Won't start, tried everything, got any ideas?

[Sunbeemer]

I spent the day trying to figure out why it wont fire.
Here's what I did:
1. Checked for spark by grounding a good plug and saw none.
2. Swapped all the relays around, no joy.
3. Removed and tested the resistance of the ignition coil, it test ok (BTW, Clymers is wrong about the resistances, for my single spark they read primary = 0.7 ohms, secondary = 7.5k ohms. I have a spare coil and they both read the same)
4. Checked the ground on the Motronic is good.
5. Turned on the fuel pump by hand-cranking the engine just past TDC (~1.5 deg.) so I think the Hall sensor is working, and computer is seeing the signal. The HES wiring looks good, but don't yet know how to test it*.
6. Checked the wiring under the steering head for breaks, and especially tested the black wire that is supposed to be from the tach to the engine electronic control unit (per Clymer's wiring diagram).
7, Pulled a plug and found it to be dry and good looking (tan), which kind of surprised me since I could smell gas coming from the exhaust upon cranking this morning, and this was 6 hours later.
8. Had to siphon all gas from the tank to remove it (it was full), and didn't notice any water in it.

* I have Dana Hager's test method, and may do that after I build a tester. What interested me about turning the engine over by hand is that after the HALL Sensor turned the pump on after TDC, continuing to turn the engine further kept the pump on for about a half rotation and it sounded like air was going through the fuel lines. The pump shut off for about a half rotation until it came up to
TDC again - is this normal?

Thanks, in advance, for any guidance. It's been a long, hot day in the garage!

Rich

[jfslater98]

Didn't see this in the description, but how many volts is your battery putting out?

[iowabeakster]

hmmm...was running and just quit...no spark...

The BMW manual says the primary coil should measure .5 ohm...not much difference.

My only idea is one you've already mentioned. Testing the HES seems like a good move. It fits the profile.

I take it that this is what you are referencing.
http://users.rcn.com/dehager/service/oi ... ensors.pdf

* I have Dana Hager's test method, and may do that after I build a tester. What interested me about turning the engine over by hand is that after the HALL Sensor turned the pump on after TDC, continuing to turn the engine further kept the pump on for about a half rotation and it sounded like air was going through the fuel lines. The pump shut off for about a half rotation until it came up to
TDC again - is this normal?

From the other link about timing... The fuel pump will turn on between 5 degrees before to 5 degrees after TDC, depending on the setting of the HES plate. It doesn't say how long the pump would run.

[Sunbeemer]

My battery reads 12.56 volts.

Will test the HES tomorrow.

Thanks again!

[CycleRob]

Sunbeemer,

The fuel pump "times out" if the engine is not running . . . about 3 or 4 seconds OR when the starter stops cranking. You'll see that happen by stopping the wrench crank turn as soon as it starts. Fuel pump should start at exactly TDC on the flywheel with a very slow crankshaft turn.

You did not give any history prior to the DNS.
--Ran fine the day before?
--Won't start after taking the tank off?
--Won't start after gassing up?
In other words, what history may be relevant.

Quick hits:
Check Kill Sw.
Push QD's together fully!

You're one of the sharper wrenches here, but sometimes the solution is hidden in plain sight. BTDT.

.

[sweatmark]

Side stand switch?
Neutral switch?

The starting interlock circuit is comprised of these plus kill switch.

[The Meromorph]

Check continuity on the plug leads.

[boxermania]

Sunbeemer

After reading your posts I'm also challenged by your problem. Lack of spark comes from:

Bad plug
Bad HTW (high tension wire)
Bad coil
Bad HES
Bad wiring between HES and ECU

Personally, I think the HES are OK because they are fairly rugged components....but you are going to test them so that will give you the answer.

The wiring is another issue and with the history of the oilheads, i.e. nylon ties I would be suspicious.

The coil to the plug circuit is easy to test, remove the power connector to the coil and turn the ignition on, one of the wires should show +12 vdc to ground, the other should show open to ground....that is the wire that via a transistor in the ECU gets turned on to ground to get the coil to fire....just like the fuel injector.

With a safety pin, prick the wire with no voltage on it and return the plug to the coil, remove the HTW, insert your test plug and ground it, then get a wire and ground it to the engine, the other end will come into contact with the safety pin once the key is turned to the on position.

By touching the grounded wire to the safety pin, you are in essence doing what the HES and the ECU should be doing. That checks everything to the ECU......and you are checking the HES, so that leaves the wiring untested......

The above might be confusing if you haven’t done it before, give me a call at (225) 445-6922 and we can talk about t.

Good luck

[iowabeakster]

In hopes that our resident professionals might be able be able to shed some light (attn: CYCLEROB)...

Here is the post Rich made a few days earlier... with some history.

viewtopic.php?f=2&t=18377

[Sunbeemer]

This is getting interesting...

Today I tested the Hall Effect Sensors per the excellent write-up at http://users.rcn.com/dehager/service/oi ... ensors.pdf
and found both the upper and lower sensors working fine, sequencing on and off with every 180 degress of crank rotation.

I tore apart three of the four wiring harnesses under the steering head and found nothing remiss, the work I had done a few years ago was keeping the wires from chafing or stretching, but the original rubber sheathing I'd taped over had disintegrated, so all of it was cut off and the individual harnesses retaped. They will be going back into plastic looms.

I also removed the original horn since the undertank Stebel Nautilus I installed a few months ago is so much louder you could hardly hear it, and the horn's sharp-edged, mounting-bracket concerns me about chafing the wiring under the steering head.

The only thing I can unhappily conclude based on the information developed so far is that the Motronic is moronic...

I am gratefull for the offer of help from you all, and may give Boxermania a call after I try his diagnostic technique, seems like that would be a definative test of spark to the ignition wires.


Thanks again.

[CycleRob]

. . . I filled it with gas and rode ~ 2 miles home, then changed the oil, washed it with a hose, and put it in the garage for the night. When I went out the next morning, it started up with a clank for a couple seconds, probably because I had not run it immediately after changing the oil, but the oil light went out immediately and it quieted down. Then it ran fine for about 10 seconds as I backed it out of the garage, but when I turned the handlbars hard left it died like I had switched the key off.

There's 3 big clues there, but the fuel smell in the exhaust and a good HS fuelpump test but failed spark test points to a broken or grounded wire in the harness. Also possible is a new burned in spark trail on the dusty/dirty coil tower that provided a conductive path when it got soapy/wet. Once it's "made" it continues.

About that spark test . . . BOTH plug wires must be connected to a grounded sparkplug. A good ground, not the painted fins. Also, looking at the spark in daylite, you may not even see it. It's a very fine/slender diameter white-ish blue spark of a very brief duration. Snit! . . . . that was it . . . . it's gone. Try it in a darkened room or at nite. When/if that proves there is a spark, then it goes back to the water in fuel.


.

[Sunbeemer]

It's fixed, , I hope , because I'm not sure exactly what the problem was ...but I have the sneaking suspicion it was a bad plug and I made the rookie mistake of only replacing the good one in the left cylinder to check for a spark while the bad one in the right cylinder was unable to complete the circuit , thus keeping both plugs from firing (in a waste-spark system both plugs are wired in series, so if one is "open" neither will fire!). Thanks Cyclerob for a good description of that in a previous post, and noting that "BOTH plug wires must be connected to a grounded spark plug". I should have known ! Well I do now, and in the process have learned a lot of good stuff about my bike! When I finally got around to trying a new plug grounded to the right-hand cylinder, I got a big, fat spark, so I replaced both plugs.

I owe thanks to Boxermania for your offer of help , it was encouraging to have such knowledgeble advice available! A "bad plug" was at the top of your list!

And thanks Iowabeakster for keeping me in the game ...(BTW, I figured out where your avatar came from; "2001: A Space Odyssey" when the apes discovered a weapon (or a tool?)? (Favorite movie )

Otherwise, I retied the wiring harnesses under the steering head and added chafing protection at critical wear points (thanks for the pointers challey , and good luck getting yours "restrung"!)

I also cleaned the ground wire to the left throttle body (both ends) and the Motronic multi-terminal connector, and all the plugs I could find under the tank, including the ignition coil and Hall Effect sensors, both of which tested ok.

While I had the tank off, I changed the fuel filter and discovered that those clamps on the smaller vent hoses are reuseable, although Clymer's says they aren't. Guess it depends on how you take them apart...

It's running strong today and It's great to be riding again after two weeks of not !
Maybe it just needed a rest after running the "Dragon" and the "Snake"!

[bikermeow]

I am curious about plug failures. I ran my first set of plugs for more than 2 years. They still look great. Then I swapped them for another used set cleaned ultrasonically (they looked like new) ... 6 months on and still no problem. How do the plugs manufacturer stay in business?

[Sunbeemer]

The plugs I had in there for ~11,000 miles were Autolite #3923 Platinum. In the one that failed, the tiny platinum tip had receeded so that it was flush with the end of the electrode, whereas in the other one, which was like new, the platinum tip stood proud of the electrode by 0.020". I could not get continuity on the bad plug until I dug into the end of the electrode a little. I do not know what caused this, but I have switched to standard copper Autolite #3923's.

And this bears repeating...
If one plug doesn't fire (because it "opens up"), neither will the other one.

And this is what I learned (repeated so it may help you in the future)...
Check both plugs to diagnose a spark problem.

[Arbee]

This is curious as they both spark at the same time, one in the correct firing position
and the other at bottom dead centre, how one knocks off the other may be a deep seated
ignitor problem.

[Sunbeemer]

Yes, this is exactly what confounded me until I read Cyclerob's post here:
viewtopic.php?f=2&t=14538&p=129587&hili ... ug#p129587

I didn't replace the bad plug in the other cylinder when I replaced the (unknowingly) working plug with a good plug. This still gave me no spark at the good plug until I replaced the bad plug with a good plug so the high-tension circuit could be completed.

I had a 50-50 chance of doing it right or wrong, so guess I was just unlucky