No spark - here is the trouble shooting I've done

[Guest]

I referenced http://members.dslextreme.com/users/...-ends.html#A17. Battery tested good. New spark plugs. Disassembled each spark plug cap to inspect resistors. Multimeter showing no continuity of any kind, fully open circuit on each resistor. Primary winding on each coil showing 5ohms. Showing fully open circuit from plug cap to plug cap of same coil (secondary windings I presume?). I even removed the caps and tested from spark plug wire ends of same coil which both showed fully open circuits. Tested resistance on the signal generator, which was 157ohms on each, the common to blue and the common the green. CDI box orange/white and black/white both tested at 12v. For step 14 on BassCliff's link above I was unable to test because it uses the spark plugs to prove with a spark that the signal from the signal generator to the coils is good, and of course my spark plugs aren't sparking.

Is it safe to say that the coils have gone bad?

[eil]

Somewhat rare for a coil to go bad, pretty rare for both unless something external fried them somehow. (Too much voltage? Too much heat?) Are the plug wires in decent shape? If the conductive wire inside them is broken on either side, your meter will show an open circuit but the coils may still fire.

I have not actually done this, but I believe a valid test of the coils in isolation would be to "charge" them up with a quick 12V pulse with the spark plugs connected and laying on the engine (or any piece of metal). When current is removed, both plugs should spark.

[rustybronco]

I referenced http://members.dslextreme.com/users/...-ends.html#A17. Battery tested good. New spark plugs. Disassembled each spark plug cap to inspect resistors. Multimeter showing no continuity of any kind, fully open circuit on each resistor. Primary winding on each coil showing 5ohms. Showing fully open circuit from plug cap to plug cap of same coil (secondary windings I presume?). I even removed the caps and tested from spark plug wire ends of same coil which both showed fully open circuits.

Is it safe to say that the coils have gone bad?

Before condemning the coils try a different multimeter. It's very unusual to have both secondary windings showing as open circuit.

[Redman]

.....Disassembled each spark plug cap to inspect resistors. Multimeter showing no continuity of any kind, fully open circuit on each resistor. Primary winding on each coil showing 5ohms. Showing fully open circuit from plug cap to plug cap of same coil (secondary windings I presume?). I even removed the caps and tested from spark plug wire ends of same coil which both showed fully open circuits. ....
.....

I too suspect some error in use of the meter.

Resistors in sparkplugs can go open (no continuity), but by my experience of a couple of them more likely to just go to some high value like 50K (instead of normal 5K). But you seem to say that all are no continuity (infinite resistance), an all of them, which whould be unusall.
And you say the same about both coil secondary, again, unusall.

One way to check things with meter when measuring resistance (ohms, continouity) is to see what meter reads with leads touching each other (zero ohms or near zero ohms) and then with meter leads not touching anything (infinite ohms). Also need to notice some indication if meter is displaying in terms of ohms or 10K ohms or 100Kohms and/or where the decimal point is. Maybe the meter "auto ranges" for that, or maybe you can make it step through the various ranges, but anyway, need to be aware of what range or what units it is displaying in.
So if you are trying to measure ohms and suspect what you are seeing and want to check how you have the meter setup, you can do that, touch leads together to see that reading goes to about zero, and then also with leads apart reading goes way high (some digital meters do something like flash a "1" or display something to indicate out of range or something.).

No need to disassemble caps, can reach in with meter leads.
(actually I did not know they could come apart to get at the resistor, until a recent posting showed that)

Caps can go bad, usally high ohms. And can be easily replace for about $5 each. Are available at most any cycle shop, not neccearily a Suzuki shop.
NGK are a common brand most any cycle shop will have (but not autopoarts store).
.

[RGM]

"I even removed the caps and tested from spark plug wire ends of same coil which both showed fully open circuits. "

That doesn't sound good. You can always disconnect the 12v wire to the primary then run a wire from the battery+ and quickly tap the terminal while holding both ends of the plug wire close to the chassis and see if it sparks. Could be your plug wire which I think you can get a kit to replace them.

[williampkerr]

Before condemning the coils try a different multimeter. It's very unusual to have both secondary windings showing as open circuit.

I don't have a spare multimeter at the moment. I think the one I have works fine though. When the meter is set to 200ohms the primary winding on each coil is showing 5ohms and I tested resistance on the signal generator, which was 157ohms on each pickup, the common to blue and the common the green. Maybe I should just buy new caps to rule that option out?

[williampkerr]

I too suspect some error in use of the meter.

Resistors in sparkplugs can go open (no continuity), but by my experience of a couple of them more likely to just go to some high value like 50K (instead of normal 5K). But you seem to say that all are no continuity (infinite resistance), an all of them, which whould be unusall.
And you say the same about both coil secondary, again, unusall.

One way to check things with meter when measuring resistance (ohms, continouity) is to see what meter reads with leads touching each other (zero ohms or near zero ohms) and then with meter leads not touching anything (infinite ohms). Also need to notice some indication if meter is displaying in terms of ohms or 10K ohms or 100Kohms and/or where the decimal point is. Maybe the meter "auto ranges" for that, or maybe you can make it step through the various ranges, but anyway, need to be aware of what range or what units it is displaying in.
So if you are trying to measure ohms and suspect what you are seeing and want to check how you have the meter setup, you can do that, touch leads together to see that reading goes to about zero, and then also with leads apart reading goes way high (some digital meters do something like flash a "1" or display something to indicate out of range or something.).
.

I have the meter set to 200ohms with the meter leads in the plug caps of the same coil and it's showing open circuit. When I move the meter dial through each of the other ohms settings I still show open circuit. I think my meter works fine though because when I test the primary winding on each coil the meter is showing 5ohms. I also tested resistance on the signal generator pickups, which was 157ohms on each, the common (red) to blue and the common (red) to green. Both of these reading were taken with meter set to 200ohms.

[Steve]

I have the meter set to 200ohms with the meter leads in the plug caps of the same coil and it's showing open circuit. When I move the meter dial through each of the other ohms settings I still show open circuit. I think my meter works fine though because when I test the primary winding on each coil the meter is showing 5ohms. I also tested resistance on the signal generator pickups, which was 157ohms on each, the common (red) to blue and the common (red) to green. Both of these reading were taken with meter set to 200ohms.

You are not getting "open circuit" readings, you are getting "out of range" readings, which, unfortunately, look exactly the same on the meter.

The secondary windings on the coil are in the 20-30k range, so setting the meter in the 20k range might still give you "open" readings. Try the 200k range, you should see a number of 20-30 on the readout. To verify that the meter is working, touch the leads together IN THAT METER RANGE to see that they go from what ever your "open circuit" reading is to approximately ZERO.

.

[tom203]

Unscrew plug caps from a coil- stick meter probes in coil wires, put meter in 20k or 200 kohm range - you should measure about 12 kohm wire to wire.

[williampkerr]

You are not getting "open circuit" readings, you are getting "out of range" readings, which, unfortunately, look exactly the same on the meter.

The secondary windings on the coil are in the 20-30k range, so setting the meter in the 20k range might still give you "open" readings. Try the 200k range, you should see a number of 20-30 on the readout. To verify that the meter is working, touch the leads together IN THAT METER RANGE to see that they go from what ever your "open circuit" reading is to approximately ZERO.

.

I set it to 200k. Leads not touching it shows out of range. When the lead are touching it shows 00.0. I tested the resistance again from spark plug #1 to #4 and from #3 to #4 and the meter is showing out of range.

[williampkerr]

Unscrew plug caps from a coil- stick meter probes in coil wires, put meter in 20k or 200 kohm range - you should measure about 12 kohm wire to wire.

In my original post I mentioned that I did this already, but I decided to test again, this time it tested successfully with a 12kohm reading for each coil's secondary winding. I apologize for posting in error. At this point it sounds like I need four new spark plug caps, right?

[rustybronco]

A 12K ohm reading from plug wire to plug wire (minus caps) is about what I would have expected to see. If you're not getting any resistance readings on the plug caps themselves, or the individual resistors when the caps have been dis-assembled, then yes, you need new plug caps.

[Redman]

So it does sound like you are familiar with using the meter in the ohms check.

Other possibility of suspicious readings might be the meter needs new battery.
Reading all caps open and both coils open is quite suspicious.


.

[williampkerr]

I received new spark plug caps in the mail today. Sadly, after installation I'm still not getting spark. Any suggestions on what to troubleshoot next?

[JayWB]

Ok, look, it works like this.

Your coil is just exactly that, a coil of wire. There’s nothing mysterious about it, it’s just a length of wire wrapped in a coil. Take away the fact that it’s wound into a coil and you’d have a long straight piece of wire.

So your piece of wire should have about 12 volts on the positive end at all times when the key is on. On the other end it should vary between 12 volts and pretty close to zero volts. When there’s zero volts at the negative end there is current going through the wire, from 12 volts to ground. When the negative end is also at 12 volts there is no current going through the wire.

Wrap this wire into a coil and things change only slightly. When the negative side is at zero volts (ground) the current flowing creates a magnetic field. When the negative side sudddenly goes to 12 volts the current quickly stops. That means the magnetic field suddenly goes away. A quickly changing magnetic field creates a high voltage spark in the secondary winding – and there you go, you just made a spark.

So you’re looking for 12 volts always on the positive side of your coils, and a changing voltage on the negative side, from 12 to zero and back to 12. If the negative side isn’t changing you have signal generator problems. If you haven’t got the 12 volts at the positive side you have no power to make any of this work.

These are both pretty simple to look at with a volt meter.