Riding to work the other morning (it was raining but I've ridden the bike lots of times in torrential rain, so thinking it was a coincidence) the bike just cut out two miles down the road. All lights are working and starter is whirring but I can't hear the fuel pump power on. Checked ground connections and fuel pump connector under tank, both look good.
Found the very useful EFI troubleshooting guide and have been working through it and it has been very informative. I bought a multimeter as a result ie. I am very (very!) new to electrics and EFI. Moving through the 2nd troubleshooting flow diagram - the fuse is ok and I am getting power to pin #86 of FI relay.

The next step is where I'm having trouble - I don't think I'm getting power to pin #85 of FI relay. The reason I don't know for sure is that I'm not positive I'm doing the testing correctly. I have the ground of the multimeter in pin 7 of ECU, test probe in pin #85 of FI relay and ignition on - no volts. If this is the problem, the flow diagram has "Electronic Module??", does that mean I need a new ECU or FI relay? Thanks for any and all help and suggestions,
Geoff

Hi Geoff,
If you are searching for the presence of power you connect the negative of the meter to either battery negative or a good earth on the frame of the bike then use the + probe on the pin you are trying to prove is powered.

For instance if you had a blown fuse and you connected your meter across it one lead on each end of the fuse with the ignition on you would read 12 volts or so because that is the potential difference across an open circuit fuse. If the fuse was fine you would see no volts across it when the ignition was on because the fuse conducts and hence there is no voltage difference between the two sides. In practice there is always a small difference because of the resistance of the fuse but for all practical purposes consider there is none.

If you put one lead on the frame or battery negative and probed across the dud fuse first one side then the other you would see volts on one side and none on the other. With a good fuse the probe would show volts both sides.
Regards,
K-BIKE

Geoff,

Before starting to check the computers (could be overwhelming for somebody new with electronics) let do some basic checks and find if the problem is related to the pump itself or the electrical power.

- Can you hear the pump whirring when you turn the ignition ON? You should hear it for one or 2 seconds.

- Is the water temperature light ON or OFF when you turn the ignition? (If the temperature is too high or the temperature sensor has a problem, the pump will not turn.)

- If you remove the fuel pump connector under the tank, do you have power at the plug when you press the starter button?
(Set your multimeter to measure12v and touch the green/white and the brown wire with your tester.)


Bert

No, the fuel pump is not whirring when ignition is on. The temperature light is NOT coming on when ignition is on. Is a bung temperature sensor the answer or are there tests I can do to confirm it? Thanks!

If the temperature light is not ON, you could almost discard a problem withe the temperature sensor.
I would be interested to know if the pump is turning when you manually energize it.
One quick way to check if the FI relay gets power is to remove the connection of one fuel injector and see if you get a 12V positive.

As an electronic component usually fails when it's power on (due to the internal rapid increase in temperature) and your bike stopped working when you were riding, I'd rather prefer starting the troubleshooting from the pump side and going toward the computers.

How would I go about manually energizing the pump?

Tested one of the fuel injector connections, no power. I assume this was meant to be tested with just the ignition on and not depressing the starter?

no you have to test with the starter turning over. been there a few months ago.

Hi Geoff,
With the early K's like yours the fuel pump only runs initially when you push the starter and then carries on once the engine is running, with the 16 Valve the fuel pump runs for a short time when you turn the key on to pressurise the fuel rail, it then restarts running when the starter motor gets the engine running.
Regards,
K-BIKE

You could try to power the pump by applying +12v directly at the fuse panel. (Just plug a wire on the positive of the battery and touch the fuse with the other end).
If the pump doesn't turn, check at the pump connector under the tank to see if you get the power (the wire could be broken).

Ok, here's a summary of where I'm at:
1. Power to pin #86 of FI Relay.
2. Fuse is ok.
3. No power to pin #85 or #87 if FI Relay.
4. No power to FI connection when hitting starter.
5. The fuel pump does whir/power-up/energize when manually done as Crazy frog described as above.

Is this all pointing towards a dodgy FI relay?

I am a bit confused with your explanation.

1st, we ruled out a bad fuel pump which is a small step.



Pin #86 of the FI relay should get +12v
Pin 85 of the FI relay should get -12v
Pin 30 of the FI relay should get +12v at any time even with the ignition key turned off.

Now here is how to find if the relay gets the signal to energize the fuel pump.
- remove the relay
- Put the red lead of your tester on pin 30 of the socket and the black one to a good ground. You should be reading 12v at any time.
- Put the red lead of your tester on pin # 86 and the black one to a good ground. When you turn the ignition key ON you should be reading 12v on the meter
- put the red lead of the tester to the positive (+) of the battery and the black lead to pin # 85 of the socket. When you press the starter button you should read 12v on your voltmeter.
Please report your finding and we will continue troubleshooting.

Bert

In answer to the above questions:
- Put the red lead of your tester on pin 30 of the socket and the black one to a good ground. You should be reading 12v at any time. IT DOES
- Put the red lead of your tester on pin # 86 and the black one to a good ground. When you turn the ignition key ON you should be reading 12v on the meter. IT DOES
- put the red lead of the tester to the positive (+) of the battery and the black lead to pin # 85 of the socket. When you press the starter button you should read 12v on your voltmeter.IT READS ABOUT +10.9

As a side note to all other virgins to electrical testing, your multimeter should be set to (ahem), DC. I am learning a LOT thanks to the kind folks here but don't assume I know anything about electrics!

In addition, I DO have 10.6V at one of the FI connections I tested when hitting the starter.

Very good. I think we are rapidly progressing to a resolution of your problem (or at least find its origin).

to resume:
Pump is OK (or at least it mechanically turns when it receives 12v)
Power to control the relay's coil is OK as you get power to the fuel injector. This also tells me that EFI and Ignition computers seem to be OK and the relay's coil is responding to the control signal from the ignition computer.
(10.9v is not too high, but you have to consider that the starter was energized when conducting the test and it drains the battery).

Next step is to check the power from the relay to fuse #6 (the one where you apply 12v to test the pump)
To do so, reconnect the relay.
Get a good ground on the black lead of you voltmeter and when pressing the starter button, touch each side of the fuse with the red lead. The expect reading should be theoretically 12v, but in practice it could be 10.9v.
Please report your finding.

Bert

Each side of fuse 6does read ~10.8-10.9 when tested.

Geoff

I am confused....

I would like you to redo another test for me:
Remove the FI relay again and get the voltage at pin #30 of the socket. This time, report what you get when pressing the starter button.

Pin #30 is getting ~10.6V when depressing starter button.

Geoff,

You are getting the same voltage at the pump as the voltage feeding the relay. As this point, the only idea that I have is to open the relay and look at the condition of the contacts.
The only 2 other devices controlled by the FI relay are the injectors and the temperature relay. it could be a slight chance that one of them is sucking the power, but I have my doubts.
I believe that even with 11 volts supply, the fuel pump should be turning.
I am a bit puzzled.
Let us know the condition of the relay's contacts.

Bert

How about swapping the fuel injection relay with the horn relay, I believe they are the same model of relay from memory. That will tell you quickly if the relay is ok. Checking on Max BMW for my bike shows the following
This relay is assigned to multiple uses. Including: fan, starting, load shed, horn, Motronic, and your fuel pump
Regards,
K-BIKE

According to the 1985 2 valves schematic, these 2 relays are different.
The horn relay is a single pole single trow (SPST) and the FI relay is a double pole single trow (DPST).

In the Max BMW Schematic which relay are we talking about one of the two 13's or the 15? http://www.maxbmwmotorcycles.com/fiche/DiagramsMain.aspx?vid=51752&rnd=03192010

Regards,
K-BIKE

Sorry to repeat myself with the same schematic, but if you look at the following picture, you will see the location and the number of pins in each relays.
The load shed relay and the horn relay can be swapped but the FI relay is different. I check my spare FI one and yes this is a DPST. The FI relay is #15 on the MaxBMW Website

At $13.96 from Real OEM or so each at least it will be a cheap fix if the relay is damaged.
Regards,
K-BIKE

The relays contacts all looked nice and shiny to me, couldn't see any breaks in the wire either. I'm going to get a new relay tomorrow, loathe to go down the shotgun path (bit of an exaggeration, I know) but it's only $13 as K-Bike pointed out. Will keep you all posted, thanks for everything so far!

Crushed. So, the FI relay is NOT the problem.

Is testing the the temperature relay my next step? How would I go about doing that?

Geoff

Maybe, let me think how you can conduct the next test.
During this time, could you boost you bike battery with your car battery?
It looks like the electronic function of the computers and sensors are working well but the battery is not able to deliver full power.
This is simple, just take some booster cables and connect both batteries together. Push the starter button and at the same time get the voltage at fuse #6.

Bert

I can but that's probably going to have to wait till the weekend, where I have the bike is not car accessible, have to push it up a hill which I can't do by myself.
Thought of the battery initially of course but didn't make any sense to me, given it quit while riding and I'm able to manually energise the fuel pump. Stranger things have happened though! Thanks Bert,
Geoff

Have you absolutely ruled out a bad connection at the plug between the fuel tank and the bike? That would stop it running if it was either open circuit or high resistance.
Regards,
K-BIKE

I was thinking the same. Have you confirmed that you have/dont have power at the plug where it fits into the pump? Mine is like that sometimes, no power to the pump, wiggle the wires and way it goes. I have the same bike as you...

Being able to manually energize the pump through that connection rules out any problems with it I think but I'll give it a "wiggle" when I get home tonight!

What's indicating here that it can't be a Hall sensor? Should I bother testing that or is there something saying it can't be that? Just asking cause I'm sure I had nearly the exact same symptoms on my R1100 twelve months ago and that turned out to be the problem.

Geoff

geoffallen50 wrote:What's indicating here that it can't be a Hall sensor? Should I bother testing that or is there something saying it can't be that? Just asking cause I'm sure I had nearly the exact same symptoms on my R1100 twelve months ago and that turned out to be the problem.

Geoff

This true that the Hall sensors can affect the fuel pump, but if you had a bad Hall, the FI relay would not be energized (and you would not read 10.9v at fuse #6).
Obviously, the ignition computer gets the signal from the Hall sensor because the FI relay is energized.

Here is a reminder of the starting sequence when you press the starter button:
The starter relay and Fuel Injection relay close, Hall sensors get power.
The FI relay energizes (+) the fuel pump, the idle switch, the injectors and the air flow meter.
The Jetronic receives (pin #4) the signal that the engine is starting and it sets itself on starting mode (enriching the air/fuel mixture)
Electronic ignition module pin # 9-10-14 send power to the ignition coil
Electronic ignition module pin #8 send engine rpm info to pin #1 of FI computer
Electronic ignition module pin #7 send ground to the coil of the FI relay as soon as the starter switch is depressed. The ground will stay on after the starter switch is released as long as the Electronic ignition module receives a signal from the Hall sensors.

Question:
you said that you cannot hear the pump...
Have you disconnected the pressure hose on the tank to confirm that no flow or pressure is coming out of the tank?
When you tested the power at fuse #6, did you measure it for 2 or 3 seconds. You should read 12v (in your case you get 10.9v) as long as the starter is turning.

Here is another point of concern:
The idle switch normally doesn't affects the fuel injection when the engine is starting but.... it is prone to get the water in when riding under very wet condition. it could be a slight chance of this switch being filled with water and draining the electrical system when trying to start the bike.
Just disconnect it. The engine should be able to run without it.

Ok, feel like we've made some progress but are still nowhere! Here's we are:
1. Fuel pump is now running, not whirring when ignition is turned on but is whirring/pumping when the starter is depressed and the fuel is reaching the fuel rail.
2. There is spark (I checked two)
3. Fuel does not appear to be reaching the spark plugs (dry)
4. Reading ~10.6v at one of the FI plugs when depressing the starter and have hooked it up to the car, little difference.
5. I did disconnect the idle switch, no difference.
6. Everything seems to be good except no fuel being injected into the chambers.

Very confused! What's my next step here?

Geoff

Hummmmm. I am relieved as I started to doubt about my troubleshouting skills. I was really confused.
Let me think overnight what will be the next cheapest and more efficient step into the troubleshooting of your problem. I tend to go with the pressure regulator but tomorrow morning may brings a better idea.

Bert

Bert - I think it's more likely the issues lie with my testing and diagnostic skills rather then your troubleshooting!

geoffallen50 wrote:Bert - I think it's more likely the issues lie with my testing and diagnostic skills rather then your troubleshooting!

No sweat! The outcome is to have your bike on the road again. It's a good exercise and reward to have a 'novice' being able to troubleshoot a problem. The resolution may help others too.

Geoff,

Now that we are certain that the pump is powering, I think at this point we have few options:

1) - You should check the fuel filter inside the tank. (I heard of some BMW one collapsing) You can replace it with an OEM or substitute it by the one of a 1996 Ford mustang GT (4.6l engine).
2) - remove the injector ramp to see if they spray. You will have to replace the O rings on the injectors before re-assembling.
3) - install an LED on the injector to monitor the pulse of the negative 12v.
4) - Install a gauge and measure the pressure. you can find how to install the gauge at the bottom of the FI troubleshooting page.

Have read through the thread, thought I'd chuck in my bit. My K (84 model) did the same thing, eventually traced it to the central pin on the fuel injection relay block connector, it had become dislodged from the connector block, and dropped down slightly, so even though the relay was securely mounted this pin didn't make contact meaning no pump, once pushed back into position all worked fine

HTH Garry

Same problem on my 2 K's. Seized fuel injectors were the culprits on both of mine (remember all that last year Bert?). Bought a refurbed set off ebay (the Ford ones) for $100 the first time, and a used set for $30 the second time. But first you need to confirm you have power at the injectors.

Now having read your first post on this thread, you were riding and it cut out, so I'm thinking it's not seized injectors (my bikes were sitting a long time before I got them).

club_c wrote:remember all that last year Bert?

Yes I remember. I didn't think that 4 injectors could be seized at the same time.
Mind you, I have been seized on the throne for the last 3 months. You never know, it could be the same problem

Crazy Frog wrote:

club_c wrote:remember all that last year Bert?

Yes I remember. I didn't think that 4 injectors could be seized at the same time.
Mind you, I have been seized on the throne for the last 3 months. You never know, it could be the same problem

lol soo funny

Here you can find Ford F150 injectors at a decent price.

This thread is fascinating you guys certainly know your stuff, but tell me am I so dense as to understand that certain FORD Injectors will fit a BMW K100.

BIG D

Big D, I'm having a look at Ford passenger vehicles (Australian 6 cylinder, EL model) and I have a mate that likes Volvos, to see if the injectors are similar and could possibly be used.

Thanks guys.
Some good info.

PS.
I see this is an old post however if Ford type fuel injectors are still in question I believe the older F350 type fit....

Update:-

Your side stand switch may have failed failed......

Quick ref for K1100 riders.

Even though an old thread I found it really informative and useful for chasing a fault on my K100.

GregC wrote:Even though an old thread I found it really informative and useful for chasing a fault on my K100.

Why don't you share the tale of your chase here, Greg, and tell us where it led you? It might inspire somebody to avoid setting a match to a stubborn K for insurance purposes.