I posted this in electrical but had no response. I have a 71 firebird with a 350 and a hei distributor. The car turned on normally but a few seconds later it became really weak and turned off. I replaced the rotor, cap and had the module and coil checked. there is only spark going to some cylinders. the car almost turns on but there is not enough spark. I have no idea what the problem is, any help or suggestions would be greatly appreciated.

Make sure you have a full 12V going to the distributor when both cranking and running. If you use the stock resistor wire, it may drop down to around 9V, which won't work for HEI.

it worked before, so im almost positive it has 12 volts, but I'll check tomorrow. I'll post the results tomorrow.

Wow, no response in Electrical after 1 hour. The guys in there are slugs. Ever figure out why the modules kept burning out? Suggestions before to check the HEI BAT input for a full 12 volts.

If you replaced the coil + rotor and module is new and have a full 12 volts all thats left is the pole piece the one with the 8 points. You will have pull out dist to remove gear and shaft and replace pole piece. They do go bad not often but car hesitates similar to like a bad vac adv can. Good luck .

i've finally checked the voltage. i have about 12.5 before cranking, and 9.5 while cranking. This might be my trouble, but my distributor worked before, why is it not working now. Also, all my other wires seemed to drop to 9.5, is this normal. I also checked the battery wire with the same results. Im really confused and could use some tips.

what does the battery voltage say with a load ?? if charging system is down & battery is marginal with only a surface charge you'll see results like this

dont know what you mean with a load and surface charge.

dont know what you mean with a load and surface charge. OH... ok I'll put this anther way...... turn on your lights & Hi fan motor ... then check what the battery voltage is... thats a load .... (for people without a real battery tester) surface charge means the battery shows full voltage with no load ... no UMPHhhh so to speak.. HEI ignitions only work when there is proper voltage if battery show no reserve (UMPHhh) charge it then start car & check if your charging system is charging ...thats as down to earth as I can put it :)