The stop engine light comes on my ford f-650 truck with a 5.9 cummins and goes off

Priming here

https://www.justanswer.com/medium-and-heavy-truck/i1m0k-manual-fuel-pump-primer-5-9l-cummins.html

More here

https://www.google.com/search?q=1999+Ford+F600+prime+lift+pump

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If you hit a bump hard enough you might have tripped the inertia switch. Look in your owners manual, it should be under the drivers side of the dash I believe.

there is a reported issue with wire harnesses.
this repair will require systematically working through.
My first guess would point to a module with a bad solder joint.

When you turn the key the light is tested along with all other warning lights in the dash. If on when started you have a problem with ABS.

You most likely have a abs sensor problem with one or more .

The oil light coming on when stopped at a stop sign tells me your engine was already damaged before you had the power loss problem. I would not waste the 650 to put in an oil pump. You would be further ahead to just replace the engine.

There is less oil distributed to the engine in idle position than when you drive. So when the oil light comes on, you may have to put a little oil in your car. While driving, the oil reading may be enough for your sensors in your car to not send a signal, but when you stop and the oil pressure goes down, it may not be enough and that's when the light comes on. When you drive 20 to 30 minutes, your oil gets thinner because it is warm. That also will send a different reading to the sensors. You may want to try a thicker oil (instead of 10/40 try 5/20 ... ask before you do this!).

Coolant sensor may be the problem. It is located near the thermostat housing. It may be sticking between modes & not operating properly.Also make sure coolant is circulating in system.

Have you located your local Cummins Dealer for this. It should be no issue for them to copy/email a diagram. Good luck...

Sounds like your oil pressure sensor may be faulty. Or your oil level is very low. Your engine should idle as low as 650 rpm without your light coming on.