Fuel Pump whirs but doesn't prime

Discussion in '6th Generation 2002-2013' started by Captain 80s, May 22, 2020 at 4:43 AM.

  1. Captain 80s

    Captain 80s Member

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    2003 VFR, 30K miles.

    Bike was dropped and wouldn't start after previous owner tried to put it back together. Cranks over good with no weird sounds. Looks like the ignition switch and fuel cap have been replaced with aftermarket, which had me kinda nervous, and makes me think we didn't get the whole story. Scorpion slip-ons, PCIII, decent Avon tyres, Helibars, brakes and rotors excellent, replacement fairing kit that doesn't really look that bad. Decided we would roll the dice at $1000.

    I knew I should hear the pump prime when turned on and it didn't. After checking all the simple stuff (good battery, kill switch, side stand switch, fuel in tank, loose connectors) found the fuel cut relay and bypassed it, and we had power to the pump. Re-connected the plug to the pump and it lit up. Thought we had it! But, the fuel pump whines and doesn't stop. Just doesn't seem like it's actually pumping anything to build pressure. It is definitely under fuel. The kill switch will stop and start the pump and the FI light goes on and off accordingly. Oh, and we gave it a few good smacks with wood dowel too while it was "running".

    That sounds like a bad fuel pump, eh? Contemplating buying a cheap shitty pump just to verify and sort the rest of the bike before buying a good one.
     
    Last edited: May 22, 2020 at 5:08 AM
  2. GreginDenver

    GreginDenver New Member

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    What if the force of the "drop" caused the fuel pump assembly to come loose (partially) inside the fuel tank? What if the fuel pump is pumping perfectly (good PSI, good volume) but it has become disconnected from its fuel delivery hose? It's not hard to remove the fuel tank from the bike and investigate.
     
  3. Captain 80s

    Captain 80s Member

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    Yeah, that is a good point. I was already going to pull the tank and pump assy to investigate eventually, but that gives me some hope.
    Thanks for posting!
     
  4. raYzerman

    raYzerman Insider

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    Not sure the stopping of the fuel pump is related to pressure, but rather a time-out ..... fuel cut relay. You could test you are getting fuel returned or fuel pressure... if so, leads you back to fuel cut relay?
     
  5. Captain 80s

    Captain 80s Member

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    I don't think they time out. Pretty sure they pump until they reach a pressure limit, and then kick back on when needed. Could be wrong.

    Edit: Pretty sure I'm wrong. Stupid fucking spaceship.

    Took the tank off and removed the unit. Nothing seems obviously wrong unfortunately. The return line filter is weird, looks like a cast iron pan scrubby.

    20200522_175428.jpg
    I can put power to the unit and cover both spigots with a finger and doesn't seems to be doing anything except make noise. Gonna remove the pump from the assembly and try and test for any kind of flow.

    It seems weird that every other VFR pump problem is just getting power to the unit. Or they just don't work. But this bike did take a shot when it was dumped.

    Edit #2: I think the fuel pump is just fine.
     
    Last edited: May 23, 2020 at 5:59 AM
  6. GreginDenver

    GreginDenver New Member

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    I know that the Maintenance Manual calls it a "filter" but it's just an anti-splash, anti-foaming measure to help the fuel to quickly and reliably pool around the fuel pump intake during low fuel situations.

    Your Edit #2, "the fuel pump is just fine", does this mean you "wet tested" the unit? Did you give it something (gasoline) to suck up and pump in a bench-testing situation?
     
  7. Captain 80s

    Captain 80s Member

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    I will before moving on since it is out. That's why I said "I think". When the unit was still on the bike, I ran it with the full cap open and a flashlight. The fuel was being slightly agitated but I couldn't for sure tell if it was vibration or flow.
     
  8. raYzerman

    raYzerman Insider

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    I gave a hurried reply the first time, I had to go to a job.... The ECU controls the time-out and activates the fuel cut relay, so electrically, that relay and connections should be checked. There is no pressure sensor with any feedback to the ECU for pressure. The pressure regulator will allow pressure to build and if the pump runs continuously, excess fuel will go back to the tank via the return hose. So..... you could check that there is flow via the return hose without having to tap into the pressure hose.
    But I think the issue is fuel cut relay/connection most likely.
     
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