BMW K bikes (Bricks)

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1Back to top Go down    Fuel injection problems on Tue Jun 07, 2016 9:08 am


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Just joined here yesterday so feel a bit guilty about asking for advice already but here we go as I'm just hitting me head against a wall right now...well it feels like it...

I've an '84 k100 that I bought as a part project and supposedly a runner....wish I'd checked first. Anyway, I digress, after sorting out what I thought was the problems for it not starting, a k75 broken fuel pump now replaced with a new proper k100 pump, replaced filters, cleaned out the fuel return line as the one way valve going into the tank was rusted shut. How rust got into the aluminium tank I'm not sure but there it was. Checked the injectors and they're good, charged up the battery, hit the starter and....and the fuel pump works, the engine turns over, then every now and again it runs but literally a second later it cuts out completely. Put the choke on and it just turns over without even trying to start. Had the plugs out and they spark lovely, took the injector rail off with the injectors in situ to see if it's delivering petrol ok and here lies the problem, if I hit the starter button then release it a second or two later the injectors squirt nicely once but that's it, hence starting but cutting out straight away, however if I keep my finger on the starter button they don't work at all.
I've worked on a few bikes over the years but never a bmw or a bike with fuel injection so my head is totally baffled as to what this might be.
If anyone could point me in the right direction of what to check I'd be really grateful or if you've had a similar problem then I'd really love to hear about what it was.
Many thanks, paul.


2Back to top Go down    Re: Fuel injection problems on Tue Jun 07, 2016 10:10 am


under seat computer plug come apart slightly ?

cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O

3Back to top Go down    Re: Fuel injection problems on Tue Jun 07, 2016 10:43 am

RicK G

Once you release the start button the pump will only run for 1.5 seconds unless the computer is getting a signal from the ignition sensors. If you hold the start button down the injectors will or should fire at every revolution of the engine.
The choke is only a fast idle and does not enrich the mixture the ECU does that if necessary according to ambient temperature.
Check the fuel pressure regulator is working correctly, we have seen a few fail recently.

If everything seems under control then you aint goin fast enough:- Mario Andretti
Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now

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