I have a 91 F150 5.9L with a starting problem...Its not cranking, Replaced starter, starter solenoid, checked battery wires and battery. When i turn the key on i get about 11v then i go to start it and it drops to like 2 volts??? Used a charger on 50 amp n the solenoid sounds like a machine gun but no starting. Overnight my battery all of a sudden started dying, i replaced it and the same thing happened again ANy body have a clue where to look next

Check the ignition system with a timing light to see if you are getting spark to the plugs.

-Check for spark and fuel.


mai

check all wires to starter motor for bad earth.....make sure power reaching starter motor.....check starter motor isnt stuck

Check your wires for good connections.

But those are ignition parts. If the car won't crank, there is a problem between the battery, ignition switch, and the starter.
Try this, Darren: With key on, does your dash light up, gauges working and check engine light on? Turn key to start. Do you hear a click form the area of the starter? If you hear the starter solenoid click, and you know the battery is charged up good, then likely the starter is out, and needs to be taken off for testing or replacement. But that is assuming that the battery cables and their.connections are good and allowing full battery power to the starter.
If you hear no click in start, turn the headlights on and watch their intensity while someone turns key to crank. If the lights dim noticeably and no cranking, then the starter is bad or needs testing. If the lights don't change intensity when key is at crank position, then possibly the starter solenoid is bad or the circuit from ignition switch to the starter solenoid is not allowing current to pass. Take off the small wire (brown, I think) from the starter solenoid and see if it has power when key is in crank position. If it has power, the starter has to come off-it or the solenoid is bad. If no power on the solenoid wire with key in crank, then the circuit from ignition switch to the solenoid will have to be checked. There are at least a couple of components in that path- one is the starter relay, another is the neutral safety switch (or clutch switch on manuals). Also if no power on the solenoid wire, check the 30 amp fuse in the power distribution center by the battery. It may be fuse # 10, at least it is on a '97 Jeep. Heck, check all your fuses while you're at it.
Good luck.

Replace the starter solenoid. Make sure you hook the wires back properly. Try jumping across the solenoid with cables to see the starter crank. That makes a direction to the starter. That's what the solenoid does. It connects those 2 cable ends together to make the starter crank over.

Check the starter relay for operation. It should be in the engine compartment fuse box. If the relay is good, you can make a jumper wire and connect directly from the battery positive terminal to the starter solenoid terminal--the single small wire going to the starter. If you get cranking, the starter soleniod is good and the problem is in the circuitry that includes the ignition switch and starter relay. If the solenoid still doesn't click, it's bad.

When its hooked up, you should be able to put 12 volts on the little stud on the solenoid and it should start. One large stud will have 12 volts on it, so just jump it right there. Did you get the wires in the right place. The solenoid should have 1 large wire going down to the starter. Be sure the battery cables are clean and tight ( both ends) Check battery voltage when cranking, should go to 10-11 volts. Check voltage between negative terminal on battery and engine, should be ZERO when cranking. The solenoid has 2 large studs, make sure the battery positive wire and all the other wires are hooked to this stud, the other large stud should just have the wire going to the starter.

youve got the wires on the starter wrong. there are usually two small connections on the starter, but only one small wire. if you install wire on wrong one, it grounds without the key being turned to start. check it and swap that wire only. large cable to battery and large connector wire should stay on the large bolt to the solenoid

The Starter relay is bad.