[Ruben]

I have a 77 308 with a Crane X700. Recently my mechanic told me one of the coils is weak and I should replace it so after reading all that was written on the subject here I purchased two Accel 4180 coils and installed them myself. I also pulled the plugs and gapped them to .034. The result was a disaster. During acceleration and deceleration the most awfull backfiring sound came out of the car. I checked it out at idle with someone steping on the gas and puffs of flame came out of the tail pipe when it backfired. Can anyone please help me figure out why this happened ?. I love my car but right now it is undrivable. Any advise is greatly appreciated. As far as the wiring goes for each coil the yellow cable from the Crane 700 goes to the negative while all the other cables from the resistors plus the red wires from the Crane go to the positive.
Thank you for your help.

 

['75 308 GT4 (Peter)]

-Make sure the coil wire is firmly seated in both the cap and coil.

-Check the ignition cables and plug extenders

-Check the resistance of the coils themselves. You should read about 1.5 ohms between the primary terminals (positive and negative). If not, install an appropriate resistor between the yellow XR700 wire and the coil. The positive XR700 wire should go straight to the coil - no resistors inbetween.

 

[Ruben]

Thank you. I just checked the resistor and for both coils it reads 1.5 ohms. I also made sure all the cables are firmly in place. One clarification on the wiring. The red wire from the XR700 does go directly to the positive side od the coil and not through the resistor. After all this the problem is still there. Any other hints you can give me would greatly be appreciated. Are there any other conditions which can cause such a terrible backfiring with the installation of new coils ?

 

[Pete04222]

My car did the same when I had the original points - loss of power, huge backfire, undriveable, etc. What I had was one complete bank shutting down and then when it would kick back in..........Bang!

This winter I converted the point type ignition to the Crane XR3000 ignition (which uses high power coils and does away with the ballast resistor)

Your problem could be as simple as a loose connection that is shutting down one bank.

Just an idea.

 

['75 308 GT4 (Peter)]

I know its unlikely, but check (listen) for vacuum leaks at the carbs. It "suddenly" happened once before to my car without any warning, I had terrible leaks around the throttle-shaft bearings. Same backfiring/lack-of-power symptoms. At the time, I too thought it was ignition (same symptoms as well if it fails), but it checked out okay...