stops then starts then stops

my van is 1996. 3.3 motor it starts then might run for 20-30 minutes then stops might start in 2 minutes might start in 20 minutes just can't understand what's wrong could it be the fuel relay or is it the alarm systam cutting out and then back in after some time.Any sugestions
Nick

Start with Feul Pump Relay, a semi-bad relay???? loose contact once it get hot???

Mai
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