Fuel leak on holiday - urgent!

Discussion in 'Mech Tech' started by dazzaxjr, Aug 24, 2011.

  1. Hmmm at the moment it has electronic ignition connected to the coil +ve and -ve.

    The pump is also connected to coil, but there is no relay. Just connected direct the same as the electronic ignition. This was the way that the garage in france set it up, so I did the same when I installed the new pump.

    Do I really need to run the pump from the battery instead of the coil?

    Cheers. Darrell.
  2. Try fastening a jerry can to your roof and gravity feed the carbs directly
    Go for a short drive and see if your problems persist or the symptoms change at all then report back

    Please take care when setting up this temporary measure as im sure you know petrol is highly volitile
  4. Ok, I've just done a bit of digging. If you are running a resistor or resistor wire in the ignition coil circuit it will lower the voltage to the ignition coil when the pump is operating. This may be what is happening with you. Your pump may be loading the coil so that it's voltage drops and so you aren't getting the spark you need. Maybe you need to think of rewire/relay/better coil. Afraid I can't offer alternatives at this stage as my knowledge of these set ups is scant to say the least.
  5. he might have a point, feed the 12v straight to the battery and go for a spin..Remember to diconnect it when you stop..
  7. You should very definitely be running a relay setup!
    See this post on Volkszone:


    It describes a setup that will cut power to the fuel pump if the engine isnt running. It triggers a relay from the starter motor solenoid on startup and then the alternator when it's running.

    I did some posts on this on version 2.00. :(

    Dont forget to fuse the power feeds.

    I'll write this up with some pics soonish, I'm just about to fit my setup

    To test if it's a problem with power from the coil try connecting the pump direct t battery +


  8. Ok. Been ringing round this morning and have a new fuel pump on the way. :)

    Also got onto vwheritage who are couriering me a set of ht leads, sparkplugs, and a new coil.

    Hopefully something in that lot will fix this!

    In meantime I'll hookup pump direct to battery +ve and chassis -ve and take a test drive to see if things improve. If they do I'll try and source a relay and fuse and set this up.

    At this rate I'll have completed a full resto! ;)
  9. Ok hand now hovering over the light switch at the end of the dark tunnel. :)

    Wired up the pump direct to battery and chassis, and went for a test run. Only went a few kms but got up to 60 easily. And was hitting 45-50 in third with no hesitation. :)

    But before I turn on that light at the end if the tunnel. .....

    This fuel pump (empi square job) is red hot. Can anyone confirm if this is usual? The fuel pipe and filter before the pump is cool, so the pump is definately running hot.

    Off to French halfords now to see if I can find a relay, switch, and inline fuse. Then I'll make my bodge permanent.

    Tomorrow I should get loads if parts from courier, so if coil, ht leads, or pump needs changing ill be good to go.

    Cheers, Darrell.
  10. Fuel pumps run hot and why manufacturers put them in the fuel tanks for cooling. Also, they need to always be pumping fuel for cooling and lubrication. How hot yours is running is unfortunately not something I can help with but if it's outside it's tolerances it will fail early ;)
  11. Thanks. Im in two minds just to tidy up the electrics and leave as is.

    I'll have a new pump, coil, and ht leads just in case. So may just go for it and see how we go.
  12. I'm hoping "as is" is with the relay and that the set up allows for fuel pump cut off if the engine is off. The last thing you want is fuel pumping all over the place unintentionally. But really pleased you got this sorted at last. Time to enjoy what's left of your holiday?
  13. Yep. I managed to get a relay and inline fuse. So plan is to wire up relay to the coil so that when ignition is on it connects the petrol pump directly to the battery.

    Unless anyone has better suggestion? Want to keep wiring in the engine bay if possible, but not sure where oil pressure sensor is as I believe from earlier posts this can be used also.

    Cheers, Darrell.
  14. If you wire the low current circuit of the relay to the coil you should be all right and there shouldn't be sufficient draw to degrade the coil's performance (unless you have a weak coil). Therefore the oil sender shouldn't be needed. Also, the coil should act as a switching source whereas the oil sender would be permanent. Not to clever if engine stops and you have no return feed.

    Good luck for tomorrow.
  15. Experiment 1a:

    Well got a replacement fuel pump for the faulty one in the first experiment and hooked it up the same way.

    After 4-5 minutes I gave up as it had only pumped less than half a litre. Go I guess I'm sticking with the dodgy empi one for now. :(

    However it does prove that the first one is definately faulty.

    So onto tidying the electrics. .....,
  16. So sat down this morning to cable in the fuel pump relay. Here was the plan:

    Hooked up the +ve to the battery terminal:

    Hooked up -ve to a convenient connector on the bodywork:

    Hooked up switching circuit of the real to the coil:

    Then finally connected all up to the relay. First using a multimeter to check terminals switching ok:

    You can see above the relay that I've added a switch and a 10a fuse between the battery and the relay just in case I need to isolate the whole circuit.

    So I turn on the ignition and the pump runs!

    Now just having sone breakfast whilst I pluck up the courage to go for a test run. :)

    Cheers, Darrell.
  17. So went out for a test run, but the bus was back to it's stuttering old self. When I put my foot down in 3rd or 4th it just dies.

    So as a double check I cabled the pump directly to the battery (at least via a switch and fuse) and it runs just fine. Foot down in 3rd from 30 to 45, and in 4th from 40 to 60 all great. Pulls like a train.

    So looks like I can't even connect the relay to the coil without messing something up. Could be power drain or upsetting electronic ignition. Either way need to find somewhere else to switch the pump. Otherwise I'll have to go with a switch in the engine bay to he'd us home.

    Anyone got any advice? In the meantime I'll get the Haynes out and look for options.

    Cheers, Darrell.
  18. Honky

    Honky Administrator

    How about this:-

  19. The trouble with simply wiring the pump to a constant live source is that you will be pumping the same volume of fuel irrespective of engine speed. So danger is that fuel pressure will build up in the system when the engine is not using the fuel being supplied (and why some systems have a fuel return loop). So, assuming the pump is supplying sufficient fuel when blasting down the motorway, if you get stuck in traffic jam, pump is still pumping same volume of fuel but it has nowhere to go. Floats in carbs shut off the fuel to float chambers so the pipes just build in pressure as the pump keeps pumping. Worst case - kaboom!

    Try changing your coil. It seems that the relay has too high a resistance for your old one. Maybe a newer one will help. I'll see if I can think of something else in the meantime, unless someone else comes up with a brighter idea.

    Edit: just been thinking. It could be the fuel pump has a pressure relief valve in it. If you can find this out then straight into an ignition switched live should be fine.
  20. Thanks guys. Reading through all this again and the volkszone thread posted earlier I think I can see what I've been missing.

    The volkszone thread uses an ignition switched live to feed the pump whereas I've wired mine to the battery. This means that I'm trying to get the relay to switch with ignition to allow me to stop the pump from the cab.

    Looking at Horts diagram, which is similar, is there anywhere in the engine bay I can get a switched live feed apart from the coil?

    I do also have a spare coil that arrived yesterday so will swop this out as well and try coil one last time.

    Btw pump doesn't seem to run at a constant speed. Which is what made me think it was faulty, but perhaps it does have some pressure sensor?

    Cheers, Darrell.

Share This Page