Rough running/cutting out

Discussion in 'Mech Tech' started by jonspadge, Jul 11, 2019.

  1. Hey all,

    Been a while since I posted but I did not use the bus much over the last year or so. Got it serviced in Feb and decided to get back into using it. Went out today and reconnected both the earth and positives and she fired straight up. However I did smell fuel so stopped and checked. Fuel was dripping from the t-connector and one way fuel valve that I have upstream of the twin Weber ICT's.

    Isolated that while I did a few other checks and cleaned it all up. Could see no obvious splits or leaks in the pipes so wondered if we had an issue with fuel expanding in the heat and the long stand. Anyhow, left it all to dry for 30 mins and tried again - this time no leaks or issues, left running on the drive for 10 mins and all good - still no drips etc.

    Decide to take it out for a quick 2-3 miles shake down and I got very sluggish performance, lumpy running and it cut out at low revs a number of times. struggled home and back on the drive I noticed it now sounded a little poppy from the exhaust and sure enough when I revved I got the slightest backfire.Also the last time she ran for a long while back in Feb I got a bit of running on when I stopped at the end of the journey.

    So I'm wondering do I have a fueling issue, timing issue or something else? Its a 2lt Type 4 with electronic ignition so not points related.

  2. Is the fuel valve working?
  3. That's a good point - could be blocked/duff. Assume I'd have to take it off and blow through it?
  4. I’d take the whole thing off, join the pipes and see if the problem goes away.
  5. Have you put any fresh petrol in it? If it's been sitting for a length of time the petrol will have gone stale and give symptoms as you describe. I would stick £20 worth of fresh in and go for an Italian tune-up:thumbsup:
    mgbman likes this.
  6. Running on is often carbon buildup from running rich.
    Popping like that is more like lean running..
    Probably the one way fuel valve has stuck having been pressurised hard from the carburettor side.
    Depending on the order of installation in your system, it could also be the fuel pump sucking in air from leaky hose connections downstream of the one way valve. What leaks petrol when stationary becomes an air leak when running..
  7. Could do - the only reason I put it on there in the first place though was because fuel was being pulled by the carb when it was stationary and ended up filling the crankcase. Luckily I got wind of this and drained/refreshed the oil before driving it.


    Empty tank and put fresh in.
    Check for leaks.
    Run without the fuel valve and see what happens - replace if required.
    valve adjustment and then I'll check the timing as well.

    I may well be back.
  8. I’ve had similar issues ( not yet cured) so watching this closely :thumbsup:
  9. Just been out and checked the carbs with the air filters off as per Zedders suggestion. No overfuelling on idle and the float valves appear to be doing their job and delivering fuel when I rev the throttle linkage. There is moisture in the exhaust though - almost like unspent fuel and still burbling. Also the one way valve is no longer leaking. so no leaks but still not convinced fuel ix is right or timing.
  10. The moisture is likely to be water.

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