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Discussion Starter #1
Anyone experienced fuel pump issues when riding in HOT conditions?

My 03 GSXR 600 exhibited fuel pump failure behavior at the track. Temperatures were well over 100F. At first there were a few "cut outs" (losses of power), eventually not starting at all in the pits. I raised the tank, rapped on the fuel pump can, and it fired up and ran a couple more sessions.

I removed the pump motor and applied 12V directly to the motor terminals. the motor did not run until I rapped on it with a wrench. I can repeat this very reliably. So...problem solved...new fuel pump motor needed (so I thought).Installed new motor, rode at track in cool conditions..no problems.

Fast forward to next track day in hot 100+ temperatures. bike stalls out and won't start in pits. Raise the tank and rap it with a wrench. Starts right up, but runs unreliably and dies repeatedly.

So, what are the odds that I got a bad motor immediately after replacing a bad motor? not very high. So now I am suspicious of the ECM, or the starter relay. However, I can't figure out why rapping on the starter (the old-fashioned fix) resolved it if it was anything but the motor. Remember, I bench tested the motor directly to the terminals, so it is not a wiring or connector issue.
 

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Captain Obvious ... because obviously it’s obvious
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It's possible that there is a restriction in the internal fuel filter, which is creating additional stress on the pump due to the backpressure. If this is the case, when the gasoline is cooler in cooler weather, it's enough to remove the heat from the pump, but it may still be wearing the motor in pump. When the weather gets too hot, the gasoline is no longer cool enough to cool the pump and it starts having issues. Tapping it knocks the brushes so they are back in contact, and it resumes function.
Just a conjecture.
 

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I know things... A lot of things.
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Another possibility, assuming you only changed the pump motor itself and not the whole assembly, is that some part of the wiring from the connector (which might have loosened due to overheating) to the motor is making intermittent contact due to being loose. The temperature-dependence would presumably be due to thermal expansion in such a scenario.
 

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Discussion Starter #4
So, I heated up the ECM with a hair dryer and was not able to replicate the issue. I removed and bench tested the fuel pump, wiggled wires traced for shorts, etc., and tested and heated up the fuel pump relay....all without any effect. I will replace the relay, and I suppose get a spare ECU to put in the toolbox in case it comes up again...at a bit of a loss for any other ideas...
 

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Captain Obvious ... because obviously it’s obvious
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What is your fuel output when you perform a fuel flow test?
 

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Discussion Starter #6
Hmmm...definitely possible scenarios.....

I am wiring up three LEDs:
-One to illuminate when the ECM is grounding and activating relay
-one to illuminate when the relay is activated
-one to illuminate when the fuel pump is receiving 12V

This way when the intermittent failure happens I can identify which component is malfunctioning, or if they are all functioning it may point me to another culprit (like filters, internal pump components, etc.)

Thanks for the suggestions...I'll post up when I get results. Its a track only bike so it may be a while...
 
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