Evening,

My bike has a problem that needs to be fixed. As it was sitting on the stand a few days ago, warming up, it made a strange little sound and then would not run past ~2,000 rpm. It would only idle (where it sounded pretty good, actually, minus the very occasional miss) with the choke on. I'm going to try to summarize what I've checked out here and see if you guys can figure it out.

-Spark appears to be good on all 4 cylinders (checked this via sticking needlenose pliers in the plug wires, it will spark to the engine), and plugs are brand new.

-Hall effect sensor should be OK. Tested this by throwing bike in 5th gear on centerstand and rolling the rear wheel. Fuel pump pulses every so often.

-Pulled fuel line, the pump is spitting fuel out. 

-Something weird I noted is that the starter will now run no matter what RPM the engine is turning.

-Vacuum caps over the throttle bodies and vacuum line to the FPR are all new

-I have done no work on this bike on the 10k miles since I have owned it, with the exception of resecuring the fuel sender under the tank.

-The bike idles very erratically, and there is a small amount of white smoke.

What could this be?

Sounds to me like a Fuel Pressure Regulator is returning too much fuel and has low pressure. The FPR is not an easy thing to get at so it would pay to get a pressure gauge and test the pressure is correct. Ideally it should be 2.5bar (36psi) but could be as low as 2.2 (32psi) and still be running OK through the range.

How much fuel flow should I be looking at if I just pull the line off the fuel rail before the injectors/FPR?

It shot some out, but not a lot of pressure behind it. I did not block it with a finger or anything.

With the hose disconnected is not regulated there but you should have great difficulty holding it back with your finger over the hose. I should be about 6 bar (90psi) but that only tests the pump pressure before the regulator can do its job. Because you test there you have disconnected the FPR unless the gauge is inserted and the line rejoined. You need to use a pressure gauge to test for correct pressure.

Went ahead and threw on a new FPR- the old one was a generic aftermarket (junky) adjustable.

The problem remains. Bike won't idle at all. Any ideas?

time to test the temperature sensor

measure the connector to the under seat computer

pins 10 and 13

there are many posts about this  
 the flow chart for "efi issues" details some of the likely culprits
 http://hrsbstaff.ednet.ns.ca/bvogel/K100/download/bike-wont-start.htm

does the start process  automatically happen at switch on ?

The start process seems to be good- I think I get what you're asking. The bike starts, but doesn't really run, if that makes sense.

Here's something that might be interesting- it's about 30* here (just below 0 Celsius) and the water temperature sensor seems to be reading about 11.5k ohms resistance. Bike has not been running at all. Is this correct? The bike does seem to run awfully rich.

Might also be worth noting that I found a red/green wire and a black wire with the copper exposed right near the fuse panel. Anybody got any idea where these go? I think I'm missing them on the wiring diagram above...

That red/green wire supplies power to the fuel injection relay and the injectors, if it is disconnected the whole FI system has no power. It goes to fuse 6 which is second from the bottom fuse.
That resistance for the temperature sensor is OK.

Uh oh. That is odd, because that is a new issue. That's not what's causing the problem, else the bike would never have run at all.

The green/red wire and the black wire is most likely for the altitude corrector plug.
You Connect them together when going above a certain altitude, search the forum....

I should be safe to insulate the wires, right?

Info added to my previous post.

Right, right, if it is the altitude plug thingy I'll wire up a switch. That wouldn't cause a no-run condition, would it?

Sorry, I mean: having the plug in when it shouldn't be (and vice versa) wouldn't cause the bike to be undrivable, correct?

Normally these two wires is separated......but when traveling above 4000 feet
the wires should be connected together to lean out the mix.

Check these values out, I think my air flow meter is toast.

Pins 7-5, 167
7-8, 402
8-5, 363
8-9, 204

Values in ohms, bench tested in an approximately 68* F room.

What now? Crack it open, check internals?

Just to clear up my issue...

I doubt there are any wiring problems, personally- the bike starts up as normal, it just doesn't want to run. Seems to be giving itself enough fuel to flood itself.

FissionMailed wrote: I think my air flow meter is toast.

Pins 7-5, 167
7-8, 402
8-5, 363
8-9, 204

+1, if you compare them to the ones in the troubleshooting diagram at the portal.

This does lead me into asking a few more questions, though. Can these airflow meters really "die"? It does not appear any moisture got into the system, no real corrosion is evident. Think adjusting the little vanes on the resistor track will help?

They do die. I seem to remember charlie doing a fixit on one of those that worked. If you have a search of his resto thread you might find it or just a general search of the forum.

Did enough toying with it- I went ahead and ordered a (supposedly) good air flow meter off eBay. We'll see what happens.

the resistance measurement can be confusing ...but take note of the good and bad in the the efi trouble shooting thread

but for what its worth this is what I have found

if you can get a good power supply (perhaps a spare old battery with 12 volts still available) some telephone connectors ( about 3mm spade types ) you will need 3 of them attached to some cables (any size will do ...small is good )
you will also need a multi meter set to 10 volts  (or 20 volts full scale )

  this is where the afm fails on all sorts of vehicles ,,,, especially on the early versions ...later bmw models have a braided link between the 2 pieces






heres the connection details

  5 = earth
  9 = +12
  7 = output

the flow or opening measurements versus the output voltage

Yep, I had a pretty good idea how it worked after I cracked it open and looked around. I noted the little arm and how it connected to the wiper. After adjusting the wiper up or down the shaft, I airways verified via meter- and visually- that I had connection from the pin to the wiper itself.

It appears my issue was the resistive strip. I never could get a good connection to it.

you can move the plate holding the resistive strip fractionally by undoing the fixing screws  and tweeking it a little

could be an idea to get some firm but thin cardboard and get under the wiper with the card board soaked in some flux remover ...it cleans just about anything ...but be carefull where it gets

I moved mine just a smidgen ...and took it from reading 1.86  volts  down t about 1.35 volts ...and a new sweep range across the carbon strip

don't forget to lock down the screws for the pcboard with some thread locker ...or nail varnish





 I have seen heard of some of the connectors breaking away from the tag strips that lead off to the external spade terminals as well .\some thing that could be cured with a little cautious soldering work but if the conections break away from the pc board  ...( have seen this )  could be a dump run involved



good luck

Replaced the AFM...Still no luck. Bike now starts up strong but only runs for a few seconds. I know I have an injector that may be an issue (17ohms resistance) but I can't see that crossing this particular issue. I'm wondering if this is a fuel pump now. It is making an erratic sound when the bike is running and RPMs jump around a lot, but never over 1500k or so.

Ideas?

FissionMailed wrote:Replaced the AFM...Still no luck. Bike now starts up strong but only runs for a few seconds. I know I have an injector that may be an issue (17ohms resistance) but I can't see that crossing this particular issue. I'm wondering if this is a fuel pump now. It is making an erratic sound when the bike is running and RPMs jump around a lot, but never over 1500k or so.

Ideas?

Next time you fire it up, keep your finger on the starter button for a few seconds. If it stays running with your finger on the starter button suspect an interruption to the signal from the Hall sensors to the unit under the seat resulting in no fuel pressure. We had that issue with a K75 here and it was the plug connection to the unit under the seat.

Also, no mention of the multipin connector into the underside of the fuel tank but check that connection under the seat first.

Oh, I think I get what you're saying. Initial fuel pump activation is independent of the hall effect sensor, but continued operation requires signal from the sensor. Yes?

Alright, might be narrowing this issue down finally.

It does run (beyond the starter just turning) if you hold the starter button down. Tach jumps around a bit, but it will run. I pulled out the ECU connector, cleaned it with electronics cleaner, and reconnected with no real effect.

I'm working on this bike on the side of the street that I live on, which makes things a bit harder. Can I get to the hall effect connector and ignition unit without pulling the tank?

One more question...Can I use a meter to test the hall effect wiring? I'm worried about burning it up because I don't really know how to test resistance on it.

FissionMailed wrote:Can I get to the hall effect connector and ignition unit without pulling the tank?

No.

FissionMailed wrote:I'm worried about burning it up because I don't really know how to test resistance on it?

In the troubleshooting diagram at the portal you find a "how to" test the sensors.

Sorry, I was thinking "I need to test the wiring" and forgot that the test procedure tests at the wiring plug so that issue is solved. And I can test it off the bike, so...

Just to make sure, I couldn't find a power supply at radio shack, so I'm good to hook wires directly to the battery, right?

Pulled the sensor out and tested. Works fine when room temperature. Did not test with a hairdryer to get it hot, but the bike has the same issue when it's cold.

Also the local RadioShack has Deoxit, so that's my weekend project.

I apologize, but I'm lost here. How would I test to make sure the hall effect sensor signal is actually getting to the ignition module? I've tested the sensor and it is fine, so now what I need to do is test resistance with a probe from the negative battery terminal and a probe on the ground/shielding (two sperate tests of course) female ignition connector, right?