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Old 05-10-2004, 03:45 PM
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Electric Fuel Pump Install??

Can anyone tell me how to wire in an electric fuel pump for my 1984 GMC truck with a 305. I am guessing it should not be on with the turn of the key but with the rotation of the engine. ANy help would be appreciated.

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Old 05-10-2004, 05:55 PM
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An electric fuel pump should be on when the ignition switch is turned to the "ON" position.

Centerlne
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Old 05-10-2004, 05:58 PM
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You need an Oil Pressure switch wired between the Ignition switch and the Electric Fuel Pump. The Oil Pressure switch turns 'ON' when the oil pressure exceeds 4 lbs. This normally happens when cranking the motor.

If you have low oil pressure when cranking in hot weather, you may need a toggle switch to bypass the Oil Pressure switch.

If you use a Single Pole Double Throw (SPDT) Center Off switch, one pole will power the fuel pump directly, the other pole will power the fuel pump through the Oil Pressure switch, and the Center Off position is an Anti-theft device.

It is also convenient to connect a Light Emmitting Diode (LED) to the Fuel Pump Power lead, so you will not forget to power the Fuel Pump when starting after you shut it off.
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Old 05-10-2004, 10:13 PM
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Most pump manufactures recommend using an Electric Fuel Pump saftey Switch. Mr Gasket sells one and Summit, Jegs, Ect sell them for under $20. It works off of oil pressure and is usually installed by putting a tee fitting where the oil sender unit is located, putting the sender in one outlet and safety switch in the other. It has three connections: 1. Power to the pump 2. Power from ignition side of key switch and 3. power from "S" terminal off the starter solenoid. You have power to the pump when you turn the key to start the engine, power from the ignition switch the rest or the time, as long as you have oil pressure. If you loose oil pressure the switch shuts off the pump automatically even if the key is left on. If you crash or blow the motor your pump doesn't continue to pump gas and make things worse. Pumps mount inside the frame rails close to the tank with a hi flow filter before the pump to protect it. A regulator if used is mounted close to the carb.
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Old 05-10-2004, 11:41 PM
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Opps!

Last edited by Pony; 05-11-2004 at 10:30 AM.
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Old 05-11-2004, 09:00 AM
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What should I expect to pay for a pump? The cost at Napa was $152. Which I thought was high, does this seem correct?
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Old 05-11-2004, 10:41 AM
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Summit has a Carter street pump for $60 and pumps can run up to several hundred dollars. In the end you will spend around $125-$150 just for the cheapest set up. Unless your cam/pump push rod is bad and is forcing you in this direction, you might rethink the electric pump idea. Your 305 won't make any more power with the electric pump over the stock engine mounted pump and you could use that money for changes that would make more power.
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Old 05-17-2004, 09:02 AM
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This is what I have so far. The ignition to the NO on the Press Switch then the NC to the Positive side of the battery then the C on the press switch to the relay but What point ? there is 30, 85, 86, 87. then from the relay to the battery(pos?), then from the relay to the fuel pump(pos?) than from the fuel pump to battery(neg?) is this correct?
ps. I have a fuse between the relay and the battery and between the ignition and the press switch.
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Old 05-22-2004, 04:55 PM
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Find a circuit that is live with ignition on (IGN). Use the wire that goes from the ignition switch to the S terminal on the starter solenoid (starter sol). I added the toggle switch so that I can run the fuel pump manually (not necessary). Use 5 amp fuses on the IGN and Starter Sol circuits. Use the proper size fuse for your fuel pump at +12 V.

Last edited by 32vicky; 07-16-2004 at 08:13 PM.
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Old 05-25-2004, 08:54 PM
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Thank you for all the help guys. Thank for the diagram 32 vicky, that is what I needed to tie in the relay. Unfortunately I now have no oil pressure. One thing leads to another...and another...
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