BMW K bikes (Bricks)

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Tomso

Tomso
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I have been working through the troubleshooting guide and have 1 anomaly that I need help on. The troubleshooting guide states that the measurement at pin 1 for the FICU plug should read 10-20mv when the starter is cranking. I am getting about 450mv (it was 900 but reduced after cleaning the hall sensor plug???).
My big problem is that when cranking, the injectors pulse once or twice and then stay on. This immediately floods the engine which won’t start. Fuel leaks out of the exhaust just aft of the collector. Is this linked to the voltage reading at pin 1? Is the high voltage telling the controller that the engine is running and needs more fuel? Maybe the ignition controller is at fault?
I have checked everything else in the guide and all readings at the other pins are very near the guide’s recommendation. I have replaced the temperature sender (just in case) but no improvement. There is a problem with the throttle position sensor for full throttle setting (idle is OK) but I have disconnected the switch as I read that it should at least start OK without it. The airflow meter and air temperature sensor all OK (though the vane in the airflow meter was completely seized!)
I have a new fuel pump and replacement injectors, I have no means to check fuel pressure but fuel does return to the tank so I believe the regulator is doing it’s thing.
My bike is a project that I bought as a partly dismantled non runner and my initial aim is to get it started so I can assess before stripping it down. It apparently hasn’t run for many years and is a real mess! But I have hopes the the brick will live again!
I would be very grateful if someone in the know can confirm if the high voltage could be causing the FICU to flood fuel, or if either of the controllers or even the hall sensor are at fault?
Many thanks

    

2Back to top Go down   Voltage at Pin 1 Fuel injection controller plug. Empty No go Wed Aug 05, 2020 4:56 pm

daveyson

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Hi

There have been a few cases like this lately. Clean all the other connections too. That might do it.

If not, the earth signal to the injectors should be pulsing (the positive continuous) resulting in pulsing fuel to the cylinders. You might have constant earth.

A quick test. With a 12V computer safe test light clip on battery positive, and probe to one of the two sockets of an injector plug, the light should remain off while cranking. That will be the positive socket. With the probe in the other socket, the light should flash on and off while cranking.

If constantly on there might be a short on the earth wire, or a FICU problem. Unplug the computer and repeat the test, if the light is still on, I would guess the wiring is the problem. If off, replacing the computer might fix it.

I know that sounds funny, a short on an earth wire, but there it is, it's a problem in this case.

An excessive amount of fuel might have got past the rings and dumped in the sump during these gross flooding starting attempts.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Tomso

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I have been plugging an LED across the two terminals of one injector plug, is that incorrect? Should I see a pulsing light when cranking?

    

4Back to top Go down   Voltage at Pin 1 Fuel injection controller plug. Empty No go Wed Aug 05, 2020 6:14 pm

daveyson

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Yep, that should work too, as in Bert's guide. I haven't tried that though. I did it the other way, at idle, it flashed on and off rapidly.

Yep, it should pulse while cranking.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Tomso

Tomso
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Thanks. Mine pulses two, maybe three times then stays on. I have to let the FI relay reset to get the same result, or if I press the starter again before the FI relay clicks off, the LED stays on, doesn’t even pulse twice. Hope I have explained that OK.
Any ideas about the voltage reading at pin 1?

    

6Back to top Go down   Voltage at Pin 1 Fuel injection controller plug. Empty No go Thu Aug 06, 2020 5:09 am

daveyson

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I've not checked pin 1, I'd clean all connections and let them dry, then deoxit them and let them dry again. I'm purely guessing pin 1 reading might be high due to constant earth to the injectors if the problem remains after cleaning. The fuel injection relay should be constantly on.

I think of pin 1 as the RPM signal from the ICU. If the light is still constantly on with the FICU unplugged, I would be susso of the earth (yellow/grey) wire.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Tomso

Tomso
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Thanks again, I will try what you suggest.
What I meant about the FI relay is that when the starter is pressed, it activates, sending power to the injectors via fuse 6 (I understand). When the starter is released, after a second or two, the FI relay clicks again, cutting power power to the circuit.

    

8Back to top Go down   Voltage at Pin 1 Fuel injection controller plug. Empty No go Thu Aug 06, 2020 6:28 am

daveyson

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Yep that's normal. If the bike fails to start the fuel pump continues for a second or two after you release the start button. If you have a spare or know someone else with a brick, it would be a quick check to replace the FICU to see if it then starts.

I got a brick that had not been started in ten years.  It was not flooding but cutting out. I tried quite a few things to get it going, without luck, until I opened the FICU and cleaned both circuit board surfaces with electrical cleaner, then it started quick as a flash. Try the other stuff first tho, I guess.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Tomso

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Thanks, I have opened both units up just to check for any obvious water damage etc, but I was too nervous to delve any deeper in case I broke something I don't understand! 😉
Has luck would have it, my brother knows a guy with a K100 of similar vintage and this evening (UK time) I am going to take my units to try on his bike - didn't like to ask to borrow his and I wouldn't want to be responsible for messing his up if there is a shorting problem on mine!
I will update this later...

    

10Back to top Go down   Voltage at Pin 1 Fuel injection controller plug. Empty No go Thu Aug 06, 2020 6:59 am

daveyson

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Even better. I also remember a spot that needed a fresh dab of dielectric grease.

If the light remains on when unplugged, I'd look at the wiring before testing the computer.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Tomso

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OK, I’ll check with the plug out first.

    

Tomso

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Just checked the LED test with the FICU unplugged and it doesn’t light up at all.

The loom covering under the tank on my bike is a complete mess, most of the sheathing has rotted away so I won’t be surprised if there are some shorts going n somewhere. I have cleaned all the earth points and put some silicon grease on them but nothing gives my 100% confidence. I’ll keep plugging away at it and hopefully this evening can confirm the control units I have.Voltage at Pin 1 Fuel injection controller plug. 66216410

    

Point-Seven-five

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None of the five bricks that have taken up residence in my garage over the years has had rust on the frame tubes under the tank.  I would suspect corrosion in every connector on the bike and do a good cleaning with Deoxit to insure that everything is working correctly.  Wouldn't hurt to hit all the relay sockets in the relay box along with the fuse block.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

14Back to top Go down   Voltage at Pin 1 Fuel injection controller plug. Empty No go Thu Aug 06, 2020 10:08 am

daveyson

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It's just dawned on me that your pin 1 test would have been with the computer unplugged so a constant earth to injectors won't relate to the excessive volts. Maybe the iCU is a problem. Looking at Bert's troubleshooting starting chart, the airflow meter might be a problem. Maybe bring that with you too, and Bert's guide looking also at the flow chart


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Tomso

Tomso
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I am fairly happy with the airflow meter as all the readings corelate with the troubleshoot guide, but it's a good idea to take it - don't know cheeky I can be to dismantle the other bike though! 😅
I have printed the relevant tables of checks for both units and noted my readings to compare 😉

    

Tomso

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UPDATE - the FICU is at fault. We tried my unit on other bike and using a NOID, there were a couple of pulses and then it stayed on. Also the bike flooded and wouldn't start. After refitting the original, it was back working.
So now I need to find a replacement and get mine going 😊
Thanks for all the advice.

    

17Back to top Go down   Voltage at Pin 1 Fuel injection controller plug. Empty No go Thu Aug 06, 2020 7:19 pm

daveyson

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Hopefully the extra Voltage at pin 1 doesn't make the next FICU go bad. Maybe look inside it again especially where pin 1 comes in and goes. Dunno what NOID stands for.

I wonder if it's the ICU.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Point-Seven-five

Point-Seven-five
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Just curious, I seem to have missed what model brick you have.

I recall that there is an output transistor in the FICU that switches the injectors on and off.  In my time around here I think there have been a couple instances of that transistor failing.  Before I binned that FICU, I would take it to an electronics guy and see if he could change that transistor.  Even if you get a replacement, you could keep the old one as a spare.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

Laitch

Laitch
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@Tomso wrote:the FICU is at fault.
Pin #1 voltage of the fuel injection control unit is coming from Pin #8 of the ignition control unit. Substituting the ignition control unit for testing could verify its function, too. Did you try that?


__________________________________________________
1995 K75 81,000 miles
Voltage at Pin 1 Fuel injection controller plug. Usa-lo10
    

20Back to top Go down   Voltage at Pin 1 Fuel injection controller plug. Empty No go Fri Aug 07, 2020 1:17 am

daveyson

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Just noticed in Bert's ICU test it should be ~15mV when cranking and ~3.5V at idle, so hopefully it's just a bad FICU. Are you feeling lucky, I am but it's not my bike, or I'd probably chicken out.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Tomso

Tomso
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A NOID is a posh version of my cobbled together LED test light, garages and those with more knowlede than me use them 😉
My bike is a 1986 K100RS
I didn't test for voltage at pin 1 on the other bike and now wish I had! Maybe I could go back and try again before fitting a replacement FICU to mine...
I will make enquiries about getting someone to look at my unit but from conversations last night, such people are difficult to find around here (South Wales, UK)

    

Tomso

Tomso
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Has anyone ever checked the voltage at Pin 1 on the FICU? Just wondering id there are other bikes functioning perfectly well with a higher than expected reading? Be very useful for me to know...

    

Tomso

Tomso
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I have been thinking this over - it occupies most of my waking hours and quite a lot of time when I should be sleeping! - as pin 1 of the FCIU can receive around 3.5v at idle, would 0.9 voltage cause damage at startup? I obviously don’t understand how the internals work but if it can cope with 3.5 (and maybe high voltage at higher RPM, I don’t know) it surly can manage 0.9?

Any views?

    

24Back to top Go down   Voltage at Pin 1 Fuel injection controller plug. Empty No go Fri Aug 07, 2020 5:23 am

daveyson

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I don't understand either, but here's the thing, are you feeling lucky? That's the best I can offer.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Laitch

Laitch
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@Tomso wrote:I have been thinking this over - it occupies most of my waking hours and quite a lot of time when I should be sleeping! - as pin 1 of the FCIU can receive around 3.5v at idle, would 0.9 voltage cause damage at startup?Any views?
Here's my view. The problem is not the tolerance for voltage at Pin#1 of the fuel injection control unit. That pin receives two different signals—the startup signal enrichment signal (10–20mV) and the engine running signal (3.5V). The problem is the size of the startup enrichment signal being received at that pin. It seems like you intuitively understood my view of the root problem at the beginning of this thread before you even knew it was my view. Smile The level of mV being delivered from the ignition control unit Pin#8 to fuel injection control unit Pin#1 during startup enrichment mode (900mV) when the starter button is depressed is five times greater than specified and is causing increased injector opening time that results in enough excess fuel that it runs out the exhaust pipe.

When the starter button is released after the engine starts running, different enrichment mechanisms take over at higher voltage but that is only likely to happen when the injectors deliver the correct amount of fuel at startup to allow ignition—not flooding.

How's that for a view? Laughing


__________________________________________________
1995 K75 81,000 miles
Voltage at Pin 1 Fuel injection controller plug. Usa-lo10
    

Tomso

Tomso
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If that is the case, the excess voltage must have caused damage to the FICU because it was still 'full on' when plugged into the other bike.
Hmmm... It's going to be a risk when I plug the replacement unit in (ordered today).
Wish me luck then 😉

    

Laitch

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@Tomso wrote:If that is the case, the excess voltage must have caused damage to the FICU because it was still 'full on' when plugged into the other bike.
Hmmm... It's going to be a risk when I plug the replacement unit in (ordered today).
Wish me luck then 😉
My view is luck isn't part of this equation. Smile


__________________________________________________
1995 K75 81,000 miles
Voltage at Pin 1 Fuel injection controller plug. Usa-lo10
    

28Back to top Go down   Voltage at Pin 1 Fuel injection controller plug. Empty No go Sat Aug 08, 2020 3:34 am

daveyson

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I think I've confused myself by over thinking it, and maybe it's just a faulty FICU.

I just tested pin 1 a few times and got readings from 85 to 125, it was a bit of a lucky dip. I'm using an El cheapo multi meter, as a wild guess I'll say it's not accurate enough to read 20mV or 120mV,  they are both tiny amounts anyway. I'll also punt that your using an El cheapo, that could be the reason and you're good to go.

Good luck.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Tomso

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Thank you VERY much for tesing the voltage, it gives me a little more confidence!
I have borrowed the multimeter and dont know how accurate it is...

    

Tomso

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Quick update - new FICU arrived today (excellent service from Motorworks) plugged in and the bike started immediately! Plenty of running issues to sort but it seems sound.

Thanks to all for your help.

    

mike d

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cheers

Mike

    

32Back to top Go down   Voltage at Pin 1 Fuel injection controller plug. Empty No go Sat Aug 08, 2020 8:40 pm

daveyson

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Bonus.

The satisfaction of fixing it yourself is a good feeling, anyone can take it to a shop. That was a quick result too, some people spend months trying to get a non runner going. It's a bonus that bricks have so much metal that doesn't rust.

If the oil level is higher I'll guess some fuel has got in. Even if not higher I'd replace the oil anyway for piece of mind, especially if it's years old.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Tomso

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Thanks, yes it's a great feeling to sort something out yourself - with some helpful tips and advice of course 😉
I had changed the oil before tryimg to get it going as I had no way of knowing how old it was. I also intended it to be temporary as I will be draining it down again.

    

Dai

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Do the same with the coolant - effectively, flush it through.


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

Tomso

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Yes, I have a leaky radiator and the hoses are lined with sediment! Much to do!

    

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