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Hi all.

My fuel pump stopped triggering randomly a little while ago after I left my F4 in the garage without regular enough worship for a few weeks. I tracked it down in the end to the fuel level sensor not passing through the current, so I got hold of a brand new one and swapped it in. The pump now triggers and all is good… except the reserve light is stuck on.

I've only just filled the bike up since working on it, so I wondered whether I'm missing something obvious, like does it have to go through a cycle to calibrate, or something? From what I've read the sensor is thermister based, so perhaps that could make some sense? Or do you think I could have managed to get a faulty sensor?

I can't see how I could have installed it incorrectly since it's literally two push fit connectors that only go in the right way around.

Any thoughts would be most welcome!

Thanks

Nick
 

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Hi Nick, I think you had a bad connection (maybe corrosion) in the 4-pin plug.
You fixed the one connection by unplugging and refitting, but you moved the problem to the sensor now (or you bought a bad sensor).
The fuel level sensor has nothing in common with the fuel pump, nothing at all.
My money is on the connections in that plug.
 

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Discussion Starter #3
Thanks for the reply. Visually all pins on the connector seemed fine, but I'll have another look once I've emptied the tank a bit, and give it a clean just in case. Be good if that's all it is.

I confirmed with the old sensor that there was no continuity from the 4 pin end to the two that plug into the fuel pump. I never found a diagram showing definitively what each pin *should* be doing mind, and made an educated guess. The issue seemed to be only with the wiring inside the old level sensor and therefore not in the connector it attaches to, and with replacing the sensor fixing the pump it it seemed to confirm this.
 

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From the manual....

Here is the wiring diagram, Dash pin-out, and test procedure for the Fuel Level Sensor:

F4 1000 Fuel pump electrical.png

F4 1000 Dash Pin Out.jpg

F4 1000 Fuel Level Sensor Check.jpg
 

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Because it is a thermistor, the check is not as simple as a continuity check.
 

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Discussion Starter #6
Thanks for those @silentservice703. The checks would all help if determining a problem with the light being always off, but as the light always on I'm not sure what the lightbulb test would tell me, other than the sensor is stuck one way for whatever reason.
 

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The check will tell you if it is a problem with the (very expensive) sensor, or if it is a connection issue.

Ade Critten, on the IOM, is an excellent resource for MV issues.
 
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