I have a model 4s5/73c marine 3-1 gearbox behind a ford lees 120hp deisel engine that has always ranat good pressure and temp untill the other day i pulled up and then had no drive at all/

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One video here

https://www.google.com/search?q=2003+Ford+Escape.+Tachometer+not+working

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all gas or deisel engines have a oil pressure sensor.

bad bearings on crank or worn oil pump. Pressure will be up when cold, but will drop when engine warms up. Check for knock in lower end. If so, bad crank bearings.

Always find the source first, The rear water ports are directly behind the rear lower intake bolts and the front ports are directly in front of the front bolts. The rear ports are cast into the lower intake manifold and are dead ends, air can get trapped in that area. In cold weather your thermostat may open slower, resulting in a pressure build up at the rear ports. Any trapped air will compress. Normal coolant system pressure occurs when the glycol is operating temperature. I would try refilling the system and getting the air out,the leak may only occur when the system is full. With a cold engine, open the radiator cap and add 50/50 mix, fill the resevoir to the low mark. Run the engine with the radiator cap off until the thermostat opens, the upper hose will be hot when the stat opens. Turn the car off and refill the radiator to the top. Sqeeze the upper hose to remove any air. fill if necessary. replace cap, run car again until it reaches operating temp. Now with a full system check for leaks. When replacing lost coolant should also have the heat at max temp. Get a good mirror to check for leaks. The outter mating surface of the rear water jacket gasket is flush with the block and the edge of the lower manifold, sometimes you can see where it blew out.

good old fiesta with a endure engine ,run for ever this motor maybe not the fastest thing on 4 wheels but what a work tool ,anyway gearbox oil is EP 90 and if its completely empty then i would expect to top up to the filler plug with around 3 pints 1.9 litres acording to my alldata book .but then i always pump a grease gun full of LM grease into a box as well then top up with the EP oil as this grease settles to the bottom of the box and seals up any leaks in the casing .Old fleet fitters trick from the days when mechanics were mechanics and not unit changers

just go to the fixing center get your car`s computer restarted
or at night parking remove one the positive (red) battery terminal then put it back in place next day should restart your ecu

when mr deisel invented the engine he used peanut oil (diesel fuel wasnt invented)you can use biodiesel in any diesel engine although the makers(ford etc)will tell you NO(they dont want any warranty problems).
the only downside is biodiesel will clean lines/tank and any free floating bits will clog filters.some fuel lines will need to be changed {LOOK UNDER BIODIESEL IN HAWAII) marine engines in the islands use only biodiesel as it is NOT poisonous to marine life.

I HAVE A 7.3 DEISEL AND I DONT KNOW IF THE 6.0 HAS ONE OR NOT BUT MY CRANK SHAFT SENSOR WENT BAD AND THE TRUCK WOULD NOT START( JUST TURN OVER ) DEALER PUT NEW CRANK SHAFT SENSOR ON MINE AND FIXED THE PROBLEM...HOPE THIS HELPS...

should be a two wire switch on floor under clutch pedal...connect those two wires together to bypass switch....good luck...Lee

do not understand you what you mean. assuming your car was ok before you changed f/filter you need to bleed the fuel system of air. esiest to do would be to loosen fuel line at the injectors and have assistant crank the engine while you observe for clear fuel leak without any air bubbles from fuel line.tighten fuel lines and start engine. might have to repeat a few times. good luck.