1986 Petrol 110 started up just fine this morning. Tried restarting it about an hour later and it just wont turn over. It will not start and stay running unless I have the gas pedal to the floor. As soon as I release the gas pedal, the truck dies. When I turn the key to the ON position I can hear the fuel pump engaging, so I have no idea what else it could be. I am new to the defender world and appreciate any help that I can get. Ideas??