[SOLVED] Another misterious K11 "don't start"

[Timmy]

Hello, brick-riders :)

My story is next: last year I bought K1100LT ABS Police '95. Several times the engine stopped on the move, but then started after some rest or sometimes with adding extra gas during the start. Then the problem disappeared until this year, when the engine suddenly stopped (luckily, 15 meters from home) and starts no more. Under "suddenly" I mean it didn't cough, just like enabling kill-switch. All electric works fine - headlight, turns, stop, horn, lamps on the panel etc.

So, what I already did and checked: I cleaned contacts on motronic, removed fuel tank and clean ALL contact under it, together with central ground. I removed and cleaned (although i was pretty clean) the ignition lock. I took off the kill switch and sprayed it with contact cleaner (again, it was clean as new inside). Bypassing the sidestand don't help as well. I cleaned all spark plugs and checked for the spark all 4. I removed the injector rail - all 4 spit fuel when starter cruncs the engine. I removed and cleaned air intakes, all 4 open with gas. Tried disconnecting the idle run sensor. The fuel is rather fresh (filled at April), pump turns on with key. The battery is loaded. Motronic self check (using 3-contact connector under sit bench and oil lamp) blinks "4444".

Still no start. Any ideas? The last thing I can't fully check is motronic, so already started looking for a neighbor with k11, but this is a kind of luck :)

[kennybobby]

Did you check the engine temperature sensor?  Motronic won't start without it.

A big culpit for sudden stoppage is a broken or cold solder joint in the Motronic, usually at the big transistors that fire ignition and injection (mounted to heat sink on the board).  It's fairly easy to remove the cover and inspect.

[TrueAce]

Hmmmm...........what voltage tests the battery? Starter relay working?

[Timmy]

Did you check the engine temperature sensor?  Motronic won't start without it.

A big culpit for sudden stoppage is a broken or cold solder joint in the Motronic, usually at the big transistors that fire ignition and injection (mounted to heat sink on the board).  It's fairly easy to remove the cover and inspect.

Yes, I did. Measured resistance 3.5K corresponds to ~15C outside. Also, opened Motronic, the soldering seems solid as for me.

Hmmmm...........what voltage tests the battery? Starter relay working?

12.6V after several start trials. Here is a small video:

[Laitch]

You are persistent, thoughtful, and orderly in your approach to this challenge. I was reading Vogel's trouble shooting map and noted one check that you haven't listed—checking the function of the Hall sensor as Vogel describes deep inside this page.

Is that a possibility?

[Timmy]

You are persistent, thoughtful, and orderly in your approach to this challenge, Thor. I was reading Vogel's trouble shooting map and noted one check that you haven't listed—checking the function of the Hall sensor as Vogel describes deep inside this page.

Is that a possibility?

You caught me, Laitch. I didn't check it with the LED. Although it looks good and I cleaned the connection. Yet still I think how to arrange this check: I have no 12V battery to check it without taking off the motorcycle and don't know how to remove its cable properly to test it home.
Also, ordered used motronic today. The drug motorcycle withdrawal hurts too much.

[Laitch]

Although it looks good and I cleaned the connection.

I had a GMC plow truck that looked good, but I think some of the electronics were influenced by subtle changes in sea level, especially the various lights—gear indicator lights, dome light, dashlights, reading lamps. Being in the cab at night was like sitting on a porch watching fireflies in summer.

I haven't needed to perform this test, Timmy, but looking at Vogel's diagram it seems that a connection from the test LED to the positive terminal of the battery is all that is needed. The battery can stay where it is.

I understand the effects of moto-withdrawal and the desperation it triggers. I believe you've narrowed this down to one or the other of these components.

[Timmy]

Just to inform.
Finally, checked the Hall sensor (both are good) and its wires.
Bought motronic on e-bay. No effect as well.  :dunno2:

[kennybobby]

you said there was spark and fuel pulsing, which indicates that the motronic and all it's sensors are good and working--and you checked and cleaned the air filter, so no blockage there.

When fuel was pulsing from the injectors, was it a strong stream or just some drops of fuel in the catch pan?

If the fuel pump or filter or lines were clogged to cause a lower-than-expected rail pressure, then the amount of fuel per pulse would not be enough to start or run.   Or water in the fuel.

[Timmy]

So, finally the problem is localized.  :eek:

Yes, the fuel from injectors just spits (no cloud). I bought the manometer, it showed no pressure (although I'm not 100% sure that connected it correctly). Plus applying the "instant start" spray to the air intake area started engine for several seconds (which is the best evidence I think). Still, the pump humms for the second when the ignition key is on and squirts some gas inside the tank.

Probably, the problem could be located immidiately by the characteristics of injectors' work. Unfortunatelly that's my first combustion engine to repair, so I had no idea how the correct work looks like :dunno. At least now I have some knowledge. Anyway, spurk plugs are cleaned, all found connectors deoxidized, air intake cleaned as well and the pump will not break somewhere thousand miles away from home. :deal:
Thanks to everyone who patisipated in discussion. I'll write the summary after the finish.

[Timmy]

Finally I found the problem: it was the filter pipe "semi"-disconnected from the output metal pipe.

Sometimes the connection keeped the pressure, sometimes not, but it wasn't detectable until I took off the tank to remove the fuel and the filter finally dropped off. I put the hose back, tightened it and two-month charade was solved.