I took the starter back to the store and got another. I installed that and I have the same problem of it not staying engaged. I have not had the truck running since this not staying engaged problem.

Do you think these are poor rebuilts? All my rebuilt starts have been from PEP boys. I don't think anyone else carries them. Can I purchase just the starter drive and how hard is it to change out?

Tim, I just wanted to let you know the results of my starter problem. The starter would not stay engaged because the gear at the end of the armature was freewheeling in one direction. I ordered another rebuilt and they sent the wrong starter in the right box. My starter must have an aluminum nose cone. They sent a starter with a steel nose cone. They look the same but the steel nose cone is a little over an eight inch shorter in the nose cone and will only allow the gear to go half way into the flex plate gear. I ordered another starter and it came with the aluminum nose cone but the case did not have the tapped hole for the support bracket that bolts to the engine block. The bracket also doubles as a heat shield for the starter wires. This starter is heavy and must have the support bracket to hold the end up. It takes five days to get the starter from the rebuilding factory so I alread had 10 days waiting. Because of that, they let me swap the case. I took the starter apart on their parts counter. It works great now and I have about maybe 30-40 starts on it since I installed it. I used to be an auto mechanic when I was a kid, but talking to someone helps solve a simple problem. A starter gear should not turn easily by hand in either direction. Regards, John