At the end of my tether!! Help!!

[Burbs]

Yet another evening spent pushing my 1150!!
Has anyone had an issue where a fuse blows due to the side stand?
It's the fuel pump fuse....
Having gone through most things at the weekend - test this and that - and testing that the side stand switch works.....I've just been out and done a good 15 mile run, on the way home (still 4miles out) a small pot hole made the bike judder - to which I heard the side stand 'clonk' and the bike cut out - the same fuse again.....just as I had gone through fuse no5 and thought I'd better start pushing.....I wiggled the side stand sideways and bingo no more fuses blown!
I had had the stand down - blew the fuse, the stand up - blew the fuse....
Can someone please please tell me this is normal and yes it's the side stand wiring - get a new switch?
I see that the side stand switch has issues.....but no one has said about it constantly blowing fuses???
If anyone lives near me - and wants to help solve my dilemma - I make a mean cup of tea!

 

[AberdeenAngus]

Sounds like you have an intermittent earth on the feed to the side stand switch. Follow the wires till you find where it's chafing.

 

[Dusty]

CHeck out motorworks for a used side stand switch... they accept returns if its not what cures it.not worth the hassle of trying to find needle in hay stack.

Its easy to remove to check for chaffing. Connector to the left underside of tank.

 

[Ian J Hartley]

All the side stand switch does is switch an earth path. When the stand is up the earth goes to the motronic relay to power the motronic. The motronic then sends an earth signal to the fuel pump relay. The fuel pump relay closes and power feeds through the fuse through the fuel pump relay down stream. I suspect at this point you get a high a high current draw on the green/white wire causes the fuse to blow.

The green/white wire feeds the fuel pump, both fuel injectors, lambda probe and the redundant connector tied to the frame top tube.

Have you checked the wiring harness to the lambda probe. If it's chaffed then a bump could be enough to cause a short.

Ian

 

[Ian J Hartley]

Let me clarify. A faulty side stand switch will stop your bike from running. It will not cause the fuel pump fuse to blow.

 

[Burbs]

Thank you....
I shall again be removing everything this weekend....
I am going to bypass the side stand switch.....clean up all the connections and check where I can for any signs of chafing!
The fact that a simple 'wiggle' of the side stand stopped the fuse blowing and we could run again, leads me to your thoughts....
I'm hoping that this will sort it all.....and if it does I will then put a new side stand switch in.
Again thank you all for your input!!

 

[Karlread]

Drop steptoe a PM, I bet he will know and it may save you ripping the bike apart which could cause even more problems...

 

[Ian J Hartley]

Symptoms
Fuel pump fuse blows
Bike runs until hit a bump then splutters and stops.
Wiggling the side stand seems to have some effect.

Cause
Pump fuse blows due to excessive current draw on the green/white wire either through a temporary short to earth (chaffed wire) or a faulty component such as faulty injector, faulty fuel pump or faulty lambda probe.

This is a difficult fault to trace because the fuel pump relay is under the control of the motronic. When you turn the ignition on the relay closes momentarily to prime the pump, then the motronic opens the relay. The motronic does not close the relay again until it receives a signal from the hall sensor that the engine is turning.

This means that your best means of locating the fault is through a visual inspection of the wiring loom where the green/white wire runs. From the fuse box out to components or from the components back to the fuse box. The only other method is to start the bike and wiggle cables and or thump parts of the frame etc to try to recreate the "pump".

A GS911 may help if the motronic is recording any fault codes, to point you in a particular direction with respect to faulty components. For example if the lambda probably is breaking down (the green/white wire is used to heat the probe), then those fault codes may be present.

But I suspect that somewhere on your bike you have a chaffed green/white wire that is the cause of all your woes.

Ian

 

[Steptoe]

Drop steptoe a PM, I bet he will know and it may save you ripping the bike apart which could cause even more problems...

I couldn't put it any better/clearer than Ian already has in this thread.

 

[Ian J Hartley]

Here are a few cable routing diagrams that may assist you in your diagnosis.

This is for the left hand side.

Pay particular attention to those areas that were suggested to you in your previous thread.

You will notice, that from the left hand side of the bike the routing at the forward most point passes from the left to the right hand side in a metal conduit. You will need to lift the tank to see this routing.

 

[Ian J Hartley]

This is the routing from the right hand side.

 

[Ian J Hartley]

This is the unused connector at the rear of the bike.

 

[golfy1]

Hey Ian
Those are incredible and useful exploded diagrams ! - where did you get them !!!
Thanks
Golfy

 

[Grizzly]

Hi Burbs,
I had the Fuse 5 issue - it just blew one day and replacement fuses did the same - I didn't have the confusion of the sidestand symptom but I eventually traced it to the unused connector that's usually tucked up on the RH side of the rear mudguard/tray.
The wires going into it had been chaffing on a frame web
Although only used in California I think, probably for a charcoal cannister - it's called a "control valve" on the wiring diagrams - it's fed with a constant +ve 12v, as are all the other outputs contolled by the motronic, the motronic controls them by switching the -ve 12v

So, worth locating this plug and releasing it if it's cable-tied, and checking.


Good luck..................Grizzly

 

[Ian J Hartley]

Hey Ian
Those are incredible and useful exploded diagrams ! - where did you get them !!!
Thanks
Golfy

They are from the Electrical section of the official BMW workshop manual, which is available from various sources. I got mine from a CD purchased from BMW, but there are PDF versions available on line.


Ian

 

[DrAlf]

Ian really knows his stuff and has helped me trace a couple of nasty electrical gremlins in the past. Follow his advice and you wont go far wrong.

I've previously had a Fuse 5 issue which also started with a bump - (badly landed wheelie on private land). In my case the filter sock on the fuel pump fell off which ultimately caused the fuel pump to seize. Are you 100% certain the side stand is the cause here? When I was trouble shooting my problem - Mike O also commented on checking the wiring loom under the battery cage - this is another known point of failure so well worth a quick look.

Good luck.

 

[Nin]

Just had my entire loom out as part of my rebuild and went over it with a fine-tooth comb. Found six or seven spots where wires were chafing within the wrapping (so invisible) and within a micron's thickness of losing their insulation. So well worth investing the time to check. You can get good quality loom tape from eBay as well to get that authentic look where you're done.

 

[MikeO]

Ian really knows his stuff and has helped me trace a couple of nasty electrical gremlins in the past. Follow his advice and you wont go far wrong.

I've previously had a Fuse 5 issue which also started with a bump - (badly landed wheelie on private land). In my case the filter sock on the fuel pump fell off which ultimately caused the fuel pump to seize. Are you 100% certain the side stand is the cause here? When I was trouble shooting my problem - Mike O also commented on checking the wiring loom under the battery cage - this is another known point of failure so well worth a quick look.

Good luck.

Yes - Ian once took his own bike apart to answer an electrical question I had - top chap

As Dr Alf said, I had a similar problem and traced it to where the main loom passes under the battery cage on the left side of the battery. The cage is rubber mounted and chafes against the loom there. Once I repaired the loom, I put a piece of plastic (actually an offcut from an old flexible plastic chopping board) around the loom there, so it'll be a while until that is a problem again...

 

[Burbs]

Cheers!

Thank you everyone....all of your input is greatly appreciated!