remote start problems

I recently installed an alphaguard remote start on my truck. The system is a very cheap system without the abiltity to change the amount of time the engine turns over. It sends out a positive output for appx. .5 seconds. This is not long enough to start my my truck. I have installed relays so that the engine will keep turning over until the tach wire gives a power to the relay and stops the cranking time, but it still stops the cranking time to early. I was wondering if I could add some sort of resistor or timmer on the relays to increase the cranking time. My question is how do I go about adding a timmer or other device that will learn when the engine is started and will kill the starter.   Any advice at all would be grateful. I have been messing with different configurations for about a week so I am open to any Ideas at all.     Thanks,           Kyle        

have you thought about adding a pulse timer and a relay to make the crank time adjustable to you needs

No, I haven't tried a pulse timer, and don't even know what that is. Can I purchase one at radio shack or other electronic store. Thanks a million for the reply.