95 K75rt fuel pump fuse keeps burning

Hi all, this is my first post and am new to bmwmoa. I have a 1995(1996 actually) K75RT. It has developed an issue where the fuel pump fuse keeps burning out. I replaced the fuel filter and that seemed to fix the problem but it happened again today. It has died on me twice as I am parking it with the wheel turned all the way to one side and the engine idling(obviously at the end of a ride) I also washed it today and am thinking it's maybe a short somewhere under the tank. Maybe when the wheel is turned all the way it pulls a wire that creates the short? I'm asking two things: any thoughts and is there a decent wiring diagram floating in the webs somewhere? I have the clymer manual and have tried to decipher the diagram but I just can't do it captain! (I have haynes/chiltons manuals for cars and trucks and have been able to make some sense of those) I appreciate any thoughts or ideas!

Welcome to the Forum!

Is it fuse #1 or fuse #6 that is blowing? Let me know and I'll check the schematic.


Haynes manuals have slightly easier to read color schematics.

98lee said:

Welcome to the Forum!

Is it fuse #1 or fuse #6 that is blowing? Let me know and I'll check the schematic.


Haynes manuals have slightly easier to read color schematics.

Click to expand...

Thank you, glad to be here! It's #6

drneo66 said:

This may help a little, but it's not in color...

Click to expand...

Thank you sir! I believe I can follow that diagram a little better.

gbschreiber said:

Thank you sir! I believe I can follow that diagram a little better.

Click to expand...

That one is big enough to print on legal size paper (or take it to Staples for 11x17) - then get a pink and yellow highlighter. Highlight one circuit at a time in yellow, run it and if it is ok go over it again with the pink making it darker but still see-through. Makes process of elimination easy.

As for the fuse blowing, I seem to remember another thread with similar symptoms, turned out to be the fuel pump. Sometimes pumps die a slow death, seizing (and blowing the fuse) when hot then unsiezing when cooler - gradually gets worse till it goes for good. Could also be a hot line that has worn through the insulation, especially where the wire bundle has been zip-tied to the frame - replace with Velcro cable tie or another zip tie (just not so tight!)

The fuel pump itself as a part is very common and used in wide variety of equipment. My story doesn't specifically relate to a K-bike but might help. My neighbour had a BMW 325i(?) and it kept blowing fuses. I checked the current draw and it was pretty good but when we shut the car off, for a brief moment current draw went through the roof. It didn't blow the fuse but after repeated starts and stops, the fuse blew when shutting the car off. I put a circuit breaker in it and eventually, a year or more later, we had to change the pump.

Many years later, at a school for diesel engines, the instructor pointed out a similar situation. Current draw normal, etc. and he said it was due to the electromagnetic field in the pump breaking, much like an ignition coil and causing the amperage and voltage to flow backwards.

Don't know if this helps or adds more confusion but it is a good story.

Funny you mention an e30 - years ago I was stranded in Ohio with a 325iC that just suddenly wouldn't start. I had it towed to a dealer and the next morning when they went to look at it, it worked perfectly. A few days later the exact same thing happened, fortunately in the hotel parking lot. I hopped onto the Pelican boards and a poster recommended I pull up the back seat and give the gas tank a whack. That did the trick, it sprang to life and ran perfectly for a day until it happened again. I ordered a new pump and while waiting for it to come in kept a jug of washer fluid in the back seat - whenever it died I'd reach back and give it a thump. I ended up replacing the pump late at night in the middle of a blinding snow storm a few days later. More posts revealed they can and will blow fuses when it dies, but mine did only once.

Gb,

Sorry for not getting back to you sooner. I've been dealing with a pinched nerve in my neck that's affecting my whole right side. Percocet and Nortriptyline don't exactly make you want to answer posts.


There are only two things on fuse #6. The hot lead for the water temperature sender that runs through the temperature sensing switch, and the fuel pump.

It is unlikely that the temperature sender or the sensing switch are shorted out, and if they were, they would probably be shorted all the time.

As others have stated, it is very likely that the pump is failing (especially if it is a bike that has spent long periods of time sitting.)

Bikes that sit for long periods of time have issues with the gas breaking down. When the gas breaks down it turns to something that is corrosive to the rubber vibration damper that holds the fuel pump. When the rubber breaks down, it puddles below the intake to the pump. Guess where it goes when you fire up the pump. This can put added drag on the pump or completely jam it.

The first thing that I would do is remove the filler neck (4 screws under the gas cap) and look into the tank. If the inside of the tank is bright shiney aluminum, there MIGHT not be a problem with the damper, BUT if there is ANY brownish tinge to the tank, the damper is definitely breaking down. You can reach into the tank and forcefully rub your finger across the damper (the black rubber between the pump and the white plastic mounting collar). If anything comes off on your finger or if it feels softer than a tire, the damper is going bad.

Pumps and dampers from the dealer are very expensive. There are several good aftermarket pumps and damper kits available. I have found the kits from Euromotoelectrics to be of good quality.

There are three sizes of pumps that are used on the K75. The first is the 52mm pump. It was used on all the early bricks throughthe mid '90s. The second is the 43mm pump used in thelater bikes (this is probably what you have). The third is the 37mm aftermarket pump which is very common, used in many cars, and available at most car parts stores if you get the right specs.

Euromotoelectrics has all three sizes in factory and aftermarket brands plus dampers and adapter sleeves for changing sizes. If you need a pump or damper, give them a call.

http://www.euromotoelectrics.com/category-s/928.htm

Hope you get feeling better , Lee.

BB

I'll second that! Pinched nerves are no fun at all.

K75s / fuel pump fuse issue

So did anyone ever trace the issue? I have a '90 K75s that is blowing fuel pump fuses. Hit a bump in the road while riding on a very hot Texas summer day and bounced a bit...pump died. Replaced the fuse, started and ran fine for 10 minutes. Stopped at a convenience store to buy more fuses and upon returning to the bike, it wouldn't start. Fuse #2 was toast. Put a 10a fuse in and limped to the mechanic. He found no issues, but replaced the fuse. He parked it in the sun on a 95-degree Texas day, waiting for me to pick it up. When I tried to start it at his shop, fuse #4 was blown...after he inspected and tested it repeatedly. I suspect interior tank heat is a contributor.

Two possibilities jump in to my mind. I would check the wiring where the bundle passes through the bulkhead on the bottom of the tank. This calls for an ohm meter and checking every wire to each other wire and to ground, wiggling everything that can be wiggled. You are looking for a short or a short to ground at this bulkhead pass through. It is a known trouble spot.

Secondly, clogged fuel filters can stress a fuel pump and cause blown fuses. Since this seems to be "bump" related this is an oddball possibility but worth checking anyway. A dose of water can clog an OEM filter, and a bump can splash a dose of water from the bottom of the tank to the pickup, so this is worth checking.