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Fuel injection

Discussion in 'Fuel System & Electrics' started by tomar, Sep 1, 2018.

  1. tomar

    tomar Member

    Messages:
    170
    Location:
    Burpengary
    I have a 76 2ltr fuel injectedmotor, the motor starts and runs for a second and then stops. The power to the electric fuel pump stops once the starter motor disengages. The dual relay to the fuel pump is ok, thinking maybe it is the ignition switch ? Any advice appreciated, cheers Tom
     
  2. Dapom

    Dapom Well-Known Member

    Messages:
    637
    Location:
    Brisbane
    Hey Tom. Your issue is the fuel pump
    Cut off ‘tag’ in the afm. Basically double relay provides power to the pump whilst cranking then as engine starts the afm flap opens and releases the fuel pump cut off which takes over from the double relay to provide pump power. Easy way to check is to pop off the rubber boot from the engine side of afm and push the flap open. With the flap open and ignition on the pump should run. Don’t leave ignition on for long periods as it can burn out electronic ignition modules ;)
    Have a look at the tuning afm guide on http://www.itinerant-air-cooled.com/index.php
    I would advise that you touch nothing else in the afm except for adjusting the cut off :)
     
  3. tomar

    tomar Member

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    Location:
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    Than
    thanks for that,I will give it a go
     
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  4. David H

    David H Well-Known Member

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    Last edited: Sep 1, 2018
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  5. Dapom

    Dapom Well-Known Member

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    637
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    That was one of the articles that taught me so much when I was trying to get my bus running properly. The afm isn’t something that should be messed with...generally speaking...but certainly good to have an understanding of how it all works ;)
     
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  6. David H

    David H Well-Known Member

    Messages:
    3,439
    Location:
    newcastle
    I've been lucky & never needed to mess with 'em:D but nice to know it's possible if I ABSOLUTELY need to;).

    Thanks again & cheers
     
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  7. tomar

    tomar Member

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    Well I really blew that , inadvertently left the ignition turned on over night , not good this morning . Where do I go from here ?
     
  8. cbus

    cbus Well-Known Member

    Messages:
    10,889
    Location:
    sunshine coast
    Battery flat?
    Sort that.

    Coil cooked ? Symptom...was hot and now no spark once battery charged.
    If it doesn't come good when cooled, replace.

    Should be the only issues.
     
  9. Dapom

    Dapom Well-Known Member

    Messages:
    637
    Location:
    Brisbane
    ..... unless you’re running electronic ignition in which case your module could be cooked too :(
     
  10. tomar

    tomar Member

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    thanks
     
  11. cbus

    cbus Well-Known Member

    Messages:
    10,889
    Location:
    sunshine coast
    Mmmm.
    Another good reason to run points :)
     
  12. Dapom

    Dapom Well-Known Member

    Messages:
    637
    Location:
    Brisbane
    Nah ;) a good reason to buy a pertronix igniter 2 instead of all the other generic Chinese made copies hehe the ignitor 2 is the only one I’m aware of smart enough to shut itself down before it cooks itself lol
     
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  13. cbus

    cbus Well-Known Member

    Messages:
    10,889
    Location:
    sunshine coast
    Essential feature.
    They blow quick if power reversed.
    :)
     
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  14. tomar

    tomar Member

    Messages:
    170
    Location:
    Burpengary
    Hi all, battery charged , coil and igniter ok, couldn't find a rubber boot on the arm to test. Adjusted the cut off tag in the afm although it looked pretty good. Same thing happens , starts and runs for a second and then shuts down. When I move the wiper with the ignition on the double relay comes into play and loud humming noise comes from the fuel pump ? Maybe a faulty fuel pump.?
     
  15. Dapom

    Dapom Well-Known Member

    Messages:
    637
    Location:
    Brisbane
    Next test :) attach a test light to the positive lug of the pump and ground it somewhere you can see it. Try starting. My bet is that it lights when you crank and then goes out when key is released. Let us know what result you get :)
     
  16. tomar

    tomar Member

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    Location:
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    No power to the fuel pump when not cranking, ignition switch ? Had my suspicions.
     
  17. Dapom

    Dapom Well-Known Member

    Messages:
    637
    Location:
    Brisbane
    I reckon it’s still your fuel cut off.
    Open the top of the afm. Turn ignition on. Slide wiper along its track. If pump runs then it’s your cut off tag which needs adjusting.
    Pump shouldn’t be running with ignition on until either key is turned to start or there is sufficient airflow to open the afm flap...ie engine is running.
    The way it works is that when you crank the starter the double relay powers the pump up. During starting the fuel is delivered causing the engine to fire. When the engine fires the afm flap is opened by the ingress of air. This releases the fuel pump cut off tag. You release the key (because the engine is running) and power is now supplied through that pathway, not the double relay. The cut off tag is designed so that if the engine stops due to accident etc the pump doesn’t keep pumping petrol everywhere :)
    Let us know how you go :)
     
  18. Mr Beckstar

    Mr Beckstar Well-Known Member

    Messages:
    701
    Location:
    Bateau Bay, NSW
    It's a shame you don't have carburettors; much simpler to diagnose and get running on the road. Isn't that right @David H ;):D
     
  19. David H

    David H Well-Known Member

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    3,439
    Location:
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    :p

    Don't know. F/I too reliable to ever need to worry:D.

    This may be the twin relay & it's not switching from 12v start to 7v run. Check the output from 7v relay or alternatively just keep key on & starter engaged (if you can overcome the cringe factor from the meshing attempt of the starter/ring gear clash) & see if it continues to run. If it does it's the relay. This also happens on carb engines:oops:.
    Cheers
     
    Last edited: Sep 4, 2018
  20. Dapom

    Dapom Well-Known Member

    Messages:
    637
    Location:
    Brisbane
    The double relay shouldn’t cause these symptoms. The double relay doesn’t deliver 7v....it powers the ecu, coil etc which require 12v. As far as I was aware there is no double relay on a bus running carbs.....?
    http://www.ratwell.com/technical/DoubleRelay.html
     

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