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frank, Chevrolet Technician
Category: Chevy
Satisfied Customers: 3420
Experience:  33 years experience,24 years of Chevroler/GM experience and training .ASE Recertified Master Tech,
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1987 s10 blazer: 2.8 v-6..fuel pump..fuel relay

Customer Question

have a 1987 s10 blazer 2.8 v-6. replaced the fuel pump, fuel relay and oil switch. the engine will try to turn over, but can not. do not hear the pump come on. relay lights up with a tester, but does not click either. can put gas into injector ports and pump comes on. but if i try with just the key, nothing.   put tester to plug going to pump and there is no power with key on????????
Submitted: 10 years ago.
Category: Chevy
Expert:  frank replied 10 years ago.
The ecm powers the fuel pump up by activating to relay for only 2 seconds or until it starts. The relay will have 2 power circuits,a circuit for the fuel pump and a ground. Have you checked all 4 wires to the relay?
Customer: replied 10 years ago.
Reply to frank's Post: red wire to the relay has power sometimes and sometimes it doesnt while the key is on. the relay is new we replaced it after the fuel pump was replaced and the truck still would not crank.
Expert:  frank replied 10 years ago.
Back to what I said -! wire goes to the fuel pump,and also there is a prime connector close by to the relay.You have 2 powers and a ground.The ecm will power the relay for only 2 seconds at key on after that it runs on the oil pressure switch and the tach signal tells the computer that its running and wil keep the relay energized.The purple with white tracer at the distributor is the tach signal.With the wires disconnected from the distributor you can false that signal with a test light looked up to battery positive and tap the wire.The ecm should power up the relay and injector.