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Fuel Pump whirs but doesn't "prime"


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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.

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Basic understanding of fuel pumps... the pump doesn't build
pressure... the pressure relief valve (10) builds pressure... if the
pressure relief valve offers no resistance then fuel circulates from
pump back to the tank at 0 psi...

 

 

VFRFuelSystem1.JPG

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On 23 May 2020 at 1:22 AM, Captain 80s said:

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.

If you've bypassed the Fuel Cut Relay, then it will run continuously. The ECM controls the relay coil switching Ground so if you were not hearing the 2 second prime at switch on (Kill Switch to RUN) with the relay installed then the relay, ECM or wiring could be at fault.

The Service Manual shows how to check the Fuel Pump for flow. I wouldn't assume you have a Fuel Pump issue without checking it's flow first.

Once you're happy with the Fuel Pump and the switch ON prime function is working, but it still doesn't start, then perhaps the Ignition Enable logic for the ECM may need checking, this relies on Neutral and Sidestand switch logic.

 

With the Fuel Cut Relay installed and listening closely at the relay, Ignition to ON, Kill Switch to RUN, do you hear it click on then off after two seconds? This should happen irrespective of your Fuel Pump status.

 

This drawing might be easier to see how the Fuel Pump is powered.

image.jpeg

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On 5/22/2020 at 12:16 PM, BusyLittleShop said:

Basic understanding of fuel pumps... the pump doesn't build
pressure... the pressure relief valve (10) builds pressure... if the
pressure relief valve offers no resistance then fuel circulates from
pump back to the tank at 0 psi...

 

 

VFRFuelSystem1.JPG

Thank you.  I was just so used to the pumps on my other bikes that actually do build pressure.    Not long after posting I thought about the return line and realized my error.

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10 hours ago, Grum said:

If you've bypassed the Fuel Cut Relay, then it will run continuously. The ECM controls the relay coil switching Ground so if you were not hearing the 2 second prime at switch on (Kill Switch to RUN) with the relay installed then the relay, ECM or wiring could be at fault.

The Service Manual shows how to check the Fuel Pump for flow. I wouldn't assume you have a Fuel Pump issue without checking it's flow first.

Once you're happy with the Fuel Pump and the switch ON prime function is working, but it still doesn't start, then perhaps the Ignition Enable logic for the ECM may need checking, this relies on Neutral and Sidestand switch logic.

 

With the Fuel Cut Relay installed and listening closely at the relay, Ignition to ON, Kill Switch to RUN, do you hear it click on then off after two seconds? This should happen irrespective of your Fuel Pump status.

 

This drawing might be easier to see how the Fuel Pump is powered.

image.jpeg

Thank you very much.  I will check some more items.  Sidestand and kill switch are operating normally and Bank Angle Sensor is new..  Don't think I have heard a click, but I will check closer.

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It now primes properly (2 seconds) and has spark. Turned out to be 2 things. An aftermarket ignition switch (brand new installed by PO) that wasn't routing power properly. It would make the main connection (red + red/black), but it wasn't supplying power to the other 2 wires (weird). After a combination of a couple jumper wires, still nothing. Fuck. Swapped out the FCR with the High Beam Relay (AGAIN!) and it primed for 2 seconds. Checked for spark... Yes!

This is going to be a pretty fucking nice $1000 2003 VFR. I'll post some pics when I get it back together.

Thank you for the responses and suggestions.

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  • 2 weeks later...

New air filter arrived and installed (mouse nest had to be cleaned out).  Bike fired instantly.  Rolled outside and let it run until thermostat opened and fan kicked on and off.  Runs pretty much perfect. 

20200531_125012.thumb.jpg.e9b255219ab571d03976bf541a0f7f31.jpg

 

Rode it to a buddy's.  Pulls pretty damn hard, the PCIII seems to be fairly dialed in.  Brakes feel really good.  Exhaust sounds nice but not obnoxious.

20200606_162009.thumb.jpg.3682ac76bcece8c1a07e4077067eeb21.jpg

 

Needs a front turn signal bulb (running light) and a front brake switch (WD40 didn't help).  So.....    probably a $1050 2003 VFR then.  Not bad.

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