Engine just quits

[quvia1]

Recently my engine just quits. It could be two minuites after start up or after a moderate run. I just took a two day trip and it quit 4 times. I Had a brain storm and changed the fuel pump relay but it still goes on. In the past I changed the PMD and it helped but not sure this time. I hear a lot about the OPS causing problems but once again I'am not sure..The ground on my heat sink seems good. No codes when this happens either. Any idea's. I have a spare PMD I could try BUTTTTT! The engine starts right up if I pull over and turn key off then start.

[CAdiesel]

Sounds like pmd. Ops controls lift pump. If it went out you would be more likely to feel hesitation on hard acceleration as injection pump had to suck fuel from tank.

[quvia1]

Thanks. I have a spare sooooooo, I will put it in and see. I have always wondered about the OPS because I hear so much about it on tis forum. I have never seen my oil press fluxuate and was wondering if I had a bad connection. Thanks again..

[CAdiesel]

OPS is just a switch that just shuts off power to lift pump in the event of a wreak... to kill the motor. (Some people bypass this.) Oil pressure is from a separate sending unit plus these electric dashes are marginal in their accuracy. If you want true readings use mechanical gauges.

[quvia1]

I changed the PMD and will see if this helps. So far so good but the true test will be in two weeks when we go camping again.

[Racer5551]

Ignition switches have been known to fail intermittantly on these trucks.Jiggle the key when it stalls.
On OBDII vehicles the OPS is not the only source of power for the lift pump,the ecm is the main source of power to the lift pump relay as long as it gets a signal from the crank sensor.
The ecm also controls the prime function of the lift pump at initial key on engine off start up cycle.
IF the fuel solenoid ground(pmd harness ground) has been relocated to the pmd heatsink-move it back to the optical sensor screw on the top of the IP.