Ignition Problem?

More and more this is sounding like it could be a bad ground situation somewhere in the wiring. Perhaps adding a few temporary ground wires to coils and other locations and see if this helps. Also wondering if the battery may have an issue and is partially shorting out internally - (vibration induced?) Not sure if that could happen or not.

If it were the battery I would expect a loss of power, but that's not what the scope results show.


-Jeff

Thanks to Adam K. for loaning me a set of O2 eliminators to see if I could force feed a new signal from the O2 sensors into the ECM. I'd read and been told that the ECM will remember the last signal it had from the O2 sensors when you disconnect them and not revert to a default map. If this information is true, it casts some doubt on the reliability of the information I got when I tested the bike with the O2 sensors disconnected. Unfortunately, once the bike warmed up the misfire was still there.

I removed the tail section and ECM which frees the rear part of the harness for a more thorough inspection as I can lift it up and examine the underside. Again no obvious damage anywhere and thoroughly reexamining the connectors and all the wires shows no visible problems. Also good conductivity is present checking all the conductors leading to the various sensors. This latter bit was expected, since the problem only appears under very specific conditions. I'm going to make a test plan and beg Jim to bring his oscilloscope back over for some additional testing. If that fails to lead to a solution I will reassemble the bike and offer it up for sale to someone with more patience or knowledge than me. It's actually pretty rideable on back roads where you're not trying to run a constant 70-75 MPH.

I'm thinking $2000 and there's about $800 worth of Race Tech suspension on the bike. If someone wants to offer that right away I won't even bother Jim again. At this point I want it fixed or gone, since the former seems nearly impossible, I'm leaning toward the latter.

Just make sure whoever you sell it to knows about this thread so we don't get 30 posts into the next one and realize it's that bike.

--Mark

Blrfl said:

Just make sure whoever you sell it to knows about this thread so we don't get 30 posts into the next one and realize it's that bike.

--Mark

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Yeah, I've documented everything tried so far and will provide that.

Sad to hear. What would a Honda shop do with this kind of problem if it was still under warranty?

WOW! Just got a call from Pat at American Honda Customer Service. She's going to forward all the information I sent them (Letter describing the problem, the list of things I tried & the oscilloscope traces) to their model specialist. She mentioned that they usually work through the dealer and I told I don't have a problem with that as long as the mechanic there as some specific targets to check and that I didn't want to get into big time and materials, trial and error process (BTDT already). She seemed very understanding and promises to get back to me. Maybe a ray of light here??

That would be nice!

Wow now that is some customer service!!! Let's hope they find the problem.

970mike said:

Wow now that is some customer service!!! Let's hope they find the problem.

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Me too, but to be clear I told Honda I was not looking for a freebie, just some expertise that as far as I can tell does not exist at the dealer level.

It seems to me that I have seen a ground wire junction block up near the front of the bike. Sorry for the vague response but I have no access to the bike at this time.

woodybelle said:

It seems to me that I have seen a ground wire junction block up near the front of the bike. Sorry for the vague response but I have no access to the bike at this time.

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Thanks. I'm formulating a plan to construct a jumper wire that I can use to back probe various ground wires in connectors and take them directly to ground. Hopefully this would by-pass any interruptions somewhere in the harness or elsewhere. I'll start with the ground wire coming from the injectors and coils and associated connectors. IIRC, the coils and injectors have a common ground in a sub-harness somewhere, but I might be confusing that with some of the sensors located near the TBs. I'll have to look at my wiring diagram again.

Big group of grounds under right side fairing pocket? Yellow connector with bunch of green wires. Don't want to re-read all 25 pages if this was covered.

Pete in PA said:

Big group of grounds under right side fairing pocket? Yellow connector with bunch of green wires. Don't want to re-read all 25 pages if this was covered.

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Don't recall seeing that but will take another look, thanks.

Post 65 here.

https://www.st-owners.com/forums/showthread.php?98008-Lights-stay-on-when-ignition-switch-in-Off-bike-won-t-start&p=1841298&highlight=#post1841298

Whole bunch of grounds go through here. (stupid design)

Don't forget the 24 pin connector on the left also. Pull any connector you can find apart, look for melting/corrosion and reassemble.

Thanks, I'm definitely going to check this out. I've inspected every other connector I could see/find.

Found it. No burning or other funny appearance to it. Maybe run a ground jumper anyway?


-Jeff

I had a 1985 V-45 Magna that would regularly not restart after filling the gas tank. It ran perfectly before stopping for gas. If I only filled it half way there was no problem. Every time I filled it completely the bike would not restart. Other than that it ran perfectly. I figured it had to be something to do with the weight of a full tank pushing down just enough to disrupt a connector somewhere underneath the tank but I could never find anything that was causing it. I eventually ripped the bike apart and removed every terminal from every connector everywhere (not just under the tank) and inspected every single one and found nothing wrong. Before reassembling it I re-crimped every single terminal and put a touch of solder between the wire and the terminal before putting them back in to the connector. I never found anything wrong with any connection and never figured out which connector was causing the problem but after doing this I never had the problem again. This anecdote doesn't help you solve your problem at all I know but just a word of encouragement that you are doing everything that you can and eventually you will triumph even if you never find out how you did it- and not knowing was the frustrating part for me.

wjbertrand said:

Thanks, I'm definitely going to check this out. I've inspected every other connector I could see/find.

Found it. No burning or other funny appearance to it. Maybe run a ground jumper anyway?


-Jeff

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Some have ganged all 11 together and grounded them but if it looks fine, don't.

It occurs to me that it's been a few months since I updated this thread. Sadly my ST stills sits in the corner of the garage awaiting a moment of inspiration and motivation to try the next thing. Since the last update I have done a few additional things:

• Left the bike at a local shop (Jett Tuning) with a great reputation. They were able to confirm the cutting out problem but not able to locate it. What they did do was to prove there were no mechanical problems. Compression was 195 -205 PSI and leak down was 5% across the cylinders. not bad for an engine with 150K on it.
• I think I've determined that the problem starts to occur once the bike is fully warm and switches into closed loop running mode. The bike runs in open loop while warming up or at full throttle, conditions where the miss is not present. It also runs in open loop above about 50% of redline. That works out to be pretty close to the 4250 RPM where I experience the misfire. At higher RPM, under deceleration or at constant throttle, the system runs in closed loop mode. The difference between open and closed loop is that the ECM uses O2 sensor data in closed loop. I finally convinced myself to change the O2 sensors. Unfortunately as with everything else, this had no effect on how the bike runs.
• All grounds and ground cap assemblies have been thoroughly inspected with nothing but pristine looking results.
• All the sensors have been replaced or tested, so I am now left with suspicion of a fault in the main harness.