BMW K bikes (Bricks)

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active member
active member
Good evening all (well its evening here in France)
I have inherited a bobber project 1987 K100 that will not run.

To summarise the earth trigger to the injectors is constant, so when the starter button is pressed it coughs splutters and immediately floods.

I have removed the injectors and can confirm this is true and petrol in the eye hurts!

The earth remains constant with the ECU unplugged.

Any ideas where to look next please?



Gold member
Gold member
As you seem to be aware, the injectors bank fire i.e. they are all wired together and fire together.

Fortunately for this problem, the injectors (and air flow meter and coolant temperature sensor and throttle position sensor) have a stand-alone loom that connects them to the ECU. Easy to identify and examine. This mini loom connects to the main loom via a 5 way connector. If you want to get an idea what you are looking for, hop on ebay and find a 'K100 Injector loom'.

Just checking (you may be new to Ks) the 2v K has 2 ECUs - one near the headstock for the ignition, and the larger alloy one under the seat for the injection.

The +ve supply to the injectors (and ECU etc.) comes from the FI relay. It is the green with red wiring within the FI loom. The switched -ve for the injectors is yellow with grey wiring in the same loom. The only components on the yellow-with-grey circuit are (or should be!) the injectors and the ECU. Nothing else.

Suggest you have a look at the loom for damage, or 'damage'. You may have a short to earth - look for an exposed yellow/grey wire.

Last edited by chris846 on Thu Feb 15, 2018 3:46 pm; edited 2 times in total (Reason for editing : forgot about the TPS - haven't got one!)


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