BMW R100GS electrical problem
 

Hi All,

Just got back from a trip to Mt Ararat with a couple of German mates one of which was riding a R100GS. On the way he stopped for a break and tried to restart the engine. The starter motor turned over but there was no spark at the plugs. Is there a known electrical part weakness that could be the likely cause of this problem? I'm trying to get some info because the bike is still stuck here in Turkey.

Many thanks,

Dicky

I know that the alternators on these bikes can be prone to problems.

It's quite common to have to take them apart and repair/replace bits, you start there.

David

I think the coil would be the first thing I would look at.
Check all the connections ar the coil.
The input is a small plug that powers both outputs that would stop both plugs from firing.

Check whether the coil is perfectly dry. If you're driving in the rain and the coil has a minute crack, you won't get a proper spark. The coils tend to crack after a while...

yes, i had this problem on my R65. wd40 and duct tape fixed it while on the road.check this first maybe.

The system consist of three parts that can be faulty (and all the wires and spark-plugs of-course)

For all the tests turn ignition on a few seconds before you do the test.

Various testpoints:

• Check kill-switch
• Green wire on coil: 12V
• Green/Blue wire (4/15) on ignition-module: 12V
• Brown wire (2/31) on ignition module: 0V

Coil:

• Remove the black wire
• Connect a lead to where the black wire was and short this to ground.
• There should be a spark every time, if not the coil is faulty

Ignition-module:

• Find the three-pin connector located underneath the starter cover (Brown, Blue Green/Yellow)
• Disconnect the plug
• Short the brown wire in the female plug to earth
• There should be a spark every time, if not the module is faulty
• Connect the plug.

Hallsensor:

• Put a voltmeter between 12V and the brown wire in the previous mentioned three-pin connector (the plug has to be connected).
• Rotate the engine and se that you get a reading in the area 6-12V every time the swingwheel passes the S-mark

I've never suffered this type of failure on an R80/but was told that the ignition module was the most prone to sudden failure, so I carry a spare (that I should test sometime). Coils breakdown and cause a misfire but rarely fail completely and whilst other hall effect trigers fail from time to time it's apparently very rare with the BMW one.

Excellent summary by Ali Baba covers all posibilities.
Just to add one point though. - just because there is indication of a spark at each correct firing point does not of itself ensure that the spark is powerful enough. I had such a problem once on my R80GS The motor refused to fire and only gave sporadic pops. . A shop which used to deal BMW could not trace the problem . Then at another official BMW service point with more diagnostic tools it was determined that the ignition coil was bad, the sparks were too weak to cross the gap in a cylinder under compression. Replacement of the coil with a new unit solved the problem .

Yes.
The ICU is broken. Renew.
This will work nicely:
Art.no.: 53-2600 = Bosch original on R80-100. Affordable - merely about 20,- EU -:)
Tändingssystem och Motorstyrning Audi 100 STYRENHET TÄNDNING - Biltema
Happen to me once - had tuned a R100. Just switched the ignition off. Checked all was ok. Turned the ignition back on again, but... the bike was now -dead- !
Took me about 8 h to figure-out what was wrong... it never dawned on me that the ICU would fail that suddenly...


OR - it may be, even though highly unlikely:


HT-lead failiure.
Do you have access to a multimeter-gauge?
Check secondary resistance by just pulling the sparkplugcaps off - measure across (cap to cap) - should read about 25kOhm.
Then pull the pluggs and measure them - they should read anything between 1-7kOhm.

It could also be a broken ground wire to the coils...

By the description you give I do not think the ITU have broken, but in case it has... expensive... Alibaba have given you a very good guide on how to locate the fault, what ever it may be.
Look up my thread " www.horizonsunlimited.com/hubb/bmw-tech/impulsgenerator-gone-bust-broken-itu-41532 " for further info on what to do if the ITU is broken.
Why I do not think it is broken is because you did not mention any of the cardinal symptoms of a bad hall-sensor, still it could be that the hallsensor just died on you...

Dear All,

Very many thanks for taking the time and trouble to answer my queery. I've got loads to work with and will keep you posted.

Best wishes,

Dicky

Dicky,
As I´m experiencing the same issuesbeing stranded :-) - what was your result?
Kind regards from Puerto Madryn, Argentina,
Synt

The German mate whose bike it was had a load of new stuff shipped over from Germany including the Hall sensor, a CDI unit and goodness knows what else. A friend of his put it all back together and the bike worked. Unfortunately I have no idea which single part was at fault. Sorry about the reply to your pm but I had completely forgotten about the incident. I sincerely hope that other, wiser, heads will be along soon to help you out.


Cheers,

Dicky

I have found the ICU to be very reliable, but I have had a failure with the insulation cracking on the old grey ignition coil. left me on the central reservation of the M25 at 1600 hrs Friday December evening. Oh Good.
Chile_bike is running a Ford Mondeo coil, the primary wired in series and the 2 secondries used to twin plug the beast, and it´s getting me fine to Ushuaia at the moment. The coil requires engineering to fit properly, if you jury-rig one of an old car - ENSURE THE COIL FRAME IS EARTHED....
If you are not twin plugged use just one primary and one secondry. Don´t run the coil without a load. I do know of a case with failed pickup coil, easily diagnosed with a meter, not so easily fixed. Don´t be frightened of electrics - it´s not wizardry.
sdk

I'm having a similar problem with my 94 gs pd. I can't get it to fire but it does have a spark. I'm wondering if the spark isn't strong enough.

Following the Clymer manual, I turned the key on and tested the voltage between the green wire and a ground and got 12(12.6) volts. The next step said to turn the key off, disconnect the black wire & connect a jumper from the wire to a ground and then turn the key on. The voltage should be within 1.5 volts of the original reading in the first step but I got a reading of .03 volts. If I turn the key off that jumps to 12 volts.

The way the troubleshooting directions are written once you get an unexpected result you should replace that component so I didn't test anything else to prevent a false positive.

Does this sound like a fault coil?

They're $260 from Max BMX (model 244 426) but I found one on EuroMotorElectrics.com for $165.

How old is the petrol? Have you dropped the float bowls and checked there is no water?

Mine needs full choke on nice fresh petrol to start easily. A faulty coil usually causes rough running but doesn't affect starting.