Question about Duraspark 2 Ignition System

[Jesse3877]

Hello, i made a short video asking for help regarding higher than wanted voltage at Ignition Coil.

Let me know your thoughts and thank you for your time.

 

[ArdWrknTrk]

If you want to test for the resistor wire disconnect the coil and DSII power plug.

Ohm between the coil power and the red and the white wires in the DSII plug.

How high is the truck voltage when it is running?

If the resistor is working but the alternator is putting out 15V what you see may be entirely normal.

A simple Ohms law calculation will show you that.

[Gary Lewis]

If you want to test for the resistor wire disconnect the coil and DSII power plug.

Ohm between the coil power and the red and the white wires in the DSII plug.

How high is the truck voltage when it is running?

If the resistor is working but the alternator is putting out 15V what you see may be entirely normal.

A simple Ohms law calculation will show you that.

Jim is spot-on. You really need to measure the voltage or resistance when the engine is off. That's because when it is running the ignition module is making and breaking the circuit several times/second.

So your meter is in DC mode and seeing a very complex signal of maybe 7 - 9 volts when the circuit is closed, then a rising voltage to something like 35 volts due to the ringing as the circuit opens, then down to battery voltage while the circuit is open. And a DVM cannot properly "read" that.

Here's a pic from my oscilloscope of a DS-II ignition primary circuit while the engine was running.

[ArdWrknTrk]

Jim is spot-on. You really need to measure the voltage or resistance when the engine is off. That's because when it is running the ignition module is making and breaking the circuit several times/second.

So your meter is in DC mode and seeing a very complex signal of maybe 7 - 9 volts when the circuit is closed, then a rising voltage to something like 35 volts due to the ringing as the circuit opens, then down to battery voltage while the circuit is open. And a DVM cannot properly "read" that.

Here's a pic from my oscilloscope of a DS-II ignition primary circuit while the engine was running.

I don't have any 'fancy' test equipment at hand, but I will say the resistor is only going to show while the coil is actively sinking current.

I hadn't really thought about ringing but it obviously there, EMI is its artefact.

[Gary Lewis]

I don't have any 'fancy' test equipment at hand, but I will say the resistor is only going to show while the coil is actively sinking current.

I hadn't really thought about ringing but it obviously there, EMI is its artefact.

With the coil and DS-II module out of the circuit, as you suggested, he should be able to measure the 1.1 ohm resistance of the wire.

As for measuring the voltage, I've often wondered if the DS-II module sinks current regardless of where the rotor is if the engine isn't turning. In other words, as if the points were closed. I haven't checked by bumping the starter, but every time I've put a meter on the coil it is obvious the module is sinking current.

[ArdWrknTrk]

With the coil and DS-II module out of the circuit, as you suggested, he should be able to measure the 1.1 ohm resistance of the wire.

As for measuring the voltage, I've often wondered if the DS-II module sinks current regardless of where the rotor is if the engine isn't turning. In other words, as if the points were closed. I haven't checked by bumping the starter, but every time I've put a meter on the coil it is obvious the module is sinking current.

The reluctor wheel needs to be spinning past the pickup in order to induce a trigger pulse for the transistor in the module.

So, you have your answer.

[Gary Lewis]

The reluctor wheel needs to be spinning past the pickup in order to induce a trigger pulse for the transistor in the module.

So, you have your answer.

Makes sense. Thanks.

[ArdWrknTrk]

Makes sense. Thanks.

You can check by tapping the distributor with a screwdriver handle.

That should be enough to trigger the module.

In fact this is the Ford diagnostic procedure.

[Jesse3877]

With the coil and DS-II module out of the circuit, as you suggested, he should be able to measure the 1.1 ohm resistance of the wire.As for measuring the voltage, I've often wondered if the DS-II module sinks current regardless of where the rotor is if the engine isn't turning. In other words, as if the points were closed. I haven't checked by bumping the starter, but every time I've put a meter on the coil it is obvious the module is sinking current.

Hello and good morning Gary and Jim,

 

 

Here is some answers to your questions/ recommendations:

Engine Idling= 14.5v at battery 

Engine Idling= 10.5v at coil

 

Testing results:

 

 

With ICM plugs disconnected & coil disconnected and truck battery still connected I get:

 

1. Coil (+) to Red ICM wire=1.2 ohms

2. Coil (+) to white ICM wire= 25 ohms But if I pull the s wire of fender relay it goes to OL (open lead) 

So test #1 should verify that I DO have a resistor wire correct? 

Not sure if this helps what Gary was saying but I also noticed I have continuity between Power and ground through the distributor pickup (tested between ICM supply power and mag pickup negative). It’s 25 ohms but if I pull the distributor plug it goes OL. I forgot to pull the cap and see if the rotor was pointing. Headed back out to truck shortly. 

Warm regards,

Jesse

 

 

 

 

 

 

 

 

 

[ArdWrknTrk]

Good morning Jesse.

1.2 Ohms seems a little high (1.05-1.15 is spec) but that could be down to a little oxidation in a connector or even the leads of your meter.

Remember, you're not testing by putting any kind of real load on the system.

But you have proven that the resistance is there.