I want to put a new ignition cylinder in my truck but all the information I get tells me to turn the key on. I lost the key. I bought a new cylinder and keys, but can't get the cylinder in.

Hello. It seems the new ignition switch/lock cylinder won't 'communicate' with your vehicle's anti-theft system; causing it not to start/run normally. That ignition switch/lock cylinder must be 'programmed' by a 'certified' locksmith shop. They have equipment to 'pair' the switch and your car's anti-theft system together. Good luck and keep me informed; if you want to.

You must get a new cylinder from a locksmith and he can cut and program the new keys into the system

Which van? Which year? How about some basic info?

You have to turn the key cylinder to the on position in order to remove it. You have a few options, you can call the dealer and have key cut by the vin, you could call a locksmith and have him cut a key to match the cylinder, or you can drill the original cylinder and tumblers out. If you choose to drill it out, you will still need to turn the mechanism inside to the o position before you can insert the new cylinder.

the key will have to be programmed to the car's immobiliser

is your battery dead?

I don't know how you will do it but the procedure is to insert the key and turn the ignition to the on position and then the lock cylinder will pull straight out. Since you don't have a key you may have to force it with a big screwdriver turning the cylinder.

Remove the shroud cover, and the plastic ring around the lock cylinder.WD-40 the lock cylinder, Put the key in the ignition. Rap(Hard) on the back of the key while try to turn key. If it turns leave it in the ON(not run)and I'll tell you how to remove the cylinder.(If You need). The cylinder NEEDS to be replaced.

Go to the dealer with the VIN and they can cut a new key to fit the original cylinder.

Well,

From what I remember you need to put the missing key in and then press the cylinder release, a small hole by the ignition switch. Without the key, I guess you would need a locksmith to turn the tumbler then press the switch. Lock pick set anyone?