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GMC V6 and V12 Engines Engine repair and rebuilding

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  #1  
Old April 8th, 2019, 08:05 PM
azcbass azcbass is online now
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Default Starter Issues

I've been dealing with a starter issue for awhile now. I have the 305E. A reputable shop here in Tucson that i've sent it to twice now and the same thing happens both times. After the first and second rebuild of the starter it works great for about a dozen or two starts. Then the starter appears to hit a flat spot and makes a horrible sound. If i turn off and on again it will turn over normally but will hit this flat spot again eventually. This continually gets worse and worse until yesterday when no mater how many attempts i make to turn the starter its always in a flat spot that makes a gravely bad sound. Anyone else have this issue with a bad starter? Is there a modern replacement option for this part? I have replaced the solenoid with a high temp option due to it being right by the exhaust manifold. This has cured the issue of having to bang on it after i stop to get gas on a longer run. It used to get stuck from getting too hot on longer road trips.

The last time i took the starter in they ran it on their test bench and it works just fine. It seems like when it has a load on it that this starts happening.

Any suggestions?

Thanks
AzCbass
Tucson

66 GMC 305E 4 speed dually Open Road Camper Conversion
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  #2  
Old April 8th, 2019, 08:29 PM
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AZKen AZKen is offline
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Default Re: Starter Issues

Well, if they are a starter place, they would have tested it under load, is that right? Did you ask that? With this much trouble with a simple starter, I would start thinking of other issues than the starter itself. The first one may seem crazy but has happened to me on another vehicle.

1. Hydraulic lock. Water in cylinders causing huge "compression". Serious issue, take plugs out and check. Check oil, check radiator. Probably not that but........
2. Bad battery cables. Clean and inspect
3. Bad ground connection. Clean and inspect at battery and at starter
4. Bad battery. Clean posts
5. Bad battery. Check static Volts 12.6V at rest.
6. Possible relay, if a relay is involved.

7. Something causing motor to be semi seized
8. Connections to solenoid and ignition switch
9. Bad ignition switch
10. Bypass wiring not functioning
11. Starter mis aligned somehow
12. Wrong starter
13. Teeth on flywheel worn/broken, flywheel loose/warped
14. Clutch dragging
15. Starter rebuild company does not know what they are doing
16. Forget the "flat spot" idea. I assume you mean a place on the starter commutator? No such thing.
17. FIRST THING TO DO IS have your battery checked under load. Most FLAPS will do it free. Go to several places. O'Reilly's, Autozone, Walmart, Napa, whatever.
18. Next time is won't rotate or makes a noise, STOP and hook up a jumper cable from another vehicle and try.
19. Report Findings

Last edited by AZKen; April 8th, 2019 at 10:16 PM.
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  #3  
Old April 8th, 2019, 10:20 PM
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FetchMeAPepsi FetchMeAPepsi is offline
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Default Re: Starter Issues

I agree. You shouldn't be having that much trouble with the starter if it's the right starter and everything else is OK. time for a head scratching moment!

Did you ever replace the starter or have a mechanic "try" to replace it with something close?
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Old April 9th, 2019, 01:47 AM
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Default Re: Starter Issues

Napa has a replacement starter, 246-4841. If the starter shop can't fix it, get this one from Napa.
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  #5  
Old April 9th, 2019, 03:40 PM
jrmunn jrmunn is offline
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Default Re: Starter Issues

Maybe it is just me, but I am not clear about the problem. When you turn the key with the starter at a "flat spot", does the starter spin? If yes, you have broken/worn teeth (flat spots) on the flywheel, an engagement problem (usually a bad spring) on the starter, or a combination of bad teeth on the starter gear finding worn spots on the flywheel. If the starter gives a clunk (engages) but can't turn the engine, the most common causes are bad connections, a weak battery, or a bad solenoid. From my experience, this is usually accompanied by a single click of the solenoid, or the solenoid will clatter (multiple clicks). It is hard for me to imagine problems that make the engine difficult or impossible to turn over going away by trying later or rebuilding the starter. If the starter itself won't turn over, it is time (especially after a rebuild) to get a different starter that you know works and is appropriate for the vehicle. Just because it fits (bolts on) does not mean it is right for the vehicle.

JRMunn
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  #6  
Old April 9th, 2019, 04:48 PM
George Bongert George Bongert is offline
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Default Re: Starter Issues

Quote:
Originally Posted by azcbass View Post
I've been dealing with a starter issue for awhile now. I have the 305E. A reputable shop here in Tucson that i've sent it to twice now and the same thing happens both times. After the first and second rebuild of the starter it works great for about a dozen or two starts. Then the starter appears to hit a flat spot and makes a horrible sound. If i turn off and on again it will turn over normally but will hit this flat spot again eventually. This continually gets worse and worse until yesterday when no mater how many attempts i make to turn the starter its always in a flat spot that makes a gravely bad sound. Anyone else have this issue with a bad starter? Is there a modern replacement option for this part? I have replaced the solenoid with a high temp option due to it being right by the exhaust manifold. This has cured the issue of having to bang on it after i stop to get gas on a longer run. It used to get stuck from getting too hot on longer road trips.

The last time i took the starter in they ran it on their test bench and it works just fine. It seems like when it has a load on it that this starts happening.

Any suggestions?

Thanks
AzCbass
Tucson

66 GMC 305E 4 speed dually Open Road Camper Conversion

Greetings AzCbass!

The first thing that I would look for is a badly worn flywheel ring gear. That's what your description sounds like to me.
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  #7  
Old April 9th, 2019, 05:15 PM
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Rockdriller Rockdriller is offline
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Default Re: Starter Issues

What George said. It's time it seems to be on a flat spot, manually roll the motor 15 or 20° either direction and see if it doesn't engage. Most of these engines will shut off and land in the same position on the flywheel. At least that has been my experience. Good luck.
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  #8  
Old April 9th, 2019, 05:46 PM
azcbass azcbass is online now
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Default Re: Starter Issues

Thanks everybody.. Sorry my description of the issue is a little foggy. Im thinking its a power issue the more i dig into trouble shooting. The starter is the original one and no modifications have been made to it. When i'm attempting to describe the issue of what i'm calling a "flat spot". The starter does spin and so does the motor its just slower and makes a completely different sound. Its like gravel rolling around in a tumbler. If teeth on the fly or the starter were worn or missing the drive gear on the starter would show evidence of that. I haven't noticed anything like that, neither has my mechanic or the electrical rebuild shop. Thanks for the replacement part number on the starter. I didn't think those were available any more new. I still have my original alternator and will check that as well. If i wanted to modernize that part and get rid of all the auxiliary stuff that the original has, what part number am i looking for?

Thanks for all your reply's!

AzCbass
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  #9  
Old April 9th, 2019, 07:10 PM
jagarra jagarra is offline
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Default Re: Starter Issues

I once a had bad positive cable that looked good, but was badly corroded in the area right after the battery lug and under the insulation. So visually it looked great, but it wasn't allowing enough current to get to the starter.
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  #10  
Old April 9th, 2019, 07:21 PM
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Default Re: Starter Issues

Well it could be that the ignition switch is getting weak. Low voltage to the solenoid thru the purple wire. I ran mine thru a five pin relay. If ya would like help with diagnosis, just mention it. Twelve volts to the smaller post closest to the block (purple wire) should stroke the solenoid completely and engage the start circuit.
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