Weird no spark condition

My 83 750 Maxim got an extensive rebuild this past winter, ALL the normal maintenance stuff is in check and the bike has been running like a champ. I mean just awesome.

Now there is no spark at all in any plug. Tested in my dark basement, zero spark. Obviously it won't start. Starter turns fast and strong. On a couple of tries it fired for one second but didn't hold it, which must mean there was at least one spark, but I haven't seen one at a spare plug in cap to ground test yet.

This whole scenario played out a week or so ago, then it ran great after a charge. Then I parked it for a week. And around I go again, but now a charge makes no difference.

The AGM battery is about 2 years old, shows 13.2 volts and drops to 11.6 - 11.8 under starter load, measured at the battery. Measuring at the TCI, on the Red/White stripe and Black wires, I get just 9.5 - 10.2 volts and 8.4 - 8.6 under starter load. After a few hours on the charger just for kicks, it read 14.2 until several attempts to start brought it down to 12.4 and lower. 14.2 seemed oddly high to me, especially as the charger didn't show it's green light yet.

I have checked and double checked the kill switch. Ditto the sidestand relay, and safety cutout. I have pulled and wiggled a bunch of multi-pin connectors. Nothing.

The weird thing to me is that the voltage is so different between the battery and the TCI. Fuses are updated and their connections are soldered. For both coils to fail seems highly improbable, though I have not tested them. Where else would voltage drop between the battery and the TCI?

The winter rebuild included going through the harness with a fine tooth comb, cleaning every contact point, connector, button I could and taping up the various bare spots.

I have read this excellent guide: <http://www.xjbikes.com/Forums/viewtopic/t=21932.html> and still can't seem to make heads or tails.

Any and all suggestions are most appreciated.

Missed out on a three day camp/ride with my wife as a result. Had to take the car. LAME!

 

A little more info. With battery showing 12.8V, I checked voltage at main fuse - 11.6V -and at ignition fuse - 10.5V. Red/white at TCI shows 10V. No particular location for voltage drop, just a steady fall. I also checked coils by ohming plug cap to plug cap - 1/4 at 2250 ohms, 2/3 at 2350 ohms. Hmmm.

Jumper wire in the ignition switch plug made no change in voltage. Also got weird resistance readings on the clutch lever switch. Jumped that, no change. Sidestand switch and relay both check out.

 

Eliminate the safety circuit first. Unplug the safety cutoff relay and see if the bike will start.

 

Thanks Fitz. That is a point of a little confusion for me. I have read in more than one place that disconnecting the safety cutoff relay disables the circuit and should allow the bike to start even if the clutch, neutral, or sidestand relays won't. If I pull the safety cutoff relay, that is the only condition under which my starter will NOT turn. The oil light comes on with a push of the start button, but no starter action. Even a bad relay there would be irrelevant once removed.

 

Are you sure you're unplugging the actual safety relay and not the sidestand relay?

The safety circuit disables the TCI by dropping it to ground. Locate and disconnect that wire from the TCI and see what happens.

Another member is fighting the same fight: http://xjbikes.com/Forums/viewtopic/t=46822.html

 

I am sure it's the safety relay. I did just go down and try disconnecting the Black/White tracer wire at the TCI with the safety relay re-installed. Starter turns, still no spark, but I did get one hell of a backfire or something like it when I turned the key off.

 

A couple more observations:

I disconnected the black/white trace bullet connector just before the TCI and checked continuity to ground with key on. On the TCI side of that connector there is continuity. On the other side there is not.

Sometimes, but not often, when I turn the key off there is kind of a whoosh sound that I can't make much of a guess at. Kind of sounds like a sudden rush of air, either intake or exhaust? Or some sort of electrical discharge?

I can't decide if I'm chasing the voltage drop at the TCI or if that's a red herring and I should be looking for some other reason for no spark. Or is this all just a battery that tests OK but for some reason lacks what electronics experts would call "balls"?

 

Still a little more data.
Primary coil resistance: 1/4 - 3.0 ohms; 2/3 - 3.1 ohms
Secondary coil resistance thru caps: 1/4 - 22.5 kohms; 2/3 - 23.5 kohms
Secondary c.r. direct to wires: 1/4 - 13.1 kohms; 2/3 - 13.02 kohms

I'm a decent mechanic, but the electrical side has always been a little beyond my comfort zone. Those numbers are all good, right? Or are the primaries just too high? FSM says 2.5 ohms +/- 10%. By the book, I'm out of spec.
Caps show 5000 like they should.

 

I think you're chasing your tail. Or more accurately, chasing voltage when amperage is the key.

Take the battery to a competent auto parts store and have it load tested. It's a common trait of the XJ electrical system for everything to appear "fine" and spin the starter quite nicely, etc., but no fire because the battery is just flat enough to not provide enough power to also be able to fire the ignition. Your clue is it firing when you switch off. Does it also occasionally fire right when you let off of the starter button?

It seems counter-intuitive, and I wouldn't have believed it myself if it had not happened to me, and more than once. And in every case it was simply a weak battery.

I'm betting that's what's going on here. Especially if you take the "long view" as to how the problem occurred.

 

I am following this thread closely as I have a no spark condition going on as well on my 1982 XJ750 Maxim.

Mamster, keep us updated as to progress.....thanks

 

unplugging the safety relay on that bike isn't all there is to it. there should be two red/white wires in the safety relay plug, they need to be connected for the solenoid to work. just put some wires in the connector.....safety relay is out of the picture.
if you think the battery doesn't have the beans to start it, you could try to push start it.
seems like your loosing a lot of electrons on the way to the tci. try this, unplug your headlight, so you don't kill the battery this might take some time.
put your charger on the battery and the meter on the tci where you measured the 9.5, 10.2 (r/w---b) now try r/w to a good clean frame.
should be the same. now wiggle all the connections on the fuse box, fuses and any others you find handy, see if one of them gets you more volts

 

My experiences indicate simply your battery needs replacing.

 

Polock, you da man. She runs.

I did have the battery load tested. It is 100% fine. It did not have the classic fires-on-starter-release. That was why I got the new battery a couple years ago.

As you suggested, I pulled the safety relay again and jumped the R/W wires. Then I measured V at the TCI-Red/White first to the Black/White on the TCI: 10V, then to the engine: 12.4V. Then I went fishing. Wiggled a ton of connectors, checked resistance in a ton of places - fuses, kill switch, ignition switch, yada, yada, go fish. Finally, I moved the shifter out of neutral. Bingo! Instant 12.4V at the TCI. And, drumroll please, she fired right up.

So, I know the nature of the problem, but still, I didn't fix anything yet really. It could happen again, perhaps at speed. The safety relay was disabled at this point, so this is still beyond my understanding. Where are two volts going sometimes, and apparently only when in neutral, maybe? I did have a weird instant shut down while rolling away from parked/cold a month or so ago, chalked it up to lack of warm up, but was never comfortable with that explanation.

So, how does the neutral sensor work? Never been in there. Is there a way it might lose volts without a complete short? The neutral light is an LED "bulb" and works fine and safety is removed temporarily. Diagram shows little else in that circuit besides the light and the diode. Do the diodes get weird sometimes?

Fiveofakind: Good luck finding yours. This was the most frustrating damned thing for 3 days. I looked at it as being in one of three realms. Bad battery, bad safety circuit issue, and the voltage drop at the TCI. A professional load test, and Polocks safety relay plug jumper eliminated the first two. And getting very systematic looking for the voltage drop got me much, much closer. Post up what you learn, I'd be curious and maybe this thread will help somebody down the road. Or on the side of it.

 

Fiveofakind, looked back at your post and noticed you've an 82. Mine is 83. I know even less about yours, but I do know that my dash is a heck of a lot simpler and I would think my wiring is too.

 

Yamaha inline four neutral sensors are stupid simple.

What they are is a plastic plug that sits in the engine case at one end of the shift drum. The drum has a contact on it, the plastic plug has another contact. When the drum is in neutral, the contacts meet and the wire screwed to the outside of the plug gets grounded.

 

So, the bike runs great, but I still haven't actually fixed anything. Today after stopping at a store, I came out and hit start and it did not start. Starter turned, no fire. It usually starts quite easily, especially warmed up. So before I wasted any more juice, I put it into gear and pulled in the clutch. Instant start and rode all around town with several stops and no further problem. The problem is still there, at least intermittently. It worries me that my ignition could cut out while rolling, though so far it only has interfered with starting. I have a new neutral switch, but it looks like a hassle to install. And, as JPaganel has said, that switch is stupid simple.

So here's the question: In what way could I be losing 2 or 3 volts at the TCI, that likely relates to the neutral switch, and that bypassing all the safety cut-out stuff would not remedy?

 

If you were in gear and pulled in the clutch, you'd be coasting with the clutch pulled in with the clutch disengaged. I think you meant to say you pop-started it and it fired up instantly.... That is a prime symptom of a bad battery. How old is it? But if you say it's new, I don't care..... Can still be a bad battery -- I've seen enough bad ones from the store.

 

No pop-start. Sitting in the parking lot, I just pushed the shifter down into first, pulled in the clutch lever, and hit the start button. Fired right up by the battery. Had a solid go at this mystery last week. I am pretty convinced that the root is in something on the neutral side of the safety circuit. During lots of testing, my voltmeter on the TCI jumped from 10V IIRC to 12.4V when I moved the shifter out of neutral. And then it easily started for the first time in days. The battery isn't very old, but I had it load-tested anyway: 270 CCA. A substitute car battery didn't change anything last week. I will second you on the new batteries CAN be bad. Learned that first hand just last Thanksgiving eve, with Grandma in the truck, heading for the highway, the brand new battery wouldn't start the truck. They were VERY apologetic.

 

An. In that case, sounds like you should investigate your neutral safety switch

 

I just went back to read through the whole topic again ...... Saw the original numbers on voltage, and it seems to me you're dropping way too low. I also see where I said I'd suspect the battery.

You probably don't want to hear this, but I'm going back to still suspecting the battery.

 

in the diode block b/r to g.....look for about 8.2 ohms, no polarity
something doesn't look right with my drawing of the diode block, so just test the whole thing
look at the kill switch and the side stand relay.....jump r/w to b/w to eliminate side stand switch and relay....it's not quite the same as the safety relay

 

Well, I keep wishing it was my battery, that would be a straight fix, but the battery from my truck gives me all the same numbers that I get with the bike's own battery. I'm not just jumping the battery. Disconnected the bike batt and cabled up the truck batt. No good.

I did what you suggested, Polock. 8.4 Ohms on the diode block: b/r to g; and jumping the sidestand relay changed nothing.

One curious sequence of voltages: 12.9 at the battery, 12.4 at the main fuse, 11.9 at each of the lesser fuses, then at the kill switch: 11.3 IN/10.8 OUT with the switch on, or 12.4 with the switch off. Checked resistance on the switch at the plug inside the headlight and got 1 Ohm, but later I only got .4 Ohms. Through it all, I get 10.2 at the TCI. Key switch shows .1 or .2 Ohms. Makes me wonder if there is no single source of drop, just cumulative from all the connections. I have cleaned them all.

This is about the most frustrating puzzle ever. The bike was running great, so I know the rebuild was at least reasonably successful. But . . .

 

If it will start with the clutch pulled in the bike thinks it's in gear and you're way over-thinking this diagnosis.

The neutral "switch" is SO primitive that it seriously doesn't deserve to be called a "switch." It's also primitive enough that if worn, could be shorting to ground and causing you to beat your head against the wall.

Replace the bloody thing.

Here's a good one:

The front brake light switch in my Norton WOULD NOT illuminate the brake light. Yet it "tested good" continuity-wise with a DVM. Replacement was the solution.

Replace the neutral switch.

 

here's another good one, never use a digital volt meter to check continuity, use a test light or a analog meter.
see if you have a big white connector just to the left of the solenoid or there abouts, one wire in one out, big flat connector inside, maybe you missed it.
i can't see how you loose .5 v from the battery to the fuses. maybe try taking one fuse out at a time and check the tci volts. try to isolate the loss

 

It's been a couple months of good riding since I resolved this, but I thought I'd post a follow-up to this whole mystery to complete the thread for others similarly troubled. I tried 3 different batteries with the same results, returning to my old one. I replaced the neutral switch for no change. But I kept coming back to the voltage drop at numerous places and just decided to pull apart every connection and switch I could find including the ignition switch which I had given a deep clean to over the winter. Cleaned everything meticulously one at a time, testing for drop as I went. I steadily picked up voltage, especially following the ignition switch clean. When I was done it fired right up. And it has fired right up a hundred times since. That was a little frustrating since I rebuilt the bike from the frame up over the winter and thought I had given good attention to the harness. My best guess is that maybe I used an inappropriate cleaning product or technique for the winter effort, and left some residue or abrasive (800 grit IIRC). Everything else from the rebuild has been good, so I shouldn't complain. It's been a great summer here for riding. Thanks for all the help with this, I learned a ton getting to the bottom of it and I know my bike even better.