veets wrote:Hello Laitch, good suggestion.  I did replace the crankcase breather hose this past weekend along with the vacuum line for the fuel pressure regulator because they both had some cracks in them.  Unfortunately, it did not make any difference on the performance but they are back to good operating condition.

I'm going with the ancestral curse theory then.

veets wrote:Holister, you wrote:  



Is there a good procedure explaining how to check the throttle position sensor (TPS) and wide open throttle (WOT) switch on a 85 K100?  

Also, before I do anything else, I think I should also check all of the electrical connectors.  Starting with the MAF.  Is there a good diagram with all of the main electrical connections?  I have a bottle of DeoxIT and need to rule out the connections and grounds.

Firstly, go to the Portal page and click the Trouble Shooting link in the middle. There is a diagram there of all the connectors under the tank.
I read somewhere a while ago that there was a Bosch article somewhere that said that 80% of fuel injection related problems were caused by earthing issues. There are some critical ones on the K-Bike. I'm pretty sure the fuel injection harness is one of the many earths that connect to the main spare under the tank. Deoxit this and anything else you can find. Another earth that is critical for fuel is the temp sensor. The body of this sensor earths to the engine case and the thread can get a lot of oxidation causing an open circuit.

Secondly. Before you test the TPS switches it needs to be adjusted correctly. With ignition off/not running and throttle closed, you should hear the Throttle Closed Sw click juuust as you open the throttle. If not, undo the 2 retaining screws, first turn the TPS unit clockwise then back counter clockwise till you hear the click. Tighten the screws. You won't hear the WOT switch as it doesn't click. Its just at the other end of the throttle movement.
To test the TPS switches.
1) remove the FICU (Jetronic) plug.
2) ignition on/engine not running.
3) DMM @12VDC
4) probe between pin #9 (power) and pin #2 (Throttle Closed). You should have 12V with throttle off and zero when throttle open.
5) probe pin #9 (power) and pin #3 (WOT). you should get 12V with the throttle wide open.

The engine will run ok with zero volts across the TPS but not if either switch has a closed short ie; 12V across the throttle range. You can pull the plug on the TPS. That will remove any closed short from the equation and many here actually do this to on purpose to avoid the harsh decel as the FICU shuts down the fuel above 2k rpm on throttle off. My thoughts are that this is not a good idea as the FICU uses this switch to adjust fuel mix at cold start-up.
Whats the throttle position switch for?


Lastly. If you want to quote someone like you did above with the screen shot, you can simply click the 'quote' button on the post you want to quote and then edit out any text not needed. Or ther is a quote button on the tool bar.

Cheers

I DeoxIT'd the grounds and I went through the trouble shooting guide for the LE-Jetronic

TPS switches - No voltage!!!! (I can hear a clicking sound when I just start turning the throttle and then again as I just release the throttle)

9-2: At zero throttle 0V (should be 12V)
9-3: @WOT - 0V (should be 12V)

Since both pins (2&3) are connected to the Throttle Butterfly Switch, Does that mean that mean the switch may be bad?

Airflow meter readings check out
7-5: 70 ohms
7-8: 328 ohms
8-5: 365 ohms
8-9: 329 ohm (@15C)

Water Temp Sensor Checks out:  2.6 Kohms at 15 C
Ground to Injectors Checks out:  4.4 ohm (w/ 4 injectors)
Pin 13 to Ground: 0 ohms

veets wrote:
TPS switches - No voltage!!!! (I can hear a clicking sound when I just start turning the throttle and then again as I just release the throttle)

9-2: At zero throttle 0V (should be 12V)
9-3: @WOT - 0V (should be 12V)

Since both pins (2&3) are connected to the Throttle Butterfly Switch, Does that mean that mean the switch may be bad?

Do you get 12 Volts at pin 18?

Crazy Frog, 0 volts on pin 18.  I measured this with ignition on & throttle off 

Is it normal to have a battery voltage of 12.5 volts in off position and 11.7V when in the on position before starting?  I know the lights and everything is drawing the battery down but that seemed low to me.  I had no problem starting the bike and a load test indicated the batter was fine.

How low does it go when you hit the starter button?

veets wrote:Crazy Frog, 0 volts on pin 18.  I measured this with ignition on & throttle off 

Is it normal to have a battery voltage of 12.5 volts in off position and 11.7V when in the on position before starting?  I know the lights and everything is drawing the battery down but that seemed low to me.  I had no problem starting the bike and a load test indicated the batter was fine.

I am sorry, I should have given you more details.....
You should get 12 volts when the engine is running or when you are pushing the starter button. If the engine is not running, you should get 0 Volts.
11.7V seems to be low but what is important is to know how many amps/milliamps the system is drawing when you turn the ignition key on.

kennybob wrote:How low does it go when you hit the starter button?

Goes to about 10.8 volts when starter button is pushed.

Crazy Frog wrote:

veets wrote:Crazy Frog, 0 volts on pin 18.  I measured this with ignition on & throttle off 

Is it normal to have a battery voltage of 12.5 volts in off position and 11.7V when in the on position before starting?  I know the lights and everything is drawing the battery down but that seemed low to me.  I had no problem starting the bike and a load test indicated the batter was fine.

I am sorry, I should have given you more details.....
You should get 12 volts when the engine is running or when you are pushing the starter button. If the engine is not running, you should get 0 Volts.
11.7V seems to be low but what is important is to know how many amps/milliamps the system is drawing when you turn the ignition key on.

I just tried it and it goes to 12 volts when running.

veets wrote:I just tried it and it goes to 12 volts when running.

Ok good... When the engine is running, can you get 12V at pin 2 & 3 of the iddle switch?
One pin will be 12v on idle, the other pin will be 12v on full throttle.

Crazy Frog wrote:

veets wrote:I just tried it and it goes to 12 volts when running.

Ok good... When the engine is running, can you get 12V at pin 2 & 3 of the iddle switch?
One pin will be 12v on idle, the other pin will be 12v on full throttle.

When engine is running, it backfires and stalls when i try to go to idle.  I assume I am still making the measurement on the 3 pin connector.  Is that correct?

Fuel injection system - I measured the pressure of the fuel system and when I press the start button and don't start the engine, I get about 36 PSI.  When I start the engine, I get a pressure reading that fluctuates (needle rapidly oscillating between 30 and 40 psi).  Is this normal?  

When I turn off the engine, the pressure in the system slowly decays.  It takes about 15 seconds for the pressure to drop to 10 psi.  Is this normal?  or is the pressure regulator supposed to hold the pressure longer?

veets wrote:Any other ideas?

There is a concise description, diagnostic method and treatment of a similar problem in this post.

When perfoming a fuel pump test, the pressure went up higher than 65 psi as expected from the Trouble Shooting Guide for EFI.  The pressure went over 100 psi during my test.  If the relief valve in the pump was not functioning properly but the fuel pressure regulator was working correctly, could this be the cause of a rough idle, rough running and backfiring at low RPM?  The PSI of the fuel system while running is right around 36 psi.

So you did a visual check of the vacuum line from the rear throttle body to the FPR, or you put a mity-vac on the line and pulled a vacuum to see if it would hold? 

With 30-40 psi fluctuations in supply pressure and 100 psi at the pump (deadheaded?), then something is not right in your fuel system---start at the beginning, the pump and verify it is meeting specs, filter, lines, rail, injectors, FPR

kennybob wrote:So you did a visual check of the vacuum line from the rear throttle body to the FPR, or you put a mity-vac on the line and pulled a vacuum to see if it would hold? 

With 30-40 psi fluctuations in supply pressure and 100 psi at the pump (deadheaded?), then something is not right in your fuel system---start at the beginning, the pump and verify it is meeting specs, filter, lines, rail, injectors, FPR

Kennybob, I replaced the vacuum line from the rear throttle body to the FPR.  I do not have a mity-vac but using a syringe, it seems to keep both pressure and vacuum from the syringe.  When I gave it pressure, the engine rpm went up, when I pulled vacuum, the rpm went down.  

I have checked the system again and everything checks out.  The only thing that seems strange is the pump relief valve does not kick on at 65 psi.  Regardless, I have a new Fuel Pressure Regulator coming tomorrow and I will try another pump.

No fear fuel lines off the FPR are connected wrong way round....?

92KK 84WW Olaf wrote:No fear fuel lines off the FPR are connected wrong way round....?

No.  I always take a picture first before removing anything to make sure it goes back the same way.  

I did replace the spark plugs today with D7EA and it ran a little bit smoother.  If I held the choke on as far as it would go, it would idle without backfiring; however, not sure what this tells me.

Wet plugs indicate fuel is not being burnt properly due to excess fuel delivery, poor ignition or engine timing is out. The back firing is most probably unburnt fuel igniting in the exhaust manifold. This could be due to incorrect valve clearances. Given that you've checked everything, and we assume you've done that correctly, then it may be time to check your valve clearances. Easy to do. Chris Harris has a couple of very good videos on Youtube explaining the procedure.

Also, could be worth checking to see if the ignition timing plate is set correctly or hasn't come loose.

Could you post the part # from the reconditioned injectors you installed? Thanks

Holister wrote:Wet plugs indicate fuel is not being burnt properly due to excess fuel delivery, poor ignition or engine timing is out. The back firing is most probably unburnt fuel igniting in the exhaust manifold. This could be due to incorrect valve clearances. Given that you've checked everything, and we assume you've done that correctly, then it may be time to check your valve clearances. Easy to do. Chris Harris has a couple of very good videos on Youtube explaining the procedure.

Also, could be worth checking to see if the ignition timing plate is set correctly or hasn't come loose.

Could you post the part # from the reconditioned injectors you installed? Thanks

Holister, thanks for the suggestions.  I will check those next.

The injectors I installed were:  Bosch 280150710

What do the new plugs look like now?  Do you still have two plugs showing wet and dark?

Does it only idle with the choke at full stop and no higher revs possible? 

Is there any evidence that the air flow meter has been tampered--like cammed-out screw heads, the air bypass screw (turned fully closed off),  or the black plastic cover pried open (and someone "tuned it up" by adjusting the spring tension)?

The main signals for injector duration are the air and water temperature, the air flow, and rpm.  You've checked the temp sensors and they appear okay; the rpm signal comes from the ignition control unit and it wouldn't start or idle if that was hosed; the only thing left is the air flow signal and the jetronic unit itself.

kennybob wrote:What do the new plugs look like now?  Do you still have two plugs showing wet and dark?

Does it only idle with the choke at full stop and no higher revs possible? 

Is there any evidence that the air flow meter has been tampered--like cammed-out screw heads, the air bypass screw (turned fully closed off),  or the black plastic cover pried open (and someone "tuned it up" by adjusting the spring tension)?

The new plugs look better.  1&3 are darker than 4&2.  And no one has ever tampered with the air bypass screw or black plastic cover.

I wonder if the BMW Motorcycle shop has an old Jetronics they would let me try to see if that was the problem.

I haven't been following this whole thread but:

Due to how the K100's wasted spark system works, 1 & 4 fire together and 2 & 3 fire together so I doubt it is an L-Jet problem.

Are you SURE the spark plug leads are tightly secured on the fouled plugs? (I use pliers and my other hand to pound the hand holding the pliers to them to make sure they are snugly installed.)

Have you tested the resistance of all 4 plug leads?

duck wrote:
Have you tested the resistance of all 4 plug leads?

Duck, thanks for the response.  I have tested the resistance of the old wires and I also purchased a new set.  They both check out within speck and the bike reacts the same with either set of plugs.

SPs can be deceiving. Best to test them with a DMM as well. They should measure <1.0Ω
I've found that at around 150Ω they start to fail.

Also, do you have the terminal nuts screwed to the top of the SP. Without these the HT lead cap will not make good connection.

The new plugs look better.  1&3 are darker than 4&2.  And no one has ever tampered with the air bypass screw or black plastic cover.

Cylinder 1 and 4 fire at same time, one is a wasted spark.
Cylinder 2 and 3 also fire together but at different timing 180 degrees and again one is wasted spark.

If 2 and 4 are 'correct colour' this suggests BOTH coils are in good order producing sparks.

Is it possible it is suggesting plug lead 1 and 3 are swapped and therefore out of sync? They are both long leads and Cylinder 3 has a long lead that loops around plug 2 and then back to no 3 cylinder and I think is actually longer than the lead to cylinder no 1. [No 1 being near the front timing chain end and no 4 being rear near the battery- for the benefit of any new readers not familiar with the numbering].

Reversing 2 and 3 would not make any difference as they are on the one coil and fire at the same time but 1 and 3 are not and reversing them will throw things out.

Also Holister mentioned plugs failing and I have had that happen even with brand new plugs failing in a very short time.

92KK 84WW Olaf wrote:
Is it possible it is suggesting plug lead 1 and 3 are swapped and therefore out of sync? They are both long leads and Cylinder 3 has a long lead that loops around plug 2 and then back to no 3 cylinder

It's the HT lead for cyl. 4 that is looped around cyl. 3.

Inge K. wrote:

92KK 84WW Olaf wrote:
Is it possible it is suggesting plug lead 1 and 3 are swapped and therefore out of sync? They are both long leads and Cylinder 3 has a long lead that loops around plug 2 and then back to no 3 cylinder

It's the HT lead for cyl. 4 that is looped around cyl. 3.

More beer for Inge!.

Is it a case that 2 and 4 are on the correct coils but 1 and 3 may be swapped? As in check that no 1 lead is on the same coil as no 4 lead, also check no 3 lead is on same coil as no 2 lead.

92KK 84WW Olaf wrote: More beer for Inge!.

Thanks ............

What you have listed is correct for a K75.
All spark plug caps is pointing to the rear, exept the rearmost one
.....to avoid sharp bends as the space becomes more limited.

It sounds like no change on the plugs--1 and 3 were wet, black and sooty before, while 2 and 4 were wet and dark but no soot.  If it runs longer they will end up looking like the old ones in the photo.

Puzzling how one of each coil pair is darker--may be related to the timing of the wasted spark versus when the fuel is injected to all 4 at the same time, and two of them get a better burn.

i have an 4-zylinder Jetronic that i bought just to use for parts if needed to repair kbike units.  It is Bosch 0 280 000 544, and is used in the '85-89 Volvo's, bunches of them are on ebay brand new for cheap. 

i haven't traced it out yet to determine if the circuits are the same, but it looks like it has more digital elements (memory chips, ADC and microcontroller) than the previous analog Jetronics (ceramic wafer with chip-on-board processor)--maybe a precursor as they transitioned to the digital Motronics.

Take a look at your jetronic unit to see if it has been opened, the bottom aluminum tabs will be scratched if they have been previously bent back.

Is your bike stock, OEM exhaust, or any intake modifications that you know of?

ps. if anyone with a k100 is within ridin range of huntsville alabama i will ride to meet up if you want to do a swap test with this Bosch ...544 FICU.

I think I would be swapping the two plug leads that are dark.

It doesn't point to a Hall Sensor wiring failure because it would affect either 1/4 or 2/3 or both but definitely not 1 and 3 together as they are 180 degrees apart. Things like bad valve clearance come to mind but a compression test would show that.

Some plug leads have the cylinder numbers on them but make sure they are connected to the correct coil to start with.

I am sure the cables are correct. I'm now thinking it is a timing issue or needs a serious tuneup. Could that be the problem?

veets wrote:I am sure the cables are correct.  I'm now thinking it is a timing issue or needs a serious tuneup.  Could that be the problem?

In response #69 of this thread, Hollister suggested both checking the valve clearance and also the timing plate.  A serious tuneup also would include balancing the throttle bodies and checking their bushings (spigots) as suggested in a link in response #63. 

Hope springs eternal in the human breast. It would seem the answer to your question would be "yes."

If its a Hall Sensor issue is it possible the timing plate is not correctly aligned? That would put the ignition timing out on all cylinders.