Hi everyone,

I have done something to my bike and need some help. I replaced my failing battery and now the engine will only run at a very slow idle for a few seconds. I have done a lot of troubleshooting to no avail. Here is what it is doing. The bike was runnig well and normaly just before the change of the battery.

It will run only with no throttle applied, roughly, with no power, only below 1000 rpm, for a few seconds. If I add any throttle at all it instanlty dies. Here is a list of things I have checked.

Ground at the battery, ground wire at transmission attachment point, and ground point under the tank on frame are all good.

Symtoms are the same with the idle switch conneceted or disconnected.

Fuel pressure is 35 psi, pump runs untill engine stalls.

plugs have spark at all throttle positions.

Symtoms are the same whether I release the start button or hold it down.

Starter cuts off at about 750 rpm when holding button down.

Pulsing 12v at fuel injectors at all throttle positions.

All inputs to fuel injection computer when measured at the connector are in normal range as per the troubleshooting guide.

So I am stumped. Again, the engine dies instantly whenever the throttled is opened at all but will lope along at less that 1000 rpm for a few seconds when attempting to start with no throttle. When trying to start with no throttle the engine tries to run, add any throttle while cranking and you can hear that the engine loses that almost running sound and just cranks with no firing. There is spark however in this condition. Please help before I go nuts! Thanks very much.

I am very impressed with Berts troubleshooting guide. It is very practable and contains information that no other source has concerning the operation and repair of the K bike fuel injection and ignition system and componants!

Jay

Hi Jay,

Based on the fact all you did was change the battery it "should" be something really simple. Did you disconnect the FI computer and if so have you double checked the connection.

Regards,

Phil

Question:
If you re-install the old battery, Does the bike run correctly?

My guess from the symptoms is the system is not seeing the air flow sensor opening up as the air flow increases so it is supplying fuel as if it is at idle. Hence when you open the throttle air rushes in and no more fuel is delivered than would support an idling engine so the engine dies as there is not enough fuel for the air volume.

Look carefully at the connections to the engine management module and the connection to the mass air flow sensor at the other end as well, but my further guess is that it is at the engine management module end of the line with the plug not making good contact.
Regards,
K-BIKE

Hi all,

Thanks very much for your help. I too have been thinking that the problem "should be" at the FI computer connection. It is the one that has to be disconnected to change the battery and the symtoms seem to fit. I turned in my old battery as a core when I purchased my new one but I had the same thought about the battery being defective so I have tried connecting to a car battery via jumper cables with no change. I also have checked to be sure that the air flow meter is free to move which it is and that the reading at the FI connector was changing with it's movement and within the troubleshooting guides listed range of values. So I agree that the connector is the first suspect. I have cleaned the male parts of the connection and have sprayed contact cleaner very carefuly into the female side. No joy. I have retraced my steps and now wonder if I made a fatal error. When I first replaced the battery I know that I forgot to reconnect the FI computer and tried to start the engine. What I might have done after that was to plug in the FI computer with the ignition on. I don't know if I really did that or not, I just can't recall, but is it possible to damage the FI computer by doing that?

I see a listing on ebay for a FI computer for $90, which seems reasonable, if it comes down to needing a replacement. What do yall think?

Again, thanks to everyone for your help,

Jay

Hi Jay,
I think find another K 100 bike that works and persuade them to allow you to disconnect their FI computer and connect yours on, does the bike still work OK? Put theirs back on their bike, does it again work OK. You have then effectively proved yours is dud. There is a Japanese guy who repairs them but I am sure he is more than $90.
Regards,
K-BIKE

jaybutter wrote:

Ground at the battery, ground wire at transmission attachment point, and ground point under the tank on frame are all good.
√

Symtoms are the same with the idle switch conneceted or disconnected.
√ With the switch disconnected (unless one of the wire is shorted), engine management computers 'think' that the engine is running between idle and full throttle

Fuel pressure is 35 psi, pump runs untill engine stalls.
√ The Ignition computer controls the FI relay. When engine stalls, the ignition module shut off the injection.

plugs have spark at all throttle positions.
√

Symtoms are the same whether I release the start button or hold it down.
? When holding the starter button, the Jetronic receives (pin #4) the signal that the engine is starting and it sets itself on starting mode (enriching the air/fuel mixture). This is difficult to test if it's working or not.

Starter cuts off at about 750 rpm when holding button down.
√ When engine runs over 710rpm, the Electronic ignition module shuts off the ground to the coil of the starter relay (pin #11)

Pulsing 12v at fuel injectors at all throttle positions.
√ Power to the injectors is controlled by pin #12 of the FI computer. If the unit was dead, you wouldn't get any power at the injectors

All inputs to fuel injection computer when measured at the connector are in normal range as per the troubleshooting guide.
√ Again, the power comes from pin #12 of the FI computer

So I am stumped. Again, the engine dies instantly whenever the throttled is opened at all but will lope along at less that 1000 rpm for a few seconds when attempting to start with no throttle. When trying to start with no throttle the engine tries to run, add any throttle while cranking and you can hear that the engine loses that almost running sound and just cranks with no firing. There is spark however in this condition. Please help before I go nuts! Thanks very much.

Time to start drinking!

What is sounds is that when you open the throttle, the vane in the air flow meter is moving and more air is supplied to the engine. For an unknown reason, the signal from the vane is not supplied to the FI computer and no extra fuel is supplied to the engine

Jay

Can you test the Mass air flow sensor (air box) at pin 4,7,8 & 9 of the FI computer plug?
Your problem could be a bad wire and when you moved the loom to replace your battery, you lost the connection.
Stupid way to try fixing: Try to twist and shake the wires going to the FI computer.

I don't believe that you have burn the FI unit, but it's always good to have spare one on hand. I would buy the spare one on Ebay. The cost of a new one is $700 .

Bert

Hello again!

Tonight I will try the stupid way, I'll flex the wiring to the FI while cranking and see if anything happens. If not I will but the replacement unit. The ebay lister has video of his engine running on it so I feel pretty good about it's condition. Boy, I feel like a dumb-ass, but, as suggested, a few beers might help with that.

Thanks to everyone!

Jay

When you connect the big cable to the fuel injection computer is there an audible click when the clip clicks over as it seats home. If that is not present that is an immediate warning of a problem. Sometimes it is necessary to trim some of the rubber boot off to allow that to happen.

Now you say you used contact cleaner, what brand exactly did you use?
Regards,
K-BIKE

Dear Mr K-Bike...I know what you are going to say. De-oxit this and De-oxit that. Give it a rest.

GIVE ME A CHANCE TO SAY HOW GOOD THIS STUFF IS!

This stuff IS the duck's guts. It's all that K-Bike says and more! It cured a persistant crackling noise on my home phone after I tried a lot of contact type cleaners. I've since thrown them all out.

Now it goes on every electrical connection that I touch on my bike, car and even my lawnmower.

Hunt this stuff down and use it! It is that good.

Hi All,

I received the replacement FI computer yesterday and with it installed my bike started right up an ran normaly! So, the lesson learned is to be darn sure the ignition is OFF when plugging or unplugging the connector to it. I really don't remeber having done that but I must have. One good part of all this is that I have a much better understanding of how the FI system functions and how to troubleshoot a non-starting bike.

Thanks to everyone, especally those responsible for all the technical information posted!

If anyone is in the Savannah area and wants some local insight just let me know! My email address is jaybutter@comcast.net

Now I can get started on re-assembling the fairing!

Cheers, Jay

Well done for sorting it and good news, from memory there is a Japanese guy who repairs these, not cheap but keep the dud unit in time they will get costly even second hand.
Regards,
K-BIKE

To all,

I think that I will set an auto search on ebay for another module and maybe the ingnition module too. Having these as spares in hand can save a LOT of $$, sort of an insurance policy. As an example, I drive a 1995 Mercedes S500 (w140). I lost the ingnition modual (ezl) about a year ago to intermitancy(car would refuse to start from time to time). I almost s**t when the dealer told me the price, $2300 . The freaking car is only worth about $5000! Found one on ebay for $100 . Then I found another for $100, which I keep in a box in the trunk along with the wrench needed to mount it. I do not want to be stranded again! The MB electronics are really weak during this time period, and this module is Siemans, not Bosch. I might be shooting myself in the foot here by increasing demand and therfore cost, oh well. Ah, toys, you want to play, you got to pay!

Jay

One of the things that kills ignition modules is heat, often they are installed with a sheet of polythene between the metal bodywork of the car and the heat-sink compound. Polythene is too much an insulator I believe so the module should be screwed direct to the bodywork with just enough heat-sink compound to fill voids between the two surfaces.
Regards,
K-BIKE

Exactly, when I installed the replacement I put on a light coat of silver based heat-sink compound. It mounts on the left side fender well body work. The original one had the white paste but no polythene. I know Georgia USA is hot but what does MB due for cars delivered to say Saudi Arabia? Oh well!

Jay

My original MB one had the polythene and died, I recall a while back on the MB list there was debate and the popular wisdom said leave the polythene there. Given when I bought the replacement that had the polythene and it had a peel off tab my thought was they put the tab there for a reason and polythene is a poor conductor, take it off, so I did no further dead modules. I know they can be dismantled and repaired it is often a cold solder joint that causes the problem.
Regards,
K-BIKE