New Electrical Issue Ignition Coils Sometimes

First I must admit I have yet to do any tracing or testing yet for this problem. I have been living with it a month or so but its getting worse.

82 xj750 maxim

this problem existed before my headgasket issue and continues.

this season since coming out of storage I have noticed my ignition coils are intermitant but in a particular way. usually I leave the run switch on all the time. lately if you go to start it you will either get spark right away and it will pop or run. or it will crank and do nothing. I have learned on the do nothing situation. if you cycle the run/stop switch it will energize the coil and everything is fine. sometimes it takes a couple rocks of the switch.

things of note.

this is happening more often now. it will always crank (engage starter motor) but not always spark. also if good spark and it starts/runs it has yet to die on me. so its more of a if it works it works.

so I suppose the switch contacts are suspect/wiring. but I wonder if I have a sketchy relay in the mix here, and which one/where would it be? I am speculating it isn't always latching. but unsure what is inline of the run/stop switch/ coils.


I have manuals, with wiring diagrams. they have very crappy font on them and are hard to read/tiny.

 

I'd start by cleaning the switch. One thing at a time.

 

+1 on cleaning the run/stop switch.

Other thoughts would be the condition of the battery. If the voltage reaching the TCI / ignition coils drops too low the spark becomes weak and the bike will not start. It would be advisable to do a voltage check to determine what voltage the battery is maintaining when the starter is engaged. It should stay above 10V.

There is no relay involved in supplying power to the ignition circuit. However, it is common to have some losses along the way either through the main fuse, ignition switch, run/kill switch, and connectors. The better the condition of all of those connections will result in a higher primary voltage to the coils and consequently a stronger spark.

 

New battery installed a volt meter in my fairing to keep an eye on charging. I will measure at the coils. But it must be switch related if nothing else interrupts ignition circuit. And playing with it makes it work. Perhaps I will relay mod my coils, pending test. Harder to picture but I suppose one or both of the coils could be acting up, testing required

 

It could be the sidestand switch, or sidestand relay. The switch is more likely though since moving it temporaraly solves the issue.
The sidestand switch and relay do interrupt source power to the the TCI (via the safety circuit relay) so that one does not ride off with the kickstand down.

 

Doesn't the safety mechanism disable the starter motor? In my situation the starter always works

 

The sidestand relay disables the ignition. Try to to pull away with the sidestand down, you'll see.
Both it and the safety relay work together.
This is a common enough issue that I recommend the sidestand switch be cleaned and dry-film lubricated annually in order to prevent it sticking and randomly cutting the ignition off while riding (BTDT).

 

Yes it should kill the ignition. But also in gear it won't let it crank without pulling clutch lever. Correct? So there it's preventing starter motor maybe ignition too. And doesn't that all work though the one safety relay? So ignition coil part and starter relay signal go through safety relay?

 

thats how the clutch safety switch works and if side stand is down no crank . when in gear and running putting sidestand down kills motor

 

clean the kill switch , check the connector that the harness connects to in the main harness and also clean your starter button. use electric cleaner and some dielectric grease.

from ignition fuse red/white wire runs up to kill switch and then directly to the tci and ignition system the only relay that will prevent the spark is the sidestand safety relay .
remove it . if you nolonger have problems then clean your sidestand switch.
the neutral switch closes the starter safety switch by connecting to ground.


if you still have glass fuses replace the block or at least the ignition fuse with a blade fuse holder

 

starter system

 

Well, you noted if you flip the run/stop switch the bike will start. So yes, start with cleaning that switch and associated connectors as xj550h just suggested.

Note also as stated earlier that the ignition will become weak with lower voltage and the bike will not start. The starter cutoff relay (starter safety) and side stand relay (ignition cutoff) can operate on a significantly reduced voltage. Consequently, the starter safety circuit can behave normally with a drastically reduced voltage, however, this would be way too low of voltage at the coils to produce sufficient spark.

If you can easily duplicate the situation it would be prudent to check the 12V on the output side of the run/stop switch. The R/W wire at the TCI is a very convenient place to check. This way you will know for sure what the issue is.

 

I will do so and post results

 

Pulled switch cleaned with contact cleaner. It wasn't a real disassembly friendly switch mechanism. But honestly it tested fine before and after. Slightly better after. See what happens. If continues I'll check the whole wire run but also then suspect ignitor

 

no tube fuses converted to blade. I went through and tested the whole of the red/white stripe circuit and it tested fine relative to turning off and voltage drop and putting power to the coils/ignitor.

but I cleaned and lubed every connector on the bike. I had done this previously but that was a few years ago now.

time will tell on this, after cleaning it started but it was supposed to do that. just have to use it a bit and see how it goes and hope I don't get stranded.

*observation

after cleaning things improved as they should, voltage drop and such. which makes sense but now my charging voltage is 15v at the battery. which seems a little high. if driving around and I turn on the aux light it will go 15.2. in the manual all I can see is 14.5 +/- 0.5 V so ok 15 is the top I guess but I didn't see a hard number on replace. opinions on this charging voltage? it is a wet cell battery but new​

 

A bit on the high side and may dry that battery out rather quickly.

One issue that would cause that is any voltage drop along the way to the regulator assembly brown wire, which is used as a voltage sense to determine the output voltage of the charging system. I see you did a lot of cleaning to improve the connections, but did not see anything on the ignition switch, which can be an issue causing some loss of voltage. You can check the output of the main fuse and the input to the other fuses to determine if cleaning the ignition switch might be worthwhile.

http://www.xj4ever.com/clean and lube the ignition switch.pdf

 

Voltage drop throughout the system is minimal when checking extremities. I'll check the brown wire. I did not disassemble the main switch. Fyi previous charging was 14.7 since cleaning the brushes and face of stator. After cleaning contacs last night now got 15.

 

from this link
The Ultimate Relay, Switch, Sensor, and Diodes Guide

If your charging voltages are too high, suspect your Regulator - Rectifier unit first, and perhaps dirty or corroded electrical terminals. The procedure for checking these is too detailed to describe here, and you should consult your service manual for additional details.

For all XJ-series models, the maximum available charging output VOLTAGE should be as follows (all values are approximate):

* approximately 500-2000 rpms: 1.8 volts gradually increasing to 14.2 volts
* 2000+ rpms: 14.2 volts up to about 14.8 volts, with a maximum of 14.8 volts (all models except XJ700-X and XJ750-X)
* 3000+ rpms: 14.2 volts up to about 14.8 volts, with a maximum of 14.8 volts (all XJ700-X and XJ750-X)

 

since the total cleaning, I have not had any ignition troubles or need to cycle the switch. it has been starting reliably. so that is good.

still tinkering with charging voltage. I have a few RRs on hand interestingly each time I plug one in it will do something different. then even going back to the original one I get different numbers. so wiring between is suspect. ill find it im sure just not yet

 

Still starting great, new RR installed with new plug on the harness side. Now a peak 14.5 14.6. Normal