Low pressure out put, Pump has been repaired ,

While an electrical fault or a faulty switch could put the light on, it is such an important light it should never be ignored and the reason for it established immediately. As far as the owner is concerned that means lifting the bonnet and checking the oil level and adding more if the level is low. If it isn't low the car should be recovered to a repair shop. Driving further could be very expensive and very inconvenient...

If the oil pressure light has switched on because the oil pressure is low then continuing to drive will soon wreck the crankshaft bearings or cause crankshaft or camshaft seizure. Damage happens so quickly if the oil pressure is lost at motorway speeds the engine is likely to be severely damaged by the time the car is stopped.

I strongly suggest you have the reason for the light switching on established and repaired.

Hi John, Im AL the owner of Big As Auto Repair.

John, Low oil pressure can be many things. BUT, first you need to hook up an oil pressure gauge just to make sure its not the oil pressure sensor. If you have already put a new sensor on and it still has low oil pressure then you still need to check pressure with a gauge to make sure its not in the wiring or connector. If you find good oil pressure with the gauge then it need to be check to see why the pressure is low. It could be oil pump OR bearing issue. Hope this helps and please visit my auto-repair-website here: http://www.bigasautorepair.com/

Attach a pressure gauge to the oil pressure gauge after removing the oil pressure gauge, to see if the pressure is within specifications. If it is low, then the oil pump is worn out.

Good luck on this repair.

Oil pump or other issues
Cam bearings,etc
Bad sending unit

I would put a mechanical oil pressure gauge on it,to verify oil pressure.

Certainly stop driving it ,until you find and repair

Check the fuel pressure with a gauge. Also check to make sure the gas tank is not building up vacuum. See if leaking the cap loose helps?
Change the fuel filter.
If pressure too low, probably pump.
If too high, then pressure regulator.
Running out of gas is not good for the fuel pump, but it should not be that delicate.

Sounds like pump is not making pressure. Thats why you get flow, but no pressure.
If it sat for awhile, check shaft connection to pump. Sometimes the impeller or shaft will shear partially due to corrosion when stored. Seals on pump valves could be gone too. Get an exploded diagram, usually from owners manual, easily found for this model. Parts list should have "pump repair kit" with everything needed to bring it back to life.
You and a friend put it on the bench to work on it and save your back. The pumps are pretty easy to take apart and put back in working order.

Replace your oil pressure sending unit. many have a low pressure shut off feature that will prevent engine from running. Also, don't check oil on a hill, you will always get a false reading.
If the problem continues you will need to have a mechanical gauge put on the engine to verify actual oil pressure. then plan a repair according to those results.

If low oil pressure is verifiable the only repair is replacement of the oil pump assembly.

Start by verifying oil pressure with a mechanical oil pressure gauge. If oil pressure is low then replace oil pump.

could be a sensor. Need to put a gauge on there and check the oil pressure, If ok, replace the sensor. If you have low oil pressure at idle, it is likely the oil pump is shot or the pick up screen is clogged with debris. In either case, this is going to require major repairs.

glow plug relay should be on the front are rear of intake.you have a mechanical low pressure pump on the passenger side low near the front. or a electric low pressure pump on the starter side. your truck should have the low pressure electric pump. to check fuel pressure you disconnect the out let line to do a out put test.on the electric low pressure pump.put out let line in a container.crank engine for 20 to 30 sec.you should have a good flow of fuel no dribbles.if dribble replace low pressure electric pump.the mechanical low pressure pump out put test you disconnect fuel line from the fuel filter inlet line.disconnect wire at fuel injection pump electric shut off solenoid .place the fuel line in a container. crank engine for 20 sec. fuel flow looks good.pump is good .if dribbles.replace mechanical low pressure pump.to check glow plug relay you need a .diesel repair ford manual to show you where to put a test light to check the relay.WEAR SAFETY GLASSES WHEN WORKING ON DIESEL ENGINES.DONT DISCONNECT THE INJECTION PUMP LINES WHILE ENGINES IS RUNNING.THE FUEL PRESSURE IS SO HIGH SPRAY IN YOUR EYE CAN CAUSE BLINDNESS.GET IN SKIN OR SORE CAUSE BLOOD POISON. CAN ALSO CAUSE A FIRE BE VERY CAREFUL.