K100 4v '92 long time to ignite & randomly hesitate, stutter, stalls.

[LeMoeur]

Latest updates, guys.

Not really a big progress but any new discover is still something isn't it? Went straight ahead with the plan to disassemble the TPS after having checked what i think it's the most important culprit of its malfunction: the fact that a full open throttle shows me much more ohms than when it's only 3/4 from the limit.

Only thing was that the soab is in a sealed plastic box.. impossible to open if not broken apart. So i just settled on cleaning it with some contact cleaner, shaking the thing to assure for the product to reach every part inside.

Before mounting it back i tested it on the bench with multimeter and it seemed to work ok. After re-bolting it back on the throttle rail, checked for the right voltage between pins 1-4 as inge's guide suggested and retested. All fine.. ~2k Ohm at full throttle and ~1,8k Ohm @ 3/4.

Now the interesting part: when tested with the cable connected (both at the ECU end and right at the bottom of the connectior on the TPS) the readings went haywire, like always!



I happened to find this schematic of the motronic 2.1 that gave me an idea... disconnected the CO pot that shares that 25 pin as shown above (even if I didn't realize what's its function) and voilà.. TPS in range again!
(Also tried messing with the CO pot screw, but with no luck..)

Any idea?

[^Adrninistrator]

LeMoeur:

I am Acute Toxicity, the BMI (Bureau Of Motobrick.com Investigations) Agent In Charge (formerly known as Brunhilda).

It has been brought to my attention by the DMJ (Department Of Motobrick.com Justice) that you violated motobrick.com protocol by not exhausting the Posting Guidance Requirements provided to you here at motobrick.com.

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[LeMoeur]

LeMoeur:

I am Acute Toxicity, the BMI (Bureau Of Motobrick.com Investigations) Agent In Charge (formerly known as Brunhilda).

It has been brought to my attention by the DMJ (Department Of Motobrick.com Justice) that you violated motobrick.com protocol by not exhausting the Posting Guidance Requirements provided to you here at motobrick.com.

This is your notification that another occurrence will trigger disturbing sanctions.

AT

Oh man, you mean the signature! I'm utmost sorry... I was sure of having added the specs but that stupid tapatalk app didn't let me see! Now that i've updated my profile i hope to be back into legality  :yes

[John Lang]

7km/liter equates to about 14 liters/100km. That is about three times as high as it should be. No wonder you smell gasoline. My K75 uses about 4.3l/100km.

[LeMoeur]

Hi guys, long time no see!

I have some updates for you.. being a mindless clumsy pal i decided on Monday night to make pour about 7 liters of diesel in my K (obviously on an almost empty tank [emoji6]) . The bike didn't take it too well.. she ran fine for like 1km the started to sob and make a big white smoke screen then stopped. Even then I didn't realize the mistake made.
Once i found out (with the help of a more sensible-nosed friend) i disassembled my fuel lines to pump out the bad blood from the tank.. to do this i intermittently switched on and of the ignition key to get help from the fuel pump priming.
In fact only draining the tank and adding fresh petrol wasn't enough so i went on to:
1. Change plug sparks
2. Change fuel filter
3. Disassemble injectior rail
4. Remove injectors, spray them w/ carb cleaner and replacing old (and quite expensive) o rings

Still the bike wouldn't start.
I noticed that after about 5 seconds of having depressed the start button the fuel pump would make a noise like bubbles coming out of it. So i pointed my attention to the fuel pressure regulator, disassembled it and drained its fuely content.
No change.
Then i tried to disconnect the fuel return line from the FPR to the tank (@ the tank) and retried to start. The bike started fine (still some smoke) no fuel dripping fron the disconnected hose. Then i reassembled the hose, the bike started but died after a short while. Unsuccessfully tried to start it again. Then disconnected the very same hose from before et voilà. Started again!

Have i a bad FPR?
It's possible that this also caused the problems pictured in the first post?
Could the vacuum line from FPR to the first TB be the cause? (It's old and seems in a bad shape but no visible leaks)

Thanks again!

[Laitch]

Have i a bad FPR?
It's possible that this also caused the problems pictured in the first post?
Could the vacuum line from FPR to the first TB be the cause? (It's old and seems in a bad shape but no visible leaks)

The straightest course of action now is to replace the hose that is old and in bad shape (perhaps that means unattractive or un-stylish to you).  :yes Anyway, it's cheap and simple enough to do.

Good persistance, LeMoeur. 

[John Lang]

I did the dumb diesel fill-up, discovered only when the bike stalled about 10 feet from the pump. I replaced the diesel in the tank with gasoline and after about 5 seconds of coughing and belching black smoke, the engine started and has run perfectly since. No need to change any parts.

[LeMoeur]

Hi everybody!

Long time no see.... again!

Had strange times since i decided to force my bike to run on diesel... Last thing i said before we parted was that i started the bike and then managed to take it home to the garage, well there are some updates.

When i started the bike again from the garage last weekend all went (quite) well.. long starter down to fire it up as usual for me.. few bogs downs, revved to up 2k RPMs and she was ready to ride. It ran like never before with perfect throttle response and steady idle! Went down to my local DIY shop to search for a (rare as an unicorn) 8mm T joint to fit my brand new fuel pressure gauge (involved in diagnosing my endless bike-probs), when back on saddle the unfaithful one wouldn't start.
So started doing random things like key on-key off, opening fuel cap, disconnecting return hose and such. Finally quite randomly she fired up.

Back home, safe again, i foolishly recorded this event on my register as "sometimes can happen". Silly me.

Next day, i drive down to get my belly overstuffed by my grandma.. nice lunch, pasta, cuz ya know we're in italy mammamia! Happy as a sumo fighter on drugs i hop on my bike and.. guess.. no start! This time random fiddling didn't help.

So i had to pull off again the spark plugs to find them quite wet. changed them with spare ones. still no start. metal-brushed the previous ones and cooked both on kitchen fire to clean them. disconnected fuel hose from injector rail to FPR to make sure pressure didn't build up too much in it and found that there was quite few pressure, instead. lastly checked values from CO2 pot and brought them to 70/30 (leaner). the bike finally ran.

Following what Laitch said i checked my vacuum hose and it seems to keep pressure and not leaking.

The straightest course of action now is to replace the hose that is old and in bad shape (perhaps that means unattractive or un-stylish to you).  :yes Anyway, it's cheap and simple enough to do.

Good persistance, LeMoeur. 

So... to avoid further stranding at the side of the street i decided to order a brand new FPR. today it arrived. i installed it.
Guess what?

NO F**KIN START!

Ah... only sometimes i can hear bubbles from the pump just as it would pump back out fuel excess. Moreover, i think that's unrelated but...: from under the seat i have found a cut off cable that goes to the first pin of the diagnosing plug (brown black wire).

I'm really starting to run out of ideas

[LeMoeur]

Hi guys. Always me. Decided to not start another thread just to reduce the pollution on the forum.
The problem's still the same. I replaced, shortly after last post, the TPS. The brick fired up after few revs but kept on white-smoking from the exhaust and after shutting off there was no way to start her again.


Decided then to change fuel filter and put new sparks, in the meanwhile i managed to clean the fuel tank from very dirty fuel and lots of debris. While reassembling the fuel pump's output nipple broke off so i went to my local dealer to change iit... checking with him we found the specs for the old pump i had.. it spat out only 1.5 Bars of fuel (2.5 from OEM)! Could have been the cause of all the trouble?


So i bought a new one (3.8Bar, bit overpressurizing but i heard of a guy in another foorum that fitted a similar one in his k100 and ran fine.. that's what the FPR is here for, isn't it?). Back home i installed the new pump and what i get is this:





Sounds pretty alarming to me. Watcha say?
I doon't know where to bump my head atm

[Laitch]

Decided to not start another thread just to reduce the pollution on the forum.

That was a good move. Keep with this thread until there is a solution. :2thumbup:

• What were the gap settings of the spare plugs you installed? 
• What is your battery's resting voltage? In the video it sounds weak.
• In Reply #29 you write that you sprayed the injectors with carb cleaner and replaced o-rings. Since then, have you checked the injectors for their ability to spray fuel? Are the plugs still wet when the bike won't start?
• Are you activating the choke or twisting the throttle when attempting to start the bike?

[LeMoeur]

That was a good move. Keep with this thread until there is a solution. :2thumbup:

• What were the gap settings of the spare plugs you installed? 
• What is your battery's resting voltage? In the video it sounds weak.
• In Reply #29 you write that you sprayed the injectors with carb cleaner and replaced o-rings. Since then, have you checked the injectors for their ability to spray fuel? Are the plugs still wet when the bike won't start?
• Are you activating the choke or twisting the throttle when attempting to start the bike?

Laitch you are always on point. Thanks :2thumbup:


1. I didn't check the gapps but they are brand new NGK from the recommended compatible ones (had pretty new X5DC Bosch but decided to test if Diesel could have fouled them after the mistake..even after the cleaning with metal brush)
2. Yep battery it's pretty low like 11.8V but i thought it wouldn't make so much difference since last time it started. (Ok i see that i am a fool)
3. I didn't check for the spray pattern ATM but last time they did spray, altough not in a very "sprayshly" style...
4. No choke, i try with no to very little throttle twisting (increasing at each retry).


Aren't you worried by the burst of smoke that you can see from the video? I'm pretty preoccupied by what it could mean!  :mbird

[Laitch]

1. I didn't check the gapps but they are brand new NGK from the recommended compatible ones (had pretty new X5DC Bosch but decided to test if Diesel could have fouled them after the mistake..even after the cleaning with metal brush)
Aren't you worried by the burst of smoke that you can see from the video? I'm pretty preoccupied by what it could mean!

New plugs need to be checked for gap meeting specifications.

I'm not worried about the smoke because that's happening on your bike, not mine. :giggles  Don't get preoccupied. Don't twist the throttle when starting it. Don't increase the twisting when it fails to start. Start it with a fully charged battery.

The injector fuel stream should be a strong stream but it doesn't need to be a mist.

[LeMoeur]

Hi guys! Happy holidays... at least for you... owners of working bricks  :dunno2:


I'm reporting back after some homemade good wrenching done with the wise supervision of the great Laitch.


To write down all the frustration and disappointment my bike is giving me in these needy times i made up a scheme-timeline of all that has been done to track down the problem.


Hope you'll enjoy it as much as i DON'T do!


And here's a link to the video i made 2 days ago (yep Christmas eve!) of what my K is doing now...

[The Mighty Gryphon]

It looks like the fuel pump is priming the injector before starting, but doesn't run once the engine starts.  I think the signal to make the pump run comes from the hall sensors.  Since the engine fires on the starter then quits, this signal may not be getting to the Motronic.  Have you checked and cleaned the large connector on the motronic unit?

Do you still have the side stand cutout switch?  While unlikely, it's still possible that this switch is causing trouble.  I'm thinking that vibration may be making it switch off the engine. 

[LeMoeur]

It looks like the fuel pump is priming the injector before starting, but doesn't run once the engine starts.  I think the signal to make the pump run comes from the hall sensors.  Since the engine fires on the starter then quits, this signal may not be getting to the Motronic.  Have you checked and cleaned the large connector on the motronic unit?

I checked seated and reseated a lot of times... I'll try to spray again some connector cleaner just in case...

Do you still have the side stand cutout switch?  While unlikely, it's still possible that this switch is causing trouble.  I'm thinking that vibration may be making it switch off the engine.

That's great! i have it and it is in a REALLY bad shape as the cables are kinked and twisted... so i repaired itsome weeks ago with some tape! I'll try to jumper it,then!

[Inge K.]

I'll try to jumper it,then!

You can use a IEC 60320 - C1 plug (as commonly used on shavers) for this.

[LeMoeur]

Nothing to do... connector-cleaned all the connectors (along with the fuel tank one) on the right side under the fairing + jumpered side stand switch.
10 starting attempts: 7 no go, 2 just 1 second, 1 few seconds then shut off.  :dunno


Just a doubt... when replacing the fuel pump, i had no clue of wich terminal of the new pump would have been positive or negative (no indications) so... given that i have A LOT of fuel and pressure in the rail... could the pump's terminal swapping affect my bike in any way?

[Laitch]

Just a doubt... when replacing the fuel pump, i had no clue of wich terminal of the new pump would have been positive or negative

Does that mean you are not using a workshop manual to guide you, LeMoeur, and instead are following instructions sent by the mothership into your dental work and from there directly into your brain? :giggles Is the mothership responsible for guiding you to the diesel pump? I'd give up on that method if I were you.

Following is a tip from one of the many manuals downloadable for free online but you might need to test those Hall Sensors and their connections after all.

[LeMoeur]

Does that mean you are not using a workshop manual to guide you, LeMoeur, and instead are following instructions sent by the mothership into your dental work and from there directly into your brain? :giggles Is the mothership responsible for guiding you to the diesel pump? I'd give up on that method if I were you.

You are right my dear... my bad for being so clumsy that day, at the gas station! :falldown:  However I have that workshop manual by bmw and i often read of your previous experiences here on the forum, but this time in my defence i have to say that i already had a non-OEM fuel pump with different connector cables that are really the same size, and on the pump there're no sign of orientation marks. It meant that makes no difference to me  :yes  but wanted to check anyway with you guys!

Following is a tip from one of the many manuals downloadable for free online but you might need to test those Hall Sensors and their connections after all.

That's for sure... i have it written down for the to do list of the next days  :2thumbup:

[Laitch]

It meant that makes no difference to me  :yes

It only makes a difference to the fuel system, but with your lighthearted approach, I believe success is just around the corner anyway. Just keep the wheels planted. Before you know it, you'll join the rest of us in telling people to do things for their bikes that don't often work for them, then buying their bikes to salvage the parts from them.
 :2thumbup:

[rbm]

You can use a IEC 60320 - C1 plug (as commonly used on shavers) for this.

... in Europe.  IEC60320 C7/C8 (Figure 8 style) plugs are more prevalent in North America.  This style might still fit; worth a try.

[Inge K.]

... in Europe.

The OP lives in Italy.

IEC60320 C7/C8

C7 C/C distance is 8.6mm, C1 C/C is 6.6mm.

[LeMoeur]

Just tested Hall Sensors.. led light goes perfectly off when magnet activated! So no problems here

[LeMoeur]

Hi Guys! Tired of sitting brainless riding your flaming Ks on the streets all smiling and such while i weep in my garage? Now it's time to get brains going!


My story stopped in december when for pure luck i found a way to reset the motronic wich involved simply pulling off fuse #5 for like 10 mins. Bike started, i went for a little cautious ride then back to the garage to finish all the aesthetics.


3 weeks ago i decided was time to go for a test ride. bike started... big white smoke... not keeping idle... then shut off... i managed to fire it up once or twice after, but always like that. soaking wet plugs. Assumption: too much fuel pressure (againnn!?)


messed around with fuel pump.. switched to an old one that gave few psi less than advised.
now can't even start once. the engine is turning but somehow not firing up... spark plugs: dry. doubt: injectors are working?
i pull off the whole rail. no spray. at all. from no one. although if i directly put one injector shorted to battery and ground it sprays. same if i ground them (Mind: only while pressing the starter button, obviously).


Bad Motronic?


I tryied the old fuse-reset method: no way.


Now the fun part.. i've found a post from a guy on another forum that states: "to reset motronic you should ground pin #1 on the 3-pin diagnose connector under the seat, turn on the ignition but do not start the engine, count 5 seconds, remove the ground momentarily and then ground it again for 5 seconds, turn off the ignition".
When i do this, as soon as i remove the grounding the fan goes on, and it "flashes" in the same way as the speedometer bulb does. :yow  [Edit2: ok, i'm a fool, this is fan test...  :dunno ]

[Edit: things that i know that work.. i have fuel pressure (fuel gauge indicating about 30 psi); fuel pump running; battery just charged]


Please.. i beg for another little fix of K Wisdom


Yours Truly,
LeMoeur

[LeMoeur]

Guys i’m happy to say i quite randomly (then in the end, instead, very specifically) sorted things out.
I’ll spare you all the thorough research i had to do altogether with my trusty neighbor working things out by ourselves on the Motronic 2.1 scheme... lastly the culpritfor all this mess was the....

(Suspance)

... Ignition Switch!!

Found out that at its terminals it sucked up 9v of current giving only 3v to the poor pump & injectors. So i pried it open, cleaned and brushed the contacts, put it back together with sone tape (cuz obviously the plastic casing of the switch blew into pieces on my opening attempts) and now she fires up like a charm! [emoji7]

I still have white smoke and rough idle to fix... but that’s.......... a start (pun intended).

Thanks for the attention and cooperation!