R1100rt no spark

[danielroth]

i have an R1100RTP.
it will only make a spark @ the plug/(will start and stay running) if i jack up the floor charger amps to 50a. then i can remove the cables. will not restart untill reapplication of chargeer.
i can ground a spark plug and watch it do nothing until the charger is turned up during cranking, then a weak spark will appear.

have done:
new odysse battery, ohmed out the HES and compaired values to 2 other known good HES's. they all seem to give no change in spark. visually inspected wiring to/from motronic; looks fine. ohmed coils and associated wires. seem fine. tryed new coil and wires to no avail. swapped starter motor with known good; no start.

noticed and concentrating on the volatge coming out of motronic to HES.
reading voltages at the HES/motronic connector when plugged in and ignition ON: orange wire has 12.5v, red has 3.5v(if i turn up the charger to 50a during cranking i get just over 5v at this junction and i suspect this as the main indication of the cause; just don't know the cause), and 12v at the black wire.
UNPLUGGED(HES to motronic connector) with ignition ON i get about 12v on orange, red and black.

any thoughts on why i need the supplimental current?

[danielroth]

as additional info, the bike came to me not running. i wonder why?

[danielroth]

is there a pinout or other testing procedure to follow for the motronic?

i have a good amount of testing equipment avail, ie o-scopes and such.

another note; the origional HES wires had no insulation on them and were all exposed and running together within the sheilding. i'm sure this COULD have killed the motronic but i would like to know.

suggestions?

[PGlaves]

It will probably come as no surprise when I tell you that something is seriously wrong.

And it seems to me that the issue is one of voltage - irrespective of the fact that you have to overcook the battery with high amperage to get there. I believe there is a significant short somewhere which causes the voltage to drop below the cutoff voltage for the Motronic or some other element of the ignition system.

It may be in the Motronic itself - but it could be any number of places in the wiring harness. And if it is not in the Motronic but reflects voltage delivered to the Motronic - then my hunch is that there is a significant risk of fire associated with this fault.

I would disconnect the ground lead - and then fully charge the battery. Then using just the charged battery and a quick release device like a small spring clamp, or even vice grips start looking for where 12 volts becomes something less than 12 volts. Even this risks letting out some smoke, and I would not allow the motorcycle to sit unattended with the battery connected until I was positive I didn't have a serious short.

If you can't find a short - then suspect the Motronic.

[genen8kua]

A couple of thoughts along the "keep it simple" lines before you start messing with the Motronic (which at least seems to work once the bike has started):

A high resistance connection at or near the battery will cause a bigger voltage (E=IR) drop once the starter draws current. Once you've addressed Paul's important safety issues, you might check for resistance anywhere between the battery and the Motronic as well as try measuring voltage when cranking (with a fully charged battery). I figure you nicely cleaned up the connections to the battery when you installed the new one, but you wouldn't want to go dealing with expensive stuff if there's a mess of corrosion or a poor connection between a connector and the wire it's attached to.

Is it possible for an ill starter to draw so much current that the Motronic sees a voltage less than it needs to start the bike? If that's the problem, it should be possible to kick start the machine.

The RTP has an auxillary battery. Even if removed, could some vestigal wiring be a potential source of your short? I personally have no idea how that particular critter is wired, but it's a thought.

Regards,

Gene

[danielroth]

the bike is wired like the spaghetti factory exploded.

i can guarantee the starter is good and the heavy leads are shiny and carry a resistance under an ohm.

something else interesting: i swapped all the like relays in the fuse box and the bike would have good spark every time i tried it. then back to the same condition. note also that earlier i had suspected the starter as drawing excess current so i cleaned the contacts on all the terminals and thats when i tested and cleaned the high tension cables. the bike would have a good spark every time; for a little while. the back to the original condition.

[genen8kua]

D'oh! Sorry, guess I need to work on my reading comprehension!

Any luck tracing down Paul Glaves' short concern? A happy solution would be if there's some problem with the connections to/from the Motronic - per my Clymer and Haynes manuals, it looks like pin 15 provides power, but there's a myriad of inputs. Plus never discount the hell you'll go through with anything electronic if there are ground problems.

I still read from your first post that you can start the bike by using the 50 Amp jump start setting on your charger and then it will run, right? Sure sounds like too little voltage to the unit while cranking and then enough once the bike has started. So imagine a Motronic unit that needs at least 9 volts (for the sake of argument, I can't find any specs) and sees barely that through its faulty connections when the battery is fully charged. Voltage across the battery drops while cranking and the Motronic sees just less than it needs. No spark, no joy.

Other resources (I do this in order to expand my knowledge base - just in case) about my own machine:

Search this forum for "motronic failure" and you won't get a lot of hits - I think some of that is because computer failure in fuel injection systems is relatively rare. There's a neat string started by guitardad that might give you some baseline info re: current draw and voltages, though related to the usual ABS issues.

Anton Largiader has a little info on troube codes: see http://www.largiader.com/articles/motronic.html . If the Motronic unit is fried, it may not show errors, but it might be reassuring to see the unit actually return info. The hardest part about looking for trouble codes might be finding whereinhell that old analog voltmeter got put away.

And I found this link:

http://www.geocities.com/fwarner_au/mc_things/K_fuel_injection.html which applies to K - bikes, but it looks as if it's the same Motronic unit.

And here's a real gem from my search of this forum:

http://users.rcn.com/dehager/ which was linked to in response to another posters Hall Sensor issue.

Hypothetically, the Hall sensor wiring insulation issue is common & has happened to a lot of folks, usually necessitating a wiring and/or sensor+wiring replacement, but one doesn't see many reports of that problem's frying the Motronic. Hopefully your charger didn't produce too much voltage for the Motronic (but it could've been saved by whatever's dropping the voltage it sees).

You're doing this (trying to resurrect the RTP) at least in part for fun, right? Don't forget that as the inevitable frustration mounts.

Regards, Gene

[PGlaves]

It may be the starter - taking so much current the voltage drops way off while cranking. A loose magnet (common problem) can cause this, as can a worn nose bushing causing armature drag.

I think maybe you need to pull the starter next!

A bad starter is more likely than my precautionary short possibility.

[genen8kua]

It may be the starter - taking so much current the voltage drops way off while cranking..

Though he did refer me back to his original post where he "replaced starter with known good," I'd still like to know that the voltage doesn't drop way down when cranking. With a fully charged PC-680, my R1100RT drops to about 10.2 V when cranking (and at that voltage, doesn't trigger the cursed ABS fault). I still wonder if (especially in a "rescue" bike) there's not some high impedance between the battery and Motronic (including possibly a high impedance ground).

Quite a puzzle that would likely have me going cross-eyed between the bike, the wiring diagrams and the multitester, hopefully resisting changing more than one thing at a time.

[GSAddict]

It will probably come as no surprise when I tell you that something is seriously wrong.

And it seems to me that the issue is one of voltage - irrespective of the fact that you have to overcook the battery with high amperage to get there. I believe there is a significant short somewhere which causes the voltage to drop below the cutoff voltage for the Motronic or some other element of the ignition system.

It may be in the Motronic itself - but it could be any number of places in the wiring harness. And if it is not in the Motronic but reflects voltage delivered to the Motronic - then my hunch is that there is a significant risk of fire associated with this fault.

I would disconnect the ground lead - and then fully charge the battery. Then using just the charged battery and a quick release device like a small spring clamp, or even vice grips start looking for where 12 volts becomes something less than 12 volts. Even this risks letting out some smoke, and I would not allow the motorcycle to sit unattended with the battery connected until I was positive I didn't have a serious short.

If you can't find a short - then suspect the Motronic.

+1 on the short somewhere......It is an RTP which has has wiring added/changed past factory OE. Good luck.

[danielroth]

thanks for the great replys so far.

i did swap that starter out. that was 1 of the first suspects.
and no, the voltage stays well above 10v even after 5+sec of cranking.

removed ALL that cop wiring this weekend. of course no change but now things are a little less hectic.

i wish i had the paperwork with me. i went through and noted every voltage or resistance at the motronic plug both connected and not with the key ON. any reference onto what those values should be on a good unit? we had all these numbers published for components like this in the navy.
i have a number of 3-5v outputs from the motron. tried unpluging all of these 'suspect' outputs downstream and looking at the change in value @ the red wire going to HES but had nothing going for me. i think the real suspect is the motron but can't prove it.

hooked an oscope to the hes during cranking just to see whats there. hooked to the blk, orng, or red lead, no change in signal during cranking (not triggering ground within the motron? i told you that the injectors don't fire also right?). i have the correct timing box with LED. if i just plug it directly into the HES and crank the motor, the light flashes like it should; i compared the ohm values to other known good units; i'm darn sure the HES mounted is good.

won't touch it till tomoro morn

any bench tests for a motronic?

[GSAddict]

thanks for the great replys so far.

i did swap that starter out. that was 1 of the first suspects.
and no, the voltage stays well above 10v even after 5+sec of cranking.

removed ALL that cop wiring this weekend. of course no change but now things are a little less hectic.

i wish i had the paperwork with me. i went through and noted every voltage or resistance at the motronic plug both connected and not with the key ON. any reference onto what those values should be on a good unit? we had all these numbers published for components like this in the navy.
i have a number of 3-5v outputs from the motron. tried unpluging all of these 'suspect' outputs downstream and looking at the change in value @ the red wire going to HES but had nothing going for me. i think the real suspect is the motron but can't prove it.

hooked an oscope to the hes during cranking just to see whats there. hooked to the blk, orng, or red lead, no change in signal during cranking (not triggering ground within the motron? i told you that the injectors don't fire also right?). i have the correct timing box with LED. if i just plug it directly into the HES and crank the motor, the light flashes like it should; i compared the ohm values to other known good units; i'm darn sure the HES mounted is good.

won't touch it till tomoro morn

any bench tests for a motronic?

Is there a constant 12V+ on the green/white feeding the injectors? Is the yellow/grey pulsing to ground from the motronic pin 20(verv) on same?
Is the fuel pump running when cranking over?

[bmwmick]

noticed and concentrating on the volatge coming out of motronic to HES.
reading voltages at the HES/motronic connector when plugged in and ignition ON: orange wire has 12.5v, red has 3.5v(if i turn up the charger to 50a during cranking i get just over 5v at this junction and i suspect this as the main indication of the cause; just don't know the cause), and 12v at the black wire.
UNPLUGGED(HES to motronic connector) with ignition ON i get about 12v on orange, red and black.

any thoughts on why i need the supplimental current?

Dan,
The 3.5V on pin 19 of the Motronic (Red wire on the HES connector) is your problem. Get a T30 security Torx bit (Harbor Freight has the set for about $8) and open your Motronic. Gently pry the cover off after you remove the 4 screws. The cover is sealed with clear silicone sealant and you should re-seal it with the same after you fix it.
You will most likely find a burnt 22 Ohm resistor on the circuit board. It's on the right side, just below the big connector. This circuit supplies the 12V to the HES. I have successfully repaired a couple of these Motronics with the exact same failure. I simply clipped the leads from the failed resistor and soldered in a new one above the board, I did NOT tear the circuit board out of the housing. In the picture below, I soldered 2, 10 Ohm resistors in series because I didn't have a 22 Ohm resistor handy.
The original resistor was burnt because the 12V was shorted to ground at some point, probably when the HES wire insulation deteriorated.
Open it up and get back to us.

http://i175.photobucket.com/albums/w132/bmwmick/1996%20R1100RT%20Stuff/IMG_3610.jpg

[GSAddict]

Dan,
The 3.5V on pin 19 of the Motronic (Red wire on the HES connector) is your problem. Get a T30 security Torx bit (Harbor Freight has the set for about $8) and open your Motronic. Gently pry the cover off after you remove the 4 screws. The cover is sealed with clear silicone sealant and you should re-seal it with the same after you fix it.
You will most likely find a burnt 22 Ohm resistor on the circuit board. It's on the right side, just below the big connector. This circuit supplies the 12V to the HES. I have successfully repaired a couple of these Motronics with the exact same failure. I simply clipped the leads from the failed resistor and soldered in a new one above the board, I did NOT tear the circuit board out of the housing. In the picture below, I soldered 2, 10 Ohm resistors in series because I didn't have a 22 Ohm resistor handy.
The original resistor was burnt because the 12V was shorted to ground at some point, probably when the HES wire insulation deteriorated.
Open it up and get back to us.

http://i175.photobucket.com/albums/w132/bmwmick/1996%20R1100RT%20Stuff/IMG_3610.jpg

Makes total sense! :thumb
I'll bet you are right! Good going!

[danielroth]

too much to do today to mess with the old girl.

i'll crack that motronic open tomorrow and have a look.

i just bought a used unit from ebay at a good $.
maybe i'll have this unit repaired before the replacement arrives.

[danielroth]

i had tried to pry the motronic open a week ago but the cover had so much resistance i gave up assuming it was built to be destroyed if opened. see the price of a new unit!

cracked the case this morn,
i can confirm that the resistor in question is FRYED! can't even make out the color codes. i'm going by an electronic shop @ lunch and will by a few 22ohm resistors as per your suggestion.

however, the pcb wire that runs under the resister looks burned too. i will hope for the best.

[bmwmick]

Dan,
I put 2 Watt resistors in the ones I repaired. I think the original was a 1/4 Watt. If you follow the circuit board trace, I think you can find another place to install the resistor. You could also just duplicate the circuit trace with wire (28ga or so) and hot glue the resistor to the board somewhere. The dark spot under the resistor is probably OK. I was lucky on the first one I repaired. The resistor was totally burnt but the color code could be seen on the bottom side, Red, Red, Black Silver.
Have fun!! What did I win? :)

[danielroth]

just installed 1watt 22ohm resistor and rode that sucker 'round the block like it just rolled off the factory line.

bmwmick p.m. me!
i owe you a brewski this summer.

[bmwmick]

Great!!

Glad you fixed it without spending big bucks.

Mick

[genen8kua]

Very cool, guys, thanks for the lesson!

[MotorradMike]

What are the odds?
Do you guys know each other?

Dan provides precise voltage on pin information.

Mick correctly diagnoses the low voltage issue and informs Dan of the failed component, location, and value. Plus he supplies the method for taking apart the Motronic(including Torx size).

Unbelievably, Dan is fine with electronic brain surgery and dives right in to find everything is as advertised!

Mick's original post is going in my manual.

But consider the following:
You fixed it and rode around the block but the original fault that burned the resistor is still there. Unless you're happy with short 'around the block' rides, you're going to have to track it down.

[bmwmick]

But consider the following:
You fixed it and rode around the block but the original fault that burned the resistor is still there. Unless you're happy with short 'around the block' rides, you're going to have to track it down.

MIke,
No, I've never met Dan but he's only about 120 miles north of me. :)

He said his original HES harness wires were all shorted together in the sheath, that was the problem that created the high current on the failed circuit. He replaced the HES and removed the problem but the damage was done.

[MotorradMike]

Oh, yes I see post 3 states that.

I guess he got a bargain on a bike that didn't run!