MOSFETS and Solenoids

[timmers]

Try lowering the value of the gate drive resistor. Mosfets have a very high imput impedance and the gate-source charge needs to be thought of as a small capacitor. I have seen values less than 1k used here for mid frequency applications.
Also I do not see any flyback catch diodes. They release the back EMF energy of the solenoid as current/heat to ground. A high voltage spike on the drain will certainly make life for the MOSFET difficult as the built in flyback diode is configured for low side drive not high side as in your case.
If I was designing a driver I would put battery + to one side of the solenoid and put the N channel MOSFET from the solenoid to ground. The built in protection diode will then act as your protector diode and catch the back EMF spike. Alternatively a more efficient method is to recycle the energy through a snubber network.

Just my thoughts...
Tim.

[Tobias]

I went with the P channel because thats the way the teams want it. Its more of a build what customers ask for deal. Right now the teams turn on and off the + side with relays.
I will give the lower gate resistance a go and see what happens.

Thanks to everyone. Once I get it sorted out I will let everyone know the results.