MCI 102c3 Start Switch Problem

[Jcparmley]

I have a 89 MCI 102c3 with a 6v72 Mechanical.  Two weeks ago I went to start the bus after it has sat for a year.  It turned over but never started so I assumed it wasn't getting fuel.  Perhaps it lost prime?  So I purchased an 12 volt universal in line fuel pump and installed it just before the first fuel filter and ran it for 5 min or so. 

Then I went to start the bus and nothing happened when I hit the master switch or the start button.  No buzzer like usual, no master relay contact click, nothing.  So I checked the batteries and they were low on volts.  So I charged each one separately overnight.  The next day I realized my batteries were not putting out 24 volts so I bought two new batteries and installed them. 

Today, with new batteries, I have 24 volts, however the bus won't crank or turn over, much less start.  The switch in the rear junction box is set to engine on and front start.  The same result when I try to start from the engine compartment. 

So I have 24 volt at the main disconnect in the battery bay.
I have 12 volt at the front junction box on stud 55
I have 12 volt and 24 volt at the vanner
I have 24 volt on master switch CB

When I stand next to the front junction box and reach through the window and press the master switch nothing happens, the contact block does not click.  However, when I reach through the window, press the master switch and then press the engine start switch the contact block engages and the alarm sounds but the starter doesn't engage. 

Any help would be greatly appreciated.

[Jcparmley]

Here is the front J box label. 

[Jcparmley]

I'm not sure where to go or what to test from here.  Could it be a CB that I am missing?

[Dave5Cs]

Go to the auto parts store and get a starter jumper switch Hook it to the starter and hit the switch. If it starts that way then the starter isn't the problem. Could be the neutral switch or the rely in the rear left fuse panel. Check the two clear ice cube rely fuses there.

You can pull the heater one from up front side panel and exchange it for the one back there to see if it starts and if it does then that is all it is. You can buy a new one at any electrical supply. Neutral switch is at the right hand side of the tranny by the shift linkage and can be jumped with a paper clip to test.

[luvrbus]

Go to the auto parts store and get a starter jumper switch Hook it to the starter and hit the switch. If it starts that way then the starter isn't the problem. Could be the neutral switch or the rely in the rear left fuse panel. Check the two clear ice cube rely fuses there.

You can pull the heater one from up front side panel and exchange it for the one back there to see if it starts and if it does then that is all it is. You can buy a new one at any electrical supply. Neutral switch is at the right hand side of the tranny by the shift linkage and can be jumped with a paper clip to test.

I love your high tech testing equipment Dave and it works 

[Jcparmley]

I switched the relay in the rear left panel.  Still nothing.  I do hear a click in the left panel when I hit the start switch.  My guess it's the solenoid.
I am looking for the neutral switch now.

Go to the auto parts store and get a starter jumper switch Hook it to the starter and hit the switch. If it starts that way then the starter isn't the problem. Could be the neutral switch or the rely in the rear left fuse panel. Check the two clear ice cube rely fuses there.

You can pull the heater one from up front side panel and exchange it for the one back there to see if it starts and if it does then that is all it is. You can buy a new one at any electrical supply. Neutral switch is at the right hand side of the tranny by the shift linkage and can be jumped with a paper clip to test.

[Dave5Cs]

Clifford you taught me that LOL with the Paper clip.

You should have two wires about where your linkage shaft is on the right hand side of your tranny. Put the paper clip into both wires and then try to start it. If it starts it is the switch because you just by passed it. If not then remove the clip and try the starter switch button on the starter solenoid .

[luvrbus]

Clifford you taught me that LOL with the Paper clip.

You should have two wires about where your linkage shaft is on the right hand side of your tranny. Put the paper clip into both wires and then try to start it. If it starts it is the switch because you just by passed it. If not then remove the clip and try the starter switch button on the starter solenoid .

All tool boxes need 3 sizes of paper clips and I use the hell out of the remote starter button especially on GM buses   

[Jcparmley]

Ok  tried the paperclip and nothing happened.   Same rear relay click..
Bought the remote start button and connected it to the rear relay..  it clicked but didn't turn the starter.
How do I connect the remote start switch directly to the starter?   When I tried to jump the starter I got sparks.

quote author=Dave5Cs link=topic=35547.msg410289#msg410289 date=1624378012]
Go to the auto parts store and get a starter jumper switch Hook it to the starter and hit the switch. If it starts that way then the starter isn't the problem. Could be the neutral switch or the rely in the rear left fuse panel. Check the two clear ice cube rely fuses there.

You can pull the heater one from up front side panel and exchange it for the one back there to see if it starts and if it does then that is all it is. You can buy a new one at any electrical supply. Neutral switch is at the right hand side of the tranny by the shift linkage and can be jumped with a paper clip to test.
[/quote]

[Jcparmley]

So the remote start button failed to turn the starter.   I hooked it up first to the large post on the starter solenoid and the small wire on the solenoid.   (I don't know which is the "s" post.) Nothing happened.  Then I touched it to the other small wire and it sparked and melted my remote switch.   

[Jcparmley]

Now I get no buzzer when I flip the master switch and the master relay contact doesn't click.  Nothing when I use the start switch. 

I can however, manually push in the contacts on the master control relay and hear the buzzer for a split second then it turns off.  I think I am shorting out the buzzer and blowing the cb.  Because when it cools off I hear a small click.  However I don't know where this cb is in the front jbox.

[Jcparmley]

I keep reading on the forum about this fuel pressure sensor that is supposed to be on top of the secondary fuel filter.  I must be blind because I can't find such a sensor.  I don't have a wire or sensor on either of the fuel filters. 

I also read about a air intake damper that needs to be reset.  I'm not sure if this is something a 102c3 has but I can't find that either. I'm not sure where to go from here.  I may need a new starter but I really think something is not working correctly in the front JBox.  The master relay no longer trips when I turn the master switch on and the buzzer chirps for a split second and then trips.

[Dave5Cs]

Have you run a multi meter on the pos and neg going to the starter to see if you have enough power if any?
It sounds like you don't have the sensor on yours probably only on older buses as is the flapper in the air intake.

Your profile says series 60 and the above says 6V72 so I would think you mean either 6V92 or 6V71

Just thought I would ask is the shifter in Neutral when you are trying to start it?

Start looking for grounds from the starter and take them off and clean and replace them both ends. Then try again.

If you have someone trying to start it while you hit the starter on the end a few times. It might be stuck. Another thing would be to pull the starter and inside the back of the solenoid there is a copper disk and they need to be clean and turned over then put it back together and try again. These are all things that can help unless you want to have it checked at a shop.

[Jcparmley]

I have two buses. One is a series 60 DL3 the other is a 102c3 with a 6v92 MUI.  That is the one that I'm working on.  I have checked the shifter is in neutral.  I cleaned all the connections in the battery bay.  I will clean the connections on the starter tomorrow.  I am concerned about the switches and the fact that the master switch doesn't flip the master control relay. Nor does it turn on the gauges and the buzzer seems like it's blowing a CB.

Have you run a multi meter on the pos and neg going to the starter to see if you have enough power if any?
It sounds like you don't have the sensor on yours probably only on older buses as is the flapper in the air intake.

Your profile says series 60 and the above says 6V72 so I would think you mean either 6V92 or 6V71

Just thought I would ask is the shifter in Neutral when you are trying to start it?

Start looking for grounds from the starter and take them off and clean and replace them both ends. Then try again.

[buswarrior]

If your batteries are at 24 volts, they are low. Should be 25.2 or better...

Voltage is the king maker, and dragon slayer...

Happy coaching!
Buswarrior