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Author Topic: are all detroit starters the same?  (Read 1749 times)
henrymc7
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« on: September 04, 2006, 07:13:09 PM »

Had a nice week at the beach until I tried to start the bus. The only thing making sounds at the back was the starter relay solenoid in the rear junction box and nothing at the starter. This all seemed to start (no pun intended) when we were picking up the last of the groceries just before the trip. Hitting the start button resulted in a very slow starter, like the batteries were low. I ended up rolling and popping the clutch to get going and when I got to the campground, I charged up the batteries. One needed quite a bit of water.
With the relay clicking, but but nothing else, I wondered if it was the starter soleinoid. So I jumped the two posts and the solenoid clicked loud and clear but the starter didn't spin.
Here's my two guesses, one the starter is seized. Two, not realizing what was going on, I've overloaded the main battery cable and it no longer is able to carry the current needed to activate the starter solenoid itself. And yes, the batteries are good as I originally thought they weren't holding a charge and I had my son bring out two brand new 8D's.
Here's my ultimate question, at work (Edmonton Transit), we've got lots of 6V-71 V drive transits. I can probably pick up a starter cheap if they are the same. Otherwise I'll find out where we get them serviced and go from there.

Thanks for your help. BTW, to get home, I plugged in the block heater overnight so the engine was good and warm, had a buddy pull me up a slight incline with his truck. Then I rolled backwards, popped the clutch and it fired right up. The folks in the campsite next to ours all cheered. Then it was straight home without turning it off.
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TomC
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« Reply #1 on: September 04, 2006, 08:19:29 PM »

You'll just have to compare the two starters and make sure they are both for a V drive.  Count the gear teeth on both and just put them side by side.  If the new one has a shorter motor, I would pass on that, since sometimes the 6V had a smaller starter than the 8V. You can also try jumping the positive motor post directly with a screwdriver that you don't care about since it might get welded. Hook up jumper cables with the negative to the big cable out the motor, and with the screwdriver clamped in the positive jumper, try tapping the other big bolt going into the starter that is connected to the starter solenoid by a big strap.  If you get no response, motor is burned out.  If you get big sparks, motor is shorted out.  If you get some sparks and the motor spins up, then you have a bad solenoid.  But from what you said about slow turning, it is probably the motor.  Replacement time.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
henrymc7
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« Reply #2 on: September 04, 2006, 09:35:25 PM »

My error for not being clear. I have an MC-7 with an 8V-71. I was wondering if Detroit simply made the same starter for all their 2 stroke engines since I have access to surplus 6V-71 parts. If not, I will find out where to get a rebuilt one. I will try your suggestion to further figure things out.

Henry
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Happycampersrus
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« Reply #3 on: September 05, 2006, 05:51:53 AM »

No, They are not all the same.

The V drive should be a CCW rotation, because the engine spins LH. 

The RH engine uses a CW rotation starter.

Then some of the older transits are 12volt and I believe you need a 24volt.

HTH, Dale
« Last Edit: September 05, 2006, 06:00:40 AM by Happycampersrus » Logged
Dallas
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« Reply #4 on: September 05, 2006, 06:04:13 AM »

Henry,
It sounds more like you have a bad ground cable.
Check the battery terminal, the cable itself, (if it's green inside, it needs replacing), the engine to body ground, and the nut connecting the starter ground to the battery.

An easy way to check, hook a set of jumper cables to the gorunds on the batteries. Then hook one to the starter ground and one to the engine ground. If the batteries are up, and the starter isn't bad, it should spin over just fine when you hit the start button. Make sure where you hook it on the batteries that you have a good, clean, fresh connecting terminal.

ALWAYS suspect a ground.
Especialy since it happened al at once. And it will turn over a little


Just my pair of pennies worth.

Dallas
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Jerry Liebler
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« Reply #5 on: September 05, 2006, 04:53:09 PM »

Henry,
     It sounds to me like you'll need  to have the starter rebuilt or find a replacement.  There are several different starters used on 8v71s.  Some are left hand rotation (used with 'v'drives)  while 't' drives and trucks use right hand rotation.  There are also 12 volt and 24 volt in each direction and there are several different mounting angles.  I've had to rebuild my starter twice due to the start push button sticking on (I found and fixed the cause after the second starer failure).  So be sure to check that your start switch isn't staying on, it'll smoke the starter if it sticks. If you are in or near even a modest sized city you should be able to find a local rebuilder, I found one in Somerset Ky (population 10,000) and it only cost $163 for the last rebuild.
Regards
Jerry 4107 1120
 
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buswarrior
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« Reply #6 on: September 05, 2006, 05:06:41 PM »

Hello Henry.

Good advice here.

Check your grounds, this is a preventive maintenance item. All busnuts should go through the ground posts once a year, disassemble, clean, goop with anti-seize of your choice, and re-assemble. The one at the battery, as well as all the battery terminals, the one at the starter, both ends and the one at the alternator, both ends.

Then, if your starter is still wrong, haul it out and use your credentials at the company's re-builders for a discount.

happy coaching!
buswarrior
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Beatenbo
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« Reply #7 on: September 05, 2006, 07:26:40 PM »

If you replace starter make sure solenoid drive is for the correct engine rotation. Had a deal about 25 years ago with a 4106. Rebuilt had a right hand starter for a left hand 8V71Had to R&R 3 times befre figured out.
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henrymc7
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« Reply #8 on: September 05, 2006, 08:37:33 PM »

Thanks for all replies. I have cleaned all the posts in the engine compartment and had a marginally lower voltage loss but something is still missing. Maybe the main power cable from the front. More to keep checking on. I certainly don't want to pull the starter, pay for the rebuild and find out that something else is happening. When I installed the two new ($400) batteries and it didn't even click, I almost cried ("no dear, these aren't tears, this is a very dusty campground.")
One further question for Dallas regarding checking my ground. When I put the old set of batteries outside the engine door and put 24Volts across the two posts on the starter solenoid, I got a very strong clunk when I hit the rear start button. It sure sounded like the pinion was being pushed into the flywheel. Shouldn't the starter have spun at that point as well? I will still check it with your first suggestion but am trying to understand in my poor head what's supposed to happen.
While at the campground the whole week, there were quite a few folks who were curious about what we were doing as I know lots of us get, and I was happy to show it off but in the back of my mind I'm thinking "Maybe you could come back on Monday and help push." :-)

If nothing else, I'm having fun!
Henry
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littlehouse
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« Reply #9 on: September 06, 2006, 12:48:39 AM »

Hello Henry
I don't know if this will help but I'll try.
The way the system works is the main power [elec.]  comes from the battery with the big cable to a large nut & bolt
on the back of the starter. Power [elec.] also comes from the starter button, or key, in a smaller wire to the back of
the starter. This unit on the starter that the wires are hooked to is called a selanoid, it is an electical magnet that
when power from the start button, or key, makes it into a strong magnet it pulls some kind of lever system to shove
the bendex gear into the flywheel. It also at the same time pulls a large copper washer against the head of the bolt
that large wire from the battery is hooked to. the elec. goes through washer to a bolt just above the starter at the
bottom of the selanoid. This bolt is hooked to a wire or strap that takes the power[elec.]  into the starter.
Sometimes this copper washer gets a burn spot that wont make a good elec. connection so even if the bendex goes
into the flywheel the starter still wont run. Now this washer and what ever system moves the bendex are inside the
selanoid so you cann't see them from outside but they're ez to fix if this is the problem. If you hook power up to the
big bolt that goes to the starter[below the bolt with the wire from battery] the starter shoud run with out trying to                                    
start the  eng.,  the starter will just spin by it's self if it's okay. So if you take an OLD wench or screw driver; something
you don't mind if it get a burn spot in; and you make contact from the bolt with the battery wire to the bolt with the
strap or wire going into the starter only, the starter shoud spin. Remember you cann't get shocked from DC but you CAN
get a bad burn.
I don't know if this helps at all or just muddys the water. If I'm wrong I'm sure someone will let me know.
  Lots of luck
Ray with the littlehouse in Kent Wa.
 
 
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bobofthenorth
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« Reply #10 on: September 06, 2006, 10:26:15 AM »

I've been battling with dying starters for going on 3 years now so bear in mind that, while I'm experienced I'm not necessarily experienced with actually solving the problem. 

Some more troubleshooting steps you may want to try:
- hook up your volt meter to test voltage at the batteries & at the bendix while the starter is engaged
- unbolt the starter & test with it hanging under the bus
- feel your cables and connections after a start attempt - hot indicates a high resistance situation that needs to be fixed
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