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1Back to top Go down   K75 running very rich Empty K75 running very rich Thu Oct 08, 2015 7:26 am

Grahame

Grahame
active member
active member
Hi I'm a new member with a problem K75RT.
The bike was running well until it stalled at a junction and wouldn't start again.
Can get the engine to run reluctantly but only with the throttle half open, lots of smoke. The engine stops if the revs drop below 3000, the bike is unridable.
The plugs are all identically black and sooty (not oily)
The indications are the engine is running very rich.
The injection control and ignition units are ok. The injectors are all ok. Examined the air flow meter and it is mechanically ok but haven't tested the air temperature sensor or potentiometer.
The fuel pump is running and there are no internal leaks within the tank pipework.
Suspect either the pressure relief valve on the fuel pump or the fuel pressure regulator (although, looking at a diagram of this unit it looks like it can only fail open which would give low pressure at the injectors) Anybody had a similar fault, I've looked back on the forum but can't match the symptoms exactly. Any advise welcome.


__________________________________________________
K75RT ABS Mystic Red 1995 7th owner
Engine No.753EA 0294
Chassis No. 03706294134
Mileage 24/12/18  40,399
    

2Back to top Go down   K75 running very rich Empty Re: K75 running very rich Thu Oct 08, 2015 7:43 am

mike d

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Life time member
If the water temperature sensor has failed, it can easily be telling the EC that the bike is extremely cold (all the time) so the mixture will be very rich.

Using a pressure gauge you can measure both the pump and regulator pressure.

If you are a member of the UK BMW club, they have a tool hire facility which includes the correct tools for measuring the pressure, plus many other special tools if required.

Mike

    

3Back to top Go down   K75 running very rich Empty Re: K75 running very rich Thu Oct 08, 2015 7:53 am

Grahame

Grahame
active member
active member
Thanks Mike,
I was thinking of joining the BMW owners club, I bought the bike of the northern area social secretary.

Grahame


__________________________________________________
K75RT ABS Mystic Red 1995 7th owner
Engine No.753EA 0294
Chassis No. 03706294134
Mileage 24/12/18  40,399
    

4Back to top Go down   K75 running very rich Empty Re: K75 running very rich Thu Oct 08, 2015 9:52 am

mike d

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Life time member
Life time member
Hi Grahame,

If you join the club now you will get the rest of this year and all of 2016 for the normal £30 joining fee. (was £27.00 but just gone up).

I am the tool hire secretary, so feel free to contact me for any tools etc.

Have a look at the downloads page of this very forum for some of the best diagnostic methods for the 2 valve models. Step by step instructions, and very good interactive diagrams.

Mike

    

5Back to top Go down   K75 running very rich Empty Re: K75 running very rich Thu Oct 08, 2015 9:54 am

Holister

Holister
Life time member
Life time member
@mike d wrote:If the water temperature sensor has failed, it can easily be telling the EC that the bike is extremely cold (all the time) so the mixture will be very rich.
+1  This is the likely problem but it may just be the sensor is not earthing due to corrosion. Try rigging a temporary earth to the sensor body and see if that makes a difference to the running.
Or, test for earthing with a DMM (engine off)


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
  K75 running very rich Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

6Back to top Go down   K75 running very rich Empty Re: K75 running very rich Thu Oct 08, 2015 10:01 am

Grahame

Grahame
active member
active member
Thanks, will check it out, but I think the bike would start as normal from cold and the problem only appear as it reached working temperature if it was the sensor.
The bike will barely start when cold and is difficult to keep running, the engine dies below 3000 revs, clouds of smoke.

Grahame


__________________________________________________
K75RT ABS Mystic Red 1995 7th owner
Engine No.753EA 0294
Chassis No. 03706294134
Mileage 24/12/18  40,399
    

7Back to top Go down   K75 running very rich Empty Re: K75 running very rich Thu Oct 08, 2015 10:09 am

Grahame

Grahame
active member
active member
@mike d wrote:Hi Grahame,

If you join the club now you will get the rest of this year and all of 2016 for the normal £30 joining fee. (was £27.00 but just gone up).

I am the tool hire secretary, so feel free to contact me for any tools etc.

Have a look at the downloads page of this very forum for some of the best diagnostic methods for the 2 valve models. Step by step instructions, and very good interactive diagrams.

Mike

Thanks Mike, I have learned all I know about fault finding from the technical support help on this site (not sure if that's a vote of confidence!)

Grahame


__________________________________________________
K75RT ABS Mystic Red 1995 7th owner
Engine No.753EA 0294
Chassis No. 03706294134
Mileage 24/12/18  40,399
    

8Back to top Go down   K75 running very rich Empty Re: K75 running very rich Thu Oct 08, 2015 10:15 am

mike d

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Life time member
Life time member
It's probably the best K series resource available K75 running very rich 112350

Mike

    

9Back to top Go down   K75 running very rich Empty Re: K75 running very rich Thu Oct 08, 2015 10:19 am

Holister

Holister
Life time member
Life time member
@Grahame wrote:Thanks, will check it out, but I think the bike would start as normal from cold and the problem only appear as it reached working temperature if it was the sensor.
The bike will barely start when cold and is difficult to keep running, the engine dies below 3000 revs, clouds of smoke.

Grahame
Not so. At 20°c the FICU should be reading about 2.5kΩ. If its not earthing then the FICU will see infinite resistance. I think charlie worked it out last week that the estimated temperature would be minus 200° or more
You can simply test by taking the FICU plug off and measuring the resistance from pin#10 to earth. Should be close to 2.5kΩ


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
  K75 running very rich Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

10Back to top Go down   K75 running very rich Empty Re: K75 running very rich Thu Oct 08, 2015 10:28 am

Grahame

Grahame
active member
active member
Kaptain Holister wrote:
@Grahame wrote:Thanks, will check it out, but I think the bike would start as normal from cold and the problem only appear as it reached working temperature if it was the sensor.
The bike will barely start when cold and is difficult to keep running, the engine dies below 3000 revs, clouds of smoke.

Grahame
Not so. At 20°c the FICU should be reading about 2.5kΩ. If its not earthing then the FICU will see infinite resistance. I think charlie worked it out last week that the estimated temperature would be minus 200° or more
You can simply test by taking the FICU plug off and measuring the resistance from pin#10 to earth. Should be close to 2.5kΩ
Ok thanks,
I'll check it out.


__________________________________________________
K75RT ABS Mystic Red 1995 7th owner
Engine No.753EA 0294
Chassis No. 03706294134
Mileage 24/12/18  40,399
    

11Back to top Go down   K75 running very rich Empty Re: K75 running very rich Thu Oct 08, 2015 10:41 am

Holister

Holister
Life time member
Life time member
Grahame, probably a good idea to have a good read of this...
troubleshooting starting
Instructions on testing sensor outputs at the FICU plug about ¾ way down.
This is the logical explanation and its easy to test. If not this then check fuel pressure.


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
  K75 running very rich Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

12Back to top Go down   K75 running very rich Empty Re: K75 running very rich Thu Oct 08, 2015 11:17 am

Grahame

Grahame
active member
active member
Kaptain Holister wrote:Grahame, probably a good idea to have a good read of this...
troubleshooting starting
Instructions on testing sensor outputs at the FICU plug about ¾ way down.
This is the logical explanation and its easy to test. If not this then check fuel pressure.

Many thanks, Its a brilliant resource clear and easy to understand.

Grahame


__________________________________________________
K75RT ABS Mystic Red 1995 7th owner
Engine No.753EA 0294
Chassis No. 03706294134
Mileage 24/12/18  40,399
    

13Back to top Go down   K75 running very rich Empty Re: K75 running very rich Thu Oct 08, 2015 6:28 pm

sidecar paul

sidecar paul
Life time member
Life time member
Grahame,
I've had a fuel pressure regulator fail where the internal valve came out of it's socket, blocking the output and causing excessive pressure at the injectors. 

 K75 running very rich Sam_0910

Paul


__________________________________________________
'84 K100RS (0014643) (owned since '85), 86 K100RS (0018891) with Martello sidecar (built as an outfit in '88),
'51 Vincent (since '67),'72 Montesa Cota (from new), '87 Honda RS125R NF4 (bought 2015) 
....No CARS never ever!
    

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