STC4345 Fuel Pump Replacement
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Thread: STC4345 Fuel Pump Replacement

  1. #1
    Join Date
    July 15th, 2013
    Johns Creek, GA

    STC4345 Fuel Pump Replacement

    My 1998 Range Rover 4.6 HSE needed a fuel pump. The housing was cracked at the nozzle, so just replacing the pump wouldn’t work, I needed to replace the housing also. This 1998 Rover requires a fuel pump that is no longer available(STC4345). My Rover previously had a WFX101030 (STC4345) that was replaced in 2004 by the dealer. I replaced this with a WFX101020. I also added a new seal ring and fuel filter.

    Atlantic British has a hybrid at $600 (STC4345ABP) that they have modified to be a WFX101030 at twice the price of a WFX101020.

    The WFX101020 was a little shorter than the WFX101030, but I lengthened it and added longer new fuel submersible hose before putting it in to make sure it would fit all the way to the bottom of the tank.

    I’ve measured the fuel pressure at the schrader valve on the fuel rail. With the engine off, the pressure is at zero. When I turn the ignition switch to ACC, the pressure spikes to 40Psi after 3 seconds then falls back down to 0 PSI a second later. If I run the starter the second the pressure reaches 40PSI the engine starts on the 1st turn and then continues to idle with the pressure at 30psi and runs fine with full power on highways and going uphill. If I try to start it immediately without leaving it in ACC for the exact 3secs the engine does start after running the starter on the 3rd time consistently.

    I don’t have the specs on the fuel pump in the WFX101020 vs the WFX101030. What could be causing it to start this way?
    I’m dreading having to drop the tank yet another time to ‘try’ another fuel pump.

    Be kind gents....
    98 RR P38 4.6 HSE (230K)

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  3. #2
    Join Date
    March 2nd, 2015
    tasmania australia

    Re: STC4345 Fuel Pump Replacement

    you are loosing pressure for some reason , leaking injectors ,bad pressure regulator pump not holding pressure . you should still have pressure when stopped . with a pressure of 40psi on prime is good but 30 psi at run is not good. gems has a pressure of 38 at run but yours is a thor and I am not familiar with the operating pressures of a thor system but it should not varies more than 2ish psi at any time from idle to full load. thor also do no have a return line so must bleed off internally at pump , this is where I would be looking?

  4. #3
    Premium Member Escape's Avatar
    Join Date
    June 4th, 2007

    Re: STC4345 Fuel Pump Replacement

    98 would make it a GEMS, and the pump should give 34-37 psi. I'd say 30-40 isn't that far off, and it should run OK. But it's definitely not normal that the pressure drops if the pump isn't running. So yes, you need to look for a leak. Leaking injectors seem unlikely, unless you have symptoms of flooding. So pressure regulator or pump, as above.

    WFX101020 is a pump for a Discovery1, the 14CUX and GEMS use the same (spec) pump. WFX101030 is the replacement for STC4345 and is correct for your Range. The later Thor/Bosch uses WFX101090, succeeded by WFX101390 which operates at higher pressure (50psi).

    4.0 SE manual, 1997, 'Priscilla': current daily
    4.0 SE manual, 1995, 'Piper', built for offroad with tuned 4.6 on MS: lost in fire
    4.6 SE auto, 1995, 'Prue': awaiting attention
    2.5 DT manual, 1996, 'Paige': retired and stripped
    D90 TD5, 2005, 'Nessie' TR2 racer: sold

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  6. #4
    Join Date
    October 17th, 2017
    East England

    Re: STC4345 Fuel Pump Replacement

    The Thor also doesn't have a separate pressure regulator and return, it's built into the pump. The rest of world equivalent to the STC4345 is the STC4344, the difference being that an NAS car has the extra connection for the evaporative return stuff which nobody else has. The 4344 is considerably cheaper compared with
    96 4.6HSE
    98 4.0 Police spec
    and a number of others I maintain for the owners.

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