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  1. #1
    Join Date
    Aug 2016
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    WELLINGBOROUGH
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    98

    Fuel Regulator on RV8 Thor engine

    I have a Rover V8 4.6 'Thor' engine. I bought it as big oily lump and stripped and rebuilt it courtesy of rimmer bros.

    It is now in my AK gen1. On first start it did not run well.

    I checked 1) All the ECU sensors OK
    2) I removed the injectors and had them tested OK
    3) I did a compression test and subsequently had the heads professionally seen to OK
    4) I found that my brake servo was not air tight. Removed cleaned and rebuilt now OK
    5) Found a leak on the inlet plenum - sealed and tight OK

    Now the engine runs very nicely on idle. Starts first time - reduces revs after cold start and sounds right.

    However, when I try to rev the engine above 1500 rpm it falters and sounds as though it is gasping for air. The fuel is set at the proscribed pressure of 3.5 bar.
    It seems as though not enough fuel is being delivered to the engine.

    From observation there is a connection (self sealing 10mm od) on the inlet plenum.
    There is another connection (8mm id) on the fuel pressure regulator.

    I was under the impression that the fuel pressure regulator is only modulated by the plenum vacuum when a turbo is being used. So I did not connect them

    Should I connect them? Is this the way the bosch injection system should work?

    Any thoughts gladly accepted.

    sceptic

  2. #2
    Join Date
    Jul 2012
    Location
    NW England
    Posts
    417
    The fuel pressure regulator needs to set a constant pressure differential at the injector outlet so needs to monitor plenum pressure (absolute).

  3. #3
    Join Date
    Sep 2004
    Location
    Bressingham
    Posts
    1,328
    Also, double check your firing order. I had one with two leads swapped and it sounded ok until the revs were picked up.
    A
    A S motorsport Ltd. 01379 688356 mob; 07909531816 web; asmotorsport.co.uk email \"andrewsoar@yahoo.com\"

  4. #4
    Join Date
    Dec 2008
    Location
    Newcastle upon Tyne
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    1,857
    Sceptic,

    The function of the regulator on the Lucas 14CUX EFI system (I am assuming that this is what you are using? - if not ignore this post) is to maintain the fuel pressure relative to the inlet manifold pressure to ensure the injectors deliver the required amount of fuel. The hose to the inlet manifold (shown unconnected in the attached picture) from the rear of the pressure regulator needs to be connected to allow the pressure regulator to function properly. The barbed connection at the front is the fuel return to allow surplus fuel to return to the fuel tank.

    Hope this helps


    Regards,
    Ian










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  5. #5
    Join Date
    Aug 2016
    Location
    WELLINGBOROUGH
    Posts
    98
    Hi Ian ,

    Thank you for your reply. I now think I understand what is going on.
    I actually have a bosch ecu but I think it works in the same way as the lucas.
    I will connect the inlet plenum and the fuel pressure regulator and see what happens.

    sceptic

  6. #6
    Join Date
    Mar 2005
    Location
    Northampton
    Posts
    1,071
    If you don’t manage to sort it, there’s always Northampton Motorsport (from whom I get no reward, financial or otherwise)
    David (AKA Firestarter29)

    Lead, follow, or get out of the way.

  7. #7
    Join Date
    Aug 2016
    Location
    WELLINGBOROUGH
    Posts
    98
    Just an update on my rover thor engine problems.

    I did NOT connect the fuel pressure regulator to the inlet plenum. This is only for Turbo engines.

    What I did do is clean both the fuel filters.

    I then found that the brake servo was leaking air. This was allowing unregulated air into the plenum. I removed the servo and greased up the seals.

    The engine then both started and idled perfectly. It would not however rev properly.

    I then had a think and decided to change both the throttle position sensor and the mass airflow sensor.

    Great joy. The engine now runs and revs properly. AT LAST.

    I can now get on and finish the car.

    sceptic

  8. #8
    Join Date
    Jul 2012
    Location
    NW England
    Posts
    417
    Quote Originally Posted by scepticwoody View Post
    Just an update on my rover thor engine problems.

    I did NOT connect the fuel pressure regulator to the inlet plenum. This is only for Turbo engines.

    What I did do is clean both the fuel filters.

    I then found that the brake servo was leaking air. This was allowing unregulated air into the plenum. I removed the servo and greased up the seals.

    The engine then both started and idled perfectly. It would not however rev properly.

    I then had a think and decided to change both the throttle position sensor and the mass airflow sensor.

    Great joy. The engine now runs and revs properly. AT LAST.

    I can now get on and finish the car.

    sceptic
    Did you try with the pipe connected to manifold? This is definitely the way it is conected in any 14CUX I've ever seen (including my own car)
    Without it you'd have either too much fuel at high vacuum or, if the fuel had been corrected for high vacuum then you'd have too little at low. Maybe your Bosch is different to Lucas.

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