ignition diagnosis

[WmWatt]

Question: Can anyone post the accecptable resistance in the inner and outer coil circuits and the spark plug wire?
I had these at one time but cannot locate or find using online searches. I think the wires might be <30K.

Situtation: Engine cuts out while running warm

Remedies so far: Cleaned plugs and wires. #4 wire which is at bottom of distributor cap had corroded clip which broke so
replaced wire with one from wrecker for 99 cents. Sprayed carburettor with carb cleaner. Vacuum guage warm engine shows
needle moving small amount indicating missfire. Suspect ignition module but want to eliminate less expensive possible
causes first.

thanks.

[Movin]

You should have around 5000 ohms per foot.

System should be capable of over 1/2 arc from wire termination to ground while running on remaining cylinders

[WmWatt]

Thanks. Assume that would be ignition wire resistance.

Second point: Is it okay to disconnect one wire at a time to see if one is causing the miss? Aim would be to watch needle of vacuum guage to see if eliminating a wire removes vibration. If so that wire (or connection) is cause of missing. Would that harm igniton components? I imagine removign one wire, sarting engine, watching needle, stop engine, replace wire, remove next wire, and repeat.

FYI: Back in 1998 I replaced the ignition module. Before replacing it was taken to an auto parts stores for free testing. They no long have that tester. Now they use and OBDII scanner to do the same but of course the old Festivas don't have OBDII connectors. I'll call around and see if any other parts stores in my area still have the old tester (mfg by www.distester.com).

Supplimentary question: Would it be possible to get an OBDII connector and wire it up to an old Festiva for OBDII scanning? Only a few of the connectors would be connected to anything but maybe that would provide some diagnostic info on a modern scanner?

[WmWatt]

Oops, I do still have the resistance numbers. Looking through my copy of the Haynes manual I see where I had written them in the margin.
6000 ohm maximum for spark plug wires
0.8-1.6 ohm for coil primnary winding (small wire)
6,000 - 30,000 ohm for coil secondary winding.

[WmWatt]

The vaccum guage drops slightly every second or so irregularly.
The tachometer does the same.
The guide says the vacuum guage indicates sticky valve or ignition miss.
I assume a sticky valve would not affect rpms on the tachometer. Is that right?
If so it must be ignition miss?
I've had dirty wires or plugs before and they make the vacuum guage vibrate quickly.
So I think the guages are indicating an ignition module misfire. Does that sound right?
The connections on the ignition module are clean and tight.
The bedding under the ignition module (a white paste) is not discoloured.
That would indicate any ignition module miss is internal?
I can'f find a way of testing an ignition module directly at home.

I checked all the coil and high voltage wire resistances and they were good.
I held a spark plug wire near a gound while cranking the engine with a remote
starter switch and the spark was mosly white but with a blue bit in it.
I warmed up the engine after dark and looked for sparks around the ignition
components but didn't see any.

[Kbaker2012]

Question: Can anyone post the accecptable resistance in the inner and outer coil circuits and the spark plug wire?
I had these at one time but cannot locate or find using online searches. I think the wires might be <30K.

Situtation: Engine cuts out while running warm

Remedies so far: Cleaned plugs and wires. #4 wire which is at bottom of distributor cap had corroded clip which broke so
replaced wire with one from wrecker for 99 cents. Sprayed carburetor with carb cleaner. Vacuum gauge warm engine shows
needle moving small amount indicating misfire. Suspect ignition module but want to eliminate less expensive possibilities
causes first.

thanks.

IF YOU REPLACED YOUR MODULE LET ME KNOW IF THAT SOLVED THE ISSUE AS MY 89 FESTY IS DOING THE SAME THING.

[WmWatt]

Hi, I posted the original thread. The problem turned out to be a weak 25-yr old original igniton coil. I guess they don't last forever. Sadly I wasn't able to determine the cause by diagnosis. The parts store was hooking up the ignition tester wrong and it took a while for me and the store manager to figure that out with the help of the tester manufacturer. Once we determined the module was testing okay I ended up replacing a couple parts until the problem went away. It was definitley the ginition system, though. Good luck.

[Movin]

Thanks. Assume that would be ignition wire resistance.

Second point: Is it okay to disconnect one wire at a time to see if one is causing the miss? Aim would be to watch needle of vacuum guage to see if eliminating a wire removes vibration. If so that wire (or connection) is cause of missing. Would that harm igniton components? I imagine removign one wire, sarting engine, watching needle, stop engine, replace wire, remove next wire, and repeat.

FYI: Back in 1998 I replaced the ignition module. Before replacing it was taken to an auto parts stores for free testing. They no long have that tester. Now they use and OBDII scanner to do the same but of course the old Festivas don't have OBDII connectors. I'll call around and see if any other parts stores in my area still have the old tester (mfg by www.distester.com).

Supplimentary question: Would it be possible to get an OBDII connector and wire it up to an old Festiva for OBDII scanning? Only a few of the connectors would be connected to anything but maybe that would provide some diagnostic info on a modern scanner?

There is some things here worth discussion considering the new OP.
When you pull a plug wire back to check the power of the spark that is okay. But, if you pull it back further to check for dead cylinders or whatever, the coil will still try to jump the gap. Because the gap is too big you will not see a spark. The spark will fire internally in the coil across the windings. This will ruin the coil, everytime it does this it will lower the maximum the coil can produce until the car starts missfiring all the time. But, when the coil discharges internally there are spikes induced into the primary coil circuit. This will dissipate through the easiest path, generally the module or maybe a tach. For this reason if you find a bad coil or a bad module you should replace both.

[tooldude]

It's worth mentioning, for those who don't know, that you should secure the loose plug wire or use a spark testing tool to prevent what Movin is describing above. It's too easy to slip or move the terminal too far from ground. It only takes one time to breach the coil wire insulation if & when the voltage gets high enough and then it can track continually. As the total resistance increases in the secondary spark system, the spark voltage increases up to the maximum it is capable of producing - probably the reason for most coil failures. Increasing air gaps cause higher resistance & coil voltage also - internal breaks in plug wire or terminal loose, rotor & cap terminals eroding away, spark plug gap eroding, or setting plug gaps wider, the engine running lean is electrically equivalent to a wider gap for the spark. Add it all up and an old coil may not withstand it.

[Kbaker2012]

Hi, I posted the original thread. The problem turned out to be a weak 25-yr old original igniton coil. I guess they don't last forever. Sadly I wasn't able to determine the cause by diagnosis. The parts store was hooking up the ignition tester wrong and it took a while for me and the store manager to figure that out with the help of the tester manufacturer. Once we determined the module was testing okay I ended up replacing a couple parts until the problem went away. It was definitley the ginition system, though. Good luck.

I replaced my coil with an ACCEL SUPER COIL and it cuts out once the motor is warmed up I have the 32/36 weber carb and FMS cam with egr delete plate