If your 1990 Ford F-250 truck won't start, then there are multiple reasons that could be preventing your truck from starting. If your truck is a straight drive, then you have the advantage of trying to pop the clutch in order to get it started again, which can overcome both a bad battery and a bad starter motor. Some of the common problems for a F-250 not starting properly can be temporarily solved on the spot without having to change out any parts.
Pop the clutch if your F-250 is a straight drive. Make sure that there are not any obstacles or oncoming traffic in the next 30-50 feet before attempting to pop the clutch. Push in and hold the clutch and put the truck in first gear. Get a push from a friend or allow the truck to roll downhill on a slight incline. You will not have much steering or braking without the powered systems. Once the truck builds up a little speed, turn the ignition key and release the clutch simultaneously.
Inspect your battery cables. Many professional tow-truck drivers use a trick which involves wriggling the battery cables to see if they are loose. If the terminals are corroded or oxidized, pour carbonated soda over them. Scrub the terminals with a wired brush and wipe them clean with a rag. Try turning the truck on once again.
Turn on your interior lights and head lights. If the lights are dim or are not coming on at all, you may need to replace the battery. Get a jump from a friend or another motorist.
Attach the positive jumper cable to the red terminal on the other vehicle. Attach the other positive cable on to your truck's positive battery terminal. Attach the negative battery cable onto the other vehicle's negative terminal. Attach the other negative jumper cable to an unpainted section of your truck's vehicle frame. Turn on your truck, which should start if the battery is drained. If your alternator is bad, your battery will only last for 20-30 minutes. If your truck turns on, drive it to an auto-parts store where they can test your starter, battery, alternator and electrical system for free.
Listen for a sound of whirling followed by a click when you turn your engine on. Trace the positive battery cable from your battery to the starter. Tap the end of the starter on your F-250 with a hammer a few times and try starting the vehicle again. If it works, then you know that your starter is bad and is not engaging with the flywheel correctly. The hammer trick will only work for a limited number of re-starts, so it is best to drive your truck to your home, auto-parts store or a mechanic's garage right away before turning it off.
