No spark

[Litchkar]

I need help! My 71 340 with electronic ignition does not have any spark. I have tried 3 coils, two ignition boxes, and two ballast resistors as well as bi-passing the resistor. I have voltage at the coil (8 volts) and it registers a dwell on the meter of 25-28 degrees. I have tried a different coil lead but nothing helps. Changed the cap and rotor too. Only thing that I have not done yet is swap out distributor and harness. Does any one have any ideas?

 

[napaguy]

i just went through same thing. change distributor thats probably your problem.

 

[Adam]

Does it crank?, is the neutral safety switch hooked up?

Also a good read: Mopar Action On-line - Tech Archives

 

[Litchkar]

yes it cranks, neutral switch is hooked up too. Great compression, but zero spark.

 

[AUSTA]

Is the module well earthed & the engine must be earthed if it cranks check the earth between the engine & ignition case with a meter it should be zero ohms if you have a tacho take the tacho wire off in case it is shorting the circuit

 

[Litchkar]

The tach lead is disconnected. There is continuity between the ECU and block, zero ohms. The negative side of the coil is grounding when the positive side is is connected. This does not seem right.

 

[AUSTA]

The tach lead is disconnected. There is continuity between the ECU and block, zero ohms. The negative side of the coil is grounding when the positive side is is connected. This does not seem right.

Not sure how the yours is wired i have an orange module with 2 wire pickup distributor with key off i have 256 ohms from ground to both sides of the coil.
How many ohms do you have to earth from the coil

 

[Litchkar]

I also have a 2 wire dist. with an orange box. With key off, both sides of coil read zero ohms to ground

 

[AUSTA]

Take wires off your coil measure the coil to ground
Check the 2 coil wires to ground with them disconnected
Unplug the dizzy & check the Dizzy wires to ground ( the reluctor coil may have a short to ground )
Check the black & yellow coil wire from the ECU to ground.

 

[Litchkar]

With both wires off the coil, no ground from coil.
With coil wires off:
- Coil wire from ECU ( black w/ yellow) grounded.
+ Coil wire from ballist grounded
Brn w/white from ECU to dist grounded
Neither of the dist pig tale grounded
With harness off ECU, only + coil lead grounded

 

[AUSTA]

The black yellow wire disconnected but with the ECU plugged in should be around 3.3 K ohms if you put your meter on diode test in one direction it should be roughly .5 in the other (reverse Leads )it should be around 2.2 volts.
If it is zero or close to then either the ECU is shorted or someone has joined the ECU wires to the original loom and has not insulated them properly & they are shorted in the loom.

 

[Litchkar]

Austa, I appreciate your help. The. Black wire reads zero resistance back to thru the ECU to ground. My meter does not have a diode test mode. I replaced the ECU and its loom a few months ago along with the dist. So, should I swap back out to my old loom and ECU ?
Thanks again for your guidance.

 

[AUSTA]

If it was working i dont see why not.
I would leave the tacho wire off until the other ECU works
Who knows could be a crossed over wire or you may have received a dead ECU i have had a blue one arrive DOA

 

[Litchkar]

Austa,
I swapped both the loom and ECU out and it started up. The loom was the only part that i had not swapped during this problem. I plugged the new ECU back in, but it is dead. One of them shorted the other out. Thanks again for all of your help, time to get new back ups.

 

[reborn73]

Just went through the same thing........Changed out everything and still no spark. The yellow/black wire in the connector that sits just at the back of the intake (passenger side) was not connected inside the white plastic connector. All the wiring was OE and it had the same symptoms that you discribed. When checking and running each wire to see if there was a bad connection, the yellow/black pulled right out. There was less than 1/32 of bare wire at the end of the yellow/black wire. I took the brass connector out of the white plastic connector and there was no wire left in the brass connector. All these years of driving and it was fine until this past fall. Fires right up now.