2010 K13GT overfueling - why? - K-Bikes.com - Excellence in Motion
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post #1 of 11 (permalink) Old Jun 9th, 2019, 1:48 am Thread Starter
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2010 K13GT overfueling - why?

2010 K1300GT, 30,000 miles, new coils, plugs, 02 sensor runs raggedy and very rich - howcum?

The plugs and 02 sensor are very sooty. Looking in the pipe the catalytic converter is glowing dully. 02 voltage is 0.9 steady rather than varying as it should. Dies when I ease on the throttle from idle, but will rev up if I twist it suddenly. All the classic signs of an engine running rich.

I recognize that K12 and K13 bikes use an alpha-n fuel injection system, where the primary inputs to the ECU are the throttle position reported by the TPS, and engine speed reported by the crank position sensor. Alpha-n is sensible for a machine with large individual throttle bodies where the intake tract, particularly at low rpm, has very little vacuum. These primary inputs are modified to a small degree by engine (coolant) temp, intake air temp and barometric pressure.

Question 1: does the ECU control fuel pressure via the fuel pump relay, or is injector opening duration sufficient?

Question 1a: what is the failure mode of the fuel pump relay? My bike (barely) runs, but fuel pressure seems constant up to 3,000 rpm at near 42 psi. I haven't tried to rev past that. That value sounds reasonable, but should it be constant throughout the rev range? My '85 K100RS ran L-jet, which used a "barn door" AFM and a fuel pressure regulator than ensured constant pressure differential between the intake tract and fuel pressure. Probably simpler to map injector duration that way. K12's and K13' don't use that system.

Question 2: How is engine load measured and communicated to the ECU? Would the failure mode cause the rich running condition I'm experiencing?

Question 3: The bike runs a non-return fuel system. What then is the function of the the fuel pressure regulator, does it communicate fuel pressure to the ECU?

I plugged in a GS-911 and read the attached real-time values.

Appreciate any suggestions, perhaps we can learn about these bikes since very little info seems to be available online.
Attached Files
File Type: pdf 6 1 2019 Autoscan WB1053903AZV97242.pdf (104.0 KB, 3 views)
File Type: pdf 6 1 2019 log.pdf (63.6 KB, 3 views)
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post #2 of 11 (permalink) Old Jun 9th, 2019, 7:38 am
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don't know answers to any of your questions.... but I think u r going to complex

leaking injector ?
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post #3 of 11 (permalink) Old Jun 9th, 2019, 10:22 pm Thread Starter
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Botus: That the answers are unknown is 1) why I'm asking and 2) illustrates the lack of public knowledge about the K4x engines.

I don't think an injector is plugged, since all four plugs were fouled. The likelihood of all four failing rich at once is unthinkable.

For some reason the ECU is telling the injectors to overfuel. The ECU only knows what the sensors tell it. So, what is "normal" to the sensors? Is 42 psi fuel pressure at 2,000 rpm appropriate? What sensors does the ECU read? How .... and so on. Still seeking answers.

HOWEVER, I have full coverage with Progressive, which should include towing, so I can have the bike transported 10 miles to the dealer... then the costs start.
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post #4 of 11 (permalink) Old Jun 10th, 2019, 11:21 am
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I don't have any info,

I do remember someone with a K12 having a mega misfire and his cat on fire. it was a dodgy injector.
as for it only does as its told... YES when it is working to specification. These days dead/dying ECUs have to be seen as part of life (becoming common in car industry) electronics no longer last like they did.

try find another and check vs what there's says?
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post #5 of 11 (permalink) Old Jun 11th, 2019, 1:17 pm Thread Starter
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the more I look at it...

The more I look at the data, I note that for somewhat varying engine speed and load, somehow the fuel pressure stays remarkably constant.

If fuel pressure should be constant why is it monitored? If fuel pressure should vary, why does it stay the same?

Next, how is fuel pressure controlled - by the ECU telling the fuel pump relay to increase or decrease pressure (pump speed). How is fuel pressure monitored? By the fuel pressure regulator on the fuel rail, I think. I have no info to confirm this, but there doesn't seem to be anything else which could do the job and have a description related to that function.

The fuel pressure regulator lives on the fuel rail and getting to it is a considerable job. I think I'm in for a tow to the dealer which should be paid for by my insurance. Imagine that for an island with a million people, there is only one dealer, and he has only one qualified tech. I hope I get on well with this guy. Heck I hope I'm actually allowed to talk to him at all.
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post #6 of 11 (permalink) Old Jun 12th, 2019, 11:20 am
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Quote:
Originally Posted by Honolulu View Post
how is fuel pressure controlled - by the ECU telling the fuel pump relay to increase or decrease pressure (pump speed). How is fuel pressure monitored? By the fuel pressure regulator on the fuel rail, I think.
on all the vehicles I've worked on with injection the fuel pressure is constant, they change fueling by the time an injector is open, if you changed the fuel pressure as well you'd never know if u were coming or going. changing the pressure could mean the injectors have a differing pattern and the mixture control would be very rough on a basic old system like this

bit surprised its not on a return, its the easiest way, spit it round and round with a more powerful pump than u need and bleed off the difference, I guess it must control the pump speed to keep constant (based on what 4 thinks it happening)

https://www.realoem.com/bmw/en/showp...diagId=13_1264
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post #7 of 11 (permalink) Old Jun 13th, 2019, 3:18 am Thread Starter
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Well then.

Botus: your response to the effect that all the vehicles you've worked on have constant fuel pressure illustrates the general lack of understanding of BMW's recent bike fueling systems. No offense intended I hope to assure you. All discussion is welcomed. In this way we hope to separate the wheat from the chaff.

Allow me to get on the soapbox a bit, there are three general types of electronic injection schemes that I know of.

First, Manifold Absolute Pressure (MAP) systems typified by Bosch D-Jetronic. In the early 1970s, BMW (3.0CSi) Volkswagen (Type 3 and 4 IIRC), Volvo (164 models) and others used an aneroid, or pressure sensor, to determine engine load by comparing the difference between ambient pressure with that in the intake manifold. Megasquirt and Microsquirt do that now, with supposedly greater accuracy. The ECU of those days were, simply put, transformers.

Second, MAF systems where there is a vane, hot wire or hot film device in the intake and essentially, movement or cooling of that hot element (or the current required to keep it hot), effectively measures the mass of incoming air. Bosch L-Jetronic exemplified this in the early 1980s with BMW. My two 1985 BMW K100RS bikes used L-Jet. In particular, L-Jet relied on a device that ensured the fuel pressure was in a constant ratio with local barometric pressure, and thus injector pulse duration computation was simplified. Vehicles using this system control fuel rail pressure using intake manifold pressure via a hose to a fuel pressure regulator mounted on the fuel rail, and controlling the quantity of fuel returned to the tank. Fuel pressure varies inversely with intake manifold vacuum. We all remember ads for "rising rate fuel pressure regulators" being a common item for hopping up an injected car. Most current EFI systems are some sort of MAF-based arrangement with digital ECU's. Oxygen sensors provide feedback to closely regulate fuel trim.

Third, Alpha-N systems use a potentiometer on the throttle valve and infer the mass of incoming air from the deflection angle of the throttle butterfly, plus temperature and ambient pressure, to determine incoming air mass. Here we are with BMW bikes since apparently 2004 as I infer from the list of bikes that use the same BMSKP ECU. Alpha-N systems use stored maps relating a throttle deflection angle and barometric pressure and a few other sensors (incoming air temperature, coolant temperature, oxygen sensor voltage, etc.) to determine injector duration. Until discovering that recent Beemers used it, I had no idea who did.

All that said, fuel pressure in alpha-n systems CAN vary, and run well, if the fueling map(s) are calibrated for it. Case in point: K1300 engines.

Now question 1: how DOES the fuel pressure vary, and how is it controlled? Again, the suspects are the fuel pump and fuel pump controller on the front of the tank, fuel pressure sensor on the injection rail, and the temp and pressure sensors mounted on the airbox. Question 2: what are the failure modes of these, and how are they manifested when they occur? Answers will point to the fault, and from there it's up to me to dive in with hammer and tongs, wrench, screwdrivers and multimeter.

I are engineer, so as suggested above, possibly I'm trying too hard. It may well be that the problem is simple and nevertheless, knowing Beemer prices, expensive. But it's me to want to be informed. This is how I "own" my stuff - by understanding the principles of operation and thus how to assess/diagnose problems when they occur. The wife just wants a comfy ride in her Benz, but I gotta know what's going on inside to enable that. If you've read "Shop Class as Soul Craft" by Matt Crawford (and BTW no mean Airhead mechanic) the philosophical ramifications of this are presented and discussed.

Anyway, it's a bit late here (10 p.m.) and in 10 hours my bike is supposed to be towed to the dealer for professional diagnosis. I will certainly post the results (and cost) of that episode. I'll sign off with a quote from "Shop Class...": “What sort of personality does one need to have, as a twenty-first-century mechanic, to tolerate the layers of electronic bullshit that get piled on top of machines?”
― Matthew B. Crawford, Shop Class as Soulcraft: An Inquiry Into the Value of Work
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Last edited by Honolulu; Jun 13th, 2019 at 3:52 am.
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post #8 of 11 (permalink) Old Jun 14th, 2019, 6:22 am
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I'm not offended.

knew about the first two, never heard of the term alpha n or this deflection idea. What the benefit of this type?
Yes would be interesting to hear how u get on.
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post #9 of 11 (permalink) Old Jun 14th, 2019, 6:38 am
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just looked up alpha N... seems to be a cheap nasty way to do injection that's very rudimental and most people struggle getting it to tune well. Also other pages suggesting its the base map for limp mode on cars

Alpha-N is also sometimes called “TPS maps” because the only sensor that is used for determination of fueling is the Throttle Position Sensor and RPM. Fuel and timing requirements for the engine are expressed as a function of RPM and TPS.

Alpha-N is used most of the time in tricky situations:
1.When the MAP sensor or MAF sensor has failed and the primary control strategy is deemed to be invalid. Something-is-better-than-nothing is the idea. (“Load with Failed MAF” is an example from Ford-land)
2.In conjunction with ITBs (Individual Throttle Bodies) due to the extremely low vacuum created by them (making Speed-Density tricky) and the desire to avoid needing to fit a potentially restrictive Mass Air Flow sensor (making MAF impossible). Again, something-is-better-than-nothing is the idea.
3.In conjunction with ITBs and MAP as a load multiplier. (PowerFC D-Jetro for GTR Skyline, most notable example) ITBs + Boost – Alpha-N output is multiplied by a MAP sensor to come up with a composite load index.
4.In conjuction with Speed-Density and some kind of blending algorithm. This approach is often used with very large camshafts that pull little vacuum at idle. Basically, TPS and MAP are allowed to contribute varying amounts to the overall load calculation. Net result: more stable and meaningful load index close to idle when MAP sensor readings are unstable. Found on the Electromotive TEC3 among others.

Alpha-N is very poor at dealing with hills (think about engine load going up and down hills at a constant throttle position), temperature variations and just about anything else that you’d care about except close to wide open throttle where it does fine.
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post #10 of 11 (permalink) Old Jun 16th, 2019, 1:48 am Thread Starter
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You've been reading the same or similar sites that I have.

SOOOOO... the bike was towed/taken to the dealer on a 25' long flatbed that would have cost me $250/hour if not for having Progressive's Roadside Assistance insurance rider. They're not making money on me now...

The dealer hooked it up and communicated with Hans und Fritz, and all is revealed. Despite the GS-911 returning suspiciously constant fuel pressure readings of about 2700, or 42 psi (which constant pressure was suspicious to me) the actual pressure was MUCH higher, causing overfueling. Apparently the fuel pressure sensor on the fuel rail was kaput. Since replacement requires a lot of "going in there" I told them to make it happen. It'll cost about a grand. Yep, USD$1000. I will review the rep-rom and see just how many FRU's are allowed and maybe there can be some negotiation; the service manager has suggested there's some wiggle room. The part will take 3-5 days to come in and they should install in a day.

Ahh, life in the Paradise of the Pacific, 3-5 days from everywhere (referring to "Brother Where Art Thou" a very entertaining movie with George Clooney).
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