I've got this IH tractor that's going to make me go gray. The subject is an 96 IH day cab with a Cummins N14 and the Celect fuel system.This truck is a farm unit, it loads in the field, pulls to town, dumps and it's back to the field for another load.

It runs fine from the field to town, about 5 miles hiway, it's good across the scales loaded, dumping it's ok, back to the scale goes fine. Leaving the scale and back to the farm is where the problem starts. The engine RPM seams to be governed to 1500 in all gears, after it sets to be loaded, 20 minuets or so, it will run fine, RPMs back to 1800 or 1900. And a way we go, untill the truck pulls off the scale empty. This has happened starting from different fields and going to an other town to dump, I don't think it's about the time running. With our little Eaton/ Auto Xray scanner, I don't find any thing wrong in the data, RPM, VSS, temp, and oil pressure look fine, the engine is not derating as far as I an tell. The one thing that I did see in the data was the voltage reading will be very low, it's low all the time the engine is running, well or not. With the engine off and the key on the voltage is battery voltage. I have checked the power and grounds at the ECM, voltage drops of .2 or .3 with a load of about 3 amps. Would you think these are too high?

A bit of history, a few weeks ago we replaced the vss sensor due to the speedo not registering until about 25 MPH, also with this problem the engine speed was governed at about 1500 till the speedo picked up.I think the programming is set to not allow higher speeds no load.

Raymond Reichert
Technician
Eichelberger Service Inc
Shickley, Nebraska, USA