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    Fait Scudo 2001 2.0ltr HDi (EDC15) Archived Message

    Posted by Dave Hill on November 10, 2007, 8:32 pm

    This Scudo came in with an intermittent cutting out fault. Fault codes & live data pointed to fuel pressure problems. When the ignition was cycled on & off (without starting up) after approx 30 seconds of the pump running, air bubbles could be heard "BIG STYLE" in the tank. We had fitted a new transfer pump a few months back for a similar fault!

    Out with the fuel tank. A vacuum was applied to the fuel supply connection on the vehicle & the return connection was blanked off. The vacuum was maintained nicely for ten minutes or so. The transfer pump was removed & inspected with no fault found. We refitted it & powered it up (power probe). Sure enough, after 25 seconds or so, it would start to pump copious amounts of air bubbles (Approx 90% air). Convinced that this was now a problem with the transfer pump or its associated assembly, I pondered about why it consistently ran for 25 seconds & then pumped air. It soon fell into place that the pump was consuming the fuel that was available within the chamber in which it sits & then sucking air.



    I haven’t considered before the finer details of the workings of these “in tank” transfer pumps. The fuel enters the pump chamber through a one way or none return valve. Presumably this will help prevent the pump from sucking air, when the tank is low & the vehicle corners (Thanks Martin for that thought).

    Here is the one way valve……





    The flow rate through this valve is very slow. It takes approximately 20 seconds to fill an empty chamber when it is immersed (dry) into diesel. The pump was now tested in a "test tank" to determine if the flow rate through the one way valve was enough to keep up with the flow rate of the pump. It wasn’t!

    Every time the pump was idle, the fuel chamber was replenished & as soon as the pump ran the chamber was emptied in 20 seconds (ish). Exactly matching the symptoms of the vehicle. It’s also worth noting that when the fuel tank is full, the van doesn’t display any problems.

    I am fairly sure that the problem lies elsewhere, but for the time being I have drilled a couple of holes in the chamber, to allow fuel to flow more readily to supply the pump. I know this is probably a “Bodge” :wink: but it seems to have cured the immediate problem.

    Now I need to know what else could have an influence on the flow rate of the transfer pump. I understand that there is a valve that diverts fuel to the fuel cooler & also the fuel flow regulator maybe a problem.

    Since drilling the holes I have done some miles with no problems & no DTC's have returned. Has anyone else experienced anything like this?

    If not, I can always save this until I see James D in December for the Common Rail Course! :D

    Any thoughts folks!

    Cheers

    Dave (Hill)

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