Hello everyone, physics finally defeated me yesterday evening and I managed to let my K100 RT go down at about 0.5 miles per hour in a car park whilst manoeuvring into a space when I probably should've followed the standard BMW protocol of just parking wherever. 

She went down gently on her right hand side (visible damage came to a big scuff and small crack on the fairing which I was naturally gutted about) and being generous was probably running for about six or seven seconds before I hit the kill switch. I righted the bike, put it on the side stand so it was leaning the other way and bought some dinner.

Came back out and she'd fire up but then just splutter for about three or four seconds then die. Toolkit out, checked the plugs and they weren't oiled and looked quite healthy. Plugs back in, cranked it over and quickly removed number one again and it was damp so spark is looking likely although not certain and fuel seems to be getting in there, possibly not enough though? Fuses are all fine. How noisy are the fuel pumps on these bikes as I can't hear much with the filler open whilst cranking and is there anything that I may have dislodged in the tank whilst tipping it over? The only thing that looks a bit suspect is a black rubber hose in the rear left of the tank at the bottom but there's nowhere obvious that it could go so I'm assuming it's a pickup, or are the pickups metal? I had thought it might be that the fuel pump had stopped being submerged whilst it was over and air had gone into the pump but I'd have thought that'd clear after a bit of cranking. I guess it could've killed a weak pump though but I thought I'd ask the experts (that's you lot!). Also, does anyone know of anything electrical around the lower right hand side fairing that I might have damaged underneath?

After a couple of hours of tinkering and Googling the starter was sounding weak as the battery slowly exhausted itself and it began to rain so I bit the bullet and called a recovery company so the bike's back at home in the garage. Put her on charge overnight and tried starting her again this morning and it's the same story, she cranks but doesn't fire or run.

Any suggestions would be greatly appreciated!

Cheers,
Russ

Could be a simple disturbed connection and my money is on one of two items:

1 Check the fuel pump connector plug to the petrol tank.
2 Check the plug connector into the Fuel Injection Control Unit under the seat. The FICU will have fallen slightly to the right and the wired plug is cable tied to the left tube. Sometimes the battery etc will break away from the gear box lugs and open this a little. Been there.

I have done similar drop down and exact same issue afterwards. Its an annoying drop but a lot of stuff moves around when it goes down.

Possible for the in tank pump to be dislodged but in my case 1 and 2 were the culprits.

No electrics to get damaged under the right hand fairing except if the Hall sensor connection to the main loom, but its up under the fuel tank, near the right hand frame tube. In its correct location it should not be vulnerable to disconnecting or damage but I did find when I changed my Hall Sensor a little while back that is easy to not have it properly connected. No electrics on the fairing panel.

Well I was writing the following message and Olaf posted his answer 2 seconds before me (with a similar answer)

This seem to be "stupid", but I would check the connection of the FI computer (the one under the toolbox). The connection is on the left side but I have seen a couple of K100 stopping running after going over a bump or pot hole. If the retaining spring on the plug is weak, the plug could be slightly dislodged.
This is an easy check.
There is a hole on the bottom of the tool box where you can insert a tiny screw driver to release the plug's retaining spring.

I will put my money on the fuel pump being disconnected because the tank lifted away when it fell and disloged the plug partialy.
Reason is that you say it splutters then stops. The Ks with jetronic fuel injection will start and idle without the pump being connected so long as they are at operating temp but as soon as they start to cool they will do exactly as you describe.
It is truely amazing just how little fuel an engine needs to idle so without the pump running the injectors still open but with no fuel pressure there should be no fuel flow but you do have fuel pressure to the amount of vacuum that is caused by an idling engine because the fuel in the tank is at atmospheric pressure so fuel does get delivered.

Thanks for the incredibly quick replies gents, much appreciated! 

I'll remain hopeful that it's an easy fix and if nothing else just be glad that it happened a few miles from home and 'only' cost £80 to have it recovered rather than leaving me stranded somewhere in Europe with no idea what to try next. I need to replace the fork seals and have everything I need to take care of that waiting patiently on the workbench (my E30 has been keeping me busy recently, if it isn't one old BMW it's the other) so I'll set some time aside at the weekend to investigate the starting issue too following your suggestions and will report back in due course. Whether that's with a smile on my face or having pulled all of my hair out is yet to be confirmed though!

Cheers again,
Russ

Its a very common thing after a lie down and I have see it a lot, often to Ks not on this forum. Falling to the right does it because the battery weight etc tends to pull everything tot he right and pull the FICU off the plug enough to cause an intermittent connection. When I took out my FICU the hard plastic loop that retains the plug [left side as you look face on from the left side of the bike] had a break in it [next task is to repair this if possible]. The clip holds the other side of the plug but that's only good if the left side is fully secured, with a crack its not secure. Its a good reason to make sure the battery tray grommets and hold down fixings are good but they too can get broken off in a drop because the battery weight and everything attached can pull them out.

My take on this now is make sure the right hand pin that keeps the FICU in position in the under seat tray is actually present, if not use a cable tie to keep the FICU in its correct position....Second, NOT to cable tie the FICU plug wire to the frame up close to the plug but keep the cable tie well forward on the frame to leave some slack, maybe use some elastic?. I would consider a cable tie around the FICU and the plug to keep that plug nicely secured.

My determination of this is that the famous Hall Effect Sensor feeds into the FICU and the HES signal is needed to keep the engine running. The intermittent or faulty connection means this signal is not being received hence the engine will turn over and will have fuel to do so but will not stay running.

Forum is quicker than Google but don't tell anyone.

Okay, I've put off a couple of other things to make time to look at he bike out of curiosity but still no joy.

I've got 12v at the fuel pump plug on the right hand side of the frame and the cables are securely attached to the bottom of the tank (although they look slightly different when compared with the BMW workshop manual which appears to be a plug to the front left of the tank, mine has a white moulding located centrally in the tank underside directly onto the pump / inspection hatch by the look of things). The FICU plug, whilst not difficult to remove is secure and the surrounding retaining areas undamaged.

Should I be able to hear the pump prime with the filler flap open when the ignition is first switched on at all? It's absolutely silent in there. How do these pumps react to running dry, would it seem plausible that when it was tipped over still running the pump has run dry and failed? There's just under half a tank of fuel in the bike (1985 K100 RT). 

Failing that what's the crack with the Hall effect sensor? If it runs behind the fairing on the RHS it might be worth me checking the wiring.

Thanks everyone,
Russ

On K75s and 2V K100s the fuel pump only gets power when the starter button is pressed or the engine is running.

Running the fuel pump when "dry" for a few seconds should not damage it.

The 12v you are seeing is for the fuel gauge if it is fitted, as Duck said you only get it when the start button is pressed and 1.5 sec after the button is released.
Make sure the plug itself is connecting, I have seen  the power getting to the plug but because the pins have opened up a tad it doesn't connect. You may need to squeeze the female side to get contact but very carefully.  I had a plug on my K100LT and finally put a 6mm 4 pin spade connector on as it just refused to work properly.  You need a meter with a needle so you can see the swing of it when the 12 volts is connected, the digital meters don't register it fast enough.
Don't do this till the ignition key is off. Put the probe of the meter on the pump + then turn the key on and watch the meter needle for movement then turn the key off before you move the probe.  Once you are in orbit we cant help you.
Falling over and getting the plug damaged is very typical of this situation, they also get damaged when people forget to unplug and lift the tank away.

The green/white wire in the fuel tank connector is fuel pump power.

If you are careful not to make sparks (connect it with the bike turned off just to be safe) you can jump power to the smaller terminal and a ground to the larger terminal on the top of the fuel pump if you suspect an issue with the fuel tank wiring - which is not unheard of.

As ever, thanks to everyone for the wealth of invaluable first hand knowledge being shared here - plenty more to consider next time I manage to make it into the garage! The fuel pump connector itself looked and felt solidly connected and the pins in serviceable condition but I'll re-assess this if it's a known weak point. What I will say though, from memory, is that there looked to be a curved push-in metal clip near the FICU box and the right hand side of the frame that it'd clip nicely into and it wasn't in there when I first checked it. I'll concentrate my efforts there and failing that will try to test the pump without incinerating my house, myself and everything in it.

I'll report back here with my findings, assuming I don't end up in space. It's only been a couple of days and I'm missing riding bike already!

Cheers chaps!

Russ

The wire from the HES is at the top of the T shaped cover and goes under the rad cover, its cable tied to the inside face of the right hand frame down tube and goes up between the air boxes to connect to the loom along the inside of the right hand frame tube under the tank. It may be buried down under the connector from the handlebar switch gear. Very unlikely to be the problem apart from the connector plug being disturbed.

As an experiment if you start the bike keep your finger on the starter button for a few seconds and if it stays running with your finger on the button then you can be sure the fuel supply side as in fuel pump connections etc are ok. If it cuts out the HES hasn't kicked in but the under seat plug connector is the likely one

 Mine looked perfect but I spotted the crack and swapped the FICU with the one off the LT and problem solved. I will repair the other one.

As a matter of interest is your tank the one with the bolt down rear? Sounds not if the connector is rear right. This was changed in 1985 and the later tank is not bolted down and with fuel pump connector at rear right.

Russ, you've got the forum dream team helping you so there's little I can add to their expertise....except for one thing, because I've fallen victim to it twice now.  Specifically, make sure that the ICU plug (the one under the tank at the headstock) is well connected/seated and clean.  I could see a tip-over jarring it partially loose or making an already somewhat dirty connection fail.  And, of course, while you are there under the tank, cleaning all connections and the main earth is a good idea. Deoxit is your friend in doing this.  

My apologies if you know all of this.  Just want to save you the massive frustration I endured recently.  Best, Justin.

Hello Justin, not at all - I'm appreciative of any help and haven't had the tank all the way off to check the ICU yet so will delve deeper at the weekend with any luck (work is taking up too much of my time at the moment but I have managed to get into the garage once or twice recently to disassemble and test more of the bike but with no joy). 

I'm not sure what's more frustrating, such a small event preventing the bike from starting or not having the time to fix it right away!

Cheers,
Russ

We've pretty much all had a similar experience with the little lie down, usually in front of the Gallery !! - That's K's for ya!

For me it's always the frustration of not having the time to fix it straight away that gets to me. Good luck with getting it running, should be something simple as suggested earlier.

Too true 88! I had a quick look over my shoulder before I picked it up and thought I'd managed to completely get away with it before noticing a bloke sitting in a van just down the way staring intently and directly at the wall in front of him pretending he hadn't seen. It was unconvincing, but I appreciated the sentiment!

I feel like I could do with the luck right now so thanks for that, it's all just part of becoming familiar with a different machine and its foibles I guess. Can't wait to get back on the road though.

Cheers,
Russ

I have had issues with both of these units.

The FICU under the seat, when that connection went wrong I had turning over but no running. Sometimes running then then cut out as soon as movement disturbed the plug to FICU connection. I simply swapped it with the one from the LT and which has no crack.

The ICU up under the headstock, when that went wrong on the LT I got no turning over. This was cured by a replacement unit as I never got the other one to work even after a good cleaning of the pins.

My friend locally who is ex BMW I called to yesterday for a coffee and he sees plenty of Ks that never appear on the forum here. Almost all of the intermittent cut out/running ones he sees are related to the FICU unit connection under the seat. A clean out of pins or sometimes replacement of the unit. The crack I got in my plastic retainer clip is very hard to see and only shows up when the plug is fitted in position- the forward section of the plug is effectively being levered off the pins and the HES pin seems to be at that end of the plug. A poor connection on this plug can replicate the Hall Sensor problem by interrupting the signal from the HES.

When under the tank do check out all the connections and make sure they are good.

Well I finally found the time to take a more in depth look with at things and have come to the conclusion that it's the fuel pump.

When brake cleaner was sprayed into the airbox she fired up straight away so it had to be a fuelling issue and whilst it sounded as if the pump was running momentarily after cranking, as you'd expect, but no fuel was reaching the injector rail. We've had it out of the tank and put it into a bowl of fuel then given it 12v and it just clicks once each time you connect it up but doesn't pump anything at all. Also, the strainer on the bottom has a tear in it so whether or not some debris has found its way through there and upset the pump is anyone's guess but unless hooking the pump directly up to the battery to test it isn't a good idea for some reason I'm hoping that's the culprit.

£299 new from the local BMW dealer or £155 for a genuine Bosch one from Motobins so I'm sure you can all guess who'll be getting my pennies. Maybe it was on its way out already and the fall was either coincidence or the final straw but if anyone has any other suggestions as to better ways to test the pump before I hand over my hard earned I'm all ears!

Thanks everyone,
Russ

They are a fairly common pump used in many vehicles. I've never had any problems with my pump but a few here have bought very cheap pumps off ebay. Not heard of any problems with those. Do a forum search on the Portal page for 'fuel pumps'
Make sure you get the correct diameter and the pre-filter. Also check that the connection terminals suit the wiring inside the tank.

Have a look round fleabay for "Mapco 22301" Fuel pump and use the filter designed for it and all will be sweet

Cheers Kaptain H and Rick, that all comes as a relief - you can pick up those Mapco pumps on eBay for £38 delivered! Amusingly it's the same pump that's in the tank of my E30 by coincidence according to the listing. I haven't found a gauze / filter for it yet but have only dedicated all of about four minutes to checking.

Thanks again for the tip, hopefully it'll be back on the road again in no time.

The pump I have in my K1100 is for a 318i

I finally managed to dedicate a couple of hours to cleaning the tank, fitting the new fuel pump, strainer and filter and bolting everything back together this evening and am happy to report that she's running again! I'm looking forward to going for a decent spin tomorrow and have hopefully learnt my lesson about concentrating whilst manoeuvring at low speeds. A K100 is not a pushbike.

Thanks to everyone for the help and suggestions, this forum is absolutely invaluable for any K100 owner. The suggestion of the E30 fitment Mapco fuel pump (£38 delivered brand new from eBay rather than £299 collected from my local BMW dealership) also saved my wallet too much pain and fits snugly with no modification to hold everything in place or clear the bottom of the strainer. I was considering removing part of the end of the pump with a hacksaw but didn't have to and wasn't keen on risking any swarf getting inside.

Fork seals next, then with any luck just clocking up a load of miles!

Cheers,
Russ

With regard to the fork seals, get the OEM seals they are by far the best and cost is only marginally more. They really worth using.

Thanks Rick, they're already on my bench waiting to be fitted and are genuine BMW ones. I wouldn't usually scrimp on parts for my toys but the thought of shelling out just shy of three hundred quid for a part that I couldn't be absolutely sure was the problem at the time was a bit hard to swallow in the case of the fuel pump!

Cheers,
Russ

I bought a pair of after market seals from the bay of fleas and first time out one turned inside out with the result of oil on the brakes.
One thing I have found is that after fixing the seals it is worth cleaning the external of the radiator fins as the oil that eascped gets into the fins and collects dust but the bucket resulting in a very poor air stream and cooling.  I just squirt some degreaser into the fins and hose it out along with the long dead and well cooked bugs.

Top tip, cheers Rick!