Motronic 2.4, 2004 R1100S comms trouble

[HECOJohn]

Schuppi, thanks.

All,

I've checked every conductor, ground, and connector.  All electrons flowing to their designed destinations except where it comes to the fuel pump relay control coil through the ECU to ground.  If your following along in the drawing, when the key is on AND the handlebar switch is on, electrons DO flow from termination 3 on the key switch to plug 15u, through the handlebar switch, through the fuel pump relay coil and I get the proper voltage at the ECU, termination 16 (EKR).  Now, this needs to connect to ground through the ECU to complete the control circuit in the fuel pump relay, pulling in the contact which then transfers electrons from F4 to the fuel pump, injectors, oxygen sensor, and tank breather.

Well, that's what is not happening.  For full disclosure, the fuel tank is off and that connector is disconnected.  Following the diagram, this should make no difference but, there could be magic in the ECU that I'm not able to see schematically.

Anyone know if there is a feedback to the ECU which tells the fuel pump relay to pull in IF... (all connections are made for example)?

Warning!  The excessive heat I described earlier may have been caused by a poor ground between ECU to chassis.  Though I had a jumper between chassis, designed ground terminal, and the ECU, screwing it in place seems to have eliminated the overheating.  I don't know how but, observation is king here.

I'm keeping this conversation going here because underneath all of this, there is still incorrect communication with the GS911.

Thanks,
John

[schuppi]

[quote
Anyone know if there is a feedback to the ECU which tells the fuel pump relay to pull in IF... (all connections are made for example)?
[/quote]

That's a safety set-up. if there's no signal from the timing sensors ( HES) -( engine is not running ), then there is no ground signal from the ECU to the fuel pump relay on "85". Cablecolour blue-grey on contact 16 ECU.

[HECOJohn]

Good morning,

I've found a thread on the Pelican Parts forum with an answer.  Though it may be tedious to track down, it is the same symptoms and troubleshooting results I've had.  Seems this user after getting to where I'm at, took his bike to a dealer tech.  They found a ground pin from the ECU to chassis not connected properly.  Up and running.

Since I've tested continuity of all grounds and found them good, I will jump the leads directly to ground insuring enough current carrying capability to get the job done on each.

http://forums.pelicanparts.com/bmw-r1100s-r1200s-tech-forum/281844-99-r1100s-no-fuel-pump-action-no-ticky-no-laundry.html

I will get back to you when I have a result and hopefully get back to the original thread.  Communication trouble with R1100S, or not.

John

[HECOJohn]

New information.  Not good but new.  I've checked all ground terminations and shorted the fuel pump B+ relay circuit at the ECU plug directly to the ground terminations on the ECU plug (simulating current flow through the ECU) insuring all conductors can carry the right current.  No problem.  Everything comes to life as designed.  Plugging the ECU back in, it all goes back to sleep.

Strange, voltage to the HES from the ECU terminal 4 is 3.6 with 12VDC at the battery AND i'n not getting a complete circuit through the ECU.  This voltage is consistent with VBAT on GS911.  I'm getting frustrated but, still think I have an illusive ground problem.

John

[HECOJohn]

Okay, it's official.  I've been sitting at a desk too long.  Remember in school when they taught you that both sides of the equation must balance.  I was so focused on the negative side I didn't look at the positive side.  Further testing on the B+ to the fuse block exposed a a section of insulation had been rubbed off right around where a tie wrap holds the loom to the front sub-frame where the left side relay box is. 

So, to answer my own questions:

1.  Does the GS911 take VBAT from terminal 6 on the diagnostic plug.  Yes.  Thanks Brent for verifying this.
2.  When VBAT is < than battery voltage and the GS911 is not reporting, be suspicious.
3.  Intermittent bike operation is NOT always the HES.
4.  I agree, the ECU pretty tough.

All working as expected now.  Thank all of you for helping me out with this issue.

John

[schuppi]

Congratulations John
and now...... on the road again.