Broken Down on Freeway Need Help!!!!

[69M4107]

Hey everyone, I'm pretty bummed that my first post is under these circumstances, but here I am and I need help ASAP. My bus is a 1969 GM model 4107 conversion with a strong 8v71t paired with a V730 automatic. It had been sitting for a couple years in covered storage when I bought it. I went through the basics and other than a typical slight oil leak,and airbag leak it fired right up and ran strong. I set out and made it about 300 miles before the temp started to rise. I pulled off before it had a chance to overheat (got up to 202) and waited an hour and when I went to restart nothing happened. It wouldn't turn over. I have power to the starter but when I looked at all the wiring in the engine bay I noticed that most of the wiring looks super old. there are 3 blocks that can be split and pulled away by hand and most if not all the wires going to those blocks and in very poor condition and the blocks themselves were full of dust and dirt. Does anyone have a repair manuals for a 1969 model 4107 and the 8v71t? Also if anyone has good wiring diagrams that would be awesome as well. Thank you all in advance!

[Melbo]

 A little help here.  I am near two interstates but have no idea where you are.  Your location would get you better responses I would think.  With power to the starter is it possible for you to jump the solenoid?? Any additional information could be helpful.  Yes most of the wiring is our older buses is old.  Some of it keeps working and some needs to be updated as necessary.  Keep us posted with any updates.

Melbo

[69M4107]

Hey Melbo, so I was able to get the bus towed off the side of the freeway to a parking lot in Grandview, WA. I have only tried to jump a starter once in my life and it wasn't pretty so I figured since I'm in a better place to work on it that I  would just take the time to fix it right. Do you have any manuals that include wiring by chance? Thanks for the reply!

[richard5933]

First - don't panic and start tearing things apart. Now that you're in a safe place you can work through this methodically. Daylight will help a bunch.

Here are a couple of wiring diagrams from the 4108/4905 book - not exactly the same as your but hopefully you can get a general idea of how GM put things together. One is for the Engine Controls and includes the start circuit. The other is for the Alarm & Signal systems which include the shut down for things like over heat. Hopefully someone will post the 4107 diagrams later on when people wake up and see your posting. I do have the 4107 repair manual and will post the diagrams of the electrical panels in a few minutes.

As sketchy as that wiring looks, it's unlikely your problem. At least not the wires themselves. Likely the problem is confined to a loose connection, corroded terminal, bad ground, or other relatively minor thing.

In no particular order:

Switch out of place - In a panic shut down, it's easy to not go through the shut-down procedure correctly. Same for restarting in a breakdown. Make sure that all your switches are in the proper place for starting. Make sure that the controls in the engine bay have not been accidentally moved to the incorrect position. Can't tell you how many people suddenly discover their bus won't start, only to find the rear controls out of position. Happens to nearly all new bus owners, myself included.

Neutral safety switch - When you shut down during the over heat situation, did you put the bus in neutral? Won't restart if not. This may or may not be a problem, as some V730s are installed so that you can't shut down the engine unless you're in neutral. Also, check the neutral safety switch itself. If the switch fails, the start circuit won't complete and you won't start.

Overheat protection shut-down - If you actually over heated, your protection circuit may have kicked in. Should reset, unless a relay is stuck.

Stuck relay - the start circuit uses a number of relays, as does the safety shut down system. These are essentially the logic circuit/computer for the bus. Sometimes taping them gently helps if one is sticking.

Bad ground - these old buses are notorious for bad/loose ground connections. You might have been lucky when you initially started it, but those few hundred miles of travel were enough to loosen the connection enough that it's not working. Could be to the starter solenoid, could be the neutral safety ground, could be any number of places. I'd start in the battery bay and check the ground there, then work outwards.

Starter solenoid - they do fail sometimes. You can jump it to test, but I'll leave that to others to explain since I have never done it.

[richard5933]

Start Circuit diagram from 4108 book.

[richard5933]

Your safety shut down system may have kicked in when your temp rose. Should reset on its own, but perhaps a relay is stuck. Unlikely, but here's the diagram from the 4108. Not the same, but might be close enough to help.

[richard5933]

Drivers control panel

[richard5933]

Engine control panel.

I can take photos of other pages from the manual if you need. The manual covers 4107/4108 so it should be helpful. Just let me know what you need.

[plyonsMC9]

Good morning Dominick,

Any updates for us? 

Also, when you say 'nothing happened', does that mean she tried to turn over but couldn't?  Or complete silence; and maybe (as with MCI - automatic trans) if the gear shift is in drive vs neutral and she won't even attempt to turnover?  Or ..?   

Please let us know when you can!  Best of success - Phil

[luvrbus]

You can jump the starter if it is not a battery problem,on a GM you need to go in from the rear floor for easy access ,only takes a wire from the solenoid (small terminal on the bottom of the solenoid) to the battery side of the solenoid 

[neoneddy]

Yeah like plyonsMC9 said, I'd be interested to know if it's even clicking, does it try and stop?  Obviously the worry here is Hydrolock.  Try and bar it over , or hit the starter in the rear real quick.  Don't want to lift the head with water in the cylinder.

[luvrbus]

If he has power it will click regardless and you can bypass the wiring,starter button or switch.safety shutdowns  and relays to start the bus,I believe that is a 24 V system so check for power at the battery terminal on the starter 

[chessie4905]

Since it is already converted, hopefully you have inside access to the starter. Some conversions covered over the access panel. If that is your case, you can easily get to it from underneath. First thing you MUST do though, is to place solid blocking under the body reinforcements where the torque rods attach, in case an air bag fails while you are under there. Now there is easy starter access through a hole in the bulkhead between engine and starter, unless you are...lets say overly thick. You sit up between differential and rear bulkhead, and there is the opening to access the starter and wiring. Btw, that is the best way if it is necessary to replace the starter. Lifting it up through the hole inside is pretty tough, as the starter is real heavy.

[richard5933]

Has anyone made contact with the OP?

It would be really helpful for us offering advice if he could provide a bit more information. Otherwise, we're all guessing of course.

I'm still hoping for his sake that it's just a simple electrical gremlin - we've all experienced those and they're much easier to fix than having to pull the starter.

[69M4107]

Hey guys, so far no change, I checked to make sure all my switches are in the proper spots, my batteries are brand new and fully charged. I'm not sure that my bus has a neutral safety switch as it does not have a neutral position on the shifter. The way it was converted, I can not access the rear of the engine from inside, I have to go in through the side above the transmission which is really making things difficult as I can't get as close to the starter and wiring as I would like. I was able to jump the solenoid a(by feel not sight) and my starter turned so I believe that tells me both my starter and solenoid are good correct? Does anyone know if those quick release blocks are in fact grounds? Cause I really believe that is my problem.  I am going to run a new ground wire to the solenoid and see if it'll turn over. Any other ideas are welcome! Thanks again for all your help. I'll keep you posted.