Want to buy a known good fuel injection control unit for my 1985 K100RS.  The L-Jetronic unit for the 2V motor.

Looking at the micro-fiche many models and years would work.

I'm located in Edmonds, Washington, USA (just north of Seattle).

I've got a known tested good one on Hood Canal.  You should've posted on Monday. I was up in 
Snohomish yesterday afternoon and took an evening ferry out of Edmonds. I could've delivered it to you.

If you want to take a passenger ferry ride I can meet you in Kingston.

the Jetronic FICU is a very reliable unit. I'd say if you have fuel and spark and the starter works then its likely to be a sensor. The temp sensor seemed to check out ok from your other thread. The symptoms sound intermittent and weird enough to suggest something is happening with the Air Flow Meter. Its a mechanical device and with older machines like yours they can wear out. might explain a few of your problems going back a while. Just a thought.
Cheers

If you are looking for a brand new FICU a google and eBay search of the Bosch part no printed on the casing revealed its the same as the European manufactured Volvo 340. Not sure if this was imported to US. There is a  big surplus of these for small money, brand new in the boxes.

Makes me wonder is the MAF is also the same.

duck wrote:I've got a known tested good one on Hood Canal.  You should've posted on Monday. I was up in 
Snohomish yesterday afternoon and took an evening ferry out of Edmonds. I could've delivered it to you.

If you want to take a passenger ferry ride I can meet you in Kingston.

Duck what would you want for it?  I'm out of town for a week starting this Saturday, but I'm interested.

Holister wrote:the Jetronic FICU is a very reliable unit. I'd say if you have fuel and spark and the starter works then its likely to be a sensor. The temp sensor seemed to check out ok from your other thread. The symptoms sound intermittent and weird enough to suggest something is happening with the Air Flow Meter. Its a mechanical device and with older machines like yours they can wear out. might explain a few of your problems going back a while. Just a thought.
Cheers

Thanks Holister.  I've run through the troubleshooting guide (again).  Values for the temp sensor and air flow meter both come within those listed in the guide.  

I had the dealer check the bike and was told that the injectors start spraying the instant the key is turned to ON position, without touching the starter button.  I'm trying to rule out the FICU altogether.

There is a big transistor in the jetronic that controls injector current and it sounds like yours is shorted on.  It's usually labelled as T410 or T420 on the pcb and mounted on a heat sink.  The part number is PH ON823 and it is an NPN darlington.  i can fix it for you if you can't get it done locally.

tonybob wrote:........
I had the dealer check the bike and was told that the injectors start spraying the instant the key is turned to ON position, without touching the starter button.  I'm trying to rule out the FICU altogether.

I don't see how they could start spraying at ignition ON. The ICU fires the FI relay when the starter button is pressed, which then applies power to the injectors. The FICU then switches the injectors to earth, triggered by a signal from the HES via the ICU

Does your fuel pump run at ignition ON or when the starter button is pressed?

However, one other thing you could check....
The injectors have a continuous connection to +12v. They are then switched to earth by the FICU. There could be an earth short on the yellow/green wire from injectors to FICU pin#12 (I think)
Pull the FICU plug and test for continuity between #12 and earth.

Holister wrote:

tonybob wrote:........
I had the dealer check the bike and was told that the injectors start spraying the instant the key is turned to ON position, without touching the starter button.  I'm trying to rule out the FICU altogether.

I don't see how they could start spraying at ignition ON. The ICU fires the FI relay when the starter button is pressed, which then applies power to the injectors. The FICU then switches the injectors to earth, triggered by a signal from the HES via the ICU

Does your fuel pump run at ignition ON or when the starter button is pressed?

However, one other thing you could check....
The injectors have a continuous connection to +12v. They are then switched to earth by the FICU. There could be an earth short on the yellow/green wire from injectors to FICU pin#12 (I think)
Pull the FICU plug and test for continuity between #12 and earth.

Even if the switching transistor is shagged the FI relay has to be operated before the injectors can spray and that, as Holister said, wont happen till the start button is pressed or the ICU is getting signals from the Hall sensors.
I doubt very much that it is that transistor or even the ECU, as was said the ECU has proven to be very reliable.
Over the years many have been quick to blame the Bosch ECUs for anything including the plague where in fact they are very rarely the problem.

Generally, as we've seen in the past, these dealer mechanics don't know their arse from their elbow when it comes to older Ks. However, this is a café and wiring can get hacked in the process. It would be worthwhile investigating.

The fuel pump is also powered from the FI relay, so if you can hear that running when you turn the ignition key ON then there may well be a problem there. This does not explain how the injectors are getting switched to earth tho.

If you don't hear the pump then the injectors won't have power either and they can't be spraying.

if this is a customized bike with modified harness then a different troubleshooting approach may be required--previously wrecked, repaired harness, custom add-ons, etc?

i just worked on an L-Jetronic unit this week that had several cold solder joints, one of which was the T410 transistor.

That may hold very true for many electrical parts on a K but the L-Jetronic only works 1 way so the same troubleshooting approach is needed even if the wiring harness is modified.
Please explain how a shagged transistor can make the injectors spray all the time considering it switches the earth when the 12v is not connected if the FI relay is not operated.

i was not saying that he definitely has a bad transistor, only illustrating thru pictures that stuff can happen within the jetronic and cause problems--they are mostly reliable but not totally.

A custom bike with modified harness is an unknown factor when it comes to troubleshooting--what has been jumpered or bypassed by a previous owner in order to get it to 'run'?

If the transistor on pin 7 of the ICU has shorted to ground then the fuel relay would become energized when power is supplied thru the key ON position power circuit aka '15'.

Three of the fuses are on power circuit '30', meaning battery power all the time, two are '15' meaning key ON, and one has switched power thru the FI relay.  Are these all intact or have any been modified from the stock routing in order to add accessories?

Got a few minutes this morning to check the pin #12 reading at the FICU plug.  I'm seeing 570 ohms, not continuity.

On reflection, what Holister says is correct.  The fuel pump is not spinning when the ignition is set to ON. It does run when the starter button is pushed.  My bad for not seeing this right away when talking with the dealer.  So the fuel rail is not being pressurized with ignition set to ON before the starter button is pushed.

Having said that, the symptom is excessive fuel flowing into the cylinders at start-up, causing a flooding condition.  So that would lead me to think that 1) there is an incorrect sensor reading to the FICU, 2) there's a wire short somewhere or 3) the FICU has failed in some way.  

Readings from the temp sensor taken at different ambient temps show its resistance is tracking the Temp/Resistance curve.  I also checked for continuity between the temp sensor body and ground and it is good.  I have not pulled the temp sensor yet, not wanting to break the cooling circuit open when it's showing the correct resistance values.

Resistance measurements for the Airflow meter and injectors also track values shown in the troubleshooting guide.

I'm at least the 3rd owner of the bike, but it is not a cafe mod.  There have been wire bodges made by prior owners I've had to fix, but overall the wiring is sill factory correct.  Could still be a short somewhere though.  

Thanks for all the advice, and I'd welcome more feedback.

Excess fuel could be an issue with injectors needing cleaning or fuel pressure regulator [FPR] letting too high a pressure in fuel rail. Both of these are known potential issues and need checking before you consider the FICU to be at fault. Sensors are also known to go or more commonly to get bad connections, again checking these before considering the FICU.

tonybob wrote:Got a few minutes this morning to check the pin #12 reading at the FICU plug.  I'm seeing 570 ohms, not continuity.

If you measured this between FICU pin #12 (counting all spaces from the lead end of the plug) and a good earth on the frame then this may be your problem. 570 ohms is not a lot of resistance so is as good as a short IMO. The FI harness comes out under the tank to a connector on the L/H side where it continues to the FICU. There's not a lot of opportunity for the wiring to short along there but one thing it could be is an earth shorted injector. That would explain the small resistance. Because the injectors are in parallel and are switched together, if one shorts to earth then they are all shorted to earth and when power is applied they will open. Hence the flood of fuel.

To test,  you should be measuring 4 ohms between pin #12 and pin #9. This is the coil impedance for all the injectors which are in parallel.
If not, pull the injectors and measure each individually. They should be close to 16 ohms each.

If it's not one of the injectors, then its probably the harness.

Make that measurement from pin 12 to pin 9 and you should see the injector resistance. 

pin 12 to ground will measure the Air Flow Meter resistance in series with the injectors, plus you are going thru fuse 6 to measure the fuel pump and temperature/fan unit in parallel to ground, so it may not be a valid measurement.

Thanks for the correction Kenny. Now that I check that out on the wiring diagram I can see you are quite right. My bad. 

Pin #12 and pin #9 is still a worthwhile test but I see also that tony has also done that, but no readings posted.

Might be worth pulling the injectors to see what they are actually doing ie pulsing or streaming.
This issue is so typical of the temp sensor losing its earth connection due to corrosion, it might be worth pulling it to give it a clean.

Was finally able to get in some troubleshooting tonight.  

Checking pin 12 to pin 9, I get 4.9 ohms.  This is when all four injector leads are connected.

I then re-checked resistance for each injector, and when 2 and 3 injectors are connected.  Here's what I'm seeing;
Only one injector lead connected:
cyl #1 - 16.5 ohms
cyl #2 - 16.8 ohms
cyl #3 - 20.1 ohms (seems a bit high)
cyl #4 - 17.3 ohms

Two injector leads connected: 
readings are between 8.6 and 9.3 ohms, depending on which combination of cylinders are checked.  For example cyl 3+4 yields 9.3 ohms, cyl 1+2 yields 8.6 ohms.

Three injector leads connected:
readings are between 6.1 and 6.5 ohms, again depending on which combination of cylinders are checked.

Next step is to check pulsing at each injector lead using a LED.  And the harness connector, as you point out Holister.

After that, it's time to remove the temp sensor and check the ground.

Those injector readings all look good, nothing wrong that would cause this.

Did you happen to check if the vacuum line from the rearmost throttle body to the fuel pressure regulator was cracked or leaking?  Or just go ahead and swap it out to be sure.

If that tube was leaking then unmeasured air could create a lean mixture and it would depress the idle speed.  But in addition the leaking tube would pressurize the FPR chamber to open the spring-loaded saftey valve at 4.7 bar or 68 psig, which would result in a rich mixture if the injectors are just operating as normal (fuel rail pressure @ 36 psig).

Also, does your K have a one-way valve in the fuel return line?  It may be rusted internally and the ball can't move to let fuel flow back.  This too would cause excessively high fuel rail pressure and rich mixture.

I'll have to check both Kenny.  I'll add to the list.

Thought I'd send an update to my query.

I picked up a used FICU off ebay and gave it a try.  Engine fired right up and has shown no problems now over the last 5 starting attempts.  Seems all is good now with the new computer.  I did not remove the temp sensor or check any other areas (for now).  

Thanks all for the advice and knowledge from the forum.

Years ago i repaired bosch engine control units, the biggest failure was due to cracked solder joints--but it's also the easiest to fix.

It would be interesting to know what exactly is wrong with the ECU. Many of us and that includes me say they have proven to be very reliable but there comes a time when even the best electronic devices fail.
We need to have the guys that do know the electrical units well to check them out as they fail and try to fix them so as to keep the bricks on the road.
I had some training in electronics many years ago but have lost touch over the last 15 years or so but still basically understand them but not the finer points.
Even the idea of building new units may be a possibility.

Having played with a lot of Ks for a lot of years, here's my .02:

Unless turned into an ant farm on a long sitting bike, these units tend to be incredibly reliable. I've never had one fail on any of my bikes.  (for whatever that's worth)

I do sell a used one from time to time but more often than not it is because someone lost theirs or bought a barn find bike with the L-Jet missing. (And of course an ant farm here and there.)

That said, they are now 20-30 years old and are subject to some vibration so it's not surprising that an odd one or two might fail out of the 150,000+ 2V Ks produced.

I would say that it will probably be a while before there are any big problems if at all but being prepared to some extent could be a good thing.

If you are looking for one of the FICU 2 valve units a search on eBay using the Bosch part no on the sticker will reveal it is the same as the European Volvo 300 series sold in early 80s and which sold in large numbers. Lots of these FICU units around as new old unused stock for small money. Anyone going to Europe could pick them up.