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Is my fuel pump going ?


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Can anyone advise on the following: About two years ago my bike displayed classic fuel starvation symptoms and I replaced the fuel filter for the first time since I'd had the bike. The bike then flew like it had never done before .... for about a week and then the fuel pump packed in completely. I bought a second-hand one from Motorworks for £55 and it worked fine and its still in the bike some 20k miles later. Today on my way to work I accelerate hard up an uphill slip road to join a motorway and suddenly at about 90mph the bike starts running rough and slows down to 80mph which is the most it could pull (about 4k rpm). I got to work and in neutral reved the bike and it would misfire like crazy above 4k. On my way home, the bike started a bit rough but within half a mile it smoothed and then it was absolutely fine all the way home (20 miles) - I accelerated up to about 110mph and it went great. Next weekend I am setting off for a 2 week tour around Europe so I am a bit worried. I guess I should perhaps change the fuel filter or take one with me and perhaps even look for a spare pump but there is possibly another explanation which I wondered if anyone knows could be valid ? The day before I had a welder do a repair to the baffles of my silencer which had been "blowing" for about 2 months. The repair was done with the silencer off the bike so no electrical/heat damage has occurred. What I am wondering is if the Motronic could somehow have reacted to the change in exhaust conditions (it was really load and "free" ) ? When I was at work I did the ignition on, crack throttle 3 times, ignition off routine (aparently a Motronic reset). So is it possible that it was a Motronic hickup which is now cured or should I still look at replacing fuel filter/pump ? Any advice appreciated.




1994 R1100RS

1975 Triumph Stag


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Fuel starvation and ignition related roughness have distinctly different feels that are hard to put into words here, but it sounds like you have some history as to what fuel starvation feels / sounds like. I'd say start in the same place you did before, with a new filter.


It's unlikely the exhaust work has anything to do with this, especially given that you did the reset dance.


Pump failure is unusual, two failures in the same bike would be doubly so!

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Could you have got some water in the fuel recently? That will clog a filter straight off. or could the tank vent be blocked - can you hear air rush in when you open the filler?


Or perhaps it is the first sign of a HES on its way out? Had you passed through rain before the fault showed up?



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Your first pump could well have failed as a result of the extreme pressure it had to deliver, it get fuel past the old clogged filter. As a filter clogs, the pump pressure automatically rises to whatever is needed to get the fuel through the filter. My pump started making louder and louder whining noise, and when I stuck a pressure gauge in line, I found that the in order to deliver the required after-filter line pressure of about 35psi, the pressure at the pump was over 120psi! No wonder it was struggling!!


When a new filter was installed, the pump pressure was about the same as the pressure after the filter... about 35psi.


Get a pressure gauge and "T" it into the pump output line. This way you can determine a) if your filter is getting clogged again, and b) if there is something wrong with the pump.


Keep in mind that a Roller Cell pump (like these) have very little that can go wrong, except electric motor problems and these are very rare.

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