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electric fuel pump wiring question.

Discussion in 'The Garage' started by cheyennesuper, Mar 2, 2006.

  1. cheyennesuper

    cheyennesuper Registered Member

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    I just hooked up an external fuel pump to a switch,straight to the power.Is this O.K?Should i have some kinda relay or regulator or something?Also,some guy told my i should run the fuel line from the electric(external)pump to the mechanical pump thats still on the motor and then to my carb..?..? :confused: Any advise will be greatly appreciated.Thankyou.
     
  2. DEMON44

    DEMON44 Low-Tech Redneck

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    I just put a Holley red on my crew cab. Don't run it through the mechanical pump, use a fused power line. I ran mine to keyed power at the fusebox. Key on, pump on. mount as close to fuel tank as possible. Electrics are pushers not pullers. Holley Reds have an internal pressure regulator, but I added an external regulator as well before the carb. Works great but don't run 'em out of fuel, they don't like that. relief valve sometimes sticks or seizes when run dry.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    You should be running a relay off of a fused lead.

    A wire from one of the accessory terminals in the cab (12V in run/start) inline fuse, to a relay. Power from the battery to the relay, relay to the fuel pump.

    I'd make sure also that I had a fusible link (or fuse) in the 12V feed line to the relay from the battery.

    If you don't, you may end up with an electrical fire if the switch can't handle the load through it, same as electric fans. (although not as much load I'm sure) Still, taking a cue from the factory is the way to make sure it's safe and reliable.
     
  4. DEMON44

    DEMON44 Low-Tech Redneck

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    Looking back on in, I should have used a relay. But it works fine. The draw isn't heavy amperage.
     
  5. TrcksR4ME

    TrcksR4ME 1/2 ton status

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    I agree, it is cheap and easy to wire in a relay. Then everything is automatic and no switches to worry about or leave on.
     
  6. cheyennesuper

    cheyennesuper Registered Member

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    Ok.Heres what I did...I have the power wire from pump to switch.Switch to relay.Relay to battery.I just hooked'em up to the OE relay already there.Is that O.K.?And whats up with this "fusible link"?Should there still be an inline fuse or what?...Sorry about all the dumb questions.I'm still learning and the electronics field is my worst.
     
  7. Storm Trooper

    Storm Trooper 1/2 ton status GMOTM Winner

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    I wouldn't do it that way myself. For one thing, you'd have to flip the switch on everytime you use the truck unless it's to override the relay.
    Here's how mine is run- I came off the factory fuel pump relay and the relay won't get power unless an oil pressure sending unit shows 4 lb.s of oil pressure (the starter will do 4 lbs.). I also have a manual override switch just in case the truck sits for a long time (to prime the carb).
    Having it this way will provide safety if you run out of oil or roll the truck/stall the engine. The oil pressure sending unit is from a Vega and is cheap. The oil tap on most Chevy's is above the oil filter. You can always use an additional switch to just shut it all off to prevent someone from stealing your truck.
    Better safe then burning to the ground.
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    You've got an OE relay in place?

    Is this a fuel injected application?
     
  9. Storm Trooper

    Storm Trooper 1/2 ton status GMOTM Winner

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    Long story, it use to be. You can add a relay to do what you want pretty easy though.
     
  10. cheyennesuper

    cheyennesuper Registered Member

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    My trucks a '76 Chevy 1/2ton 4x4 pickup with 4"lift kit+3" body lift.35"tires,TH400 w/mile marker part-time conversion,GM 350 w/crane performance cam and roller-rockers,holley carb.I just put a cab from an '87 on it.The '87 was throttle body.Thats one of the reasons I rewired everything.The truck is a I'll be postings pics in a couple days.
     
  11. Storm Trooper

    Storm Trooper 1/2 ton status GMOTM Winner

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    If you didn't take it off, then the fuel pump relay is on the firewall just above the distributor slightly to the left.
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    Ok, gotcha. Was hoping it wasn't a TBI application and you weren't wiring around everything that is already in place. :)

    I'd prefer running the relay my self as Storm Trooper said, it's just easier to have the key do everything it can, instead of having a switch that can fail, forget to turn off, etc.
     

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