I'm having kind of the same problem. Did you figure it out? I'm going to try buying a new battery because I don't know how old mine is. I just bought this truck a few months ago and it's ran fine until now. I heard sometimes the battery can get a cracked plate or something.

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88 Ranger, fuel injected V6, Manual, dual fuel tank, Red, but I found a bill of sale in the glovebox from 2007 that stated at the time of sale the truck was silver and automatic trans. It has 190k on the odometer. I used to own an 88 red ranger when I was 19. It was only a 4 banger and had just one fuel tank. I pretty much bought it because it was a great deal and for nostalgia.