F935 starts but only runs for 15 seconds

[sblight]

My F935 starts easy, but only runs for about 15 seconds. I think the fuel shut off solenoid shuts the engine down. We disconnected the solenoid (mechanical) and it runs longer. How do we debug what is shutting down the solenoid.

 

[jwinner]

Sounds like maybe either the solenoid itself is going bad, or one of the relays going bad - intermittent. There are several, the time delay control circuit contains one of them, and that is like $150 to replace. Since it runs a whole 15 seconds before shutting off, I assume it is not one of the safety switches, such as the park brake, seat, etc. I'm trying to attach a wiring diagram for the fuel solenoid system, not sure if it will work. The solenoid has a pull-in and a hold-in circuit. Sounds like the pull-in circuit is working, and the hold-in is the one not working, unless the solenoid itself is failing, have to test the wires...


View attachment f935solenoid.pdf