My 1999 Ford Ranger starts, then immediately stops?

Does it run for 3-5 seconds and then stop? When you turn you key to the run position, the computer trips the fuel pump relay for 3-5 seconds. If the computer doesn't see a crank signal, it will not turn the pump back on. There's several reasons that would cause this, you just have to find the reason. Check for corrosion under the fuel pump relay. Any further diagnostic procedures can only be done by a professional. I could tell you how to bypass the computers input, but if you jump the wrong wires, you'll toast your ecm. Just be careful and remove your pump relay. look on the relay to determine which leads are #30 and #87. 30 is a constant 12 volt source and 87 goes straight to the pump. keep the ignition OFF while you're doing this and make sure you have a solid connection before you turn the key on. If this cures your problem, you can't keep this rigged up like that, you'll kill the pump. It's just to determine the problem. Sorry, I can't walk you through the fix, but this should give you an idea of what's going on. The rest I'd have to inspect to repair. It's not that bad though, and if this is your problem - you won't have to pay for an extra hour of diagnostic trouble shooting. Good luck!
 
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