HELP! 71 911T won’t start.

[Jeremy71T]

I have a 71 911T with Zenith Carbs and a Marelli distributor. It underwent a complete restoration in the late 90’s and recently came out of a 3.5-year hibernation. After some initial work rebuilding the carbs and getting the some the brake work done, it ran great for a few days. Then the CDI unit went bad, had it rebuilt, and again ran great until 2 days ago. After a 10 mile trip I went to restart it after lunch and it wouldn’t fire up. The engine would turn over fine. Waited 20 minutes same thing. Had it towed home and pulled off the fuel line and the pump was pushing plenty of fuel. I don’t have a fuel pressure gauge, but the carbs I think only need 3 PSI. Checked for spark and nothing. I thought it might be the CDI unit again and it wasn’t singing so I took it to the gentleman that rebuilt it along with my coil and he put them through the paces including heating up CDI unit and it was working fine on his bench although the typical “sing” of the unit was very faint. He suggested I check a few things which I did. There was 12 volts coming from the center (B) pin of the 3 pin CDI unit, there was continuity between the CDI “C” pin and the distributor, and there was continuity between the “A” pin and the coil. I also pulled off the distributor cap and rotor. They appeared ok. The points would open and close as I manually rocked the advance on the distributor. Of note and this may not be related, the morning after I had it towed home, I went to attempt to start the car and it would barely turn over like it had a weak battery. I put on a charger and it showed the batteries were charged. I cleaned every terminal and connection I could find in the engine compartment and all the connections to the two batteries in the bonnet and the transmission ground strap under the car. I found a surprising amount of corrosion on the brass connections from the batteries to the starter cable. After I spent a few hours doing this the car would again turn over like a normal Bosch starter. The gentleman that rebuilt my CDI unit said I could borrow another unit to see if that made a difference which I might take him up on. What am I missing here?! Is there a fuse I am missing? Any help would be very appreciated. Thanks, Jeremy.

[Scott A]

You are on the right track. Much of what you have done was essential.

It will most likely be a ground. In the back of the car.
Around distributor. CDI. Area.

It sounds as if you done most of these grounds.
There are grounds behind the alternator.

At the back of the engine, The plastic 14 pin connector can create problems.
It can melt. Things can touch.
If a ground around the CDI or distributor is poor.... The ground the distributor needs will find another path and burn out the needed path. In a sense it will go backwards to find a new path.

I had a time, when it went backwards and I had to rebuild the 14 pin...you have to do it really careful with a diagram. Be careful when opening, certainly with battery disconnected, everything must look really really good in there...And make sure every connection in and out is perfect and strong.

There is a post about this. But I don't know how to find it without digging and digging and searching.

And if you take a few photos around distributor. And CDI and coil... We might be able to see if all needed wires are there and in the right places.

Also. It is probably essential to buy one extra CDi. Another Coil. Extra set of plug wires. Dist cap and rotor. Another Distributor and keep those in the car everywhere you go. And Another fuel pump. That's what I do.

[edmayo]

There is no fuse, a quick check is to remove the distributor cap, then rotate engine with wrench on fan pulley nut until the points are closed, now remove the coil high tension lead from the center of the distributor cap, lay it next to the coil mounting bracket nut so it is a 1/8" from touching ground. Now turn on ignition and using a thin screwdriver (touching only the plastic handle) manually operate the points with the screwdriver, you should get a spark from the coil wire to ground.