No Spark

[roadrnrd]

I am trying to start my newly restored 1970 roadrunner for the first time in 20 years. The engine turns over, and it's getting gas, but it won't fire.

I've traced the whole circuit from the battery - relay - starter - VR and control module - ballast resistor - coil - distributor (electronic). Everything has voltage, but there is no current to the spark plug wires when I test one. By the way the engine has been rebuilt and all these parts are new.

Any idea what the problem could be? Are there specific voltages I should be looking for at the specific components mentioned above? When I probe them with a volt meter they all read between 6 and 12 volts at the different locations.

 

[Pops1967GTX]

Check power at the coil in run and start position? 12 volts to blue/ylw wire in ecu harness? blk/ylw to coil. ecu has good ground? ground strap on engine? Check for rust in back of Ballast resistor.

try these sites
http://www.4secondsflat.com/Testing HR688.htm
http://www.fourforty.com/techstuff/ignition.html
http://www.moparaction.com/Tech/archive/roadside.html

 

[roadrnrd]

Thank-you for the help!

The ballast resistor I have has 4 terminals and is all ceramic material. I am not sure how this is supposed to be mounted, there are not obvious locations. Any suggestions?

I do get voltage from the coil to the distributor in run and start positions, but just no spark any further to the plugs. I will check the voltage values and ground in the morning.

 

[generaljmwlee]

had the same problem when starting mine after the rebuild. I put a electronic dist in ,and found out the air gap in the dist was set at .035 when it needed to be at .008. the dist wasnt getting a rotational signal because of it.

 

[Pops1967GTX]

Ballast should be mounted on firewall next to ecu... photo is of a 1970 RR http://board.moparts.org/ubbthreads/upload2/5417872-RREngine1.jpg

 

[rustycopcar]

if its equipped with a magnetic pickup and reluctor in the distributer it would be ideal for you to check the clearances for that while you trouble shoot. i had one randomly go bad on me a few months back. very irritating because i replaced everything in your mentoned list. take the 15 min to check it out. and i just noticed this is the same issue generaljmwlee just mentioned.

 

[WileE]

Thank-you for the help!

The ballast resistor I have has 4 terminals and is all ceramic material. I am not sure how this is supposed to be mounted, there are not obvious locations. Any suggestions?

I do get voltage from the coil to the distributor in run and start positions, but just no spark any further to the plugs. I will check the voltage values and ground in the morning.

Rotor ?

 

[racedodge]

make sure your ECU is grounded properly. If an ECU is bad or not grounded, you will not get fire from the distributor.

 

[Ron 73]

If you have a 12 volt test light hook one end to + side of coil, ground the other end (you may need help), turn your key to run position it should light up, when cranking it should get brighter.. Easy way to check ballast.. Make sure your plug in outside of distributor isint corroded and tight being its set for awhile.. Just a couple suggestions..

 

[tpodwdog]

You mentioned everything but the rotor......is there a rotor in the dizzy?...( i ask this because stoooopid me installed a dizzy years ago and i forgot to put in the rotor....i sat looking at it for an hour wondering why the damn thing wont start after i traced and triple checked everything )....just a thought!

 

[67 B-body]

you should also see 12v appear and go away with each coil saturation when measuring on the - side of the coil while cranking.