No start - very weak spark

Blue Brick · Friday at 1:48 PM

Our patient:
1977 400 with Lean Burn conversion to a 5 pin, single terminal ballast, with a Mopar distributor that has vacuum advance.

The conversion was completed by the previous owner.

Battery has 12 volts.

With the control module unplugged; the positive and negative posts on the coil have the same voltage, 11 something.

With a control module plugged in, the positive terminal is 5.46 I think, and the negative is 1.4.

There is no spark from the coil during cranking, only a little faint spark towards the end of the cranking cycle via the inline spark tester and the coil wire.

The unhooked pickup coil measures 282 ohms.

Tools:
Performance Tool Digital Automotive Mult.imeter
Old fashioned test light
High Energy Ignition Tester

New parts:
Cap, Rotor, Coil, and plug wires (replaced after the problem occurred)

This is a father-son project and it's not a daily driver. The car was difficult to start. Once it was started it would intermittently shut off. This happened in the driveway. We drove it to the gas station and the car remained running while I was putting a couple dollars worth of gas in it. After we left the gas station, it suddenly shut off. I was unable to restart it (drained the battery). I pushed it to a side road and began trying to attempt to restart it via a jump start. Starting fluid did Not cause it to bark whatsoever. After a little while it did restart like a champion, but shut after I traveled the distance of about 400 feet.

Any suggestions, recommendations, or feedback would be most welcome.

Before posting, I did use the search feature to try and find similar posts with the same symptoms.

I am familiar with the Dura spark system and I'm leaning on the control module the possible cause.

khryslerkid · Friday at 2:34 PM

$2 of gas won't get you very far now days.

Has the car ever ran right since you've owned it?

Blue Brick · Friday at 2:38 PM

khryslerkid said:
$2 of gas won't get you very far now days.

Has the car ever ran right since you've owned it

A little background. It's a fathers on project. Would I take at across the country? No. Did it start with minimal effort? Yes. Could it be driven around the block just to move the fluids around? Yes.

khryslerkid · Friday at 2:41 PM

Have you tested the ballast? A bad one will spark when letting off the ignition.

Blue Brick · Friday at 2:48 PM

Yes I checked it and it was getting power, but just so we're aligned, how would you like me to check it or verify that it works?

I will tell you it doesn't look like the OE ballast resistors. It may be some silly performance resistor. It kind of looks like an MSD resistor.

Blue Brick · Friday at 2:58 PM

I do appreciate the help.

super-bee_ski · Friday at 4:10 PM

Minimal detail but I personally would check your distributor.
The newer style distributors have something like a 12 micro-second length spark.
Unless your distributor is new...I would suspect that 1st providing you have checked the normal stuff.

Blue Brick · Friday at 4:32 PM

khryslerkid said:
Have you tested the ballast? A bad one will spark when letting off the ignition.

1.5 ohms.

Bee1971 · Friday at 10:11 PM

5 pin, single terminal ballast

Is what you said

If it is a real deal 5 pin ignition module , ECU

Requires a Factory Dual Ballast Resistor - 5th pin on ignition module requires power thru the 5 OHM Resistor side of the ballast

Anyways if your not sure - Snap some pictures of your ignition module , see if it’s real transistor or fake and you can confirm indeed five pins , not four

Blue Brick · Friday at 10:34 PM

Bee1971 said:
5 pin, single terminal ballast

Is what you said

If it is a real deal 5 pin ignition module , ECU

Requires a Factory Dual Ballast Resistor - 5th pin on ignition module requires power thru the 5 OHM Resistor side of the ballast

Anyways if your not sure - Snap some pictures of your ignition module , see if it’s real transistor or fake and you can confirm indeed five pins , not four

Not really new to Mopar, but it's been a long time.

It has two terminals. While researching my issue people were calling the two terminals "single" and the four terminals "dual'.

Yes it's a five pins. Five wires.

It's set up like the Mopar performance conversion.

Bee1971 · Friday at 10:42 PM

Just because five wires , doesn’t mean your ignition module is five pins

All those plugs where five wires

Chrysler got rid of the fifth pin when they redesigned the ignition module in the mid seventies

Four pin ignition modules will work with both single AND dual ballast resistors

A true five pin ignition module requires a dual ballast resistor

You won’t know until you pull the plug off the ignition module itself

Honestly you don’t see many factory five pin ignition modules anymore , but that’s what you stated five pins , not five wires

Anyways

Also what ignition coil are you running ?

Blue Brick · Friday at 11:06 PM

Bee1971 said:
Just because five wires , doesn’t mean your ignition module is five pins

All those plugs where five wires

Chrysler got rid of the fifth pin when they redesigned the ignition module in the mid seventies

Four pin ignition modules will work with both single AND dual ballast resistors

A true five pin ignition module requires a dual ballast resistor

You won’t know until you pull the plug off the ignition module itself

Honestly you don’t see many factory five pin ignition modules anymore , but that’s what you stated five pins , not five wires

Anyways

Also what ignition coil are you running ?

During my testing I took the connection off. 5 pins.

Do I need five pins? I don't know. I didn't set up this conversion. But I usually unless I know otherwise; I replace apples with apples.

Coil is part #2-5195.

Geoff 2 · 2025-05-31T01:38:38-0500

[1] Remove the wires from the bal res. Measure the resistance; one should be 1.5 ohm or less, other should be 5 ohm.
[2] The 'cranking' position of the ign switch. Sometimes called ign 2. This supplies the cranking cct of the ign system. If this has a break/bad connection, you get no spark during cranking & only get spark when the ign sw is released to the 'run' or ign 1 position. Your symptom.

Blue Brick · 2025-05-31T03:05:18-0500

Geoff 2 said:
[1] Remove the wires from the bal res. Measure the resistance; one should be 1.5 ohm or less, other should be 5 ohm.
[2] The 'cranking' position of the ign switch. Sometimes called ign 2. This supplies the cranking cct of the ign system. If this has a break/bad connection, you get no spark during cranking & only get spark when the ign sw is released to the 'run' or ign 1 position. Your symptom.

Is this square box on the firewall? Or the switch on the column?

Note: I have a Saginaw column.

Blue Brick · 2025-05-31T16:53:19-0500

The control module is putting 0.5 volts to the pickup coil. I was able to make the coil spark using a test light and the spark tester. In the Arizona daylight it did seem like a weak spark.

Just for good measure I did change the silicone coil wire.

Blue Brick · 2025-05-31T17:05:19-0500

Right now the battery is too weak to check the volts coming out from the pick up coil.

RJRENTON · 2025-05-31T18:24:30-0500

Blue Brick said:
The control module is putting 0.5 volts to the pickup coil. I was able to make the coil spark using a test light and the spark tester. In the Arizona daylight it did seem like a weak spark.

Just for good measure I did change the silicone coil wire.

The control module or ECU, Electronic Control Unit, does not put out any voltage to the pick up coil in the distributor. The pick up coil generates a pulse, each time the reluctor passes by the pick up coil's face, which triggers the ECU to turn OFF the coil's primary current, creating the spark. ........FYI.....
BOB RENTON

Blue Brick · 2025-05-31T20:05:50-0500

RJRENTON said:
The control module or ECU, Electronic Control Unit, does not put out any voltage to the pick up coil in the distributor. The pick up coil generates a pulse, each time the reluctor passes by the pick up coil's face, which triggers the ECU to turn OFF the coil's primary current, creating the spark. ........FYI.....
BOB RENTON

I was following/trying the test procedures here.

10:45

Bee1971 · 2025-05-31T21:23:39-0500

Geoff 2 said:
[1] Remove the wires from the bal res. Measure the resistance; one should be 1.5 ohm or less, other should be 5 ohm.
[2] The 'cranking' position of the ign switch. Sometimes called ign 2. This supplies the cranking cct of the ign system. If this has a break/bad connection, you get no spark during cranking & only get spark when the ign sw is released to the 'run' or ign 1 position. Your symptom.

Did you read my posts

Did you read his posts

He is running a FIVE pin ignition module with a SINGLE ballast resistor

Well NOT running anymore

Carry on

Bee1971 · 2025-05-31T21:26:38-0500

Blue Brick said:
During my testing I took the connection off. 5 pins.

Do I need five pins? I don't know. I didn't set up this conversion. But I usually unless I know otherwise; I replace apples with apples.

Coil is part #2-5195.

You need 4 PINS Ignition Module if your running a SINGLE ballast resistor

No start - very weak spark

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