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850r Stalling & fuel pump mystery solved


Emfour

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Bought an R850r in May. My first BMW. Great medium size bike, but it had a problem with stalling under acceleration when the tank dropped below about 2/3rds. Opened up the tank and found the mess in the first picture, along with a piece of a paper towel. The safety wire held it together, as it was broken. Installed an aftermarket pump today. Turns out the "original" fuel pump is an aftermarket replacement for Chrysler products Why did someone do this?! Bike now starts easier for sure. Test ride has to wait until tomorrow.

 

 

BMW%20Fuel%20pump%203_zpstj88oapt.jpg

 

BMW%20fuel%20tank%20system_zpspfm7nssb.jpg

 

BMW%20Fuel%20pump1_zpsfousv7qi.jpg

Edited by Emfour
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Well that explains the wire job without the proper bumper on the bottom. I imagine the vehicle pump was not creating enough PSI.

 

I've seen worse on some bikes I've worked on for local riders and I always imagine someone's thought process as being flawed (critical part = gotta save a buck and hack something?).

 

Glad its on the mends.

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The pumps usually generate enough PSI, but it's the flow ratio that perhaps is not met(110 liters / hour for OEM pump), hence the lack of fuel when going WOT.

 

Dan.

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My theory is that the pump would suck air when the fuel sloshed away from the pickup. Bike ran fine as long as the tank was over half full. As the fuel level went down, it would cut out more and more, but only under hard acceleration. Test ride today, we shall see.

Edited by Emfour
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My R1100R had the same symptoms as your bike when it had a poorly installed pump with no filter sock. Boneyard pump kit, and no more issues since. I've had it down to less than a gallon in the tank.

Dave

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