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Fuel pressure regulator question

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  • Fuel pressure regulator question

    Hi, quick question.
    My car has a bosch fuel pressure regulator. It has three fuel connections. In, out and I think an auxilary re-flow back to the tank for overflow if the pressure is too high.
    Mine is only connected in and out. The other connector has a cap on it. there is no fuel return line to the tank. Is that ok?
    I discovered this as the 'cap' had a slight leak. I made a new cap from fuel injection hose, a bolt and clamps and a bit of ultra copper RTV liquid gasket stuff. That's pretty much what had been used for the cap that was leaking.
    It's been like that as long as I've had the car.
    Paul. Birkin S3 /Dunnel zetec/emerald ECU

  • #2
    Is it smaller than the other pipes? If so I'm guessing it's a vacuum fitting that is supposed to read manifold vacuum.
    John Norris
    '91 Caterham 1700 c/f
    Green/Aluminum W/Clamshells
    '94 BMW 325I Racecar
    '94 BMW 325IS Racecar


    • #3
      No, not smaller, all three are the same size. They all fit 5/16th fuel injection hose. Here's a picture
      Attached Files
      Paul. Birkin S3 /Dunnel zetec/emerald ECU


      • #4
        Is there a part number on the regulator so you can look it up?

        It looks like it should be using a return line.

        Can you measure your fuel pressure. This is something that needs to be right before the dyno day.


        • #5
          It looks like a return line that should go back to the tank. The tank should be plumed with a return line that you can plug it into.

          In the current setup, it looks like the fuel system is pressurized to whatever the fuel pump can provide since there is no way for the regulator to alleviate the pressure by returning some fuel back into the tank. In this case you can just as well remove the regulator since it doesn't really do anything.

          The only other setup I've seen (in the Focus, among others) is a pulsed fuel pump that reads a fuel pressure sensor and regulates its duty cycle to achieve its desired pressure.

          Have you measured the pressure between the regulator and the fuel rail?

          /Magnus F.


          • #6
            You might also remove your fiberglass boot liner to get a good look at the fuel tank to see if the return fuel line barb is blocked off there too.


            • #7
              All good points, I've invited Paul to come over to check the fuel pressure. We'll also look to see if it should have a return line.

              Stan, Randall or Gert, is there typically a return barb on the tank? If so, can you access it easily?



              • #8
                Yes, the return barb should be on top of the tank and is easy to get to if you take out the fiberglass boot liner. You might have to take the roll bar off to get the liner out, but it only takes a few minutes.


                • #9
                  So, ignorance is bliss and a little knowledge is a dangerous thing, as the saying goes. But you can't go from ignorant to 'knowledgeable' without passing through the 'little knowledge stage' unfortunately! Which brings me to my fuel pressure regulator question.
                  Doug, many thanks for showing me I had the hoses all labelled wrong and what I thought was the fuel line FROM from the tank was in fact (mutter into sleeve..) the fuel re flow return BACK to the fuel tank.
                  Big thanks also for adjusting the fuel pressure and backing up my ECU settings.
                  Steadily getting the car ready for Dyno Day!
                  Thanks to everyone else who helped brainstorm my...erm... non existent problem..
                  Paul. Birkin S3 /Dunnel zetec/emerald ECU


                  • #10
                    Originally posted by prabjohns View Post
                    Steadily getting the car ready for Dyno Day!
                    Paul - Is it now ready for dyno day, or is there more to be done yet?
                    | | Sean


                    • #11
                      Originally posted by Sean View Post
                      Paul - Is it now ready for dyno day, or is there more to be done yet?
                      Hi Sean, There are several things I will hopefully be able to figure out.
                      Gert has kindly offered to show me how to integrate my LM1 sensor into the emerald ECU if he has time.
                      I am contemplating converting my exhaust to a side exit. It currently has and extension to give it a side exit at the back of the car behind the rear fender.

                      I've been pretty busy with the car. In the last couple of weeks, Moti at Blackbird Fabworx has installed driveshaft safety hoops and lowered the driver side floor. He did an excellent job, also relocated the safety harness attachment points and a few other things. Fitting new suspension in the next week or so too.
                      Paul. Birkin S3 /Dunnel zetec/emerald ECU