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.

Gas has been replaced and it won't even fire with ether sprayed in the airbox and plugs are wet when immediately removed. I have clear fuel line and you can see fuel in the line. I dropped the bowls a couple times when this first started (I could get it started but not idle) and there was always fuel in them. Now it won't fire at all.

Don't fixate on teh igntion system.
 

Once you have spark I'd be checking

Fuel? Are the spark plugs wet after trying to start it? Too wet = flooding. Too dry = no choke or no fuel in the float bowel.

Compression? Are the valve clearances set correctly? If too tight then the bike will be very hard to start. In particular check the exhaust.

I don't see how it could be fuel since I couldn't even get it to fire when I sprayed ether in the airbox and the plugs were wet immediately after.

It will be the hall sensor, had the same problem with my R1150GS! Expensive but easy to fix.

Remember these bikes are 20 to 25yrs old now. When I restored my 1989 R100GS-PD last year I was shocked at the state of the electrical connections with the build up of corrosion. How the bike worked in that state, I don't know. I cleaned each and every connection using a needle file and steel wool, and sprayed the connections with cleaners, but was only partially successful. In the end an electrician friend replaced the BMW connector blocks with new bullet connectors and shrink wrapped them. Everything then worked again.

Wouldn't a failed Hall Sensor cause it to not have a spark at all? When plug is out or with a sensor I can see both are sparking.

Well, if the timing isn't a mile off - and there is no reason why that should change anyway then it can only be a weak spark (but you would expect at least some sign of firing when you crank it) OR it's compression related such as valve clearances too tight or some sort of valve timing issue. Does it sound 'normal' when you crank it over?

How would the timing be off? Isn't the timing just the sensor by the bean can that senses the spot on the crank shaft and sends the signal to the ITU?

I threw on a new coil hoping the spark wasn't powerful enough but that didn't work.


I guess my next step is to reconfirm the valve clearance which I set a couple weeks ago and then check the compression.

It sounds like it always has when cranking.

It does fire a little but won't really start.

So did mine! Its easy to pull the front cover off and have a look!

I did have a look and it all looked good. Is there a way to test it? What am I looking for?

BMW R100GS electrical problem
 

Well after reading the clymer instructions again last night I believe the coil test that failed was checking for proper voltage from the battery. Now I need to start tracing wires....

The bean can can be rotated to set the timing - it could have moved also the bean can bob weights could be stuck in the fully advanced position.

The ignition amplifier could be faulty in some way causing a weak spark.

I'm sure you've already checked/changed plugs, caps and HT leads.

Is that something that would happen while riding? My problems started while riding when it stopped wanting to idle and eventually got to where it won't really start.

The weights could stick in the fully advanced position whilst riding - It's not something I have experience of but I would say it's worth checking.

The amplifier (ICU) is pretty reliable but could develop a fault at any time, again if you can swap one out from a known good bike it's worth trying.

Well I did order a new ICU when I ordered the coil a couple weeks ago. I'll try to check that tonight.

I had a similar failure a couple of weeks ago. At first i thought the coils were at fault, as there was a huge crack. So i changed that. Still no spark. Then i did some multimeter testing and guessed that the ICU was faulty. Changed that to the latest version, and got a spark. The bike started but ran rough. It wouldn't restart once warm. I remembered reading somewhere that a bad voltage regulator could cause that, so i changed it (from the high output version back to the standard). It then started and runs perfectly.

The coils that cracked and the regulator were only a couple of years old.

And then last week a friend's R80 G/S did exactly the same. He traced the fault to the ICU, fitted my old ICU (the one that i thought had broken) and now it run perfectly again.

Airhead electrics are a dark art. My friend is an engineering professor, but even so, still found it all quite mysterious.

Yet another cracked Bosch ignition coil.

https://pbs.twimg.com/media/BoRL2WJCcAE_Uy7.jpg

Mine has spark (and even more spark now with the new upgraded ICU that shocked me while holding the plug by the cap as I found out a couple days ago) but still won't run. I'm going to check the compression this weekend and if that's good then I guess it's a timing issue.

Would be interested to know if you've solved the problem.

No, I'm going to check the compression soon. I have a tester, I just have to read up on how to do it. I guess just ground the plug to the cylinder, open the throttle and crank it.

That should do it. If it's low squirt a little oil into the cylinder and re-run. If it improves it implies rings rather than valves.

Did the compression check last night and I got 75 psi on the right cylinder and 80 on the left. I popped a carb off and squirted a little starter fluid in the manifold and it wouldn't even fire. I have replaced the coil & ICU and I can see the plug sparking so I'm thinking it has to be out of time, right? I'll look into checking this.

Anybody have a spare bean can laying around that I can borrow?

The timing has to be very wrong if it's not able to ignite starter-fluid! On the first page in this thread I've described how to check timing with a volt-meter.

It's harder to ignite under compression. I would have tried starter-liquid with the carbs still on the bike and with the throttle closed.
Worn plug-cables will give the same symptoms, you should also check the ground-wire for the ECU (separate wire that goes to the left bolt for the upper engine-cover). Have you changed the plugs?

I've also tried squirting starter fluid into the airbox a few times with no luck. That's why I tried with the carb off.

Both plug cables are registering 5kOhms and I have changed the plugs. I'll check the ECU ground wire and timing soon.

Based on the instructions in the Clymer for testing the electrical components I think that I could possibly have a bad connection between the ignition switch (key) and the on/off selector but I'd like to test that before going through the wiring harness. It has an aftermarket enduro computer on it with the key attached so I'm not sure where it's wired in. Could I run a jumper from the battery to the green wire on the coil to gaurantee that a good 12V is supplied?

For test purposes: Yes

When you try to connect the green wire directly to the battery it will also power up the ICU (and more). Some ICU's turn off after a while (30sec?) when the engine is not running. So you have to connect the wire directly before you attempt to start.
When doing this remember that you might have to remove the wire to stop the engine.

Should I remove the green wire and hook the jumper up to the coil's spade or just attach it to the connector? Can I use a thin wire or will the power going through require a thicker wire? My jumpers are really thin.

If you leave the green wire in place you will also power up the ICU which might be a good thing. If it starts with the green wire in place you can try to remove it to see if it still starts.

Most wires will work. If the wire is to thin it will be hot, but then you can use 2 or 3 in parallel.

Update: jumped a wire to the coil's green wire and it still wouldn't fire. I did notice puffs of air coming out of the left side valve cover so I guess that seal is bad but is it normal for air "compressions" to come from above the head?

Something seriously amiss here:(

Update: Finally took the bike to the shop after realizing that I don't have time anymore to tinker in the garage due to family obligations.

$70 later she's running as good as ever (since I brought her home). The problem was the timing was off. I should have asked the mechanic how that happened in the first place.

Props to Mike at MPH Cycles on the west side of Houston.