Gremlins In The 308 GTSi Electronic Ignition

I bought a non-op 308 GTSi about a year ago. Since then, I've rebuilt the engine and fuel injection system, and have gone though all of the wiring related to the fuel injection and electronic ignition.

A week or so ago, I drove the car over to the exhaust shop (~30 mi) to put on a new Magnaflow. When I picked the car up, I kept getting a hint of misfire in the exhaust note. While driving home, the car felt flat and finally died on me. When it died, my wife said I had nice flames coming out the exhaust.

After having the car towed home (with 2x Ferrari tax), I've done diagnostics on the electronic ignition. I'm getting no spark at the coils. All of the standard multimeter tests at the digiplex connector for 700 ohms, 12V, ground, etc. check out fine. At this point, I'm at a loss for what the problem is. I'm hoping to put the oscilloscope on it tonight to make sure that the crank sensors and digiplex have reasonable output.

The electronic ignition has always been the most flakey part my car. Before committing to an aftermarket system, I was hoping that someone has an idea where the gremlin is hiding in the current system. Other than the oscilloscope, are there any diagnostics I should be doing?

 

I have a moderate tool addiction so I've got a lot of tools.

I've already checked for spark directly from the coils using a spare ignition wire and a spark gap tester. There is none. I guess I should also test with a timing light to doubly convince myself that the problem is not in the high tension part of the circuit.

When checking the digiplex harness, I checked the ground. I think it was pin 11. It had about 1 ohm relative to the engine block. Is there another ground I need to check?

 

Running a temporary ground from the digiplexes to the engine block seems like a good idea to eliminate that ground as a problem.

 

Good news and bad news. Good news is that the car magically started up and ran great as soon as I brought the scope into the garage. All traces looked great on the scope. Bad news is that the gremlin is probably waiting until I take a long drive before it returns. This is starting to sound like a Jaguar story... Maybe I should just drive around with the scope in the car to ward off the gremlins.

 

The car was running for a good 10-20min before it shut down so it was well up to temp. After it died, I tried restarting it on a few successive days. It wasn't until the scope approached the car that it started. It could be a heat related problem, but that seems weird given that the car wouldn't start in the following days. I've also redone all of the wiring connectors in the harness.

It is possible that the crank sensors or alternator are contributing and have intermittent problems. The crank sensors are currently checking out for resistance, and the battery always checks out at 12.4V so if there is a problem, it is intermittent.

If I do decide to change out the crank sensors to ensure that they aren't the problem, which vendor has the best prices?

After the car died on me, I replaced the ignition switch because I was having a problem with the starter. The car restarted for the first time after the new switch was installed. There is a chance that the switch had other problems and wasn't delivering a full 12V to the digiplex.

 

The car died on me twice in the last 2 days so I've had a chance to get more data. The first time, I drove 10 min in the morning, 20 minutes in the afternoon, let the car sit for an hour, and it wouldn't turn over. The battery was at 6V. That night, I charged the battery to try again in the morning. I verified 12V before installing the battery. When I connected the cable I heard a crackle, and my wife heard a whirring which stopped after a few seconds without putting the key in. The car wouldn't try to crank so I suspected the switch. A push start got it going without a problem. I drove for about 3 min and the ignition shut out completely, and the car wouldn't restart. After sitting about 10 min, I was able to get a multimeter on it. The battery was all the way down to 9V. I disconnected the cables and verified that the crank sensors were checking out. I reconnected the cables to check the voltage at the diagnostic plug (crackle again). I was only getting 1.5 mV. I then checked the voltage across the battery. I was getting 2V with the cables attached and 5V with the cables detached. I didn't have my ammeter, but I'm really starting to suspect that my ignition problem is a short in the starter or possibly my alternator.

 

When I'm under the car, I'll check for melted wires. I didn't see any last time.

I think the whirring sound was the starter because it came from the driver's side.

The fuse block was the first thing I rebuilt on the car. In typical Ferrari fashion, it was melted on the back side.

The ground strap should be ok but is worth checking while I'm under the car. It was a blob of grease before I rebuilt the engine.

 

I finally got under the car tonight. It was hard to miss the problem. The starter must have shorted and gotten ultra hot causing the solenoid to crumble which caused the positive battery cable to ground on the heat shield causing the whole wiring harness to melt together. This is going to be a major PITA to deal with. I sure wish I would have changed the starter when I rebuilt the motor last winter. Now I'm not sure if I'll have the car on the road again before winter hits.

 

Yea. This car is really killing my interest in Ferrari. It is by far the most labor per mile of any car I've ever owned. It makes the Jaguars I've owned seem trouble free.