Engine bay wiring, MC8

[rcbeam]

My prior coach was a 1980 GMC.  The wiring manual for it was a separate book, about 3/4 thick or so, and with great schematics, and a great resource.  That bus is not gone.  My current bus, a MC8 has the maintenance manual, and the wiring part of this is chapter 7 and sucks in comparison.  The maint manual clearly is for a MCI and my bus is a TMC.  I thought they were supposed to be the same, but lots of wiring stuff just doesn't match up and it lots of stuff just isn't there.  I even bought the CD version and it's the same.

I'm in the process of replacing the alt that the P/O had replaced (neither are the DN version) and in that found some bad wiring,  insulation missing, cut wires, etc.  I've had new cables made for the back in and putting all new in wire wrap. 

I have two wires I can't find out what the originally went to.  Bundled with the 1/0 cable that goes from the post on the rear engine panel across the engine room to the 'engine compartment stud' is another three smaller wires.   One is black and goes the the starter solonoid, one is brn or prob tan, and the last is green.  The tan and green wires go the about the starter area and were wire nuted together.  Cleanly something had been removed, but I don't know what.

In the rear panel box, the tan wire appears to go to one of the starter relay posts and the green wire was just laying there not attached to anything.  I look in the book, and the code on the metal straps on the tan and grn wires don't seem to match with anything.  This isn't the first time I could not match up the CODE on the metal stamps with the book.

Does anyone know what stud the green wire attached to in the rear panel, and what the tan and grn wire ran to that would be close to the starter area?

Does anyone have a better resource of wiring diagrams for the MC8 than I?

[rcbeam]

OK... I know I'm not the only MC8 owner on the board... I imagine the wiring in this area might be the same on the MC

[rcbeam]

Not sure what happed... next thing I knew I was back at the home page... anyway, prob similar on the MC9 also.  I did look in my lousy wiring chapter again, and I notice that one of the diagrams shows a pressure switch on the fuel filters.  When I looked at the bus today, no pressure switch is on mine... so maybe that is what these wires are for.

Does anyone have a ideas?

[buswarrior]

Are you sure that all the pages are present in your copy?

And previous owners are famous for making a mess of things in their cheap attempts to make it work for another revenue producing trip, and then there's previous busnuts who have nothing to lose....

If it has strayed too far from stock, it might just be best to move forward from here and start a fresh schematic and add your adjustments to it?

Yes, there is a fuel pressure switch, it is plumbed in near by to the fuel filters, it inhibits the starter being engaged with the fuel pressure present. Popular to bypass by cheapskates, best to restore, ESPECIALLY if the auto shut down equipment is still active. Holding in the starter button is how you bypass the auto shutdown to move the coach, makes a mess if the starter stays engaged...

happy coaching!
buswarrior

[bevans6]

fwiw, on my 1980 MCI virtually all the wires are black, with metal tags on the termination point with a number code referring to the circuit the wire belongs to.  Almost none are coloured.  If I find a coloured wire it's almost always some retrofit install.

Brian

[rcbeam]

Clearly no fuel pressure switch on mine... also no emer shut down solonoid to close the flapper either... flapper is froze in place.  God only know what else is missing.  After Grayhound was done with her, they sold it to United Charters in the Carolina's... not sure whether North or South.  Anyway they apparent just drove the life out of it and when something broke, they just took it off.  Then like others have mentioned, not sure what the P/O did either.