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Another TBI Question

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by DukeBoy88, Jan 17, 2003.

  1. DukeBoy88

    DukeBoy88 1/2 ton status

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    this might be a stupid question.
    why does TBI (and most FI) have a fuel return line? Is it to keep the fuel pump from cycling on and off? Or is it simular to a hydraulic regulator that has a drain to tank? Most fuel regulators I see in summit or Jegs don't have a return line, is this a different design?
    I couldn't find an answer on howstuffworks.com
    Also what controls the fuel pump? is there a pressure switch somewhere, or is it determined by amp draw on the pump?
    thanks in advance.
     
  2. smack

    smack 1/2 ton status

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    Well, from what I know, the return line is an important part of maintaining fuel pressure. Since the pump isn't capable of maintaining consistent pressures, a fuel pressure regulator is inserted into the system which allows pressure to build up and be maintained at a certain point. In order to keep pressure at a constant level (determined, again, by the regulator) the system needs to "bleed" pressure and it does so by sending fuel away from the injector system and back to the tank. The fuel pump itself (in my truck) is not regulated and justs keeps on pumping whenever the ignition is on.
     
  3. Sandman

    Sandman 3/4 ton status Author

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    I think it also helps to keep the fuel cooler. Instead of the fuel going slowly throught he lines and having a chance to heat up, It can recycle faster.
     
  4. Thunder

    Thunder 3/4 ton status

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    Keeps the pump cool too. They will burn out if they cant pump all the time. Cooling is also the reason they are in the tank
     

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