2008 F800ST Just Stalls When Riding

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peterwray1
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2008 F800ST Just Stalls When Riding

Post by peterwray1 »

I would be very grateful if someone could diagnose the problem I having with my 2008 F800ST.

This problem has appeared on the last two rides. The bike will just quit or stall for no reason when I am riding it. After I coast to the side of the road and I wait a minute the bike will start again and be good for another 10 minutes then it will stall again. When I first had the symptoms with the bike I just gassed it up and it rode for quite a long time. Now no matter how full the tank is it will keep stalling.

The one thing that I have noticed if after it has stalled and then after sitting around for a few minutes. If I ride it fast in low gears it will go for a long period before stalling.

Some facts:
The bike is 2008
It has 7200 miles
I use 91 Octane fuel (the best you can find in Arizona)
It still rides good with no other obvious symptoms

I am at a complete loss to figure this out. I called the BMW dealer in Tucson and he suggested that it could be Ethanol related. The problem with that theory is that my wife has the same identical F800ST 2008 and her bike does not stall and we fill up at the same location.

Please, Please somebody help. Thank you.

Peter
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sweatmark
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Re: 2008 F800ST Just Stalls When Riding

Post by sweatmark »

Funny you should mention the F800 stalling problem:

I stopped by our local dealer this afternoon to pick up some Rockster parts, and the service guy asked me how our F800S was performing... we experienced similar motor stall on a couple of occasions, and dealer re-flashed the engine controller last year with hopes for a fix. Seems the service guy had just been on the phone with another F800 owner whose bike stalls indiscriminately, and at the worst possible times.

This stalling problem is documented (at least anecdotally) over on the F800 board: http://f800riders.org/

Just looked and saw your post right there in the "F800S & F800ST" section!

I sniffed around the web following our Big Stall (viewtopic.php?f=26&t=20087) and discovered that this problem is common.

Don't have a good solution, as we're hoping that the new ECU flash will help and haven't put enough miles on the F800 during soggy winter nastiness to evaluate.
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oiasghar
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Re: 2008 F800ST Just Stalls When Riding

Post by oiasghar »

There are as many solutions as there are stalling issues. Some bikes don't actually stall but rather quit just going down the road. Others stall when rolling off the gas and downshifting. And some (like mine) started stalling after 24K miles when hot.

ECU flash is certainly one solution. But if it is happening when hot, have the dealer (or yourself) look at the idle hoses. Even though mine is a 2009 which has updated idle hoses, according to the tech they had gotten weak with the repeated heat cycles and were collapsing when really hot (fan on and stop and go traffic). So far the replaced hoses seem to work but I have only put 300 miles on it.

It is also possible the fuel pump is going bad but that normally means you have to cycle the key (off/on) before it will restart, though not always. One other thing to check, is the battery. They tend to make the bike do strange things given the role electronics play in a BMW.

Sorry this is perhaps not as much help as you need but like I said, there as quite a few possibilities of why its stalling. Do search over at f800riders.org as well, there is a wealth of information there.
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Re: 2008 F800ST Just Stalls When Riding

Post by CycleRob »

A shut off while riding can be many things - - - and a stored trouble code should show what happened. A temperature or vibration sensitive intermittent failure of either the cam or crank position sensors will trigger an engine shut down from the BMS-K computer. So will an open or short circuit in the sidestand switch!

Time to read the trouble codes. You can also set up a GS-911 with the ability to log real-time data and display it on your bluetooth enabled phone or PDA . . . . . as you ride the bike.
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peterwray1
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Re: 2008 F800ST Just Stalls When Riding - Cured by BMW Deale

Post by peterwray1 »

On Tuesday, I took the bike into Ironhorse BMW in Tucson, Arizona and I think they found the problem with the bike stalling. It appears the previous owner deliberately disconnected the oxygen sensor and tie wrapped the connector up into the frame.

When the bike was checked in the technician hooked the bike up to the computer and it was seen that the oxygen sensor was showing a fault. No other faults were seen. I took the bike on a 200 mile ride in temps averaging 80 degrees and there was no stalling or quitting. The bike ran fine.

Why would someone disconnect the oxygen sensor? I am curious. I have'nt had a return call back from the previous owner. Well I'm very happy the bike is running good.

My Thanks to Ironhorse BMW in Tucson, Arizona!

Peter
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sweatmark
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Re: 2008 F800ST Just Stalls When Riding

Post by sweatmark »

Please let us know how things work "down the road". The lambda sensor disconnection is nutty, unless some type of aftermarket device was installed to provide a pseudo-signal, as per the older Dobeck/Techlusion.
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dirty red
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Re: 2008 F800ST Just Stalls When Riding

Post by dirty red »

Check your gas tank vent hose. My bike stalled on me and then started acting funny like it was a little starved for fuel. I found the lower part of the hose 100% pinched off, bad routing. After rerouting the hose way more power, pick-up and even a little louder I think. Worth a check, good luck.

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Re: 2008 F800ST Just Stalls When Riding

Post by CycleRob »

Another easy thing to check is the tightness of the battery terminal bolts. Mine came without lockwashers. When I did my inquisitive new bike "look under the hood" I found both terminals were almost finger tight. That immediately shifted blame to the dealer prep person. Some weeks later when I added the "key on power terminals" I found the terminals were again almost finger tight. :shock: Ooops! It wasn't the dealer!!! These bolts appear to loosen from normal vibration and temp changes because there aren't any SS lockwashers. The solution was slightly longer (used) battery bolts (they are of special materials or plating) and SS (stainless steel) lockwashers.

One future recheck showed they were still tight. \:D/
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Re: 2008 F800ST Just Stalls When Riding

Post by CycleRob »

The early year bikes, <2008, did have ECU firmware shortcomings that can be cured by the latest BMW dealer ECU flash update. If there is a (!dangerous!) stalling issue, the dealer may do the flash upgrade at little or no cost.

When I performed the 12K mile valve clearance check (they were all "in"), I found both battery terminal bolts at about half the installation torque they got way back in June of 2009. So, even with SS lock-washers, it appears the lead battery lug threads the battery bolts screw into deform enough over time from vibration to loosen the connection. That absolutely can cause intermittent hot engine stalling, so checking your F800's battery terminal tightness, after installing longer bolts and SS lock washers, should be the first easy shot to make.

The engine vibration that reaches the battery has been minimized by my installing a closed cell, firm sheet of shipping foam underneath the battery shown in the 1st pic. The 2nd pic shows that the thickness of the foam lifting the battery up also requires a spacer and longer mounting bolt on the battery's plastic top hold-down bracket, which is easily done. Notice in the 3rd pic the "keep alive" jumper clip on the negative battery cable terminal connection to the starter solenoid upper terminal, keeping alive the trimmed EFI mapping, TPS parameters, clock time, MPG average reading, average speed and both tripmeter's data. Well worth the trouble of hooking it up and the extra caution required when working around live, unfused, high current 12V circuits.
Image Image Image

Mounting the battery within the airbox might have been a brilliant space saving design -or- necessary when the plastic underseat fuel tank takes up the space where the battery usually goes. It ended up being in a more hostile vibration environment than, say, the floating in rubber metal cage like on the R1150R.

My battery is now over 2 years old (June 9, 2009) and still cranks up the bike immediately, like it's supposed to. Hopefully SBDS (SuddenBatteryDeathSyndrome) won't occur for at least 2 more years. BTW, going for a 80+ mile roundtrip ride to Harbor Freight Tools right now!


EDIT: FYI, the Original battery lasted 5 years plus 9.5 months. Edit to change the photo provider AWAY FROM PhotoBucket to my faster, much less intrusive Postimage.org account
Last edited by CycleRob on Sat Sep 07, 2019 7:43 pm, edited 2 times in total.
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sweatmark
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Re: 2008 F800ST Just Stalls When Riding

Post by sweatmark »

Rob - thanks for the reminder about battery vibration remediation. Will have to do this for Mrs. Sweatmark's F800S. I did double-check the lock washer/fastener situation last year in response to one of your earlier posts, but I might add a stainless lock-nut for each battery terminal for safekeeping.
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jj91709
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Re: 2008 F800ST Just Stalls When Riding

Post by jj91709 »

As you're troubleshooting this, I'd strongly suggest calling BMW Customer Service to document the issue. This is how recalls are made. Call 800-831-1117 and have the last 7 digits of your VIN handy. I have a 2007 F800S that stalls often. I just called and they encouraged others to call as well.

This is a DANGEROUS defect and we all owe it to each other to get this on the recall list so we can avoid a tragedy.

Ride safe
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Re: 2008 F800ST Just Stalls When Riding

Post by CycleRob »

I have not had that type of stalling problem. Mine vapor locks (stalls at low RPM/idle) when 15+ miles on the low fuel lite in slow-go creeping traffic ONLY in temps over 95degF (35degC). That appears to logically be caused by an un-submerged fuel pump overheating design issue, inherent in a non circulating EFI fuel system where the plastic underseat fuel tank is bathed in rearward flowing engine/radiator heat. That means there is no return fuel line going back to the fuel tank, just the single hose going to the fuel rail feeding both injectors. The slow moving fuel in the now un-submerged fuel pump assembly (that occurs only on low fuel lite) becomes overheated to it's boiling point and pump air cavitation occurs, yielding a quick fuel pressure drop and engine stalling.

Other than that shortcoming when it is very hot outside (95+ degF) that I'm able to avoid by refueling before 15 miles on the low fuel lite occurs, the bike runs absolutely beautiful. It now has 17,145 miles (27,592 km), months ago started on it's 3rd rear tire and is 5 weeks away from the battery's 3rd birthday. THERE IS NO OTHER M/C I WOULD RATHER HAVE . . . . AT ANY PRICE.

That 800 number for BMW Customer Service is valuable info and it'll be recorded along with the bike's last 7 VIN digits.
------------------------------------


Getting back to the solution to original topic peterwray1 posted; "It appears the previous owner deliberately disconnected the oxygen sensor and tie wrapped the connector up into the frame. Why would someone disconnect the oxygen sensor? I am curious. I haven't had a return call back from the previous owner. Well I'm very happy the bike is running good. My Thanks to Ironhorse BMW in Tucson, Arizona!"



Since reconnecting the O2 sensor showed it still was functioning OK, it had to be some bright-think bench racer mod. Makes no sense to me whatsoever why anyone would disconnect it on such a highly sophisticated, finely tuned EFI system. That would force it to use a default fuel map that does not have any fuel ratio feedback with changing altitude, temperature, RPM and throttle opening. Also known as "Limp Mode". That O2 sensor is absolutely vital in proper engine running without an overly rich mixture . . . . which likely was the desired end result that the previous owner wanted.
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