I have a 1994 4.0 Ranger with approximately 321,000 miles on it. I have two issues I'm attempting to figure out now:

1) At random times after the truck cranks, the truck continues to crank/start as if I'm still turning the key. I always immediately turn the truck off and most often it continues making the attempting to start sound from the off position, and usually one or two minor key turns/bumps (not enough to crank it) will snap the truck out of it. The truck has had its starter and key lock both replaced yet will still do this at random times. Sometimes this happens once or twice a week, other times it may not happen for a few months.

2) Coolant constantly disappears with no visible leaks. I have to really stay on top of adding antifreeze in my reservoir. It will always be running low within days/weeks. I never see any visible signs of leaks, both my heater core and a new radiator cap have been installed. At my last oil change the oil looked normal and while the truck does knock occasionally, I do not experience any noticeable rough idling and I also don't notice smoke, so it I don't tend to believe its a head gasket issue. I do notice from time to time my temperature gauge will drastically jump around a bit before settling. Possible thermostat issue?

Any and all tips/suggestions are appreciated, thanks!

 

I have the same cooling problem with my 2001 ranger and I don't know where to check to fix it

 

For #1 I would replace ignition switch under the steering column, or at least pull it out and check it
The key turns a gear that slides a rod inside the steering column, this rod slides the ignition switch into its 4 positions, ACC, OFF, RUN, START

Simple diagram here: https://blazerforum.com/forum/attach...um_diagram.jpg

Yours is different but the mechanics is the same

So something is holding ignition switch in the START position, coul dbe inside the column but check ignition switch first
The ignition switch is not hard to remove, and you can test it manually by hooking it up and moving it into its positions
Video here on where it is: youtube.com/watch?v=j3I2oye8OpQ


For #2, as engine coolant heats up it expands in volume and that is what creates the pressure inside the system, the rad cap is rated for about 14psi so at 15psi it will open and send some HOT coolant over to the overflow tank, until pressure is back at 14psi and rad closes.
When engine is shut off the coolant will cool down and Shrink in volume, and if coolant was sent over to overflow tank then pressure will drop to -1 psi, the rad cap has a smaller valve in the center, that valve will be PULLED OPEN by the -1psi and coolant will be sucked back in from overflow tank, keeping radiator topped up

Your system may not leak until pressure is higher, and engine and coolant are hot, so coolant may be evaporating before reaching the ground or a visible area so you never see it

You can rent a cooling system pressure tester, its just a hand pump and pressure gauge on a radiator cap
You pump up the COLD engine's pressure to 15-20psi and watch the gauge for dropping pressure, a leak
Then you look around for dripping coolant, it can't evaporate so will show up.

There are also UV dye kits, you add the UV Dye to coolant and drive for a few days, then use a UV flashlight to look for traces of the dye and follow it back to the leak point
UV dye is invisible except with UV light shinning on it


My 1994 4.0l had random up and down temp issues, it was because heater core was partially blocked, new heater core solved the issue, $28 and 20 min work
Thermostat is not expensive and easy enough to change on this engine, so up to you, 190-195deg is what to use not 180deg