Weak spark

I think I have my no start problem narrowed down to weak spark. What are the things that can cause this. This happened all of a sudden. I am ready to get the meter out just don't know where to look.
Thanks
Marty

 

The usual suspects are the pulse coils. Notoriously weak.

 

Battery. If it's weak -

- it can still turn the starter but voltage goes so low that ignition not spark well, maybe not at all.

- draw too much current from alternator while running. Thus spark problems, and poss. alternator and regulator problems.

- cause stalling at idle if it doesn't have enough reserve to keep igntion and lighting going while alternator is at low revs.

(I lifted all that info from Aaron Berg's XJ FAQ )

 

I have a question that relates to the 'weak spark' issue. If you ground the plug and see a spark, can you assume that the plug is sparking as well in the chamber ? It's a tougher environment in there right ?

 

I once had a plug on my old DT100 that fired realy nice outside the engine. Wouldn't even sputter in the chamber. New plug fixed the problem.

So yes, you can have a plug that fires great in the open but won't work in the chamber.

 

I'll second that. Been there, seen it.

 

I want to know know how you guys saw the plugs not fire in the cylinders in 25-words or less.

 

Doh! What a "gotcha"! I'm curious to see the replys Rick. I have experienced a similar phenomenon but for the life of me I could not explain the "why" of it.

 

It's harder for the spark to fire inside the engine due to compression but it can be checked with a spark tester from any auto parts store if you don't have an ignition scope available.

 

Another patient presents itself for a non-starting issue possibly related to ignition system problems.

The calendar is November of 2006. Many moons on the XJ ignition components.

The battery needs to be capable of storing a deep charge and holding it. Seeing 12 V on your meter or having it power the headlight and instrument cluster is no indication that it has the reserve to start the bike and keep it running.

You need the battery "Load tested"
The possibility that both coils would go bad is infinitesimally low.

The OEM fuse panels on every single one of the XJ-Bikes built from the start of the run of production -- (excluding those that DON'T have glass fuses held by self-destructing pinch-clips) -- are highly suspected of causing resistance problems; a great many on the verge of fuse retaining clip failure.

[Browsing the photo gallery will confirm that fuse panel failure is common place. There are dozens of owners who have resorted to installing inline fuse holders bypassing the problematic fuse panel already.]

Alternator and Start Motor Brushes on the complete line of production, especially for bikes having clocked 25,000 miles and above are also a relevant issue to electrical and ignition-related problems.

The electrical contacts on buttons and switches of the handlebar controls, especially Start and Kill switches, must be considered now that the bikes are all 20+ years old.

The buttons and switches can be disassembled, cleaned and their contact surfaces re-newed. Those which toggle or slide Left and Right are often NOT dependent on a spring which may have rusted and failed. Push type buttons DO depend on a spring known to weaken and fail.

Replacing the spring will require "finding" a suitable replacement, either from hardware store stock or some donor appliance, and fabricating the fit.

Jump-starting the bike with cables hooked-up to the battery of a running motor vehicle, with an alternator capable of supplying nearly five times the MAXIMUM Amps (15 amps) that the bike's Voltage Regulator is designed to handle, is very likely to damage the diodes or rectifier in the regulator, causing the Regulator to operate erratically or not at all.

 

This is where I am now, cleaning everything. I am looking real hard at changeing the fuse box. I have a parts bike so if I still have this problem I am going to change out the coils, but for them both to go I don't think so but not sure. Seems more like a wire broke some where. Thanks for the help. I let you all know what I find.
Thanks
Marty

 

You guys? I didn't claim to see the plug not fire in the cylinder. CaptainKirk, you are on your own

I believe the offending plug was firing in the cylinder - through the insulator. Not sure a spark tester would give that away.

 

I have access toa "bomb tester" which applies 8o psi to simulate compression while firing the plug. No air; plug fires. Air, lights out.
That's 25 words, right?

 

I don't know if i'm a retard and I missed something, but I don't believe anyone has asked if you've changed your fuses yet? I had weak looking spark when i pulled any of the four plugs (both coils) i suspected the battery like yepper suggested, but we tried using a seperate power source to turn the starter and still nothing. I then looked on the forums here and decided to change out the stock fuse holder (one of the fuse holders was getting hot and melting the plastic). I guess the holder was causing enough of a voltage drop to affect the coils, once they were changed, it was a nice bright blue, and she fired right up. Now you're going to tell me the fuses have been changed already and i'll shy away into my little corner again...

 

Ummmm, now I do feel stupid, the post on the forum reads that marty82650 posted last, but my post still shows up last, was the above post edited, or am I quite slow today and didn't read it before i posted?

 

NM, i'm guessing that the forum space-time continuum thing had something to do with this, i'm not crazy after all...

 

Don't feel bad Killer, I get my posts bumped when I submit them too. Slow posting is not uncommon.

 

The clock on the server was incorrect for awhile yesterday (see announcements). In addition to causing some people not to be able to post, it seems the order of some posts shuffled when the clock was corrected.

 

Speaking of coils and wires, anyone have a good dependable place to pick up a set of coils for our XJ. Mins are doing good now, but always like to have a hand on set just in case, less down time this way, and can't stand going without my XJ for to long when the weather is nice. I'd appreciate it if someone could give me a heads up.

 

When doing work on my bike, we had the starter disconnected from the battery, and jump started it with booster cables straight on the starter with the key on, this should be acceptable right? i can't see why it wouldn't start and it wont damage the regulator.

 

The coils on my bike are off a ZZR1100 kwaka and work great, $10 at a swap meet and I have no idea of details on ohmage amperage they just work and have done for years,
First step is always replace fuse holder on XJ bikes.
I run a car battery in my sidecar and having a bigger battery has fixed all my starting issues.
The standard Earth lead to the engine is a bit small and getting old replacing it helps.
Check the lead to the starter motor is not getting green either.
I use a lot of WD40 a squirt into the switchblocks every year or so helps a lot I do it whenever I lube my cables.
Most XJ CDI's are prone to failure and intermittent sparking. The one off the Turbo model seems to be the exception they just keep working and seem compatable with most motors no idea of curve etc just years of use on a variety of xj's and motors from 650 to 900 works on all of them.
Hope this is of some help its my first post so some of this may have been covered before.
Dave in Oz

 

The old "Messed-up clock on the server" story ... huh?

Like we never heard that one before!