Please help/ no high idle

He's an O/O. They only have that kind of idiotic idle-reduction crap on fleet trucks.

He just wants to be able to bump his idle up to 1000 for better oil pressure, to keep the engine warm, and because it's apparently hard on the turbo to idle it below 1000.

 

Detroit recommends a minimum of 850 rpm for extended idle.

 

I would suspect the switches. Jump the wires on each switch (One switch at a time) and see if the high idle works while the jumper wire's connected. If that won't work, could the wires have been reconnected to the wrong switches during installation?

 

Okay boss I have your answer right here. On Detroit Diesel equipped International conventionals that have Opt-Idle, you have a failed mercury switch inside the hood or the wire harness is damaged or unplugged. The purpose of this switch is to protect anyone who raises the hood of such equipped trucks from accidental engine starting during Opt-Idle operation. Raising the hood causes this mercury switch to open contacts preventing Opt-Idle system from starting truck if someone is working in engine compartment. When the hood is in closed position, the contacts in the mercury switch close again allowing Opt-Idle to function. This switch is located under the hood on the drivers side just above headlight assembly. This same mercury switch also affects your fast idle / PTO idle speed. When hood is in closed position, fast idle is active, but in open hood position, fast idle is disabled. Engine can be started manually while hood is open but it cannot activate fast idle circuit. If this switch is bad such as being hit during front end accident, the mercury will escape preventing closed contacts. Also if wiring is damaged or unplugged, this too will prevent fast idle circuits from activating. On my truck since I do not use the Opt-Idle system, I had it disabled in the Engines ECM so that it cannot function. Then I took the two wires going to the mercury switch and joined them together and taped it real good with black electrical tape and used wire ties to secure wires to left headlight wiring harness in case any future owners of my truck want to use that Opt-Idle system again. Now I can set fast idle with hood open or closed. That is your only issue that prevents fast idle on International Conventional Trucks. You fix that then you fixed your problem. If you have Opt-Idle that you do use, then replacing that mercury switch and checking wiring connections is all you need to do to fix problem. This system is designed to prevent Opt-Idle system from engaging while a mechanic is working on your truck so if you use Opt-Idle, keep that system in tack and do not by-pass it or else someone can be killed or badly injured. If you don't intend to use your Opt-Idle system, first disengage it in the Engines ECM computer, then join those two wires together out by your headlight assembly under the hood on the drivers side. That's it, fast idle returns.

 

This is reply just saved my sanity. My AUTO START/STOP switch wouldn't turn on. Been trying everything for the last couple hours to get it to stay on. THIS was the fix.

 

try pulling up on the brake and clutch pedal with your feet and try to idle up. If that works it a safety switch.

 

Guess I should have read the whole thread before commenting.