Fast Idle

Jcparmley · August 02, 2019, 01:42:55 PM

I have a MCI 102dl3. The fast idle dosen't work. I searched the form but couldn't find a solution. Anyone know how the MCI fast idle works?

TomC · August 02, 2019, 02:26:08 PM

What engine?

luvrbus · August 02, 2019, 03:27:06 PM

Turn the fast idle on and tap the resume on the cruise control to desired speed is the way mine works ,make sure the ECM is programed for fast idle also

buswarrior · August 02, 2019, 04:08:21 PM

Computer controlled.

Depends on the programming, and that the signals for all interlocking inhibits are satisfied.

One tick box accidentally unchecked in the scan tool and it's wonky.

The same way we say "call Luke" for the old stuff, the new mantra will be "what are the settings in the scantool?"

Happy coaching!
Buswarrior

Jcparmley · August 02, 2019, 06:15:05 PM

Sorry, it's a series 60.

Quote from: TomC on August 02, 2019, 02:26:08 PM
What engine?

Jim Blackwood · August 03, 2019, 07:21:33 AM

Same as mine so I'm interested in knowing. The fast idle seems to work on mine but my brother tried to set engine speed using the cruise control and that didn't work. On his truck he can do that but I guess buses are different.

Jim

buswarrior · August 03, 2019, 07:47:05 AM

Buses have a fast idle switch, trucks don't.

Different ways to achieve the same rise in engine RPM.

The computer does it, no matter which way it gets told to do it.

Happy coaching!
Buswarrior

Jim Blackwood · August 03, 2019, 08:01:18 AM

OK. The truck lets you set the RPM where ever you want it though, I suppose sometimes that might be useful. So not being able to do that would be no indication that the cruise doesn't work then I'm guessing.

Jim

buswarrior · August 03, 2019, 02:56:58 PM

Buses, it is set and forget. Fast idle optimised for HVAC performance, no other thinking allowed...

Trucks can have PTO, that require higher RPM, than just advancing the throttle to raise oil pressure a bit, so they get to make decisions about how much to advance.

Just the way we have arrived here, from some very different streams of the transportation industry, and different needs.

The trivia question for the hardcore scantool users, is whether both the fast idle switch and enabling the cruise in neutral can both be done at the same time, or its one or the other...

The sky, and beyond, is the limit on how a new coach can be, or cannot be, set-up to suit a busnut's taste.

Tip of the iceberg...

Wait until we get to the settings that give the cruise control access to the jakes...

Happy coaching!
Buswarrior

luvrbus · August 03, 2019, 03:38:00 PM

For beginners the fast idle is interlocked with the parking brake valve and the transmission check the parking brake valve first those switches go bad .fwiw I like the tap for engine speed on my series 60 they shake like crazy on just the idle speed 50 more rpm smooths it out lol I miss the idle on the old 2 stroke engines

Jcparmley · August 03, 2019, 08:14:25 PM

I tried today by switching the high idle and hitting resume on the cruise control and it didn't work. Jim, how does yours work on your DL3?

Jim Blackwood · August 04, 2019, 07:59:34 AM

Been awhile since I experimented with it, the last few times I fired the bus up I already had it switched to fast idle and I left it there. It fires up and goes into fast idle right away. I think if it runs long enough the idle goes back down but I haven't tested it specifically to find out. Just seems like that might be what it does.

But from what I remember, if I start it with the fast idle switched off it starts and then eventually settles into the normal idle. I'm not sure how long this takes. Then switching on the fast idle makes it run faster and turning it off makes it run slower. This is with the bus parked, in neutral, with the brake set. I think it might drop to standard idle when the brake is released or you shift it into gear but I didn't really make a point of confirming that.

It seems to have no relationship with the cruise controls. But I haven't driven the bus yet.

Jim

luvrbus · August 04, 2019, 09:18:37 AM

They wouldn't fast idle without the transmission in natural and parking brake set.it could have other interlocks also one here in Valley will not fast idle unless the air conditioner is on, check all the connections and fast idle relay in the rear panel drivers side

thomasinnv · August 05, 2019, 07:28:56 PM

Jared do you have a fast idle switch on the dash next to or below the engine run and start switch? If so then you will not have fast idle controls through the cruise switches unless someone changed it at some point in time. You will have a fast idle relay in the front junction box and a fast idle relay in the rear junction box. The front relay is affected by the fast idle switch and the parking brake as well as the neutral switch from the transmission. The rear relay switches in a resistor into the throttle circuit. There were 2 different resistors used depending on the desired fast idle speed. This is all from memory so may not be 100% accurate but the general idea is there.

luvrbus · August 06, 2019, 08:10:20 AM

Before you spend a lot of time chasing the problem use a scanner and be sure it turned on ,if you have power to the rear relay you can jump that relay to see if the fast idle works or not.
Life is easy on the DDC responsibility side where it gets complicated is on the OEM responsibility side you never know what they did from bus to bus.Mine is a X Peter Pan Lines DL3 I was lucky and Peter Pan sent me all the wiring schematics and manuals for my serial number lol they ordered some weird programing and wiring from MCI