Fuel Pump Failure

There is a modestly interesting photo now bouncing around Facebook of Voni's R1100RS, "Big Red" on a trailer. We were in Big Bend National Park when it simply quit running. A few very simple roadside tests confirmed the fuel pump was not coming on. After ruling out the kill switch and sidestand switch I opted to go get the trailer - 45 miles away - instead of trying to rule in or out more defects in 97F temperatures with no shade except Voni's umbrella beside the road.

In the shop, in the shade, with tools and test stuff and all of that, it became apparent that the fuel pump had shot craps. All of the power supply to, and the interupts of, the fuel pump signal were golden. But 12v+ directly to the pump caused it to do absolutely nothing but mock me.

So a new fuel pump from Beemer Boneyard will be here soon!

So why this post? Because there was absolutely no warning of this condition. The bike ran perfectly until it died and costed beside the road. It stumble-started once on residual fuel and then nothing.

Roadside trouble shooting included the kill switch, ignition switch and sidestand switch. The sidestand switch and kill switch allowed starter cranking but not the sound of the fuel pump starting for a few seconds. So it was the trailer!

In the shop the circuit to the fuel pump performed perfectly. But direct wires from a battery to the fuel pump provided nothing. So, a new pump from Beemer Boneyard was ordered.

The bike has just north of 400,000 miles. Still the original fuel pump so I am not upset. At 24 years and 400K miles I am not dissappointed. Just glad it was 45 from home instead of up in Alaska, or BC or someplace else we plan to be this summer.

When bench testing the pump is it passing current or is it open circuit?

I have had a couple of failed ones that were still passing current.
One was jammed by debris due to a damaged intake screen, the other the screen had fallen off.

400,000 miles is impressive! My Chevy pickup goes thru one every 80,000!

If the pump was in my shop I would do an autopsy and inspect the commutator and brush length, I'm betting there won't be much left.

GSAddict said:

When bench testing the pump is it passing current or is it open circuit?

I have had a couple of failed ones that were still passing current.
One was jammed by debris due to a damaged intake screen, the other the screen had fallen off.

400,000 miles is impressive! My Chevy pickup goes thru one every 80,000!

If the pump was in my shop I would do an autopsy and inspect the commutator and brush length, I'm betting there won't be much left.

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I'll get back to you on what I find.

Big Red has the best manners.
She never breaks down unless my mechanic is with me.
This time a broken fuel pump.
You'd think BMW would make one that could last more than 400,000 sMiles!

Nice photo, ignoring the circumstances

PGlaves said:

I'll get back to you on what I find.

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The pump motor was open circuit. When I broke the end cap off I could access the shaft and the pump turned freely. If I had broken enough plastic to actually find the brushes they probably would have been destroyed in the process so I just tossed it in the trash can. These little pumps are not in the least designed to be taken apart.

Voni said:

View attachment 61649

Big Red has the best manners.
She never breaks down unless my mechanic is with me.
This time a broken fuel pump.
You'd think BMW would make one that could last more than 400,000 sMiles!

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I used to have trailer about that size was great 15 inch wheels, the two loading ramps made tailgate, top angle iron made it easy to tie stuff down, it was light enough to back up close than pick up tongue and move to hitch ball.i was heartbroken when my friend sold it.

PGlaves said:

Just glad it was 45 from home instead of up in.....BC.

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The Bee Cee Beemer Roadside Assistance Crew would have been there in a jiffy.

Considering your experience of "no warning", and the price of these pumps, it might not be a bad idea for me to start carrying one as a spare.

why - you getting near 400,000 miles?

mikegalbicka said:

why - you getting near 400,000 miles?

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Heck, not even close.

But I'd hate to find myself stranded. Had an electric fuel pump fail once in an MGB and I do not want to relive that experience.

PGlaves said:

The pump motor was open circuit. When I broke the end cap off I could access the shaft and the pump turned freely. If I had broken enough plastic to actually find the brushes they probably would have been destroyed in the process so I just tossed it in the trash can. These little pumps are not in the least designed to be taken apart.

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What they look like inside....this one was under 20,000 miles. Comm and brushes perfect, tiny piece of plastic in the pump drive jammed it

Paul,

On those 400k miles are you on the original engine, can you let us know what major assys were replaced or rebuilt, trannys, FD etc,

thanks,

jagarra said:

Paul,

On those 400k miles are you on the original engine, can you let us know what major assys were replaced or rebuilt, trannys, FD etc,

thanks,

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Still the original final drive. Tom Cutter went through the transmission at about 350K because the input shaft spline finally wore out. I swapped in a 30K used engine at 385,000 because of somewhat ugly bottom end noises. It got a light touch up on the valves at 300K because I had them out to clean up a wet carbon mess from a driving rainstorm allowing water into the intake snorkel. It broke a driveshaft U joint at 202K.

My K1200GT pump went bad without warning while riding. Once removed and with power applied it came back to life with a tap of a screwdriver handle. It had 80k miles on it.

My '93 RS has also had a dead fuel pump, broken driveshaft, bad HES and trans rebuilt...

I've had no reason to have the heads off but I suspect the valves look awful as they all do past 100k, and the FD has never been opened (but did get a new output seal).

Man! I also have a red 94 R1100RS. I am a pretty conservative sort of guy. So, when mine hits 200,000 miles the fuel pump is getting replaced!!! [This might not be for a while; ]