Fast Idle

[Glennman]

Back in the day when I went through my wiring troubles with my '02 MCI, the fast idle switch functioned. Then after getting it running, the fast idle didn't work anymore. However, I don't know if it's stuck on fast idle, or regular idle. It slows way down when in drive, but again, I don't know what normal is. That being said, how can I figure out which setting it is on? I was looking at checking my Allison fluid level using the switch pad, but the engine cannot be on fast idle when doing that, so I need to find out for sure where it's at. Any ideas? I suppose I can check the rpms when idling. Anyone have the rpm numbers for high and regular idle?

[luvrbus]

Around 600 for idle and 900 for fast idle ,fast idle is part of the cruise control circuit in case you don't know it has to be turn on by the cruise control on most D models ,my D had 2 rocker switches  on the dash and one on the left panel under the window and would no nothing unless the cruise was turned on.It won't be stuck on high idle releasing the park brake breaks the circuit, I don't think the B500 will even shift  out of neutral when on fast idle it reads to high of RPM

[Iceni John]

If you have DDEC II, the Fast Idle is a pair of resistors that fools the ECM into thinking the accelerator pedal is partially pressed.   I had weird FI gremlins for a while because the resistors were corroded and making intermittent contact, so I replaced them (thank you Bill Gerrie for resistance charts) and added a second pair to now give me the world's only two-speed Fast Idle...   Yeah!

John

[dtcerrato]

Caterpillar uses two stage fast idles.

[Iceni John]

Caterpillar uses two stage fast idles.

Darn it, I'll now have to make mine three-speed.

John

[luvrbus]

Darn it, I'll now have to make mine three-speed.

John

His DDEC version will be adjustable all you do is turn the cruise on and tap the set on the cruise for whatever fast idle speed your heart desires ,the electronic Cat and Cummins engines work the same way

[dtcerrato]

The Cat we're driving has cruise control but is independent of the High speed idle which has a dedicated button on the dash & when pressed lights up to show it's engaged, when pressed again it idles higher. When the brake or accelerator is pressed the FI disengages.

[Glennman]

I do not have cruise conrtol, at least that I am aware of. I do recall that before my wiring problems, there was a distinct difference noted when I pushed the fast idle button, but that is no longer the case.

[luvrbus]

I do not have cruise conrtol, at least that I am aware of. I do recall that before my wiring problems, there was a distinct difference noted when I pushed the fast idle button, but that is no longer the case.

You have a cruise all D's with the series 60 had a cruise control look on the  front dash upper  right side  corner the cruise was not a option, it is programed in the ECU it may be disabled but it is there check it with a pro link it will be there, the switch may be unreadable or missing ,I replaced all my panels and switches  Caylor was very proud of those

[epretot]

I have a cruise and fast idle switch. The fast idle is a bit intermittent when switched on. I think it's the relay

Fast idle is upper left panel. Cruise is lower left panel.

[Glennman]

Does the cruise button say something on it or is there a symbol? It seems like I would have noticed something like that by now. I'll take a look at it tomorrow. Also, where can I expect to find the relays that control the fast idle? This is all sounding pretty promising!

[epretot]

I believe the relay is in the electrical panel outside the drivers side window.

The image shows the location of the cruise control. It says "map light". I swapped that button in because the cruise button had a hole in it.