1978 460 4x4 w/ C6 transmission

Background: This truck has been sitting for a three months until the past week, and I'm trying to get it mobile. I got it into reverse the other to move it into a better area so I could work on it. It died shortly after shifting from neutral to reverse, but it did go in gear and move.

So, for today's issue: The starter has been intermittently engaging the crankshaft the last few times I tried to start it. The starter motor runs, sounds like normal, and the wiring and voltages have been checked. The starter motor runs consistently when the key is turned, it is only the flexplate engagement that is a problem (I think).
It started up earlier today, ran pretty rough for a few minutes and I turned it off.
Now, a couple hours later, starter is back to running without the engine cranking.
I'm not sure if there was some sort of jam/bind between the two that damaged the starter and now it is turning free or because the starter is intermittently going forward to engage the flexplate.

I just wanted to double check procedures to evaluate this. I haven't done the following yet, I just want to check my understanding of what needs to be done.

1. Transmission in park or neutral. Spark plugs out. At that point I should be able to turn the crankshaft by hand without any resistance from compression, correct?

2. If I'm not able to turn it freely by hand, could this be caused by a bind between the starter and crankshaft? Or is this a bigger problem? Like I said, it ran fine earlier.

3. Remove the starter, check it out.

4. With the starter out, there is no reason the crankshaft shouldn't turn, so rotate it to check out the teeth on the flexplate from underneath the vehicle.

Am I missing anything? If the starter turns out in need of rebuild or replacement, would just replacing it with a mini-starter (I'd eventually like to install higher compression heads) give me any new problems? They seem to be going for about $50 and a starter rebuild kit costs $20 anyway.

Thanks. A lot of this is new for me and the forum has been an excellent help.

 

the starter actually needs to be grounded to the trans and or bell housing .. oil leaking from above can weaken the ground or loosened bolts ..

 

I'll double check the ground and bolts, but I'm pretty sure they are okay. It started fine before it sat an no changes have been made down there.
If the ground to the starter was bad, would that cause a problem with spinning the flexplate or would it cause a problem with the pinion going forward to engage the flexplate to begin with?

 

1) Yes, "easily", you'll still be fighting spring compression. But it should be relatively easy.

2) It could be a bind, hard to say without more diagnosis

3) When you've got it out, try jumping it. Make sure that the starter drive spins AND engages.

I too would check and make sure you have proper ground potential at the starter, and no excessive voltage drop while cranking.

IMHO a mini starter aint really worth it

 

yes .. Not enough power to push the starter gear into position to engae flexplate or flywheel .. The longer a vehicle sits the more connections need to be checked and fuel contamination becomes a problem ..

 

Okay, so when the starter is activated, the the pinion going forward to engage the flexplate and spinning are both part of one movement?

 

Yes exactly .. If you bench test as was suggested you can see exactly how it works If you want worry free starts pull the starter inspect the teeth on flexplate for wear by having some one turn the motor at crank with coil wire disconnected and spark plus loose .. Clean completely the mating surfaces of starter and trans with brake cleaner before reinstalling ..

 

Great info as usual. If necessary, any thoughts on buying one of the mini-starters vs. rebuilding the current one, since it seems to only be a $30 difference?

 

2 reasons for using a mini starter
1) your trying to turn over a higher compression motor .. which if yours is stock it is not
2) you have headers and they pass to close to standard size starter so you go with the mini for clearance to avoid heating the starter to much by the headers

 

Well, I guess this explains it. Took the starter out today.

I looked at the teeth on the flexplate. Some of them have some definite wear, but none are broken off or anything.

With the starter out, it turns more easily manually, however I still have to use a wrench and a fair amount of force. I'm unable to turn it with just my bare hands. How much force should be required to rotate the engine?

 

Do you have the spark plugs removed?

 

Yep, spark plugs are removed. Also, the same force is required in park or neutral, although I don't think that matters. Dipstick says the oil is full, also.

 

Time for a new starter drive or starter.Is the starter the right one? The nose cones are different lengths on auto Transmission starters verses manual transmissions you can swap nose cones. Also check see if small spring is broken that pushes starter drive.

 

when a motor sits for a long period of time the valves can stick and if you turn the motor over using the starter motor you can bend push rods .. Verify that a bent push rod is not holding you up by removing valve covers .. turn motor over manually only until you have verified push rods are not bent

 

It is the correct one, served the previous owner well for a long time.
Is it worth it to buy a rebuild kit for the current one at $20+ when I can get a new, warrantied ministarter for $50 shipped?
https://www.dbelectrical.com/p-1324-...6-sfd0030.aspx