Ellectronic fuel pump

Discussion in 'Mech Tech' started by Peakynut, Apr 13, 2014.

  1. in the link it says it is a replacement for the VW part number 321 906 059K. I am not sure what the difference is between the C and the K though.

    When I called VW and GSF they told me it is discontinued. Don't mean to confuse just trying to get people some options if they want t get hold of one. I am considering it but currently have the system posted by Dave Whippy.
     
    Last edited: Apr 14, 2014
  2. Paul Weeding likes this.
  3. That is a neat idea, Can you run a VDO oil pressure gauge off that too?
     
  4. possibly....you'd normally just rig it up to the warning lamp....check to see what the VDO requires voltage wise
     
  5. Chrisd

    Chrisd Supporter

    Resurrecting this thread, I tested out a theory this morning regarding my engine's cold start reluctance compared to my hot start; crank once and she fires.

    I disconnected my fuel pump +ve feed from my coil and temporarily connected to the battery to test if the electric pump was drawing too much power. Lo and behold, the camper started much easier from cold on a very damp morning.

    Now to find this fuel pump relay - 321-906-059C (VWH not is stock and £40) or an equivalent. Thanks to @snotty for his advice on wiring as well. Any help in finding a relay that has a short prime function for the carbs would be gratefully received!
     
  6. mikedjames

    mikedjames Supporter

    Thats where the 2 relay solution comes in basically the second priming relay closes the priming pushbutton and is triggered by power to the solenoid on the starter. Then you have the main relay driven off the alternator. In this way you are just using 1 or 2 stock Halfords 4 terminal relays, nothing fancy.

    Or you can use 2 diodes.

    And yes, you can also connect a fuel shutoff solenoid to the fuel pump power.

    Many electric pumps like the Carter have a sealed in ball bearing and spring acting as the pressure relief valve so their pressure is fixed, but because they have constant flow, they dont suffer the wierdness of the fuel pressure from a worn demand valve style dead-headed regulator eg. Malpassi going high at very low flow.

    FI systems always use a pressure relief system because its hard with a demand valve style to keep e.g 42psi when the pump winds up to about 120psi at zero flow. Also the circulating petrol is cooling the pump and FI pipelines.

    Carter style rotary pumps also do not suffer from pressure drop like a Malpassi, if you do not put enough pressure in, the output pressure has to drop some to open the demand valve, which could be the cause of some stories of fuel starvation with big engines.

    Also if you get some dirt in or wear of the Malpassi it could basically end up doing nothing, as at zero flow it leaks pressure through.
     
    Chrisd likes this.
  7. I use a timer relay to trigger the fuel pump relay. It turns the pump on for about 20 seconds when you turn on the ignition. This gives enough time to get the engine started & for the alternator to energise & keep the pump relay on. There are several methods of wiring the pump but for safety reasons it’s not a good idea to have it directly wired to an ignition feed.

    https://www.ebay.co.uk/itm/CAR-TIME...2349624.m46890.l49286&mkrid=710-127635-2958-0
     
    Chrisd likes this.
  8. Chrisd

    Chrisd Supporter

    I am at the edge and pushing beyond my electrical knowledge with this, but learning fast.

    I was hoping for a single, simple and safe relay to take power off the starter and the signal from the coil and if possible prime the carbs first, I think that's right anyway!

    I am not sure how important the priming is for twin Weber 34icts, so this may not be needed and I think a few cranks of the starter will prime them anyway in the unlikely event the floats are empty.

    I'll look into these options you guys suggest whilst still searching for the unicorn relay
     
  9. Tried Euro Car parts for the relay? Both myself and @Mark Darby (?) got one from there, but we may have got the last two ;).

    You won’t find one that provides a priming pulse (although if you get your soldering iron out, you could make it do it).

    You can live without the fancy relay, as the chances of the cutoff feature ever being used are minimal (hopefully). In the meantime, just keep cranking…
     
    DubCat and Chrisd like this.
  10. Chrisd

    Chrisd Supporter

    You might have, if I could figure out how to get past Eurcarparts interface that does not recognise my reg, nor allows me to see the parts without a 'valid' number...aaaagh :mad:;)

    Edit, sorry that aaaagh is not directed at you, but at my lack of knowledge and lack of relay:(
     
    DubCat and snotty like this.
  11. DubCat

    DubCat Sponsor

    It is a really annoying site, I agree. Snotty is right, we got the last 2. Somebody else was looking shortly after us and they seem to be unobtainable now. Probably simpler to go for the two relay option with two bog std relays.
     
    snotty, Chrisd and Deefer66 like this.
  12. Chrisd

    Chrisd Supporter

    Thanks.
    Is there a simple connection diagram anywhere here that does not involve a push button primer (which I'd rather avoid) and a really BIG arrow pointing me towards these two relays that are in stock somewhere....yes I know that's spoonfeeding, and my ego has long gone so pretty please :oops:
     
    PanZer likes this.
  13. Thats what we went for one switched by starter one by alternator . Plus a noisy cupboard bypass to check pump still works or priming after messing about

    Sent from my SM-G960F using Tapatalk
     
    DubCat likes this.
  14. Chrisd

    Chrisd Supporter

    Thanks. I was just looking over some old diagrams to try to figure this all out.

    Can I just check why two relays, one to the starter solenoid and one to the alternator? Is that an either/or situation or do I need both? If I'm understanding the layout, they both seem to be doing the same job if I ignore the push button. Happy to learn if I've got that completely wrong.
    Thanks
     
  15. The alternator relay only let's the fuel pump run with the engine running, the starter one makes sure you get fuel while cranking in case your fuel bowl gets a bit low from standing.

    Sent from my SM-G960F using Tapatalk
     
    Chrisd likes this.
  16. 77 Westy

    77 Westy Supporter

    This should work, one relay, five wires. It might provide a prime pulse but not with a 123 distributor. https://www.autodoc.co.uk/topran/2723347
     
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  17. Chrisd

    Chrisd Supporter

    Cheers all.

    @77 Westy I had seen that one but because of the lack of information about it passed it over. I'll try that and see.

    If that one does not work I'll go down the double relay route @Deefer66.

    As ever, thanks
     
  18. 77 Westy

    77 Westy Supporter

    There’s plenty of relays for fuel injection systems that should also work for low pressure pumps. My 321 906 059 C (liberated from a scrapyard many years ago) primed the carbs with the Accuspark distributor but doesn’t with the 123.

    Relay terminal connection should be:
    15 Coil + (15)
    30 Fuel Pump +
    31 Ground-
    31b Coil - (1)
    87 +12V
     
    Deefer66 and Chrisd like this.
  19. You crazy fool laughing in the face of DIN conventions with your 30 and 87 swapping!
     
    77 Westy and snotty like this.

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