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Expected fuel pump pressure

2572 Views 2 Replies 3 Participants Last post by  KevA
Hi all,

I had left my 2011 zx14 sitting for a few years and when I came back to ride it found that there were significant issues with power delivery under heavy throttle, after a bit of reading I came across the known issue with the fuel filter being blocked. Sure enough, on taking my fuel pump out there was a bunch of grit clogging the filter, and there was quite a bit of fine grit in the tank itself. Initially I just replaced the filter, but found this didn't resolve the issue, so did a fuel flow test and found it was way down on the factory spec.

To resolve this I have ordered a new fuel pump, with regulator, from Quantum fuel systems. After installing it I did a pressure and flow test, and found that the amount of fuel I measured was about 3 times higher than the spec, and also the pressure was way higher, at about 65psi. I removed the pump and regulator to ensure everything was correctly installed and noticed that the regulator supplied is stamped 400kpa, but the service manual calls for 300kpi (43psi). I emailed QFS to enquire about this, and they said that different VIN numbers have different specified ratings for the fuel pressure, and I have ordered the correct kit, but I haven't been able to verify this information anywhere else.

Does anyone know firstly if it is possible that the 400kpa is actually the correct fuel pressure regulator for my bike, and secondly, if not, what issues would it cause running a higher rated regulator (if any). My bike is mostly stock except for some slip-on exhausts, so I shouldn't require a higher fuel flow.

One other issue I've found is when I'm running an initial fuel flow test, sometimes it seems that after the fuel pump shuts off fuel keeps running out of main fuel line. This only happens when I test the fuel rate, and doesn't happen every time. If the main fuel line has been connected, it does not run when disconnected. It's almost like there's a back-pressure valve that isn't sealing shut if the line is free. Is this something I should be concerned about, or is it normal behaviour.

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I see this thread is a year old but I did the same you had done with the quantum fuel pump. I had serious throttle issues after the new one. But I noticed my o ring blew out. So I just swapped for my old regulator and new o rings. initial pressure test shows promise with it holding almost 300 kpa(42psi) out of tank. I had a feeling the stock injectors struggled to pick up the pintle with the extra pressure.
Are you saying the Quantum pump delivers more than the Standard Pump Pressure of 42psi ?
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