Author Topic: K75 Starting Issues.. Fuel Pump priming?  (Read 25400 times)

Offline Martin

  • ^ Quintessential Motobricker
  • Posts: 4437
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #25 on: October 03, 2017, 02:34:48 AM »
If the plugs are wet after trying to start it could be a faulty temperature sensor or temperature sensor connector.  Clean the connector with Deoxit and test the sensor. Type in temperature sensor testing lots of posts on how to do it. My K75 has had this happen twice due to it's location, water and road scum gets in causing bad connectivity. After cleaning smear heavy silicon grease around the connector it will help in stopping water and scum getting in.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline Martin

  • ^ Quintessential Motobricker
  • Posts: 4437
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #26 on: October 03, 2017, 02:56:50 AM »
A faulty temp sensor or connector tells the computer that the engine is cold and it needs more fuel. This then causes flooding, the bike can be started by removing the fuel pump fuse. With the fuse removed try and start the bike it should start on the residual fuel in the combustion chamber. As the residual fuel is used up the engine will start to die, as this happens quickly ram home the fuse, you will need to manipulate the throttle to keep the bike running. It helps to have two people to do this, one on the throttle and one to ram it home, the two times it has happened to me I have limped home using this method. If the engine stops you will have to restart the whole process a bit of throttle manipulation is required at traffic lights. When I first got my Brick I was told by an Ex BMW tech to clean all the electrical connectors on the bike with Deoxit, which I did but I also used dielectric or heavy silicone grease on them. I believe that the grease around the connectors stops water and air getting in that will eventually lead to bad connectivity. A lot of inmates disagree on the addition of the grease saying it can cause problems by insulating. I've had two electrical problems in twenty years because this connector was a pain to get at. Since I've done it I've had no problems.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline bluebossa

  • ^ Proficient Motobricker
  • Posts: 155
  • K75 and R65 Owner
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #27 on: October 03, 2017, 03:00:22 AM »
Thanks Martin, will give this line of enquiry a go!


The Bike has a new Fuel Pump - but is located in Dubai, which as you may know is hot - 40 degrees C in the day at the moment.
Bike ran fine for 50km - then decided it didn't want to start.


Fuel Pump and Fuel Pump is new...   will report
  • UK
  • K75 RT
Current Bikes: K75(RT) in the UK (06/91), R65
Former Bikes:  R850R, K1100RS, Dnepr MT10-36
BMW R65 and K75 Blog

Offline rbm

  • ^ Quintessential Motobricker
  • Posts: 2281
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #28 on: October 03, 2017, 10:02:02 AM »
Have you checked the temperature sensor in the radiator stand pipe for proper connection and operation?  If the wrong resistance is fed to the EFI, the bike will not start (the EFI will think the coolant is overheated).  Remember that there are two sensors in one package; one for the temp relay and one for the ICU.
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline bluebossa

  • ^ Proficient Motobricker
  • Posts: 155
  • K75 and R65 Owner
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #29 on: October 03, 2017, 11:32:48 AM »
Thanks Robert - that's on the to do list for tomorrow.


Can you just disconnect it and try starting?
  • UK
  • K75 RT
Current Bikes: K75(RT) in the UK (06/91), R65
Former Bikes:  R850R, K1100RS, Dnepr MT10-36
BMW R65 and K75 Blog

Offline Martin

  • ^ Quintessential Motobricker
  • Posts: 4437
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #30 on: October 03, 2017, 04:20:42 PM »
No it will think the bike is cold and flood the engine.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline Martin

  • ^ Quintessential Motobricker
  • Posts: 4437
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #31 on: October 03, 2017, 04:25:21 PM »
RBM what size resistor would you need to bridge the connector with to fool the ECU. I've done it with a variable resistor but would it be possible with one.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline bluebossa

  • ^ Proficient Motobricker
  • Posts: 155
  • K75 and R65 Owner
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #32 on: October 04, 2017, 08:48:02 AM »
So 2 of us for spent 5 hours today on the K75 trying to troubleshoot and get it going again today the best we had was a couple of misfires.
Fuel Injectors have been sonic cleaned, new O Rings - Pump is working

- This K75 really does just feel like a Brick now... still not running!


Here's what we did following your advice and reading various posts from others on here and elsewhere with Similar issues...


Took the Airbox off to get to the Temperature Sensor
Removed the Temp Sensor - cleaned terminals
Measured it's resistance at Room Temp - 1.8K Ohms
Measured it's resistance in Boiling Water - Minimum it would get too was around 400 Ohms - which according to others is too high?
So this is Suspect and could well be causing a rich Mixture perhaps?
Cleaned Airflow Meter - all looks good, springs and closure and free movement.


We then set about Sparks - which seemed to have gone missing on the first plug... towards the front of the Bike/Engine
We at first thought we had none, but removing all three showed 2 out of 3 had healthy sparks
Traced ICU cables from Coils all appear OK - ICU out, cleaned out terminals
Hall Sensor - was new - cleaned and refitted


At this point plugs 2 and 3 were firing - 1 was not.


So we switched plug leads to isolate the fault as best we could
All 3 Coils Fire - be switching leads
All 3 leads work... process of elimination
All 3 plugs work... process of elimination
Fuel is reaching plugs, petrol on plugs when removed and cleaned


Measured Voltage of Fully Charged and Nearly new Battery - 13.3 standing, 12.5 cranking
Tried a Booster Pack incase it was Starter Motor related - taking all the juice.


So we're thinking the firing is down to a faulty ICU, ECU or Hall Sensor?


What say ye oh Oracle...



  • UK
  • K75 RT
Current Bikes: K75(RT) in the UK (06/91), R65
Former Bikes:  R850R, K1100RS, Dnepr MT10-36
BMW R65 and K75 Blog

Offline Laitch

  • Faster than a speeding pullet
  • Administrator
  • ^ Quintessential Motobricker
  • Posts: 10120
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #33 on: October 04, 2017, 09:26:59 AM »
All 3 leads work... process of elimination
All 3 plugs work... process of elimination

Removed the Temp Sensor - cleaned terminals
Measured it's resistance at Room Temp - 1.8K Ohms
Measured it's resistance in Boiling Water - Minimum it would get too was around 400 Ohms - which according to others is too high?
So this is Suspect and could well be causing a rich Mixture perhaps?

What say ye oh Oracle...
I'd say an oracle isn't needed.

The K100 troubleshooting guide in the Repair Guidance section gives accurate information for diagnostic tests; most of them apply to K75 bikes.
This post gives accurate information for plug and coil wire layout.

Are you using either of those for guidance? Your responses don't quite indicate where you're getting information. :yes With what source are you comparing the range of the temp sensor. Who are the "others"? Are they the bald guys with the fedoras I saw on "Fringe"?

These starting problems often end with "Well, lookee there! I didn't get that plugged in right," although some of them end with "FS: Low mileage K-bike." :giggles
 
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles
I wept because I had no radials until I met a man who had no splines.
https://tinyurl.com/RillRider

Offline bluebossa

  • ^ Proficient Motobricker
  • Posts: 155
  • K75 and R65 Owner
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #34 on: October 04, 2017, 10:55:11 AM »
I'd say an oracle isn't needed.

The K100 troubleshooting guide in the Repair Guidance section gives accurate information for diagnostic tests; most of them apply to K75 bikes.
This post gives accurate information for plug and coil wire layout.

Are you using either of those for guidance? Your responses don't quite indicate where you're getting information. :yes With what source are you comparing the range of the temp sensor. Who are the "others"? Are they the bald guys with the fedoras I saw on "Fringe"?

These starting problems often end with "Well, lookee there! I didn't get that plugged in right," although some of them end with "FS: Low mileage K-bike." :giggles


Hey Laitch been following that guide extensively for several days now.. trying everything, but have no spare parts as we are in the middle of the desert..
Also researching other posts on this forum..


First thought it was fuelling, now have only 2 out of 3 sparks which the guide doesn't cover...

  • UK
  • K75 RT
Current Bikes: K75(RT) in the UK (06/91), R65
Former Bikes:  R850R, K1100RS, Dnepr MT10-36
BMW R65 and K75 Blog

Offline rbm

  • ^ Quintessential Motobricker
  • Posts: 2281
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #35 on: October 04, 2017, 11:37:22 AM »
I would suspect one of the Hall sensors at this point.  There are two sensors that determine 2 of the three spark timings based on crank position.  The third timing is interpolated by the ICU based on the other two.  If one sensor is bad or intermittent, it could cause the problem you see.  If you can get ahold of an oscilloscope to do some probing, it would help immensely.
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline bluebossa

  • ^ Proficient Motobricker
  • Posts: 155
  • K75 and R65 Owner
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #36 on: October 04, 2017, 12:35:28 PM »
I would suspect one of the Hall sensors at this point.  There are two sensors that determine 2 of the three spark timings based on crank position.  The third timing is interpolated by the ICU based on the other two.  If one sensor is bad or intermittent, it could cause the problem you see.  If you can get ahold of an oscilloscope to do some probing, it would help immensely.


Thanks RBM.
We took the cover off the hall sensor, looks brand new.
No oscilloscope.
Cleaned and replaced...


Could this also point to a bad ICU?


Planning to see if Bosch locally can test both ICU and ECU... Don't hold out much hope though due to our location.. They are off the bike ready to take in tomorrow. No availability in country of replacements.


We don't know of any other KBikes in the region...
  • UK
  • K75 RT
Current Bikes: K75(RT) in the UK (06/91), R65
Former Bikes:  R850R, K1100RS, Dnepr MT10-36
BMW R65 and K75 Blog

Offline rbm

  • ^ Quintessential Motobricker
  • Posts: 2281
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #37 on: October 04, 2017, 01:05:25 PM »
I think you should do more than a cursory inspection and clean of the Hall Sensors.  Test the electrical characteristics of the unit.  Looking visually new is not an indicator that the unit has electrically failed.  The probability of a failed ICU is remote.
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline bluebossa

  • ^ Proficient Motobricker
  • Posts: 155
  • K75 and R65 Owner
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #38 on: October 10, 2017, 08:34:36 AM »
Update, ordered a few spares from the UK. Planning a systematic swop out...
  • UK
  • K75 RT
Current Bikes: K75(RT) in the UK (06/91), R65
Former Bikes:  R850R, K1100RS, Dnepr MT10-36
BMW R65 and K75 Blog

Offline bluebossa

  • ^ Proficient Motobricker
  • Posts: 155
  • K75 and R65 Owner
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #39 on: October 11, 2017, 08:51:08 AM »
So, another 5 hours of troubleshooting today and still no joy...


Did this...


1. Replaced with recently arrived known good spares, ECU, Ignition Unit, Hall Effect Sensor, New Plugs
2. Tried starting with Tank Fuse out, TPS out
3. Coils off and all Earths cleaned
4. Starter Motor out and cleaned internally
5. Switched out Fuel Relay, Load Relay and Start Relay - no change


Sparks on 2/3 of the plugs - but weak and yellow.
We then tried a second Battery on Jump leads - and got 2 big blue sparks... still no start.


The Bike has a new Lithium 21 to 24 Amp Battery - any issues with these as I'm suspicious that it's not up to the job.


Next area of suspicion is Fuel Pressure which we can't check as we don't have a gauge.
Plugs get a bit of fuel but not washed with it... also Pump seems to be heard sometimes and not others.


Really need help now, and can only come up with the Lithium Battery and Fuel Pressure Regulator...


HELP !!!
  • UK
  • K75 RT
Current Bikes: K75(RT) in the UK (06/91), R65
Former Bikes:  R850R, K1100RS, Dnepr MT10-36
BMW R65 and K75 Blog

Offline Laitch

  • Faster than a speeding pullet
  • Administrator
  • ^ Quintessential Motobricker
  • Posts: 10120
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #40 on: October 11, 2017, 10:24:57 AM »
Sparks on 2/3 of the plugs - but weak and yellow.
We then tried a second Battery on Jump leads - and got 2 big blue sparks... still no start.
In Reply #32 you wrote that all plugs had good spark. Then you switched the plug leads and the status changed to two out of three working. In Reply #34 you wrote that still only two plugs had spark. That is still the case in your last post. How old are those plugs? I think you don't need to consider fuel pressure right now. What was the measurement used when you "re-gapped" the plugs.

Have you compared your plug layout and primary coil wire connections to those described and pictured at the link in Reply #33? Are they the same? If they aren't, a mix-up could be the source of your problem.

After verifying correct connections, you might remove the spark plug cover from the camshaft cover, charge up the battery, turn out the lights then crank the engine and check the plug leads and coils for random spark leakage. Decaying wire wires will provide a minor light-show.

Which type of Lithium battery are you using—ion or iron-phosphate? A new battery of the appropriate output should be up to the job for a while. Is this a different battery than the one that was charged at the beginning of this thread?

This seems to be leaning to the Well, lookee there side of the remedy list, which is a good thing. :giggles
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles
I wept because I had no radials until I met a man who had no splines.
https://tinyurl.com/RillRider

Offline bluebossa

  • ^ Proficient Motobricker
  • Posts: 155
  • K75 and R65 Owner
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #41 on: October 11, 2017, 10:37:01 AM »
Hi Laitch - thanks for sticking with us...


Battery is the same one from the start - nearly new and kept on charge, conditioning..
When we jumped it with another we got Blue sparks..


Yes - we had 3 sparks now we have 2.
Re order of the plugs, yep - we spent a good 30 minutes checking which coil to which plug... though order hadn't changed, though we think at times we are going mad with it now... so changed 1 and 3 around anyway in line with Haynes... it ran with original order fine...


We also had a BEP 3 which is a wiring module for the Cafe style Speedo - we took all wiring off to eliminate it from out inquiries.


Not tried the dark test - worth a go...
We've been thinking we should resort to an old fashioned Bump start to take the Starter out of the equation - only trouble is it's still 35 degrees here in Dubai !





  • UK
  • K75 RT
Current Bikes: K75(RT) in the UK (06/91), R65
Former Bikes:  R850R, K1100RS, Dnepr MT10-36
BMW R65 and K75 Blog

Offline bluebossa

  • ^ Proficient Motobricker
  • Posts: 155
  • K75 and R65 Owner
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #42 on: October 11, 2017, 10:40:15 AM »
Have you checked the temperature sensor in the radiator stand pipe for proper connection and operation?  If the wrong resistance is fed to the EFI, the bike will not start (the EFI will think the coolant is overheated).  Remember that there are two sensors in one package; one for the temp relay and one for the ICU.


Had a replacement/spare sensor - checked and compared resistance to one in the Bike - identical
  • UK
  • K75 RT
Current Bikes: K75(RT) in the UK (06/91), R65
Former Bikes:  R850R, K1100RS, Dnepr MT10-36
BMW R65 and K75 Blog

Offline bluebossa

  • ^ Proficient Motobricker
  • Posts: 155
  • K75 and R65 Owner
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #43 on: October 11, 2017, 10:48:57 AM »
Which type of Lithium battery are you using—ion or iron-phosphate?


Lithium Iron Phosphate (LiFePO4, LFE) is new generation Li-Ion rechargeable battery for high power applications
  • UK
  • K75 RT
Current Bikes: K75(RT) in the UK (06/91), R65
Former Bikes:  R850R, K1100RS, Dnepr MT10-36
BMW R65 and K75 Blog

Offline Laitch

  • Faster than a speeding pullet
  • Administrator
  • ^ Quintessential Motobricker
  • Posts: 10120
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #44 on: October 11, 2017, 10:52:54 AM »
- only trouble is it's still 35 degrees here in Dubai !
That means something a little different in Vermont, USA. It means put on the toque. :giggles
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles
I wept because I had no radials until I met a man who had no splines.
https://tinyurl.com/RillRider

Offline bluebossa

  • ^ Proficient Motobricker
  • Posts: 155
  • K75 and R65 Owner
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #45 on: October 11, 2017, 10:54:24 AM »
That means something a little different in Vermont, USA. It means put on the toque. :giggles


Whats a Toque?#


35 Degrees C today - bloomin Hot
  • UK
  • K75 RT
Current Bikes: K75(RT) in the UK (06/91), R65
Former Bikes:  R850R, K1100RS, Dnepr MT10-36
BMW R65 and K75 Blog

Offline The Mighty Gryphon

  • Administrator
  • ^ Quintessential Motobricker
  • Posts: 6617
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #46 on: October 11, 2017, 11:14:31 AM »
Canadien head gear.
  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline bluebossa

  • ^ Proficient Motobricker
  • Posts: 155
  • K75 and R65 Owner
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #47 on: October 11, 2017, 11:16:06 AM »
Canadien head gear.


Thanks!
2 Brits in Dubai here... one K75 still not starting...
  • UK
  • K75 RT
Current Bikes: K75(RT) in the UK (06/91), R65
Former Bikes:  R850R, K1100RS, Dnepr MT10-36
BMW R65 and K75 Blog

Offline bluebossa

  • ^ Proficient Motobricker
  • Posts: 155
  • K75 and R65 Owner
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #48 on: October 15, 2017, 10:09:06 AM »
So the latest installment... still not starting...
12V Lithium Charged and 12v Booster Attached

  • We got some Easy Start spray over the weekend - took out the Air Filter and gave it a dose
  • Cleaned Earths at Frame again
  • We took out the Injectors and watched the spray pattern/volocity - looks weak to us, mild squirting going on but nothing to compare it too except a Video on Youtbe, but all three are squirting fuel. We've ordered a Manometer to measure Fuel Pressure and Drop.
  • Started to measure voltage and resistance at the ICU Female Connector
  • Sparks wise we had nothing again, went back to the troubleshooting bible and measured a low voltage on Pin 2 of the ICU - the Hall sensor Feed - not 12v, more like 11v dropping to 8v when cranking which would point to issues energizing the Coils and wiring problems
  • So we fashioned a direct permanent 12v direct to the Hall Sensor plug - 2/3 sparks came back.
In all we had it firing and popping, breifly - but only we suspect on 2/3 cylinders and only consuming Fast Start not Petrol/Gas.

Saw an online video about squirting 10ml of Oil into Each Cylinder - to get it too start, but not tried this...?
Anyone one know if this is real - Engine Oil?


In addition we've swopped out and gone back to original after no change most of the major ignition units including ICU, ECU, Hall Sensor, New Plugs, Fuel Relay, Checked all Fuses, Starter Relay, Compared Water Temp Sensor to known good for resistance = identical.

So we still have what seems like Electrical gremlins - low Voltage/bad Earth to Hall Sensor - New Earth strap ordered.
Suspected low Fuel pressure - but unconfirmed pointing at Pump or Pressure Regulator?


As ever, ideas and further lines of enquiry welcomed - the Bike is still driving us both mad..
We've also used all the other tricks learnt to date - taking the Pump Fuse out and putting it back in, taking the TPS connector on and off.

With Easy start - it needed the Choke out to part fire.. and it only ran rough for a few seconds, pointing at Fuelling issues we think. Pump is activating and all relays are kicking in.

Can anyone confirm the Fuel Pump Pressure on a K75 for when we get the Meter?
K100 Guide says 65 PSI from Pump dropping to 35 PSI at the regulator - is this the same for the K75?
Can anyone give a definitive on why we are only seeing 2 sparks out of 3 - what does that point too?


Thanks again for bearing with this sorry tale...
  • UK
  • K75 RT
Current Bikes: K75(RT) in the UK (06/91), R65
Former Bikes:  R850R, K1100RS, Dnepr MT10-36
BMW R65 and K75 Blog

Offline Laitch

  • Faster than a speeding pullet
  • Administrator
  • ^ Quintessential Motobricker
  • Posts: 10120
Re: K75 Starting Issues.. Fuel Pump priming?
« Reply #49 on: October 15, 2017, 10:37:43 AM »
So the latest installment... still not starting..can anyone confirm . . .
The fuel pressure is correct.
Did you do the dark room crank looking for sparking wires? 2/3 plugs is pointing to your ignition system.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles
I wept because I had no radials until I met a man who had no splines.
https://tinyurl.com/RillRider

Tags: