1989 MCI 102c3 Starter Replacement

[89mci]

Hi Everyone!

I'm helping somebody renovate a 1989 MCI 102c3 (6v92 MUI, Allison HT740), and have hit a snag with the starter. It's a 24v system, but the previous owner installed a 39MT Remy 12v starter. The bus also did not start from the front, and only started when using a DIY installed start button in the rear.

It worked when we would move the bus now and then in the driveway, but seemingly out of nowhere we started experiencing a no crank/no start situation, and soon after the starter smoked and gave out completely. Bench tested it and it's dead.

The issue I'm coming across is I can't figure out what to replace it with. I do have a manual, and it has a couple options listed: 42MT/7G-1-39, 40MT/7G-1-1.

I look these up, and can't find anything exactly. Every online tool I have found for matching a part to a vehicle turns up no starter for this vehicle. So basically, I'm wondering what to buy. Is it ok to have a 12v starter on there? If not, what would the right 24v starter be?

I've tried every diesel and RV mechanic within 100 miles, and nobody wants to touch it or give me advice. They all say they keep away from buses this old!

Any help would be appreciated. I'm in kind of a jam as the property owners where we are storing it need us to move it this weekend!

 

[8Muddypaws]

Well, you know the starter that was on it worked at least for 'a while'. Can you find one of those?

Have you measured the voltage going to the starter? Could it actually be 12v? On a bus that old almost anything's possible.

 

[89mci]

That was my first thought, I just don't want it to fry real quick and then have to buy another! The voltage going to the starter is 24v.

 

[Alaskansnowbirds]

I was a parts manager for Grayline of Alaska. We had a large fleet of MCI coaches.

I'm guessing that the previous owner needed a new starter and bought the cheapest one he could find. I think a 12v starter will work with 24V for awhile but will burn out.

The starter is part of the Detroit Diesel engine. If you want to buy a new starter, I would inquire at your nearest Detroit Diesel dealer. Your other option is to check with your local auto parts store and ask where they have starters rebuilt. Then check with that company to see if they can rebuild the one you have. If not, they may be able to refer you to someone that can.

If you have measured 24V at the starter, I would replace it with a 24V starter.

All the coaches we had, you could start both from the front and with the mechanic's start switch in the back. The coaches came this way from the factory. The switch in the engine compartment was a three positions toggle. Front, Off and Start. If I remember right, UP was Front, Center Off and Down was spring loaded start position. If you were working in the engine compartment, you made sure the switch was in the OFF position. This prevented someone that didn't know someone else was back there from entering the coach and starting the engine from the front.

 

[89mci]

I was a parts manager for Grayline of Alaska. We had a large fleet of MCI coaches.

I'm guessing that the previous owner needed a new starter and bought the cheapest one he could find. I think a 12v starter will work with 24V for awhile but will burn out.

The starter is part of the Detroit Diesel engine. If you want to buy a new starter, I would inquire at your nearest Detroit Diesel dealer. Your other option is to check with your local auto parts store and ask where they have starters rebuilt. Then check with that company to see if they can rebuild the one you have. If not, they may be able to refer you to someone that can.

If you have measured 24V at the starter, I would replace it with a 24V starter.

All the coaches we had, you could start both from the front and with the mechanic's start switch in the back. The coaches came this way from the factory. The switch in the engine compartment was a three positions toggle. Front, Off and Start. If I remember right, UP was Front, Center Off and Down was spring loaded start position. If you were working in the engine compartment, you made sure the switch was in the OFF position. This prevented someone that didn't know someone else was back there from entering the coach and starting the engine from the front.

Thanks. The mechanic's start switch you describe is exactly how it is on my bus. That switch hasn't worked since I bought the bus, and the previous owner rigged up a start switch directly to the relay on the starter.

I'm biting the bullet and rush ordering a 24v Delco Remy 39MT starter. The starter that has been on there is a 39MT Delco 12v, and aside from the voltage the specs are the same, so I'm hoping it works out.

If it does, I can get back to finding out the underlying issues with why the bus wasn't starting!

 

[89mci]

Ok, so I ordered this starter, and it comes today. I'm going to install it, and would like to install a switch directly to the starter to start the engine. The previous owner had it rigged up like that, but I just wanted to check with others before I did it again.

Is it ok to wire a switch directly to the starter to start the engine, basically bypassing the rest of the ignition system? I'm thinking I would put one end on the constant 24v post of the starter, and the other end on the switch terminal of the magnetic switch relay. When I push the button in, the magnetic switch relay would get 24v and engage the solenoid and starter.

Does that make sense, or is there something I'm missing? Just don't want to burn anything out or damage it.

 

[89mci]

Got the starter today and installed it. Fit just fine. I connected the switch how I described above, and it started right up!

Thanks for the input, it was very helpful... now to figure out why the bus won't start using the standard front and rear switches.

 

[89mci]

Ok, so I'm back. Went to start the bus today, and the starter turns and I see the belt moving, but the bus won't start. 24v to the starter, batteries are fully charged. Where would be a good place to start looking? I noticed I was able to push the parking brake down, and it just springs back up. Not sure if that is supposed to happen or not. Is there anything related to air/air brakes that I could check that might prevent the engine from starting?

In a huge pinch right now, need to get the bus moved off the property. Any ideas would be welcome, thank you!

 

[89mci]

I ended up getting it started! There is a lever on the engine between the belts that I have to push in to shut off the engine. That lever was stuck. As soon as I pushed it forward, the next time I tried to start, it started right up.

Anybody have an idea of what the lever I'm talking about is called?

I ended up getting the bus moved, but then came across other issues. The parking brake would engage, but wouldn't hold the bus in neutral. I also noticed my air was down to 75 after a 20 minute drive.

If there's anywhere I can be pointed to for troubleshooting air/parking brake, that would be really helpful. Thank you!