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No Spark to Rear Cyl. on MM EFI...

Electrical

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Old May 11th, 2008, 04:54 PM     #1
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Ride: 1996 Road King
 
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No Spark to Rear Cyl. on MM EFI...

...and (I think) no signal to either injector as well. (Plugs appear to be dry after trying to start). Have confirmed continuity from ECM connector to Coil connector and injectors for all wires. Have confirmed trigger signal to front coil, and resulting adequate spark at plug. Have confirmed no signal to rear coil. Have confirmed 12VDC to injectors, coil, solenoids, etc. Have confirmed grounds. Battery output, ECM power, check engine light, etc., all appear to be normal. Bike will try to start on front cylinder if I prime it with a little gasoline.

Do not have access to Scanalyzer this week, but will next week. Have not confirmed that no codes are present, but check engine light does not indicate that any are there.

This is the part number ".......97" service replacement ECM with the 43mm flash. Been in there since 1998. All PCIII, etc., are out of the circuit during diagnosis.

Note one unusual thing about this ECM: I no longer have a rev-limit, indicating that some sort of problem is occuring in the ECM--may or may not be related to the no-spark. I was out on the street "playing" one day and revved beyond 6900 RPM. I confirmed this later reviewing the data log. I'm trying hard not to have any preconceptions about a bad ECM causing the no-spark problem, but I'm beginning to suspect it.

Any ideas? Anything else I can check without a break-out box and test leads?
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Old May 11th, 2008, 07:06 PM     #2
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Re: No Spark to Rear Cyl. on MM EFI...

OK recheck something here for me. You say plugs are dry but no spark, they should be wet in the rear cylinder if there was no spark. You also say 12V to the injectors but fail to mention the trigger of the injector.
Your MM bike had a factory problem with the rear cylinder injector wiring strapped to tightly which in turn would break the copper inside the wire jacket near the rear injector plug.
It's difficult to locate because the jacket is still intact. Either trouble shoot the rear injector wiring again for continuity on all wires or try wiggling it to see if the rear cylinder fires up then.Maybe get it running on the front cylinder and try the wiggle then to see if it fires up.

Your post leads me to believe you are also talking about no spark at the plug too. The MM had a hall effect in the nose cone that has slits in the rotor to fire the plugs. Have you checked the pickup in the nose cone yet and associated wiring?
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Old May 14th, 2008, 04:45 PM     #3
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Re: No Spark to Rear Cyl. on MM EFI...

Appreciate the response, and will check the harness again for an open.
It appears that neither injector is triggered, and only the front coil is triggered. I verified the trigger signal to the front coil, and lack of same to injectors and rear coil. I have removed the EFI harness and am bench-checking it more carefully. At the same time, I am trying to cajole friends into "loaning" me a good ECM so I can see if that changes anything.

Have not checked the CMP, nor the related wiring. I assumed that since I was getting a trigger at the front coil, it must be okay. I'll check it again, however.

I have added several electical/electronic components to the bike over the years, and the areas under the side covers, seat, and tank is even more tightly packed than when stock. I have previously added wrapping and cushioning to the area under the tank in an attempt to prevent damage to the harness, but perhaps it is screwed up anyway. I'll double-check.

Thanks again. I'll post anything else that I find.
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Old May 20th, 2008, 09:45 PM     #4
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Re: No Spark to Rear Cyl. on MM EFI...

Quote: Originally Posted by Barry View Post
...Have not checked the CMP, nor the related wiring. I assumed that since I was getting a trigger at the front coil, it must be okay. I'll check it again, however...
Every now and then I allow myself to begin to think I know something about these MM bikes. Silly me! Still don't understand why, given that I think that the CMP is basically an on-off switch that tells the ECM "hey, we're on the compression stroke so wake up and do something", but apparently the missing 5 volts to the CMP does have something to do with causing only one coil to trigger and neither injector to trigger. Maybe feedback of some sort can cause one coil to fire? Anyway, there ya go. I pulled the CMP harness and a pin had retracted in the Deutsch connector. Fixed that, and it's alive!

To recap:
1). Assembled engine and tried to start. Nothing at all. Checked coil and injectors. Nothing at all. Ignition and injection dead, but all other electrical okay. Must be a primary sensor bad. Checked CKP first, as that seemed to be the likely culprit. Looks okay, but wait! That area of the S&S case is much thicker than the HD case. Could it be that the stock spacer is not needed on the S&S case? Took out spacer--which didn't fit properly anyway and had to be ground down for clearance. (Now we know why). Voila! Got spark!. It'll run now! Oops.
2). No spark to rear cylinder, and neither injector is triggered. No error code indication at Check Engine light. Checked entire EFI harness for continuity. OK. Installed known-good ECM. Same problem. (Either that's not it or I've bust up my friends ECM). Just in case, checked availability of ECM and harness at motor company. Later revison of ECM is available ( -97B. Mine is just -97. Wonder what the hell they changed? Twice? Question for another day). ECM harness portion is available, but not the sensor portion. Double-triple-quadruple check sensor portion of harness. Still OK. All right, even if it makes no sense to me, I'll go ahead and check the CMP sensor. No continuity on 5VDC Reference line. Off comes the footboard and exhaust. Look at connector. Pin has been pulled back--probably during all of the tugging and pulling removing and installing the engine. Take connector apart and put pin back. Drape all harnesses over bike, connector jumper cables to battery cables, ground plugs, turn on ignition and kill switch, hit starter. Plugs both fire. Insert test light in injector connectors. Both trigger. Put bike together and it runs!
3). Barry is suitably impressed with Glider's knowledge of arcane HD EFI "stuff". Thanks.

Now, on to the oil leaks at the filter mount and the inner primary. Did I remember to put that damn o-ring on the case?

Last edited by Hobbit; May 20th, 2008 at 10:43 PM. Reason: language
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Old May 20th, 2008, 11:20 PM     #5
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Re: No Spark to Rear Cyl. on MM EFI...

Good on you Barry. I'm glad you got it to fire up and not have to use it as a boat anchor.
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Old May 24th, 2008, 12:34 AM     #6
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Re: No Spark to Rear Cyl. on MM EFI...

Just to close the book on this thread...

I heat-cycled the engine and put the first 50 miles on it today. It starts right up, and runs great. Cruise AFR is around 13:1 most of the time, which is okay during break-in, and really much closer than I expected for a map that I just guessed at. I'll make it better after break-in. No leaks, no unexpected vibration, no bad noises, no smoke, no overheating. I'm pretty happy.

This feels like it's gonna be a strong engine when it gets broken in.

For anyone who may be curious: The bike is a 1996 FLHRI with 100k miles. I've had it for more than 10 years. This is about the third major engine iteration, and it may be the best so far.

The bike:
  • 720 lbs with half-tank of fuel and all rain gear in saddle bag.
  • 3 5/8 x 4 5/8 S&S lower end and rods. And I have to say that the machine work on S&S stuff is beautiful, and accurate. Also S&S pistons--which I milled 7ccs out of to get the CR I wanted. With .002 deck height, SE 72cc heads, 40 degree intake closing, I figure somewhere near 9.2 Corrected CR.
  • Gerolamy 42mm TB.
  • K&N 3" air filter on a TC backing plate.
  • W6H cam, which I still think might be a little short for that bike, but am trying it out anyway. Hey, I might learn to like torque that will pull trees out of the ground...
  • Red "stage 2" injectors.
  • Stock fuel pressure regulator.
  • Stock -97 ECM with the "43mm" flash, which was HDs latest and greatest for Evos. (Nice one too. Noticeably stronger than the "Stage 2 with Heads" flash, for instance).
  • PCIII-USB with my own map(s), Wide-Band Commander, Display Unit (Nice on-the-road tuning aid, but it washes out in the sunlight).
  • D&D Fat Cat.
  • Chain Final; 24/56.
  • Six-Speed gearset, 2.93/.86.
  • 25/36 primary.
  • 9-plate Barnett clutch kit, SE spring, hydraulic cover.
And that's just the driveline! Man, I've spent way too much money on this bike!
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Old May 24th, 2008, 08:48 AM     #7
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Re: No Spark to Rear Cyl. on MM EFI...

The Woods cams run a lot "longer" than you'd think they will.And they'll tolerate more compression than the numbers indicate they will.One of my favorites.I'm betting you'll like it.I'd lean it out at cruise to 13.8.
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Old May 24th, 2008, 11:12 PM     #8
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Re: No Spark to Rear Cyl. on MM EFI...

Thanks for your input.

I've run Bob's cams before, and do like them generally. I just have a hard time getting past that 40 degree closing at higher compression ratios. That's why I changed my mind and came down to 10:1. When I talked with him about that cam and my 72cc heads, (Woulda been up above 11:1) his response was "compression releases". I have them, but milled the pistons anyway to get me down to a corrected CR around 9.25:1 at sea level. That's more comfortable for me.

I appreciate that everyone's got their own ideas, so no offense meant, but cruise at 13.8 is too rich for my preferences. That's about 36-38 mpg, and I'm looking for closer to 48-50 at cruise. Back before I could make my own maps, I tried a map that a guy swore by that was in the 13s everywhere. No thank you. On mine, I don't get to the 13s until about 60-80% throttle above 2250-2500 RPM. I try to stay real close to 14.9-15:1 at cruise settings--which for me on my bike is 2000-3250 RPM at 20%-40% throttle. I've known of some dyno guys that set it in the 13s, but I think they do that because it's a little easier, and you sure don't have to worry about detonation much.

As they say YMMV. In this case, literally.
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Old May 24th, 2008, 11:59 PM     #9
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Re: No Spark to Rear Cyl. on MM EFI...

OK can't understand why you'd run cams like that and run lean.There's more to maps than AFR.But writing advance curves without a steady state dyno is russian roulette.
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