K75 won't start from cold..?

[Londonrider]

Hi all.
Can anyone advise me, please?
I have a K75s that starts and runs fine when warm, but won't start from cold.
The starter and the fuel pump just spin over, but she won't fire?

I've found that if I crank the throttle back to max when it's cold, and then turn it over, it will just about go, but this is obviously not ideal.
Anyone come acrosss this fault?
 

[Scott_]

Well, a few things come to my mind.

Is this a daily ride? or has it been setting a while?

When was the last time the fuel filter was changed.

TPS sensor acting up.

Air Flow Meter stuck/or not giving proper signal.

[Londonrider]

It's a daily ride.
New fuel filter less than six months ago.
TPS seems to click in and out ok?

Is there some sort of temperature control on the fuel injection?

[TimTyler]

I have a K75s that starts and runs fine when warm, but won't start from cold.

So what do you do, just leave it running 24/7?  I feel like part of the story is missing.

Remove a spark plug, test for spark and smell for fuel in the cylinder.

Did the problem start overnight or has it been getting worse over time?

[cowpieapex]

I want to bump this thread as I came to it in three different searches.

In my case i have a K75 I retrieved from a back yard (northern rain forest) where it had been abandon for a year.
This bike started readily after charging the battery fully and because the oil showed every clue of having been installed in Bavaria I shortly also replaced the air filter which also looked very bad (like an ant farm). I  installed a K&N filter. I know there is broad controversy around these filters but have used them satisfactorily for 30 years on everything from a Harley Streetrod to a Porsche 944.
On the 86 K75C, the quick trouble free starting was transformed to prolonged cranking and stumbling sessions. Once started the bike performed brilliantly and warm starts were trouble free.
I would presume the difficulty is associated with a reduction in vacuum through the throttle bodies.
I've received my  BMW oem filter (along with a new starter relay..!..  :bang-head:) but I think there are likely secondary issue that I should address.
I am reassured that many of the K bike veterans here  have multiple high mileage machines . Does anyone want to weigh in on where to go in renovating this neglected 70K mile machine?

[The Mighty Gryphon]

Not really the right thread, but since it's pretty old, I'll bite.

Start with all the fluids: Engine ouil, brakes, forks, transmission, final drive.  Drain and refill the cooling system.   Pull the transmission and clean and lube the clutch splines.  Ditto the drive shaft splines.  Reassemble everything with copper anti-seize and torque to the proper values.  Adjust the clutch, replace the brake pads(cheap carbon kevlar pads off eBay are fine). 

Clean as many of the electrical connections as you can with DeOxit.

Change the fuel filter, fuel lines and check all the rubber bits for cracks and leaks.  Run a couple tanks of gas with Seafoam or Techron through it and then balance the throttle bodies.

Check the brake lines for cracks or swelling when the brakes are applied.  They may need replacing. 

Then go out and get some yee-haw.

[cowpieapex]

Thanks for the rapid reply.
Specific to this thread, I'm seeking ideas pertaining to the sudden cold start problem.
I'm pleased to note I have covered 90% of the details in your excellent list. This is my 4th BMW though it is my latest model year and first Brick.

[Laitch]

Which tasks in Gryph's list comprise the 10% you haven't done yet, cowp?

[cowpieapex]

I've yet to change the fuel filter though, on examination the interior of the tank looks pretty good.
And I haven't opened up the drive line, but all lubricants have been changed (motor oil twice).
I suspect compromised intake sealing may have contributed to a low vacuum issue along with the use of a low drag air filter in place of the moldy caked-up one I removed, so rubber bits are at the top of my list.
In light of the remarkable improvement in performance the K&N filter produced does my speculation concerning plenum vacuum seem to be a realistic explanation for difficult starting ?

[johnny]

ether... worked for richard pryor...



j o

[cowpieapex]

The pain isn't THAT bad!

[rbm]

Problems cold starting could be related to the air temperature sensor (ATS) in the mass airflow sensor (MAS) since you were working in that area with the filter, or it could be related to the coolant temperature sensor (CTS) in the stand pipe on the front left of the block.

Use the instructions HERE to test the CTS to confirm or eliminate it as a possible cause of the cold start problems.  Also, clean the connection to the MAS to ensure the ATS is sending the proper information to the engine control unit (ECU).  You might also want to clean the connections to the ECU and reseat the connector to make sure it is not contributing to your problem.

[cowpieapex]

Thanks Robert!
This looks like a good start on chasing this gremlin.