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  • Fuel problems

    Message originally posted by: Gordon Thompson
    I have an 1800 SC marina engine in my roadster as a result of what I thought was fuel starvation problems (probably caused by vapour locks in hindsight), I replecd the mechanical fuel pump with a brand new one. I then started getting fuel out of the SU HS4 carb fuel bowl air vent from time to time, so I replaced the needle valve and seat. The new needle valve and seat does appear to shut off when I blow through it, the float is a serviceable plastic type but I still get fuel coming out of the vent. There is a single feed pipe from the pump to the carb. Has anyone any ideas why and how to cure it!

  • #2
    Re: Fuel problems

    Set float level to dimension in Haynes manual if you have not done so.

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    • #3
      Re: Fuel problems

      Message originally posted by: Gordon
      The float does not have any adjustment such as a brass arm. It simply butts up against the spring loaded needle. I have checked in both the Haynes manual and the SU Carburettor manual. I have even fitted a fibre washer as a spacer to drop the fuel height slightly for an earlier cut off.

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      • #4
        Re: Fuel problems

        Message originally posted by: Don
        This can be a surprisingly difficult problem to cure. I have suffered from this from time to time (on one occasion it flooded an MOT testers pit with petrol). I am inclined to think that there are some needles and seats "out there" of very variable quality.
        There are two types of needle and seat available, one has a brass end and a spring loaded plunger in the base, the other has no spring but has a resiliant "Viton" end. The float chamber lid was different for the two types and from experience fitting the wrong one to the wrong lid gives the wrong fuel level. (I should know, I have twin carbs; one of each type.) The ultimate solution is to fit a fuel pressure regulator of the "Filter king type" avilable from Holdens and others. This will cure the problem.

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        • #5
          Re: Fuel problems

          Message originally posted by: Gordon
          Thanks for the idea about the pressure regulator. I got my needle and seat from Alden's in the Birmingham area and it is a brass seat with a sprung loaded what appears to be a 'steel' tip. They didn't have any Viton tipped ones at the time. Do you have a part number or other details about the regulator please.

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          • #6
            Re: Fuel problems

            Message originally posted by: don
            Holden Part number 015.174 or try http://www.holden.co.uk under the "Maintenance" tab.

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            • #7
              Re: Fuel problems

              Message originally posted by: Matthew Sykes
              Check the fuel pressure at the carb , any more that 4psi and you'll start getting problems, I had major problems of this type on my V8 LR and cured it by fitting the viton/rubber tipped valves ( I got mine from Burlen www.burlen.co.uk I think). Another type of float jet is called a grose jet and they are available from Moss or SC parts (and probably others aswell). The grose jets have a sprung loaded ball bearing as the valve rather than the pointed tip and will supposedly cope with higher pressures, having not tried them I can't speak from experience.
              Matthew
              Matthew Sykes
              www.vermontclassicsltd.co.uk

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              • #8
                Re: Fuel problems

                Its got to be worth check carefully the float valve itself as what happens is the new fuels cause the rubber pipes etc to crumble.What happens is a flake of rubber gets in the to of the valve and can cause both your original and new problems.
                Ben Caswell probably not the last word on anything here!!

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                • #9
                  Re: Fuel problems

                  Yeah, had that happen on mine

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                  • #10
                    Re: Fuel problems

                    Message originally posted by: Gordon
                    Thanks for all of the advice guys. I've replaced the fuel pipes from the pump to the carb and rechecked and the float level. I've run it out a couple of times since then and so far so good. (I shouldn't have said that!) If it happens again, I'm going to fit a heat shield to deflect heat away from the carb area as fuel expansion is the only reason that I can think of that will cause fuel to be vented after the engine has stopped! (Allowing for residual line pressure.)

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