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  • fuel overflow pipe?

    I was out in the car today and on my return i saw a patch of fluid under the engine area.
    on investigation it smelt like petrol and i thought i may have a broken fuel line. i tried to locate the area which was difficult in a confined space and after wiping the pipes it stopped. I took the car to the garage to investigate. On talking to the garage later in the day he said there was nothing wrong with my fuel lines. He said it was petrol coming from an overflow pipe? He put the lift up and showed me the pipe in question. He said that was definately what it was it wasnt a disconnected pipe. Is it correct that the Mg montego turbo has a fuel overflow pipe under the engine bay. The next question is what causes it to result in exces fuel dripping from the pipe?

  • #2
    Sounds like the vent pipe, overflow pipe goes back to the tank.
    1958 Ford Consul Convertible, new hood going on
    1965 Ford Zodiac Executive. Sorn for the winter
    1984 MG Montego EFi in black. Digital dash and bring worked on
    1984 MG Montego EFI in red. Digital dash and being worked on
    2004 MGZT cdti. Great workhorse
    2004 MGZT V8. What a car, wife's daily atm

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    • #3
      I think Jeff is on the right track. The Turbo uses a spill return pipe to send petrol back to the tank if it is not needed to fill the float chamber. The vent pipe normally has an anti-run on type valve that opens when the ignition is switched off, to stop the engine running on when hot. If the valve is still in place - and many just clamp a bolt in the end if the valve is missing or failed - then I would be a bit concerned about petrol passing through. Maybe pointing to excess fuel in the carb throat or something like that.

      May need to investigate when the fuel is coming out of the pipe - once you have confirmed which pipe it is of course!
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      • #4
        It must be the vent pipe then. There is a bit more history to this fuel issue. Approximately 4 years ago while on holiday the car came to a halt. I had difficulty getting it started and took it a a garage. They told me that there was a fault with the aotomatic choke unit. They disconected the choke, reset the carb so the car could be used until the choke could be fixed. They told me it would only affect cold starting. I meant to get it sorted but never got round to it as it never caused me any problems. I have run the car without choke since. When the car was tested in july this year the tester saidthat the emmisions were so low it could pass a catalytic converter test. He said it might be worth inreasing the mixture some time. I added i thought it could do with adjusting as around town it did hobble a bit in the higher gears and strugled to do 30 in 4th without hobbling. The carb setting was adjusted and they told me they had connected the autochoke as it was disconnected. I told them it was not connected for good reason. They tried to disconnect it but it was too difficult without stripping everything down. I said leave as is and i would see how it went.cold starting was fine first turn of the key. I wanted to take the car away on holiday so i ran the car fir the next two weekends ti check all was well. I was satisfied all was well and so decided i had the confidence in the car it would be safe to use. I set off on holiday and all seemed well. After approximately 80 miles i got stuck in a slow moving trafic jam. I stopped for petrol and on setting off the car started to hobble again. I rejoined the motorway and the car ran fine.after 198 miles i left the m1 and suddenly i had no power and all the lights were on the dash. I coasted into the slip road .i eventually got the car started and hobbled into the service area, i called the rac and he said it was the fuel air mix.when i depresed the cltuch on leaving tthe motorway the idle speed was not high enough to keep the revs up. He adjusted the idle speed setting on the carb and it set the idle speed at about 1200/1300 rpm. The car sounded sweet and was running fine although a bit high at idle but at least it was not stopping running at junctions etc.he suggested i should get the car tuned up. The car ran fine for the next 2 weeks without issue apart from a running on issue sometimes.. I drove home saturday 340 miles without any problems. It was only when i took the car out yesterday i noticed fuel driiping from the vent pipe. Nothing has been removed from the car ie no anti run on valve removed. The garage dont know whats causing the issue. Does anyone have any ideas or plan to follow, is it a problem with the autochoke and should it be disconnected or does the carb need a rebuild.any ideas?
        Last edited by The Professor; 12th September 2017, 19:14.

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        • #5
          To disconnect the autochoke you just unplug it and don't need to strip anything down, This would only affect cold start. It's not good to run the car so lean and it would cause it to pink quite a bit I should imagine, it can also affect the actual engine and damage it. As you have said it maybe worth just stripping the carb, cleaning the internals, resetting the float and resetting the mixture, cant think it would need a rebuild, you should also think of adding a fuel filter
          Last edited by Jeff Turbo; 12th September 2017, 19:30.
          1958 Ford Consul Convertible, new hood going on
          1965 Ford Zodiac Executive. Sorn for the winter
          1984 MG Montego EFi in black. Digital dash and bring worked on
          1984 MG Montego EFI in red. Digital dash and being worked on
          2004 MGZT cdti. Great workhorse
          2004 MGZT V8. What a car, wife's daily atm

          Comment


          • #6
            Thanks Jeff, do i take it that its safe to run the car without the autochoke connected and it wont damage anything so long as the carb is set up correctly and its not too lean.?
            Is there an easier way of disconnecting the autochoke wiring plug without taking all the skin of my knuckles. its a tight space.i think a fuel filter is worthwile addition. The garage seemed to think it had one but it hasn,t. I think its the vapouriser they are confusing it with. Am i correct in thinking the efi had a fuel filter but not the turbo?
            Last edited by The Professor; 12th September 2017, 22:26.

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            • #7
              Originally posted by The Professor View Post
              Thanks Jeff, do i take it that its safe to run the car without the autochoke connected and it wont damage anything so long as the carb is set up correctly and its not too lean.?
              Is there an easier way of disconnecting the autochoke wiring plug without taking all the skin of my knuckles. its a tight space.i think a fuel filter is worthwile addition. The garage seemed to think it had one but it hasn,t. I think its the vapouriser they are confusing it with. Am i correct in thinking the efi had a fuel filter but not the turbo?
              Only very early Turbos had a fuel filter then was discontinued Glynn . I put one on my turbo and that stopped the bits from the tank getting into the carb and blocking it. Also had on my turbo project and my sons turbo. I always recommend it. As the cars are now getting on a bit in years, I have also recommended a filter from the tank to the fuel pump when old petrol tanks are having rust problems. And yes, that's the only way to disconnect the auto choke is to unplug it, Just undo the 2 bolts on the plenum and push back the heatshield a little, should give you a bit more access. It is save to run the car without it but starting might be a problem, as long as its not running too lean, and from what you've said, it is, then should be ok. If the car is coming off the road for the winter, I would sort all this then and including the auto choke, And after you've done that put it on a rolling road for a tune up.
              Last edited by Jeff Turbo; 13th September 2017, 09:50.
              1958 Ford Consul Convertible, new hood going on
              1965 Ford Zodiac Executive. Sorn for the winter
              1984 MG Montego EFi in black. Digital dash and bring worked on
              1984 MG Montego EFI in red. Digital dash and being worked on
              2004 MGZT cdti. Great workhorse
              2004 MGZT V8. What a car, wife's daily atm

              Comment

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