Hey folks have another head scratcher for ya'll. I'm working with a 96 Freightliner FLD Cummins N-14 Celect. When parked the High Idle (pto idle) wont increase the RPM's. This truck used to be able to bump the idle up to 900 RPM's while parked. It used to work regardless of the parking brake set or released. However if you roll / coast the truck slow (walking speed) the High idle will work but as soon as the wheels stop the idle drops back down. Even if you put it in 1st gear and slow roll you can hit the cruse and idle it up to 900 RPM's. Throw it in neutral the rpm stay at 900 until the wheels stop moving then drops back down to a low idle. Cruse control works fine. Clutch switch and brake pedal will knock the cruse off so I assume they are working. ECM checks out okay as well. To say the least I am puzzled and came to you folks for help. Hopefully there is someone out there who has experienced this before that can point me to the right direction.
N-14 Freightliner no high idle
Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by olpa77, May 21, 2020.
-
-
Trucking Jobs in 30 seconds
Every month 400 people find a job with the help of TruckersReport.
-
Speed sensor on transmission. Possibly.
olpa77 and Rideandrepair Thank this. -
Check trailer brake handle if it's slightly applied high idle won't work..
-
SmallPackage Thanks this.
-
I finally solved my non working high idle issue after weeks and weeks of research. I changed all the air switches and the vehicle speed sensor on my 1998 FLD 120 with the 12.7 Detroit with no help. What I finally determined was that the high idle circuit passes through the hood tilt switch and is disabled when the hood is opened. If that switch is bad or the wiring to the switch is bad and that circuit is open, your high idle will not work even though your cruise control will not be affected. I was able to bypass my hood tilt switch by unplugging it from the harness and used a large paper clip as a jumper to close the circuit. My high idle started working immediately. Hopes this will help someone with this same issue.
Speedy356 and SmallPackage Thank this. -
-
SmallPackage Thanks this.
-
SmallPackage Thanks this.
Trucking Jobs in 30 seconds
Every month 400 people find a job with the help of TruckersReport.