1984XJ6 stopping when it reaches 80+ degrees

Started By: James Crewe on 2014-08-07 11:57:42

It is a Series III with a FI-4.2 engine. At 80+ degrees I have hot start problems as of 1/20/14. When the engine is cold it starts and runs very well. When the engine reaches 80+ degrees it immediately stops.

I have replaced the following parts: coil, ignition amplifier, distributor cap, rotor arm, spark plugs, fuel pump, fuel filter, air filter, alternator, water temp sensor, ignition switch and ICU, but I still have the 80+ degree stopping problem

On 7/18/14 I had the fuel injector noid test. Cold test = blinking bright light. After 80+ degrees = light was dark and not blinking. Also, what triggers the 4.2 fuel injectors and where is that trigger located.

Thank you,


The injectors are triggered by the ECU.

More specifically, the injectors are supplied with 12volts "+" via the main relay and the resistor pack and the ECU provides the ground to actually operate the injectors.

The ECU uses signals from the Air Flow Meter, Coolant temp Sensor, Oxygen Sensor, and ignition system to determine when to ground the injectors and for how long.

There are various possibilities but 'ya gotta begin somewhere' so here are a few quick ideas/thoughts:

- Next time this happens check for 12v at the injectors
- Check the bundle of ground wires at the end of the water rail
- Check the black/white trigger wire that runs along the water rail from the coil "-" post
- Remove the connector at the coolant temp sensor and carefully examine the terminals and wires and/or jump the terminals with a paper clip and see if anything changes.


Thanks for the input, Doug.