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The dreaded cutting bike cutting out problem f800st 2008

16K views 34 replies 19 participants last post by  Chris surrey 
#1 ·
Hi Ladies and Gents

I'm new on the forum here, but have been researching this topic on the site for the last few months.

I have a f800st 2008. 24,000km (15,000miles). I bought the bike second hand from a classified ad about 3 months ago. The guy didn't ride it often so I got it for a good price.

The problem is that from day 1, the bike has had the cutting out problem where it can't idle at low revs and just cuts for no apparent reason, even when you're on a highway doing 120km / hour and drop the revs down.

This problem only happens when the bike has been running hard for 40mins - 2 hours.
When its cold, or for the first part of a ride, it rides beautifully, no problems at all.

The local dealer (Lyndhurst BWM, Johannesburg South Africa) has had the bike 6 times now and is basically stumped for answers. The various things they've "fixed" already are:

1. First they said it was common, and the throttle valve needed to be calibrated. This they did.
2. The battery died, as it had not been ridden much in the previous 6 months, which I replaced with a new battery.
3. The dealer claimed that the throttle valve was now broken (not just needing calbiration) and needed to be replaced. This they did.
4. Around this time I found info on the forums about the breather hoses being the culprits. The dealer refuted this as "a campaign to fix this problem had already been done" by rerouting the breather hoses to avoid them overheating and kinking.
5. The dealer opened a puma report for the National dealership to advise as they had no other options. The Response came back from head office that it could be the breather hoses.
6. Yesterday, I got the bike back after they put new breather hoses in (which apparently are the latest one's), and last night the bike gave the same problem.

I ride between 20mins and 40mins everyday, with at least 1 or 2 longer rides per week, This is my primary and only form of transport, so I NEED my bike.

I am out of options and would love some input from you all. You're my last hope!

Some more info:
The bike does not cut out when shifting, but does cut out when the revs drop below about 3000rpm and the bike is hot. Its not 100% consistent, sometimes I ride for 2 hours without problems, sometimes it kicks in at 30 minutes. Normally, the harder I ride it (stop, start, quick acceleration) the quicker the problem appears. It happens in all gears and once its happening, I can even sometimes replicate the problem in neutral with the bike just idling on the stand. To me, it sounds like the bike is not getting enough petrol in the engine and cuts out much like my old scrambler use to do when the petrol was not switched on properly. Also, I think it may happen more often when the fan kicks in? Im not 100% sure but yesterday, I was sitting at a stop street, a noise kicked in which sounded like a fan and then the bike immediately gave this problem.

The Bike is not under warranty, so all of the above have cost me out of my own pocket.

Sorry for making this post so long, but I thought I'd include as much as possible to not waste anyone's time.
 
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#5 ·
Fuel pump controller.

Not so sure about that, if the item you are referring to is the fuel pump control solenoid (mine just died, was yours an intermittent heat related failure Roymondo ?)
Either way if you order through these guys http://www.motorworks.co.uk/vlive/Shop/Parts.php?T=5&NU=15&M=70&Ct=EA&SbCt=BA_15_70_EA_50

You should get it in under a week (although the one in their pic is the old version, new ones are black plastic as the old ones have a high failure rate apparently)
2 min job to swap it out
 
#6 ·
I had the problem only when the temp was really warm, like in the 90 deg. F's and higher. My dealer duplicated the problem and replaced the fuel pump under warranty. We had some warm weather after the fix and I have not had the problem reoccur but it did not stay above 90 for very long. I'm waiting until next summer to see if the fix really worked.
 
#7 ·
Thats were I would think it's important to define whether it was the controller or the fuel pump itself.

I recall a few threads about heat related fuel pump cut outs, I get the feeling that it's a different issue to the controller which I understand can get flakey before dying outright. Mine just crapped itself so no perceived 'issues' prior to it's demise.

The good news for our saffer mate is the workshop computer should pick up if it's been having episodes.
My dealer said mine was on it's way but I failed to register it as an impending issue so it passed right out the other ear . . . . . .

In all reality the cost of just buying the thing and fitting it yourself (two screws - sits right under your nuts underneath the seat in the big black rubber sink plunger looking thing) is probably less than the min labour charge from the dealer. Check if it's the old style (alloy), if it is they are a known issue across several models of BMW not just the F
 

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#8 ·
Fuel pump vs Fuel Pump Electronic Control Unit

Thanks for all the input, I really appreciate it.

@Jammer: Did the dealer pick up any errors / faults on the fuel pump? Replacing the fuel pump may be a costly exercise that I'd prefer to avoid.

@gonadz: I'm gonna look into replacing the "Fuel pump electronic control unit ( F800S / F800ST ) | FUA19844" for 84 pounds, I'll probably try get it locally as shipping to SA is a bit of a nightmare and I'm planning a trip for 2 weeks time!

The dealer has not picked up any errors when plugging it into diagnostics, so they don't think its the fuel pump itself.

Generally, do you guys feel its the Fuel pump controller or the Fuel Pump?
 
#9 ·
Dylan, I don't really know what faults they picked up. I was getting a little impatient as they already had my bike for a full month before they were able to duplicate the stall. I was just happy that they did. Also you may want to keep an eye on your cooling fan. Small debris easily get into the fan cowling preventing it from turning which of course causes the motor to get excessively hot. My stalling problem only occured when the motor was hot. Unrelated issue but could be contributory.
 
#11 ·
Motorworks are very good on shipping costs, I've had a 3kg package with fork tubes get here to New Zealand in 7 days flat for something like 70 pounds. I'd be surprised if it was more than 15 to SA for an item this small.
Unlike the US sites they are very reasonable for shipping costs so are now routinely my first choice.

I'll put it this way, I had to buy this unit from the dealer (he had it in stock - it's that common an issue) and it cost me the equivalent of 220 pounds, BMW NZ gouge on their prices - even the ex Germany items they didn't even have to carry in stock.

Unfortunately I can't add much as far as the diagnosis as mine was a dead stop failure, would start and run 2-3 secs then die as the fuel pressure failed to keep up.
 
#12 ·
My 2007 F800ST would idle rough and cutout at low idle once warmed up.

Solution was to: 1. replace idle air hoses w/upgrades 2. replace idle air actuator (old one was sticking) 3. upgrade the bike's software.

No problems since.
 
#13 ·
One way to find out whether it is a heat related pump failure is to wait until it shows the problem and then cool the pump and see whether the trouble clears. The way to cool the pump is to fill the tank with nice cool gas pumped from the station's underground tank.

My bike had a pump problem which showed up when there was less than half a tank of gas on a hot day. I finally got a clue when the thing was really giving me trouble and I stopped for gas. The trouble immediately cleared. That led to testing with a GS911 and watching the fuel pressure drop off. The pump was replaced in 2010 and the bike has been flawless since. By the way, a bad pump does not log any error codes.

You can test for a bad pump controller by bypassing it and supplying 12v directly to the pump. You can find information about this somewhere on the site if you search for it.

There are several known issues that cause stalling. You'll have to methodically work your way through them to figure out which one is causing your problem.
 
#15 ·
Fuel pump controller and fuel pump. Replace them both. I have an 8, the problem cropped up at 800 miles, they changed the pump and controller, end of problem unless it gets really hot outside, like above 90F and I chop the throttle after a long cruise. It doesn't cut out, just has a rough idle for a moment. I'm going to replace the controller with the updated black and see how it goes. It won't do it until it's run in the same conditions. Mine has 13,000 miles. I'll have to also buy another fuel pump if it has severe issues again.
 
#16 ·
I had occaisional cutting out on my '07 F800S, but never at high speed. It was only when the engine was fully warmed up (ie fueling leaned out), and at low speed, or idle. Can be very embarrasing when making a delicate u turn.
I fitted a BoosterPlug http://www.boosterplug.com/shop/frontpage.html, and it cured the problem for me. It has the effect of richening the fueling slightly overall, by fooling the ECU into thinking the ambient temp is cooler than it actually is.
The BoosterPlug is expensive for what it is, but surely way cheaper than a new fuel pump. I have to say it has made the bike far more rideable.
From your good description, you may or may not have a different root cause.
Just my 2c worth.
 
#17 ·
Thanks for all the feedback. The dealer swopped out the fuel pump and tested it, but the bike still cut out. I'm still trying to get a clear answer on whether they also swopped out the controller unit.

@WallyE : I've read good things about the booster plug. I placed an order for one last week but there was some issue with the bank not wanting to release the funds. I now need to re-order and contact the bank to allow the international payment. Strange. How long did it take your plug to ship to CT?
 
#20 ·
Sorry for the late reply Dylan. It took ages for the booster plug to get to CT. About 6 weeks as I remember. Usually I never seem to wait more than 2 weeks for other stuff. No prob with credit card payment. I think it was paypal.
 
#21 ·
I had this problem for a year (F800ST 07) and tried alllll the fixes. Hose recall, charcoal canister removal, booster plug, and update--that is, my dealer claimed he updated the software.

I took it one day to another dealer and 1,hr later the bike was not stalling and has not since. 3 years stall free.

What happened?

He updated the software. Said the previous update probably did not complete.

We all know how tricky updates can be. I would say try the update again.
 
#23 ·
Good question - but the cable is the easy part....

How can you get the update? BMW doesn't post it on their site - unlike the firmware update for your printer or camera.
 
#25 ·
I'd be surprised if anyone thought it was worth their time to go to that kind of trouble. You can buy a simple diagnostic device that'll give you the status of the systems- lots of info here (GS-911) - but for hacking the code and doing your own updates, that's another story.
 
#26 ·
I do agree this sounds like the 'classic' cut-out (even though TS says it's a 2008 ) which was solved by a software update and I've seen a lot of reports where the final solution was to rebuild (so not update) the software to the latest version. The dealers don't like that option because it means you bike has to be connected to the expensive workshop computers for a couple of hours.

Installing a 'booster-plug' or similar product (the only important component is a resistor who makes the engine management system think it's a few degrees colder as it really is) does have the same effect so it could help but I would ask the dealer to do a rebuild of the software and keep the resistor-trick as a last resort.
 
#27 ·
Ah...thanks for clearing that up. My successful "update" which cured the stalling did take about two hrs...which means it was a "clean install"...to borrow a phrase from another kind of machine....
 
#29 ·
2007 F800ST. I originally solved this problem with the installation of the Power Commander. At 3 years old, the battery failed and attempting to jump start fried the computer. Replacement of the CPU ( and the Power Commander removed) has seen no occurrance of the cutout (for the last 3 years).
 
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