Well, I'm trying to help out my buddy's wife who is stranded at home with a 2000 F-150 that won't start. The truck has 135K on it, but they have never had a problem starting it. The battery is fine, it has a full charge and all the electrical stuff works fine. And the starter seems to be working because the engine cranks over just fine and it sounds like it wants to start, but it doesn't. One interesting thing I noticed as that the "theft" light on the dash flashes when you are cranking it, but she says that it has always done that, so that might be irrlevant. One thing I've read about here on the fourm is that there seem to be common issues with the PATS module losing the pairing with the key, and thus preventing the truck from starting. Does that sound like the case here? Or will the engine not even crank if it's having that issue?
Also, I noticed that I don't hear the tell-tale "click" or "hum" of the fuel pump coming on when I turn the key to the "ON" position, so does that mean the fuel pump could be bad? I have checked all of the related fuel pump fuses & relays (I think I found 2 fuses and 1 relay), and those are all good. I asked her when was the last time the fuel filter was changed, and she said they've had the truck since 60K miles and it has never been changed since they owned it.
So could a clogged fuel filter cause the pump to go bad overnight?
Also, I know that they're oxygen sensor went bad about 6 months ago and they procrastinated in replacing it so the truck has been running extremely rich for the past few months (evident by a HUGE drop in gas mileage), so could the extra stress on the pump of running extremely rich for an extended period of time cause it to bad?
Any input or advice would be greatly appreciated, as she is stranded at home without a truck right now and I'd like to help her fix it.