Ignition Coil Question

[parsok]

Folks; please forgive the double post (http://fiatspider.com/f08/viewtopic.php?f=5&t=18880) but I am quite desparate for help.

My '80 carbed will no longer start. I've done all the testing and determined that there is power to the ignition coil and it is producing voltage to the distributor. However, I am not getting any spark at the plugs. I have replaced the distributor (with a new to me from another member of the forum) that appears to be in fine shape. I have replaced the ICM.

Question - does the voltage fromn the ignition coil degrade i.e. although it is producing voltage can it be of insufficient quality/strength to produce a spark at the plugs?

[djape1977]

yes. new coil could be the way to go, but first try borrowing a coil from a running car for a test.

[majicwrench]

Coils seldom fail, they are a very simple device.
"Producing Voltage to the Dist" ---clarify, how is coil producing volt to dist?? How did you test it? Are you talking about battery voltage thru (-) term of coil, or high-voltage thru the coil secondary wire??
Keith

[parsok]

I'm hoping i get the terms correct.

I measured 12.4V to the +B side with the key in the on position.

I meant a current from the top (center) of the coil through the high tension wire to the distributor cap. I tested it by removing the dist. cap end and holding it about 1/2" from a ground on the side of the car. I had the better half crank the engine and I saw a steady flow of electricity arcing from the wire end to the ground. The colour was yellow - should it be blue?

Is there a way to actually measure the amount of volts?

Dave

[azruss]

I would worry less about the color of the arc and more about the snap and how much of a gap it will jump. might want to check your ground to the coil and make sure its clean. also might be worthwhile to make a jumper and replace the ground with a fresh test wire.

[parsok]

I measured the Ohms of the magnetic pickup and it was within spec with I put the leads into the ends of both connectors. When I then touched one of the multi-meter to the dist. body it read O.L. I assume this means Unlimited Resistance?

[majicwrench]

Stop messing with the magnetic pu etc. If you have a 1/2" spark jumping from the coil wire to ground, your coil, module, ICU and pick up are working just fine. The spark is getting to the dist. Now all it has to do is get sent to the correct plug wire. So the only things left that can cause you issues is cap and rotor. Do you have a diff rotor to try?? OR, remove cap, and hold coil wire near the center term on the rotor, where the little button from the capgoes. Now have sig other crank engine. Spark should NOT jump from coilo wire to rotor now. If it does, rotor is burned thru.

It could also be that rotor is not pointing at a contact in dist when coil fires, but that's stretching it. So tell, at what point did car fail to start?? Just driving down road??
Keith

[parsok]

Update

Well, it still does not start and it is not producing a spark at the plugs. Here is what I have tried since the last suggestions:

• Replaced the spark plug wire set
• Installed a new rotor – that makes 3 rotors now
• Replaced the ICM
• Changed the dist cap
• Put in a buddy’s ignition coil that is known to work
I tested the spark by connecting one end of a jumper cable to a good ground and the other end holding the plug on the metal just above the threads.

There is a 12.4V to 13.1V reading on both the pos and neg side of the ignition coil. The coil output wire produces a spark to the ground when tested.

Majicwrench suggested a test for a ground problem – pull the dist cap and hold the dist. Cap coil output wire lead just above the exposed rotor and turn the engine. Apparently if it sparks to the rotor there is a ground problem. I tried this and I got a mixed result. Once it arced quite spectacularly to the rotor and the other times it did not. SO it seems there is a potential problem. Not sure how to fix it though.

Also, before it quit for good I noticed that it was starting to miss. This was especially noticeable when I tried to set the timing. When I hooked up the timing gun clip to the #1 wire it would strobe intermittently and sometimes not strobe for seconds at a time. When I put it on #4 it was a better strobe but still experienced missed strobes.

I’m believing this is a ground problem, but where? I had previously put installed a ground cable (negative battery cable) from the engine post that held the now defunct emission controls air pump to a new bolt I added to the side of the engine compartment. I know this ground is good because I use it with the multi-meter to test the readings. I’m going to check the engine ground wire tonight – I’m told it’s under the car near the transmission shifter to make sure it did not come loose.

Any other ideas? What about the ground to the coil from the fuse rack?

[majicwrench]

OK, last I heard you were NOT getting a spark from coil wire?? You are now??
IF you are getting a consisatant, 1/2'" spark jumping from your coil wire to a ground when engine cranked, the module, pu, ecu, wiring is all ok.
One spectacular spark jumping to rotor does not neccessarlly indicate a bad rotor. Just like above, you are looking for nice, consistant spark.
If you are NOT getting a consistant spark from your coil wire to ground when engine cranked you have issues with pu, module, ecu, wiring etc. Since you have power (12v) getting to coil we know that is good. Now on the neg side of coil, module should ground that terminal, then open it to produce spark.

SO, let's start again. Do you have a nice zap zap zap spark coming from coil wire to ground when you crank engine??

Engine ground under car realilsticly not causing you a problem.

Spark??

[parsok]

Yes, I am getting a consistent zap zap zap from the coil output wire to the ground.

[majicwrench]

Then IF you are getting zap zap zap from coil wire to ground EVERYTHING up to there is fine. Coil, grounds, wiring, module, ecu,pu etc is all OK.
From the coil wire the rotor and the cap are the ONLY THINGS in the way of getting spark to the plugs. Want to get carried away testing stuff?? Take coil wire, take a spare rotor Tape coil wire to center of rotor, with rotor NOT ON DIST. Now take a plug wire, and tape it's dist end onto the contact end of rotor. Now stick plug into plug end of plug wire, secure to ground. Now crank engine. IF you have good spark from coil, now you should be getting good spark from plug. Report back.

[parsok]

Affirmative, there is a spark at the plug. I tested it on 2 rotors. Spark was kind of yellow though.

[majicwrench]

That is all it has to do when it fires thu the cap is make it across top of rotor. So why won't it spark at plug when rotor is in dist??
Take your coil wire-rotor-plug wire set up and have somebody carank motor. Nice zap zap at plug?? yes?? then take test light or some other GROUNDED wire and stick it up where shaft of dist goes into rotor. Now crank engine again. See if is still zaps zaps zaps.
Spark is tough to define as to color. Open plug gap up on plug you are testing to 045 or so. And when you are testing at coil wire to good ground, with partner cranking engine, spark should jump good 1/4"
Report back.

[parsok]

Ok, just so I understand correctly. I touched the grounded wire to the underside of the rotor, the circle in the middle where the rotor would touch the top middle of distributor or in this case the opposite side of the where the coil output wire is touching the rotor?

If so, then yes there is still a spark.

Also, when touching the output wire to the ground it jumps a good 1/2"

[majicwrench]

Ya done good, the rotor is not burned thru. Put it back together and see if you have spark at plugs, cause everything works.
Keith