• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Igintion No Spark

Share this page

W

WJM

Senior Member
Offline
Hi All Hope someone can help. I replaced my dissy with the one that has the electronic igintion inside the cap. It is a brand new 45D. The problem is I no longer have a spark at the plugs. I replaced the coil with no effect. I put the old dissy back in still no spark. There is 13 volts at the coil with igintion switched on. There is power at the dissy. I am at a loss. My MGB is a 72 model. Even with the old dissy in I could not get a spark at the points. I have check the wiring a dozen times now and all is wired as per the book. What have I done wrong or what have I blown up. Any help welcome. Regards from down under John
 
Points are grounded. Or electronic points or what ever.
 
Hi WJM from down under!
sign0175.gif
Seeing how your having this problem with not just one distributor but two of different designs on the same engine, I would check to make sure your rotor is not cracked. Make sure your dizzy cap has no cracks in it. A crack will sometimes lead the spark to ground. Also, check and make sure your engine ground cable is fastened securely and there is no leakage there. A bad engine to frame ground can cause the voltage to the coil to drop drastically when the starter is engaged, thus no spark or a very weak spark will be delivered. Just throwing out suggestions. Maybe one will help.
confused0031.gif
PJ
 
Thanks for replys. I still have not located the problem. The new dissy I fitted has a new cap and rotor. The ground strap is secure. The voltage to the coil is 13 volts. Any one have any problems like this before. I should have left the car alone as it was running well until I done the dissy transplant. Regards John
 
John, according to my wiring diagrams for a 77, there are two wires going to the ignition side of the coil. One from the ignition switch which is ballasted and one from a connection on the the starter. Are both hooked up? PJ

77MGBwiring3.jpg
77MGBwiring2.jpg
 
The ballast connection shouldn't be a problem... even if it's omitted. It only supplies power to the high side of the coil during cranking. During normal running the power to coil (+) comes from the ignition switch through the ballast resistor or (pinkish colored) resistor wire.

IF you do indeed have a ballast ignition system and IF you are indeed seeing 13V on coil (+)... this does not mean the points/module are shorted closed, it means there is no ground path. With a ballast ignition and closed points (or conducting module) you should see between 6V and 9V on coil (+). You'll see around 13V on coil (+) if the points are open OR if the points are closed on a REGULAR ignition system.

I put together a PDF document on troubleshooting points ignitions. Put your points dizzy back in and follow the troubleshooting section until you get spark (at the plugs... don't focus on spark across the points). Once that's working put the electronics in again.
https://home.mindspring.com/~purlawson/files/LucasPointsIgnitions.pdf
Merry Christmas!
 
There were a bunch of new electronic distributors that were shipped with the drive gear installed backwards - 180 degrees out. If that's your case, you may be dealing with no spark AND fouled spark plugs. Check to make sure your old and new drive gears are offset the same with the rotor pointing in the same direction.

Power the coil with a wire directly from the green circuit at the fuse panel to rule out wiring issues. Firing order is 1-3-4-2 CCW - double check it to be safe! Typically the #3 wire is the one closest to the vacuum advance.

What brand is this distributor - that would help us determine what's wrong!!!
 
Back
Top