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Old 09-02-2008, 19:42   #16
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Rebuild kits are readily available for most diesel starters if not all. These are really well made heavy duty units needless to say.
I have rebuilt them a couple of times and the dismantle, really thorough cleaning, armature cutting, Brush r&r, any bearing replacement when possible all takes less time that the R&R from the engine it self.
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Old 09-02-2008, 20:14   #17
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It could be the starter. Common issues with these are the bearings wearing out. The shaft twists with the torque and the armature grabs and thus does not turn at full speed and results in the starter turning over the engine slowly and high current (=leads getting hot) being drawn.
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Old 09-02-2008, 22:32   #18
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One way to be SURE if it's the starter.
Swap the starters and see if the problem is on the OTHER engine.
If it is, it's the starter. If the problem exists on the original engine, it's NOT the starter.
If that's the case, it's either the engine developing excessive bind when hot, or bad wiring/loose connections.
Either way, you have narrowed down the problem without spending money rebuilding a starter which may not need it.

Steve B.
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Old 10-02-2008, 14:55   #19
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Folks,

Here is what we found when we pulled and cracked open the starter.

2 things:

1. We found one brush (out of four sets of 2) had one of its braided copper leads partially melted. We matched that up to a spot on the case where there has been some arcing. There was a lot of powder in the case, which could have assisted making a connection between the lead and the case when hot.

2. The back end bushing (there is no bearing there, just a bushing) has a oil reservoir with set-screw cap. This reservoir was absolutely dry and lack of lubrication tot he bushing could have caused binding of the starter motor shaft when things heated up.

Cleaning everything up, replacing the partially damaged brush, putting lub in the reservoir for the bushing, and expect all to be well.

Will file a final report when the work is all done and the testing proves successful.

Thanks all,

Kip
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Old 10-02-2008, 17:59   #20
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Originally Posted by KipHansen View Post
Folks,

Here is what we found when we pulled and cracked open the starter.

2 things:

1. We found one brush (out of four sets of 2) had one of its braided copper leads partially melted. We matched that up to a spot on the case where there has been some arcing. There was a lot of powder in the case, which could have assisted making a connection between the lead and the case when hot.

2. The back end bushing (there is no bearing there, just a bushing) has a oil reservoir with set-screw cap. This reservoir was absolutely dry and lack of lubrication tot he bushing could have caused binding of the starter motor shaft when things heated up.

Cleaning everything up, replacing the partially damaged brush, putting lub in the reservoir for the bushing, and expect all to be well.

Will file a final report when the work is all done and the testing proves successful.

Thanks all,

Kip
If you have to you must but why?
Don't put that back together with junk or beat up parts....
Take it apart clean everything really well. Use Brake Cleaner if not available use 90% Isopropyl not 70%. Clean the armature and the rotor replace all the brushes with new . Clean everything inside and out! Do it carefully with 3m AL. Oxide wet dry about #1000
Fill the res with high temp oil maybe you can even find some Rotella...
Why beg for it to go south again soon? No doubt she we fail you when you need her the most.
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Old 11-02-2008, 05:18   #21
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Of course, you are absolutely right.

We are doing a very thorough cleanup, including wet/dry sanding, re-setting the brushes (which are new), cutting the armature, and will replace the bushing if it appears damaged.

Thanks for the tip on hi-temp oil for the bushing.

The proof will be in the testing, probably tomorrow.

Thanks again to all who have contributed.

Kip
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Old 12-02-2008, 18:34   #22
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Won't Start Warm

Had exactly the same problem with a skiboat I had years ago.

Had a Chev 307 V8 that would start like a dream when cold, but would give symptoms of a flat battery when trying to start hot.

Checked everything from battery to alternator to check charging etc.

Replaced starter and Hey Presto, no more problems.

Fair winds

Steve
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Old 13-02-2008, 15:55   #23
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I had a similar problem once ..... it lasted for at least a couple of years before the mystery was solved. The engine started great when cold and would run great ( all day and all night) .... if the engine was shut down hot it would not start again (in fact it would barely turn over if it would turn over at all). The problem was the small positive wire from the start button to the starter solenoid was located just above the starter when it was cold (everything worked great) when the engine and or engine room was hot the wire also got hot and sagged and touched the hot starter - when it cooled it would shrink and once again rise above the starter. Over time the insulation had been melted from the wire where it made contact. (no problem while the engine was running becasuse there was no power to the cable unless the start button was pushed, however when the engine was shut down and an attempt was made to restart the engine this cable was in contact with the engine and the current went to ground and did not engage the starter (or at least not enough) to turn the engine over.

You would not think this would happen very often but a week after I finally figured out my problem I ran into another guy who was having the very same problem!

Check it out, it could be your problem .... if it is, it's a cheap fix!
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Old 13-02-2008, 17:01   #24
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Thanks, we have a replacement starter now, and are giving it a whirl.

Will check that the mentioned wire is secured away from the motor.

Sending our problem starter out for bench testing and possible re-winding (as something seems amiss in the windings....repairs above did not resolve excessive power draw).

Kip
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Old 13-02-2008, 17:45   #25
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You might want to consider replacing your battery cables while you are at it, especially if they are old and not tinned cables.
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Old 13-02-2008, 17:51   #26
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Detroit 8V-71's are very common commercial engines. What you have is a marinized truck engine in fact. Look in some of the trade magazines and you can get some pretty inexpensive prices for a rebuilt starter ...and get yourself a spare while you are at it. At a few hundred bucks each they are not all that expensive...unless you go to the dealer to get ripped off by him. $300 is a fair price. You can bet the marine engine dealer is going to ask $500-600.

You starter cable should be 2-0 cable at minimum for that engine. Your start battery should be an 8-D start battery and not a deep cycle 8-D. Starter motors do burn up but the first thing you do before replacing a starter is to make sure your battery terminals and cable terminals are absolutely clean. This includes your ground cable which is just as important to have clean as the hot cable, and should be led from your starter directly back to your battery or negative buss terminal...and then to the battery. The crimp terminals can also go bad...check for resistance across them...there should be none.

Voltage drops across bad or dirty terminals is the major reason starter motors go bad. When the voltage drops the current has to increase in order to crank with the same horsepower. (volts x amps = watts) and when you increase the current, it heats up the coils...burning them up. Wires that are hot in temperature also have more resistance which aggravates the problem

Continuous cranking or cranking with a weak battery can also damage or burn up a starter motor.

A starter motor that cranks when cold but not when hot could also be an indication of a loose terminal that simply needs to be tightened down..I have had that happen.

Your start battery may also be getting old. They are generally good for roughly 5 years if they have been maintained and never abused.

When you do clean your terminals, spray on some battery terminal anti-corrosive. Scotchbrite pads are excellent for cleaning the terminals.
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Old 13-02-2008, 21:44   #27
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I second the connections check. Also take a good look at the terminals for that pesky "green stuff".

Also, when you take that "puppy" off, It is a good idea to secure a line around the starter. They can be awkward and you learn quickly how hard it is to fish one out of a bilge.

And....wear good shoes.....
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Old 14-02-2008, 09:31   #28
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Starter is probably a 40MT or a 50MT, very heavy and can run from $ 250.00 to $ 400.00
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