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Thread: New member needs help

  1. #1
    MR2 Lurker
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    New member needs help

    Hello i am new to forums never posted in any before so bear with me please
    i have a mk1 mica blue 1988 full but worn out leather with t bar.
    Have had car since 1989 and only coverd 20 thousand since buying, has been very good
    runner car has been well maintained over years.
    Have noticed now that when ingnition is switched on fuel pump carries on priming, were as
    before i would only here for a few seconds. car still starts but i am worried to drive just in case, it is
    flooding the engine all the time. Has anybody got any ideas what it could be?.
    help would be much appreciated.

  2. #2
    MR2 Obsessive Martin42006's Avatar
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    Struggling to find what controls how long the pump primes for.
    You shouldnt be over fueling though as the regulator will just be feeding the excess fuel back into the tank.
    I am wondering if there is a pressure switch in the pump that turns it off once pressure is reached. Cant find a record of any such switch in the diagrams though.
    Yes i talk to myself, sometimes i need a professional opinion

  3. #3
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    Thanks for quick reply was reading about cold start injector could this be cause because there used to be a definite change after a few seconds of starting car to noise coming from pump. i have also heard of some sort of timer in the circuit
    or could it be air lock in coolant system because i removed coolant hose near said injector/sensor.
    my car did look like that but had a dodgy sprayer and needs good polish and new set of stickers, so liking your car very much, thanks for the help again.

  4. #4
    MR2 Obsessive Sweetpea's Avatar
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    I have to say, I think the fuel pump runs all the time.
    Fuel pump runs, pressurises the fuel rail, then the excess fuel returns to the tank via the pressure regulator in the end of the fuel rail.

    More importantly, are you saying you hear the fuel pump when you turn the key to the IGN position but before you've turned it to START? Because, if so, I think that's wrong.

    James
    There's no rust on my car. But there are some sizable holes where the rust fell out.

  5. #5
    MR2 Obsessive Martin42006's Avatar
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    Think James is correct. i had a listen to mine when i set off home.
    Its hard to hear anything over the aerial going up though dont think it cut out.
    will keep looking into it though.
    are you sure it was cutting off before? not something else you could hear
    Yes i talk to myself, sometimes i need a professional opinion

  6. #6
    MR2 Obsessive Sweetpea's Avatar
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    Now, my car is a MK1a and the MK1b could be different. And non UK cars probably are different. But I believe...

    The fuel pump is under the control of the ECU. The ECU only runs the fuel pump if either the engine is running, or the engine is cranking.
    Of course this means that if the car has been standing and the fuel rail pressure has dropped it'll take a moment longer to start because there is no fuel at the injectors. I'm pretty sure the MK1a doesn't spin the fuel pump up for a moment on the IGN position of the key. (I'd need to check to be sure.) It's possible the MK1b does.

    Either way, fuel should just come back to the tank via the pressure regulator so that shouldn't be a problem.
    What might be a problem is that the pump should stop when the engine isn't running. That's so that if you crash the car (more than likely stalling it in the process) the fuel pump shuts down.

    I'd need to do some diagram hunting and play with the car to be certain of this though.

    James
    There's no rust on my car. But there are some sizable holes where the rust fell out.

  7. #7
    MR2 Obsessive jimi's Avatar
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    The fuel pump runs continously, the pressure regulator maintains a constant pressure and returns excess fuel to the tank.
    Cold start injector only comes into play when cranking the engine and the coolant temperature is below 35deg C, IIRC once the key is released it shuts off.
    Black is not a colour ! .... Its the absence of colour

  8. #8
    MR2 Obsessive jimi's Avatar
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    As far as I know the 1a/b run the fuel pump the same way.

    Quote Originally Posted by Sweetpea View Post
    Either way, fuel should just come back to the tank via the pressure regulator so that shouldn't be a problem.
    What might be a problem is that the pump should stop when the engine isn't running. That's so that if you crash the car (more than likely stalling it in the process) the fuel pump shuts down.

    I'd need to do some diagram hunting and play with the car to be certain of this though.

    James
    The COR (Circuit Opening Relay) cuts the fuel pump off in the circumstances you have described.
    Black is not a colour ! .... Its the absence of colour

  9. #9
    MR2 Obsessive Martin42006's Avatar
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    Jimi to the rescue again, more good info.
    Makes sense as the cor is controlled by the ecu so should shut it off in the unfortunate event of a crash.
    Yes i talk to myself, sometimes i need a professional opinion

  10. #10
    MR2 Obsessive jimi's Avatar
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    There's some info on the cold start injector and the COR in the 4A-GE engine manual and in the BGB.
    Black is not a colour ! .... Its the absence of colour

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