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    Low Fuel Pressure 2005 Mercruiser 4.3L MPI

    The gauge is new. The system was originally tested by mechanic who got same reading as us. When I pressure tested everything upstream of the fuel filter with bike pump the pressure gauge was still connected to the rail and got a similar reading as the bike pump gauge. So I believe it’s good. So...
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    Low Fuel Pressure 2005 Mercruiser 4.3L MPI

    Thanks, The pressure readings you summarised are correct. My understanding is that the pressure should be 43 psi at the rail, as that is what the manual sais and what the regulator we purchased is set to. You have got me thinking but - when the engine is running and I’m getting a reading of 33...
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    Low Fuel Pressure 2005 Mercruiser 4.3L MPI

    Yes pressure will climb to 40psi when motor off and pump running. When motor & pump running and drawing fuel, the pressure Gauge will sit at around 33. I bled the gauge in three short bursts whilst engine running. First time lots of bubbles, second time lots of bubbles, third time it didn’t...
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    Low Fuel Pressure 2005 Mercruiser 4.3L MPI

    Also on another note, with regards to the voltage test. I am wondering because I took the voltage at the relay, what if there was a bad connection down near the pump, could the voltage be lower down at the pump?
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    Low Fuel Pressure 2005 Mercruiser 4.3L MPI

    I couldn’t upload the video so uploaded some stills. You can just make out the air in the line.
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    Low Fuel Pressure 2005 Mercruiser 4.3L MPI

    Hi All, So, I ran some tests today. Firstly changed the fuel filter to OEM 25 micron. No change in fuel pressure. Secondly I disconnected the FP relay and ran a jumper over the terminals, this runs the pump without the key being on. Whilst pump running and key on (engine not running) I...
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    Low Fuel Pressure 2005 Mercruiser 4.3L MPI

    Hi, thanks I will try the clear hose test. When disconnecting the return line and doing the clear hose test there, do I need to put a closed hose on the filter connection where the hose was?
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    Low Fuel Pressure 2005 Mercruiser 4.3L MPI

    Thanks, my understanding from posts above and from my investigation is that there is no low pressure pump in the fuel tank and that the high pressure pump sucks fuel up from the tank. If that’s the case then I suppose it could suck in air downstream of HP pump. I am still yet to return to boat...
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    Low Fuel Pressure 2005 Mercruiser 4.3L MPI

    Bought from Mercruiser parts supplier. Reg cost $235 Au
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    Low Fuel Pressure 2005 Mercruiser 4.3L MPI

    Thanks will try and report back
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    Low Fuel Pressure 2005 Mercruiser 4.3L MPI

    Thanks, so that is the vacuum line you were rwfrrring to? Do I disconnect that on the fuel rail to do the test?
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    Low Fuel Pressure 2005 Mercruiser 4.3L MPI

    I don’t remember what colour it was. But this is the second reg we have had on now, with same low pressure issue, so I don’t think it’s the reg. It’s so much effort to get the regulator out to test, do really want to avoid that.last resort Thankyou
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    Low Fuel Pressure 2005 Mercruiser 4.3L MPI

    The pump originally wasn’t working along with engine loss of compression which required us to rebuild engine and replace new pump at same time. It was only after doing that work where we realised the pressure wasn’t right, assumed it was the reg so replaced that, and now here we are and issue...
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    Low Fuel Pressure 2005 Mercruiser 4.3L MPI

    Yes it’s definitely that number.
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    Low Fuel Pressure 2005 Mercruiser 4.3L MPI

    Thanks. The regulator next to the pump was the one replaced. Both the pump and the regulator were OEM. With regards to the squeezing of the return line- if I squeeze it hard and block off fully. the pressure will reach 60+. If I squeeze at just the right amount i can get it to sit at around 43...
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    Low Fuel Pressure 2005 Mercruiser 4.3L MPI

    Hi all, We have a Mercruiser 4.3L MPi 2005 model and we have just undertaken a full engine rebuild and we are now having persistent Low fuel Pressure issues. Serial number - OW324384 The pressure is consistently around 33 PSI when running at 1800 rpm. When we turn the key a few times without...
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