My 2001 f150 4x4 will not start unless i hole the gear shift up while in park. what is the cause of this??

Gday mate,geoff here, now on your shifter if column shift there is an adjustment where it goes down the box from the steering column under the hood and if stick shift should be just under the console, alternitiveley the rubber grommets on the linkage are worn and need replacement, some fuel hose will surfice here if the grommets are unavailable at the parts counter, hope this helped, geoff.

Brake Shift interlock system problem probably . This is a safety system that will not let you move the gear selector from park ,unless your foot is pressing on the brake pedal . Electrically controlled locking solenoid , wiring , brake switch used to control this .

It might be as simple as stepping on the brake before you shift gears from Park to Drive. It won't shift unless you step on the brake while shifting. I have made this mistake many times.

what happened was your fast and shift to park either sheared off the parking pin in the transmission or bent it bad enough that it will not go into park unless the engine is off

If it wont move into gear,the safety switch is malfunctioning. You can take the plug out of the hole on the upper right side of the console just to the right of the gear shift lever. put a philips screwdriver in the hole and press down. this will manually release the gear shifter mechanism.

It is probably not the shift linkage causing your concern. All modern vehicles have a feature called Shift Interlock. It doesn't allow the shifter on automatic equipped vehicles to be moved from park without the key in the ignition and the brake applied. There should be a bypass that will allow you to atleast drive the car for the time being. Check your owners manual to find where it is. It's usually around the shifter. The most common cause for this problem are the brake switch or the shift lock solenoid.

There is a switch that senses when the shift is in park, you need to adjust it from your description

The shift interlock does not allow the car to shift out of park unless the brake pedal is depressed.  Quick fix is with the car running to set the parking brake and turn the car to off and remover the key.  Put the key back in and turn one click to on.  Shift the car into neutral and you can start the car and go.  The repair for this is either the brake switch located on the brake pedal being replaced.  I had a broken wire leading to the switch that caused the problem.  It also can be a blown fuse.

You must remove the console yes, and you need to replace the shift lock solenoid.

sounds like the park interlock cable is sticking.