1997 R850R -- Possible Battery Failure?

[senseamidmadness]

The latest in the saga of the Saddest R850R You Ever Did See. Yet more disappointment!

A couple of days ago I put in the third replacement fuel pump I've had in this bike, after the quick-fix used OEM one I had started doing its best impression of a table saw cutting wood. This new pump is a Quantum. I replaced the fuel filter with a proper Mahle one just in case and put a new intake screen in, which is a very good design and shouldn't let any gunk into the pump from the filthy fuel tank this bike has. (A replacement fuel tank is planned in the future but man are they expensive and hard to find for this bike.)

I had left the battery on a 2-amp smart charger for about a day just two days prior to this. It's a Bikemaster AGM Platinum battery. I purchased one new in March and had it replaced under warranty; the current battery in the bike is the one I received as a warranty replacement. It was brand new in May.

Immediately after, I tried to start the bike, and it wouldn't run. I could hear the fuel pump priming just fine, and for the first few tries the engine did crank, but it sounded slower than I thought it would be. I thought the battery would be fully charged so this didn't seem right.

Tried to crank it a few times, with no start, and it got slower and slower. Eventually it just wouldn't turn at all -- the fuel pump primes, the starter solenoid clicks and the headlight turns off and the gauge cluster lights go dim when I hit the starter button, but the engine doesn't move.

Left it on the charger again for a full day. Checked it out briefly yesterday. The charger said "battery is fully charged" but got the exact same result when I hit the starter button -- click, no crank.

Is it a busted battery? Should I cut my losses and just buy a proper Motobatt without trying to get a warranty replacement? Should I be concerned about the starter?

 

[69zeff65]

A few things to check

Check the grounds, check the HES wiring but most important check your starter for AMP draw. The oilheads are notorious for starter problems with regards to housing magnets coming loose and jamming up the armature.

 

[pglaves]

Check the grounds, check the HES wiring but most important check your starter for AMP draw. The oilheads are notorious for starter problems with regards to housing magnets coming loose and jamming up the armature.

I agree. These are classic symptoms of starter drag.

 

[jsouth]

Check the grounds, check the HES wiring but most important check your starter for AMP draw. The oilheads are notorious for starter problems with regards to housing magnets coming loose and jamming up the armature.

I bought two batteries before resolving the issue this way! Check starter!

 

[senseamidmadness]

Thanks for the advice, folks. I'll be ordering a replacement starter shortly and will take the old one apart to see what's busted. Hopefully I remember to post pictures.

Edit: Wanted to mention that the Hall wiring has already been dealt with on this bike, as well as quite a few other things...but it's still not reliable! Yuck!

 

[miseenscene]

Good day,

I am sorry to hear of your ongoing woes with the R850R. Mine over here in Chattanooga is a great and reliable ride. I suppose the abuse the cycle suffered under previous ownership is to blame; if you ever are in the area and want to ride a 850 in good shape for comparison, please contact me.

Good luck in the ongoing saga.

Be well, ride safely.
RK

Thanks for the advice, folks. I'll be ordering a replacement starter shortly and will take the old one apart to see what's busted. Hopefully I remember to post pictures.

Edit: Wanted to mention that the Hall wiring has already been dealt with on this bike, as well as quite a few other things...but it's still not reliable! Yuck!

 

[senseamidmadness]

My exasperation with this machine continues and increases.

The new starter works great. Bike cranks strongly with a charged battery. Buuuut we're back to the "not starting" issue I had before, in the other thread. This time the gremlin has jumped to another system.

I have fuel pump action, sufficient fuel pressure, and the Hall sensor wiring has been dealt with just recently. A couple weeks ago I did a valve adjustment and careful throttle body sync. I know my compression is good and my air filter has less than 200 miles on it. What I suddenly don't have is spark. It's completely disappeared from both cylinders.

The bike ran before I did the most recent fuel pump replacement and ignition coil change and I think the coil change is the problem. I think I messed up in some way and did something that scared the Motronic into not providing spark signal.

I had bought a replacement used coil from a low-mileage 2001 R1100RL and it has the same exact part number. I was replacing my old one because this bike was still misfiring every so often on a hot idle and when I got the old coil out I observed that the plastic casing was cracking and expanding away from the epoxy fill, so it definitely needed to be changed.

For fun I tested both coils before I put the "new" one in. They both tested at 0.3-0.5 ohms on the primary at that point and around 7k ohms on the secondary. From the info I was able to find those numbers are perfectly normal.

I wasn't as careful as I should have been when I swapped the "new" coil in -- the ignition was off, but I did not disconnect the battery. Would that fry a coil's primary circuit? Would it fry the Motronic's ignition circuit? Would it break the Hall sensor? I'm doubtful, but I honestly don't know.

As far as I remember I didn't do anything extra stupid like crank the bike without the spark plug boots plugged in or anything like that.

Fast forward to now: both coils are testing at 0 ohms on the primary circuit and around 7k ohms on the secondary circuit. That first number seems like a short and I rechecked it on both coils several times with no change. I also tested the resistance between the ends of both original spark plug wires with the old coil mounted to the bike and got around 19k ohms. From what I read that is within a normal range.

I cranked the bike with a multimeter connected to both leads of the ignition coil primary plug and got nothing but the fluctuating voltage that appeared when I turned the ignition on, jumping around from about .3 to .8 volts irregularly. I should be getting pulses of 12 volts every time it turns over, right?

I also pulled fuse 5 for about 8 minutes to try resetting the Motronic and tried again; no change, still no spark.

Also tried removing and re-timing the alternator pulley just in case it had slipped or something. No luck.

What did I break when I swapped the coil out? Am I or this bike just cursed?

 

[pauls1150]

Swapping the coil with the key off will Not hurt Anything.

Multimeters (whether analog or digital) do not have a quick-enough Response time to show the primary triggering voltage; they will "average" whatever they sample in a very short period of time. (This does not include the specifically "sample-and-hold types", which require extra time to accumulate a reading.) You need an oscilloscope to actually see the pulses' true amplitude. But at least the multimeter will show the "signs of life" there.

The difference between "zero" ohms and "0.5" ohms could easily be directly caused by the test leads to the meter and how tightly you're making contact.

Used coils are not a great way to determine if an older coil is bad... the used one may also have an intermittent problem. Unfortunately, new coils are expensive for whatcha get... BMW did not always update the part numbers when they "improved" something.

I don't know if the primary side of these coils actually gets 12 volts, since although one side of coil goes to +12 (only when the key is On), the other side goes to the computer which internally completes the circuit at the "right" time, so that's going to have some small insertion loss (due to the electronic "gate").

 

[jagarra]

I was looking at a schematic for your bike, the green wire going to the coils is tied to the ignition switch, which is tied to 12v when on. So you should see 12v on the green wire when ignition is on. If you don't, there was an issue of harness being clamped too tight causing wires to break because it didn't flex properly when moved. If you don't see 12v on this wire, cut some of the tie straps securing harness to bars, flex them to see if the voltage appears.

 

[senseamidmadness]

Swapping the coil with the key off will Not hurt Anything.

Multimeters (whether analog or digital) do not have a quick-enough Response time to show the primary triggering voltage; they will "average" whatever they sample in a very short period of time. (This does not include the specifically "sample-and-hold types", which require extra time to accumulate a reading.) You need an oscilloscope to actually see the pulses' true amplitude. But at least the multimeter will show the "signs of life" there.

The difference between "zero" ohms and "0.5" ohms could easily be directly caused by the test leads to the meter and how tightly you're making contact.

I might be able to get hold of an oscilloscope, actually. Not sure how much it would help.

What I find odd is that my multimeter readings were done with the same meter and same test leads, about a week apart on both coils; I tried various pressures and places of contacting the terminals, too, and the results were perfectly repeatable, at least on the same day. I can always try again. Maybe it was a humidity change or something.


Tomorrow I'm going to test for power between that green 12v wire and ground as you folks have suggested. I also am leaving the battery disconnected and charging overnight; maybe the Motronic needs to be fully rebooted. That's the only definitive answer I could find to this exact problem (coil changed out and suddenly no spark) anywhere on the Internet and it was on the Pelican Parts forum.

Jagarra, you just reminded me -- I re-wrapped a big section of the front harness with electrical tape a few weeks ago as a previous owner had stripped it off. The bike still ran fine after that, though, at least for a few days. It occurs to me that there were a couple wiring stretches around the front frame and steering head that looked a bit too tightly wrapped -- I'll have a close look at those after testing for coil power and reattach things in a way that isn't so tight.

So changing coils out with the ignition off shouldn't hurt anything -- is there anything else I might have done during that process that would cause the bike to suddenly produce no spark on either the "new" coil or the old, known working coil?

 

[pauls1150]

Perhaps the spark plug's cable itself is intermittent? Or not fully seated at one end?

I've found (and reworked) lots of multimeter test leads that were poorly connected inside the banana plug or at the clip. This will cause a variation in readings.

 

[senseamidmadness]

I figured it out -- bike runs fairly well now and I just rode it about 20 miles.

It was an odd (to me, anyway) solution that I had suspected was the answer, and it also wasn't from Pelican Parts -- I rechecked the forum I found the almost identical set of symptoms at and it's netrider.au, so some random Australian plus my multimeter and jagarra's tip about the coil plug voltage pointed me in the right direction.

I had the tank off already and checked the green wire to the coil with the ignition on and it had 12.55 volts, exactly the same as the battery. But what was weird was that the black wire right next to it had perfect, constant continuity to ground. That is very not normal and obviously would prevent spark; the Motronic had somehow decided it wanted to keep that circuit closed all the time regardless of Hall sensor input. So I did what the Aussie rider did: I unplugged the battery for a couple of hours to completely shut everything down. While it was off I put the "new" coil back in, made extra sure the spark plug wires were fully seated, and cleaned up the ground terminal next to the ECU just to be safe. Reconnected the battery, turned on the ignition, opened and closed the throttle a few times, and cranked it over. The bike magically had strong spark again. Put the tank back on and it immediately fired right up.

I still have no idea what I did to cause this, but my suspicion is that something I did spooked the Motronic into closing that circuit all the time. Maybe in the process of my coil swap or latest fuel pump swap I carelessly grounded something out. Does the Motronic have a "panic" mode? I don't know. All I do know is that it's always got at least one power circuit on, even if the ignition is off. It not being completely off unless the battery is disconnected is something I'm not used to, as this is my first motorcycle with an ECU.

Lesson learned -- any time I'm doing any electrical work that isn't disconnecting the fuel tank plug or changing spark plugs and involves breaking connections, I'm going to disconnect the battery and leave it disconnected the whole time I work, and that should save me some headache in the future.

I did also find and fix the spots to the right of the steering head where the wiring harness was clearly zip tied way too tight to the frame. One more problem headed off before it happens.

Thanks for your help, folks. Just a couple more gremlins left to chase and it'll be a very fine riding motorcycle.

 

[jnrugg]

Ghosts in the machines....

 

[Omega Man]

Ghosts in the machines....

I Robot

om

 

[jagarra]

I am glad you fixed your issue, here is some more background on this problem as others have had it. There are two black wires coming off the coil, one goes to ground and the other goes to pin 19 on the motronic for a term Z1, this controls the spark. Here is a link to a discussion about the problem from another forum. https://www.bmbikes.org.uk/viewtopic.php?t=27467&start=150