MC8 fast idle and engine shutdown

[Zrob90sc]

Howdy guys, OE skinner valves and wiring to them have been removed from my engine bay.  Looking to add new ones, was wondering where to start from a wiring perspective, the rear junction box?  Anyone have a wiring diagram?  No luck finding them on the internet thus far.  Not sure what this conglomeration is either.

[Coach_and_Crown_Guy]

That's most likely stuff used for the OEM air conditioning system. I don't see the AC compressor in place so I'll assume it has all been removed and the lines disconnected. I may be wrong but based on the limited view in the pic that's what it looks like to me. If so, all these Skinners aren't really doing anything anymore and simply going along for the ride. Those Skinners were most likely used to control the AC compressor internal unloaders to start and stop it as required by the Driver when he turns it on. That square sealed metal box below the valves has the appearance of the old style box used in many coaches that housed the AC system HI-LO sensors used to shut it down if high side Freon pressure rose too high or the low side got to low. Again totally not being used if the OEM compressor and gear has been removed.

If the engine runs and shuts down normally, and the high idle works, then you have no issues. All those air controls are mounted on the governor housing anyway and not anywhere near the AC compressor. The Skinners for those controls are a different model and smaller in size too. Follow the air lines from the air control actuators on the governor housing back to the Skinners controlling them. Usually on the engine compartment walls above and nearby.

[Zrob90sc]

That makes sense, the ac compressor is gone.  Right now theres a manual air shutoff in the back in the first pic and thats it, nothing from the drivers seat.  The old skinner valves are still on the back wall but look to have been bypassed and no electrical wiring run to them.  Not really a big deal if i can find where to start from the back to rewire them.

[lovetofix]

I believe the ones on the engine bulkhead were for your tag axle dump control.

[luvrbus]

The 2 on the forward bulk head 1 is shut down the other is for fast idle,the 2  at the Coutler/White AC control box 1 was for the compressor clutch the other was for a belt tensioner cylinder, what they are used for now is anybody's guess.The 2 on the bulkhead are the 2 you need, the one on the left is for fast idle and the clamping cylinder. With the one disconnected on the left you shouldn't have a fast idle unless the PO cobbled up something.If you have Jakes that maybe the reason the valve on the left is plugged, they used a electronic Jake buffer switch. I have the schematics for the 8 and will see if Van can post those for you, I need the last 2 numbers on the unit numbers to get the right one,MCI changed schematics like most people change underwear by unit numbers

[Zrob90sc]

Thank you, S12710 is the serial number i believe.  Looks like all the wiring to those front bulkhead skinner valves has been cut out, cant find any trace of it.

[luvrbus]

Thank you, S12710 is the serial number i believe.  Looks like all the wiring to those front bulkhead skinner valves has been cut out, cant find any trace of it.

They feed from the bundle of wires on the back of the engine ,they are probably cut inside the black flexible loom that goes across there to the rear panel. In the rear panel stud 22 is fast idle and stud 25 is the shut off if you have toner (tracer) tone it out and find it,i think 22 is gray wire and 25 is a black wire.I recall wire number 40 is fast idle and either 3 or 6 for the shut down for the skinner valves   

[Zrob90sc]

Awesome advice!  I found the old harness, fast idle has power with the switch on.  Looks like the engine shutdown has power all the time at the moment.  Got my old skinner valves off, the one with air going in the top is i believe an original 24v mci valve.  The other one is a 12v neway valve.  I wonder if they are both supposed to be 24v normally closes valves?