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Fuel injection double relay

Discussion in 'Fuel System & Electrics' started by madchef, Mar 16, 2019 at 6:41 PM.

  1. madchef

    madchef Member

    Messages:
    111
    Location:
    perth wa
    hi all, not been on for some time, started using bus again and was driving down the road and the buss just stoped cut out, hard to start always cutting out, it’s a fuel injection, have checked most things, coil. Fuel spark all seem good will check fuel pump next, I was thinking it was the double relay on the wall, would anyone north of Perth have one that I could try before I buy a new one ..? I have volts going to mine but not sure, I can get it to start if I use the warm up injector and by pass it so I can run it when I want, then when I press it I can keep it running but soon as I let go it stops.?? That’s why I think relay as for fuel pump . First time in 11 years poor thing lol time to check everything.
    Thanks all

    Dave
     
  2. Dapom

    Dapom Well-Known Member

    Messages:
    658
    Location:
    Brisbane
    Hey Dave :) the double relay only provides power to the fuel pump during starting. As soon as the vehicle is running the fuel pump receives power via the AFM. That being said it is entirely possible that it’s the double relay causing your issue but from the ignition side. It’s also possible that it’s the ignition switch itself. I ended up making a double relay replacement for mine which runs 2 standard relays. I am happy to share the diagrams if you’re handy with a soldering iron though would suggest that trying a known good relay as you have suggested would be a good check before heading down that road :)
     
  3. madchef

    madchef Member

    Messages:
    111
    Location:
    perth wa
    I did think that, I will check fuel pump tomorrow hop it’s not the AFM , but would be good to have a go at making one, can you send in email ? Davidprice118@hotmail.com thanks for that nothing to lose , let’s see what I find tomorrow hoping it’s somthing simple.
    Thanks Dapom.
     
  4. Dapom

    Dapom Well-Known Member

    Messages:
    658
    Location:
    Brisbane
    Thinking about it it’s unlikely to be the AFM as such. Basically as the engine starts running the AFM flap opens which moves the connection on the AFM track. In its closed position the AFM arm works as a fuel cut off so for it to be the AFM causing the issue the flap would have to be fully closed which is almost impossible with the engine running.
    I do have a test rig here which i affectionately called ‘the octopus’ lol I’m happy to mail it to you so you can test with it and then mail back if you want? If so flick me your address in a pm :)
     
    cbus likes this.
  5. Dapom

    Dapom Well-Known Member

    Messages:
    658
    Location:
    Brisbane
    The info for making a double relay is on page 17 of my thread ‘Bernard the 83 T3’ :)
     
  6. madchef

    madchef Member

    Messages:
    111
    Location:
    perth wa
    Thanks for the offer, I’ll check everything here first and see what I find, prob somthing simple just can’t see it yet, shame your not around the corner lol and thanks I’ll check your page out for the double relay. I’ll let you know what I find.
     
    Dapom likes this.
  7. Dapom

    Dapom Well-Known Member

    Messages:
    658
    Location:
    Brisbane
    The other thing worth checking is the connections on the ballast resistor next to the double relay. This drops the voltage to 5v for the injectors. Usually the cables going into the crimps corrode and are only just hanging on. Let me know if these are dodgy...I have a fix for this too lol as you may have guessed I had a multitude of issues with my L-jet and so have had to find solutions lol
     
  8. madchef

    madchef Member

    Messages:
    111
    Location:
    perth wa
    well I think I am starting to find my problem,..... no fuel coming out of injectors when turning engine, but pump works as I can run engine with hot wire my warm up injector.. and it will run. Checked power to injectors and nothing, injectors have checked ok but no power going to them and no fuel pumping out, now to find out why .
    Double relay me thinks now :?
     
  9. Dapom

    Dapom Well-Known Member

    Messages:
    658
    Location:
    Brisbane
    Progress!! Check the ballast resistor as above as this is could be the issue if the middle cable is disconnected.
    If that’s all good then break out the multimeter!
    This is the best article I found for the double relay :)
    http://www.ratwell.com/technical/DoubleRelay.html
    Good luck!!
     
  10. madchef

    madchef Member

    Messages:
    111
    Location:
    perth wa
    Now no power to fuel pump when engine turns over, so no power to injectors or fuel pump, when I push the flap in the AFM the relay makes a big click ? So I’m thinking that the relay gone, The relay has power going to it how would I test it properly . Got some reading to do, might just order one from US $84 US dollars for relay so just over $100 that might be the go.
     
  11. Dapom

    Dapom Well-Known Member

    Messages:
    658
    Location:
    Brisbane
    The relay should click when ignition is turned on. No power to injectors etc implies no power to ECU.
    With ignition on and AFM flap pushed open fuel pump should run.
    Does sound like the relay is cactus :-/
    You can test following the diagrams on the ratwell link using a multimeter. A new relay maybe the go as original ones are old....when my problems started I managed to get a couple of second hand ones but none lasted long. Once I made my replacement I had no more dramas. The other bonus with making one is that if it shits out you can just unplug a standard relay and stick a new one in. I carry spare relays with me now but have (touch wood) had no dramas as yet :)
     
  12. Dapom

    Dapom Well-Known Member

    Messages:
    658
    Location:
    Brisbane
    Incidentally.. @Wondermutt is currently breaking an aircooled t3 so May have a double relay for sale....
     
  13. madchef

    madchef Member

    Messages:
    111
    Location:
    perth wa
    Cool I just asked in forum, I kinda want to make one but not to sure lol. I can solder and like messing but don’t want to mess it up lol
    Thanks for your help.
     
  14. Dapom

    Dapom Well-Known Member

    Messages:
    658
    Location:
    Brisbane
    If you get another one which is working then at that point you have a broken spare to make a standard relay version ;) fingers crossed it works out!!
    If wondermutt doesn’t have one it might be worth asking in the T3 forum on here as early aircooled T3’s used the same relay :)
    Finally as a heads up.....in the US they have 2 versions....Californian and federal. Due to the slight differences between the 2 you may have to move one of the earths to a different position on the double relay plug....there are a couple of empty slots. I got caught out by this even though my double relays were all Australia sourced lol it’s not a big drama but certainly caused me some confusion before I worked it out lol
     

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