No Spark Troubleshooting (3 Viewers)

[MatthewMcD]

Yesterday I was triumphantly driving around my neighborhood with my buddy who assisted me in replacing my leaking clutch master/slave and hardline. Suddenly the engine ran rough, backfired, ran for about 50 yards and then died. No spark.

Troubleshooting this morning and there is no spark to the plug wires and the coil wire shows a very tiny spark when held near a ground.

I popped the distributor cap off and pulled the rotor. Should the condenser be bulged like this or is that an issue? My replacement condenser does not have the core showing like this.

This is my coil

 

[charliemeyer007]

Looks bad to me. I would clean all the electrical contacts including the fuse box. Look at the inside of the distributor cap where the leads to the spark plugs - aluminum ones get a insulating scale burnt onto them - scrape clean with small blade on your swiss army knife. I like the NAPA Echlin caps with brass contacts. Good spark plug wires are worth the cost IMHO

 

[MatthewMcD]

Looks bad to me. I would clean all the electrical contacts including the fuse box. Look at the inside of the distributor cap where the leads to the spark plugs - aluminum ones get a insulating scale burnt onto them - scrape clean with small blade on your swiss army knife. I like the NAPA Echlin caps with brass contacts. Good spark plug wires are worth the cost IMHO

Thanks, the plug wires, distributor cap, and rotor are all new. It's been running fine until it just died.

 

[MatthewMcD]

More info, I scaled the contacts inside the distributor cap and the end of the rotor. I checked the plugs and they have carbon on them, but weren't horrible. I finally got it to turn over and run for about 5 minutes. I tried to get it back into my driveway and she died. No start.
I let her rest for about 30 minutes and decided to remove the vacuum line to the brake booster in case there was a loss of vacuum. She started again and I got her up the hill and into her usual parking spot.

I let it idle for a bit while I swapped the vacuum line back onto the booster. No difference in the idle except for the moment she lost vacuum while I made the switch.

Sitting idle for another 3 minutes and she died.

I hope this may help any additional diagnostics. Up until yesterday she has been running strong and idling gently without issues. The only recent changes are a fresh tank of Ethanol free gas, which I have driven about 25 miles. Here in Texas she was not driven during our 12-15 degree weather.

 

[charliemeyer007]

Bad gas. Cold weather participates out water into tanks both yours and the station. Get a bottle of yellow gas dryer and dump it in your tank. Then change the fuel filter, wet paper elements will not allow fuel to pass easy enough.

 

[45Dougal]

So do you have a good strong spark now that you cleaned things up?

I start by checking around wherever you were working most recently to see if you interfered with anything (such as disturbing the 12V ign feed to the coil or such like).

 

[MatthewMcD]

So do you have a good strong spark now that you cleaned things up?

I start by checking around wherever you were working most recently to see if you interfered with anything (such as disturbing the 12V ign feed to the coil or such like).

Using an inline spark checker, I have no spark most of the time. I thought about that. I need to look more closely at the wires feeding the coil tomorrow.

 

[charliemeyer007]

The external part of the connector can be clean, but corrosion can creep under the crimped part on the wire and the wire itself under the insulation can also be compromised.

 

[aging fleet]

Did you check the ballast resistor?

 

[MatthewMcD]

Did you check the ballast resistor?

I didn't see a testing procedure in the FSM.
FSM shows 1.3-1.5 Ohms "except US FJ series". Do you know what the resistance should be (assuming this is a US FJ)?

Today was a work day (meaning non-truck work) I'll be sure to report back when I can get back to it.

 

[aging fleet]

When mine died, I had 12v at the black/yellow wire and only like .6 volts at the other post so it wasn't providing enough power to the coil, should be easy to rule out. Here is the thread I posted when it occurred, good luck with it.

'75 2F won't start, question about voltage at the ignitor and coil

Hey everyone, hopefully you guys can shed some light on an issue that popped up this week. For background, my 40 has its original 2F with an 81+ dual advance large cap distributor and later (78-80) black box ignitor. It's been running great all year so no history of shenanigans, but a few...

forum.ih8mud.com

 

[MatthewMcD]

When mine died, I had 12v at the black/yellow wire and only like .6 volts at the other post so it wasn't providing enough power to the coil, should be easy to rule out. Here is the thread I posted when it occurred, good luck with it.

'75 2F won't start, question about voltage at the ignitor and coil

Hey everyone, hopefully you guys can shed some light on an issue that popped up this week. For background, my 40 has its original 2F with an 81+ dual advance large cap distributor and later (78-80) black box ignitor. It's been running great all year so no history of shenanigans, but a few...

forum.ih8mud.com

Thanks!

 

[fjc-man]

Once you get it running again, run a jumper wire between the battery and the ignition fed side of the coil. If it continues to run with no dying, you may have intermittent power from the ignition switch. Like poor contacts inside the switch.

 

[MatthewMcD]

Thanks again y'all are awesome.

Looks like it's the ballast resistor. I bypassed the resistor and she fired right up. It kept running for 10 minutes too. When I initially tested the resistor it read 1.0 ohm. After it warmed up it dropped to 0.5-0.6 ohms.

For the folks who are asking on other threads about using the inline spark tester and bypassing the resistor here's the process:


@aging fleet your thread was very helpful. Thanks for the part number. <3

 

[MatthewMcD]

Once you get it running again, run a jumper wire between the battery and the ignition fed side of the coil. If it continues to run with no dying, you may have intermittent power from the ignition switch. Like poor contacts inside the switch.

Not real clear on this test. Which pole of the battery? I assume + since that is the ignition side...right? Should this shut off the ignition?

 

[fjc-man]

Not real clear on this test. Which pole of the battery? I assume + since that is the ignition side...right? Should this shut off the ignition?

The reasoning is - if the contacts in the ignition switch, or the wiring between the coil and switch isn’t up to the task the jumper between the battery positive and the coil would be a known good and constant source of power. The main reason the switch would be suspect is the crazy number of times the contacts in that switch have been cycled. As a old german I used to work with said, “nothing is forever”. So if runs uninterrupted, look towards the switch. Oh, and was the ballast resistor the culprit?

 

[MatthewMcD]

The reasoning is - if the contacts in the ignition switch, or the wiring between the coil and switch isn’t up to the task the jumper between the battery positive and the coil would be a known good and constant source of power. The main reason the switch would be suspect is the crazy number of times the contacts in that switch have been cycled. As a old german I used to work with said, “nothing is forever”. So if runs uninterrupted, look towards the switch. Oh, and was the ballast resistor the culprit?

Looks that way, yes. I bypassed the ballast resistor and it fired right up.

So the jumper is from the positive of the battery to the positive of the coil and what should it do?

 

[fjc-man]

Matt, the same thing the ignition switch would do. Supply voltage/current to the igniter and coil. You would still have to activate the starter with the key. If running this way, to shut it off you would disconnect the jumper.

 

[sggoat]

Think the purpose of this external-or "ballast" resistor is to help dissipate heat from the coil(it is a big resistor--but only has 1.3 to 1.7 ohms resistance)-thus bypassing the resistor would potentially subject the main coil to higher heat load -thus reducing it's life over time--In a pinch--if the ballast resistor is difficult to get soon, and you need the vehicle to run now, you might try using the heater blower motor resistor as a substitute(in an emergency) disconnect the heater blower motor resistor connections(you won't be able to use the heater now) then jumper the ballast resistor wires to the heater blower resistor(think it's about in the same ohm range as the ballast resistor(1-5 ohms, maybe))--hope some others may comment here to confirm--

 

[jembourbe]

I didn't see a testing procedure in the FSM.
FSM shows 1.3-1.5 Ohms "except US FJ series". Do you know what the resistance should be (assuming this is a US FJ)?

Anything less than 2.5 Ohms should be ok. And make sure the meter reads steady (else broken wire making & losing continuity)