The cold start system used on Maxxforce engines is inactive above 50 degrees. This isn't in the manual but from personal experience with these engine if the ECM commands cold start assist the engine will not start until it has completed its cycle (cranks but doesn't fire). I wonder if there is a start inhibit until it cycles off? They use a grid heater with a low pressure fuel injector. This is installed in the intake and when active fuel mist is drawn across the grid heater element. It cycles on and off for a time after the engine starts.
I've tested thermistors in an A/C system using the palm of my hand and watching the readout with International BodyBuilder software
A thermistor sensor changes electrical resistance with
changes in temperature. As temperature changes
at the thermistor, voltage at the ECM will change
accordingly. Thermistors work with the control module
to produce a voltage signal directly proportional to
temperature values.
A thermistor sensor has two electrical connectors,
signal return and ground. The output of a thermistor
sensor is a non-linear analog signal.
I've tested magnetic pickups when troubleshooting an engine speed sensor on a Detroit 60 when the tach was inop. Found a clear pulse but the 0.2v reference dropped off when the gauge was plugged in. Found some damaged wiring.
A magnetic pickup sensor contains a permanent
magnet core that is surrounded by a coil of wire.
The sensor generates a voltage signal through the
collapse of a magnetic field created by a moving metal
trigger. The movement of the trigger then creates
Alternate Current (AC) voltage in the sensor coil.
I've tested a potentiometer when working on a Freightliner with surging problems. Ended up replacing the throttle pedal assembly.
A potentiometer is a variable voltage divider that
senses the position of a mechanical component.
A reference voltage is applied to one end of the
potentiometer. Mechanical rotary or linear motion
moves the wiper along the resistance material,
changing voltage at each point along the resistive
material. Voltage is proportional to the amount of
mechanical movement.
The engine has two potentiometers, both contained in
the Accelerator Pedal Position (APP) Sensor.
Week: 40
Total: 290
