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Stalling and stuttering

18K views 82 replies 11 participants last post by  Timskloss 
#1 ·
I have a 2010 F800ST that has recently (ever since the weather started getting warmer in the last 2-3 months) been giving me some low-RPM trouble.
First, it was problems taking off from a stop. I had to rev up to 2-3k, at least, to avoid stalling it. Just a few days ago, every time the RPM dropped (whether starting from 0 speed or during gear changes), the bike would hesitate as if it's going to stall before the revs pick up.
Per the extensive discussions on this forum about such issues, I have found that people usually suggest looking at:
- Idle actuator valve and/or the hoses from it
- Charcoal canister
- Fuel pump and possibly fuel controller (?)

Here what I've tried/checked so far:
1. Checked the battery - it's fine (battery tender shows more than 80% charged light when connected).
2. When taking off bodywork to check the idle actuator hoses (picture attached), I noticed that the coolant level in the overflow reservoir was lower than the min mark (I topped it off to close to max). The most recent case of RPM stuttering happened within 5 mins of starting the bike up (before the fan kicked on), so I'm assuming the coolant flow from the reservoir wouldn't have even started?
3. Checked idle actuator hoses by lightly pressing them near the bends (didn't seem cracked or overly soft). I didn't tinker with the charcoal canister circuit because I didn't have a replacement zip tie or the hose connectors required to bypass it.
4. Borrowed a wifi-based OBD tool (inexpensive one off of Amazon) from a friend to check for fault codes. Neither of us could get Motoscan to connect to it, but my friend used another app that he uses regularly with his car to check for them. It showed the idle RPM of my bike correctly and showed no fault codes. It does show fault codes when he connects it to his car.
5. Did the throttle reset cycle (5x twisting throttle from fully closed to fully open with the power on, etc.). Also tried revving the engine in neutral just after startup (i.e. not after full warmup/fan-on) - it revved up and went back to idle without any issues.

It's been at least 3-4 weeks since I rode the bike and maybe 1-2 months since I refueled, so could the charcoal canister could have dried out if it ever did get saturated (and therefore isn't the culprit)? Also, given there are no fault codes, does it mean the fuel pump/controller are OK? The previous owner said he had replaced it when the bike had trouble starting (I didn't ask when this happened). I also read conflicting reports (https://forums.bmwmoa.org/showthread.php?68499-Devilish-stalling-problem-2007-F800ST/page2) of whether or not fuel pump issues show fault codes. The engine does have that slow oil leak from up top (valve cover, I think), but there has never been an oil pressure light. I also checked the dipstick recently and the oil level is almost near max.

I'm just hoping to narrow down what the problem might be. Right now, the idle actuator hoses are about $55, the idle controller around $190, the fuel pump seems to be anywhere from $60-70 (non-OEM) to either $237 or $425, and God knows what other one-time use parts or unexpected extra parts I'll need to purchase as well. I definitely don't have the budget to test out all of them, and I'm starting to think about getting rid of the bike altogether. If you have any insights on how I can troubleshoot this issue, I would really appreciate them.
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#66 ·
@Claudio and anyone else who's changed fuel pumps: is it normal to have fuel dripping out of the plastic connector which the fuel hose to the rail plugs into? I spent about 30-45 minutes trying to pull the hose off (had to use a screwdriver to really work it off), and immediately, fuel started dripping out of the connector. Picture shows the little pool of fuel that dripped out. I connected the hose back to prevent the drip.
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I was worried there's too much fuel in the tank. I didn't wanna proceed to remove the ring and the seal for the pump assembly only to have fuel come sloshing out. The bike is on the side stand, and the fuel level gauge on the dash does say it's full, although (I believe) the gauge never starts dropping till about the half-tank level. I tried siphoning off some with a fuel hose I bought for the idle hose replacement, but it's too big I think (5/16 in. dia), so the fuel just kept dripping out.
Is this normal, or do I have too much fuel?

Edited to add: @xixi, I think overriding the pump controller needs a special tool that I need to buy from somewhere for about $20-30. The previous owner did say he replaced the fuel pump for $40, although he didn't say when. So I thought it might have been a cheap one and might have failed again. I got a new pump anyway, so I'll try it first. And if the fault persists, I'll test a different controller. Also, I think overriding it will keep the pump on the whole time, which seems unnecessary and wasteful. I feel like it's not the logic that's faulty, it's the pump and pump location design, maybe.
 
#67 ·
@Claudio and anyone else who's changed fuel pumps: is it normal to have fuel dripping out of the plastic connector which the fuel hose to the rail plugs into? I spent about 30-45 minutes trying to pull the hose off (had to use a screwdriver to really work it off), and immediately, fuel started dripping out of the connector. Picture shows the little pool of fuel that dripped out. I connected the hose back to prevent the drip.
View attachment 368227

I was worried there's too much fuel in the tank. I didn't wanna proceed to remove the ring and the seal for the pump assembly only to have fuel come sloshing out. The bike is on the side stand, and the fuel level gauge on the dash does say it's full, although (I believe) the gauge never starts dropping till about the half-tank level. I tried siphoning off some with a fuel hose I bought for the idle hose replacement, but it's too big I think (5/16 in. dia), so the fuel just kept dripping out.
Is this normal, or do I have too much fuel?
The hose in your picture is the output side of the fuel pump. It connects the output of the pump to the injectors. If the bike has been running recently, there will be some pressure in that line and a small amount of fuel in the hose. It will drain out on its own. I usually plug it temporarily with something to minimize the fuel. You should not generally have fuel coming up/out of the plastic nipple.

You do need to get the tank down to at least 50%. I would try to empty it as much as I can especially since you do not have a center stand to keep the bike more level before undoing the big ring off or you will have a fuel flood issue on your hands.The shape of the tank is such that when you remove that tank ring, the level may actually be above it (it slopes down from the rear of the bike and that area is near the low point).

I usually leave that hose connected and just work on the bike if I recall correctly. Just cover the open fuel tank temporarily to avoid dropping stuff in there.

I noticed that the previous owner is using a standard hose clamp. Those are less ideal for higher pressure fuel injection and I find them to be more fragile (don't trust them). If he also used them in the tank, I'd look at replacing those clamps with something designed for fuel injection systems (more even pressure/clamping). Like these
 
#68 ·
Claudio is absolutely correct. Do not take out the pump until you drain out a bunch more gas. A quarter tank at most should be in there so that you don't make a big mess. The top of the pump there is about half way down (gravity wise) of the tank. The tank extends up toward the back seat.

I've had my pump out three times. I remove the hose you reference and plug it with a stubby screwdriver, but I've never had fuel come out of the little connector. That's Archimedes' way of telling you there is still too much gas in the tank... That hose clamp is certainly not original as Claudio also stated. I would personally be okay with a stainless clamp like that one, but Claudio's viewpoint is certainly valid. That's why fuel lines don't come with that kind of clamp.

Other excellent points to reiterate is to make sure it's level. Getting the gasket to seat properly when you put the pump back in is very challenging. I know because I thought I had done it properly, but learned the hard way while filling the tank at the gas pump (after the repair) that I did not have it perfectly sealed. Talk about an embarrassing mess!

Also be aware that the ring doesn't really seal it. It just holds everything in place. You will have to break the seal after you get the ring off. A hammer and big screwdriver should get the ring off without much work. Also be careful when removing the whole unit because the odd shape of the tank makes it tough to get it out without bumping/bending the fuel level float and the wires for its potentiometer. Same hold true with putting it all back in. It requires twisting and leaning it around the curve of the tank. While you have the pump out, dry the fuel filter, then vacuum it assuming you will reuse it. Also shine a flashlight into the bottom of the tank and look for any gunk that might need removing.

And don't be like me. Wear gloves fort his job. Your skin will thank you.
 
#69 ·
Siphoning gas is a challenge because of the difficulty of getting a hose down deep and the risk that the hose will damage the delicate fuel lever sender float mechanism. I always made sure to start with a low fuel level in the first place.

You need not pull the hose off the plastic spigot. Just remove the two screws and pull it away from the cover. It uses o-rings to seal to the cover.
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As stated earlier use proper fuel injection hose clamps throughout. While you are in there change the fuel filter. It is a Mahle KL 315. If you change the filter be aware that it has an o-ring seal at the top. Don't lose it. The new filter does not come with the o-ring.

If you change the pump a good replacement is the HighFlow HFP-382B.

Videos to watch:



Although the videos are for the GS the internals are the same.

Because of the many reported faults with the early aluminum-coloured controllers if it were me I would certainly install the later black replacement.
 
#70 · (Edited)
I changed the pump, and, as you all said, it wasn't easy. I do have some questions, the biggest of which is about the o-ring(s) that bmwroadsterca mentioned above. I checked the previous filter, and well as the protrusion that the filter outlet plugs into, and didn't see any o-rings. I included a picture of the previous filter. I'm assuming by "top," that's the end of the filter that was referred to because the other end (where the hose from the pump connects to) surely can't have an o-ring? I checked in and around the area, and didn't find any o-rings that might have popped off when I removed the old filter, either. I didn't remove the plastic spigot, only the fuel hose that connects to it and goes to the rail. And the opening that the filter outlet plugged into wasn't white, it was black and didn't seem to have any o-rings on it either.
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Due to this concern, I haven't installed/tightened everything completely. Seating the pump was pretty tricky. I almost seated it perfectly without the gasket popping up anywhere, but then realized the tab on the right that mates with the tank was a little misaligned. I then tried applying a slight sideward force with a plier to the tab on the top (near the controller etc.) and found out the hard way (i.e. by breaking it off) that those tabs are made of plastic. Whoever designed this whole pump assembly and the installation method into the tank surely deserves the highest engineering honors.
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Other questions/concerns/comments I had:
1. The two hose clamps are at different clamping positions. The one on the filter is almost fully tightened. It looks like there's a gap in the picture, but it seemed snug enough when I wiggled it after tightening all the way. Both clamps are 11-13mm ones.
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2. Out of the 3 strainers provided with the filter, I could only fit one (as shown in pic). The orange one wasn't fitting because it was hitting the white pump holder. The bag-like one that's similar to the old one didn't have the adapter that goes from its wide diameter to the pump's inlet diameter, and I couldn't get the adapter off of the old strainer.
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3. The tank seems clean enough to me. There are 1-2 little things, but I didn't wanna stick my hand in there coz I thought it'd introduce more dirt from my gloves.
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4. The tabbed ring that screws onto the outside of the tank on top of the pump assembly is pretty rusted on some sides. It was a little hard to get off, but I'm assuming this isn't a big concern?
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Regarding the controller replacement, @bmwroadster, I'll look for one on eBay and see if I can find a black one for a decent price. What kind of faults does it usually cause? And @DJ123, is an ICV recalibration required every time it's disassembled, or only when it's replaced with a new part? I followed mokkybear's guide as suggested by Cramer, and I don't remember reading that a recalibration would be required. I'll check again, though.

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#72 ·
And the opening that the filter outlet plugged into wasn't white, it was black and didn't seem to have any o-rings on it either.
View attachment 368487
You are definitely missing an o-ring that sits between the fuel filter and the plastic pump assembly. once installed, it sits inside the "well" of the filter itself (exactly in the spot shown in your photo), sealing the filter to the plastic tube that is inserted in it. Anything approaching that size will work (doesn't need to be perfectly sized). Given that the previous owner had a non-standard hose clamp fitted on the outside, there is evidence that he did some service in there and your o-ring for the fuel filter disappeared then. I think I've swapped 4 F800 pumps over the years and the o-ring is definitely in that spot.

1. The two hose clamps are at different clamping positions. The one on the filter is almost fully tightened. It looks like there's a gap in the picture, but it seemed snug enough when I wiggled it after tightening all the way. Both clamps are 11-13mm ones.
Based on the size you used, you should be just fine.

2. Out of the 3 strainers provided with the filter, I could only fit one (as shown in pic). The orange one wasn't fitting because it was hitting the white pump holder. The bag-like one that's similar to the old one didn't have the adapter that goes from its wide diameter to the pump's inlet diameter, and I couldn't get the adapter off of the old strainer.
Provided the old one is in good condition. (no big rips/holes), I would use it to ensure there is a good fit. Thats the one part with the aftermarket pumps that they don't see to get right. The one you have fitted should also be fine to use as long as you are confident it is not going to impede the float/fuel level device.

4. The tabbed ring that screws onto the outside of the tank on top of the pump assembly is pretty rusted on some sides. It was a little hard to get off, but I'm assuming this isn't a big concern?
Just clean the inside "threaded" surface if it has any corrosion on it to ease installation, otherwise no worries. This is a "design feature" of the F800, a built in mini-swimming pool under the seat where water can collect, especially after washing or extreme rain.

What kind of faults does [the controller] usually cause? ....I don't remember reading that a recalibration would be required.
I think the faulty controllers would either overheat and simply quit (intermittently). No calibration of the fuel pump or controller is required (not an option).

Speaking of calibration, I think you had replaced the idle air control valve a while back. That definitely should be calibrated.
 
#71 ·
The only feedback I have is that the ring will be fine. Sand it down and coat with a little oil and it shouldn't corrode much more. Interesting about the different filters. I just reused the same one after drying and vacuumed it. Mine looks like the last of your 3 pics (long sand skinny). I don't remember any o rings where it attaches, but it's been several years since I had it out. I guess anything that fits snug will work as long as it fits in the bottom of the tank.

Sent from my SAMSUNG-SM-G891A using Tapatalk
 
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#73 ·
Just to clarify, the o-rings I mentioned several times, and (I think) bmwroadsterca mentioned, is between the Mahle fuel filter and the plastic spigot up top that connects to the fuel hose to the rail. If I understood it correctly, I believe they said the o-ring should fit on the black plastic protrusion that plugs into the filter here:
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You're right, Cramer, with regards to the nylon strainer not having any o-rings. I was talking about this plastic bit:
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You'll notice that that bit is missing on the new strainer I got with the pump. So I couldn't use that one, which is unfortunate because the old one fit much more firmly than the one I have fitted (the white one with the hard plastic skeleton in the second of the 3 pics).

Edit: just noticed Claudio's response. Well, looks like I'll have to go on another part-hunt to the closest auto-parts store tomorrow.
I didn't replace the idle air control valve, just disassembled it, cleaned it, re-greased it, and put it back together. Does that still require a calibration?
 
#75 ·
Just to clarify, the o-rings I mentioned several times, and (I think) bmwroadsterca mentioned, is between the Mahle fuel filter and the plastic spigot up top that connects to the fuel hose to the rail. If I understood it correctly, I believe they said the o-ring should fit on the black plastic protrusion that plugs into the filter here:
Exactly correct!!

You'll notice that that bit is missing on the new strainer I got with the pump. So I couldn't use that one, which is unfortunate because the old one fit much more firmly than the one I have fitted (the white one with the hard plastic skeleton in the second of the 3 pics).
I had the same dilemma with a few kits. I ended up using my original strainer to ensure a good fit. I your original one is in good shape, I would use that.

I didn't replace the idle air control valve, just disassembled it, cleaned it, re-greased it, and put it back together. Does that still require a calibration?
Calibration is less critical with a simple clean/replace but is really easy to do ..nothing to take apart (worth trying/doing). The GS-911 can do it and I suspect your motoscan can calibrate it too. I would focus on the fuel pump issue first to see if that solves your issue.
 
#74 ·
If that o-ring is missing you are pretty much guaranteed to have insufficient fuel pressure.

The aluminum-coloured controllers were not well sealed and would corrode internally and fail to power the pump.

Sent from my SM-T813 using Tapatalk
 
#76 ·
I took another crack at it after acquiring a couple of different sizes of o-rings. One of them was a 1/4"x7/16" (I think) and the other was a 1/4"x3/8". I tried installing the filter with both of them, but it only went on fully with the thinner (i.e. 3/8) one. The filter installation was a little firmer this time around, with the o-ring added, so I understand what you meant @bmwroadsterca. I was actually thinking that the issue might not be insufficient pressure (since the ECU has closed-loop control of it), but maybe more wear of the pump because it'd have to pump more/longer to achieve the same rail pressure. Or maybe it'll be both, who knows.
Pictures of the two o-rings I tested on the filter outlet:
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@Claudio, I decided to go with the new strainer I showed above in the picture, because it seemed to be on OK. I feel like neither the gasoline in the tank nor any jolts from bumps in the road etc. can really transfer a high enough force to that part of the assembly to knock it off.
It took me literally 8-9 attempts to insert the assembly into the tank opening without any part of the gasket sticking up. Pressing the assembly down fully into place was also pretty inconvenient; the plastic between the pump controller and the plastic spigot seemed very flimsy, and there was no other place to really get a good push on it. I also added a little bit of copper-slip grease all around the inside of the tabbed metal ring that goes on top of the whole thing.
I turned the ignition on to check that everything is OK, and it seemd a little quieter than with the previous pump. That one was making a more higher-pitched sound. I checked the previous pump more closely and discovered that it was the same one (Quantum HFP-382B), so i guess I can expect this one to fail in about 3-4 years as well.

Since I have the professional license on Motoscan anyway, I'll take a crack at the ICV recalibration as well (probably in a couple days). The idle seemed decent enough last time, but maybe that will eliminate the stray stutters I exeprienced here and there.
 
#78 ·
Be sure to report back if all this works for you. We're rooting for you!

Also, fingers crossed when you fill the tank...

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#80 ·
Well, gents, I took the same route as about a week ago when the pump fault appeared and the engine shut off while coasting in gear. No such issues today. The idle seemed to hesitate a little when I was leaving (i.e. cold engine), but I don't know whether that's actually the bike or just my hypochondria. Even when coasting to a red light, I was checking if the engine is still running by blipping the throttle (I usually don't do that when downshifting). I think it'll take me a while to regain confidence in the bike.

@Cramer, if I understand the fuel leak you had, it's not necessarily due to the rate of flow while pumping gas, but due to the fuel level rising high enough that it found the gap(s) between the gasket and the tank, right? If so, then I think I'm fine because I refilled all the fuel I drained before changing the pump. So it should have risen up to the level of the gasket already. I didn't see or smell any leaks.

@bmwroadsterca, I thought of something like that briefly, but since the fuel comes in contact with the gasket, I was a little worried about the grease washing off/dissolving into the fuel over time. Anyway, I'll keep it in mind for the next time.

I also recalibrated the idle actuator. It's one of the few service functions Motoscan can apparently do right now. There were only 2 other service functions under the Engine MOT ECU (others were idle deactivation and max RPM restriction, I think). Just a note for anyone considering Motoscan and upgrading to paid licenses - sequentially upgrading costs much more than just purchasing Ultimate outright. I believe I paid a total of $62 for sequentially upgrading from Basic to Lite to Professional to Ultimate. And, if I remember correctly, direct purchase of Ultimate was around $45 or something like that. I know for sure (because I took screenshots) that upgrading to Ultimate from Lite was around $37, but upgrading to Professional and then to Ultimate cost about $45 ($18 + $27). The app also doesn't specify what license is required for something, only shows whether or not a certain feature is available with the current license. For example, if one goes to the idle calibration function with a Lite license and presses 'Calibrate,' the app doesn't say 'Ultimate license required,' it just says 'Not available with Lite license.'
I know the $ amounts above are very small compared to a GS911, and I'm also sort of happy that it goes to an independent developer, but I'm not happy with the lack of transparency because the website just says there will be a "slight price difference" when upgrading sequentially.

I think I can't declare the problem solved until I test it more exhaustively and maybe till the fan kicks on etc., but for now, I think the symptoms have at least been addressed enough to the point where I can do so. Now onto the two other things I need to do, i.e. valve cover gasket, and steering head bearing and fork oil/spring check due to unrelated issues.

I can't thank all you gentlemen enough for all your time, effort, and inputs. I was ready to throw in the towel and get it towed to a dealer, but it seems I've averted it at least for now. I hope my documentation and pictures here would provide a good resource to anyone who experiences such issues in the future. And I hope I can pay this kindness forward or back in some way in the future.
 
#81 ·
I can't thank all you gentlemen enough for all your time, effort, and inputs. I was ready to throw in the towel and get it towed to a dealer, but it seems I've averted it at least for now. I hope my documentation and pictures here would provide a good resource to anyone who experiences such issues in the future. And I hope I can pay this kindness forward or back in some way in the future.
I hope you've solved it. Thinking about this a bit more, I think you have. That missing o-ring likely caused loss of pressure and/or the pump to work overtime (overheating and/or failing prematurely). Keep running local errands to build confidence in the fix and do report back to let us know how things faired.
 
#82 ·
Took a longer (~20 miles) ride yesterday with about 6 miles at highway speeds. That first stutter after the first time I come to a stop definitely wasn't just my imagination. It seems to have something to do with engine temperature, because when I started it after about 10-15 mins of stopping at a grocery store, it wasn't that bad. After that first stutter, everything was fine and all subsequent launches from red lights were OK.
I checked for fault codes and found nothing. So, I decided to jump firmly into the deep end today and went on a longer trip of around 200 miles total to some twisties (or the Ohio version of them, anyway) with a friend. I don't think I noticed any stuttering anywhere, although I was also being extra-careful with the clutch and giving it a bit more gas while taking off as well. By now, I think most of the injection system cleaner I added a while ago should've also gone through the system, so maybe it helped a bit?
No problems during the trip, except for the bike trying to cook my left thigh for dinner while I was riding it.
 
#83 ·
My 2007 F800ST idles poorly and sputters when I run gasoline that has ethanol in it. After switching solely to the 'recreational premium gas' with zero alcohol my idle problems went away. My understanding is that the bike idles pretty lean to start with and alcohol in the gas (up to 15% here) effectively leans it more causing the rough behavior.

Since these bikes can't be turned over by the rear tire after the engine stops it is important to do what we can to make sure they don't die while downshifting.
 
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