Join Date: Mar 2002
Location: Austin, TX, USA
The injector pulse shouldn't be too short for a MOSFET. I suspect something else is going on. But I think your idea of using a PMOS transistor is a good idea. Just be sure to insert a bit of resistance between the gate and source to help protect it from voltage spikes off the injector coil. In fact it would be a good idea to have a zener diode installed at the gate to protect it from large spikes (but the resistor is a must). You'll have to look at the break down voltage spec on the gate. If it is 20 volts, for example, a 15 volt zener on the gate to ground with a 10K ohm resistance to the ground side of the injector should work well. Any chance the FET popped? Have you looked at the injector pulse width with an O-scope to see what it looks like? It should be plenty slow for what you are trying to do. Perhaps some other portion of your circuit has a slow response time.
68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI