77 Weber 32 adf Carb spacer

[FordPrefect]

Come to think of it, the charging light on the tach never comes on, just the light on the oil pressure gauge.

[18Fiatsandcounting]

Kinda dragging this one up from the dead,

Well, it is getting close to Halloween...

OK, let's see if I have the story straight. The car starts fine. That means it has fuel in the carb and the ignition is working. The car idles fine for a while. That tells me the idle circuit is fine. After 30 seconds or so, the engine speed increases rapidly. That would indicate either a vacuum leak has been introduced, or your ignition timing is changing, but neither would seem to be the case. Then the engine dies. That usually means it has run out of fuel, or something has died on the ignition. But, if that were the case, it shouldn't start right back up again.

Do you have an electric fuel pump or a mechanical one? Maybe a fuel filter somewhere that is getting plugged when fuel is flowing but then opens up again when fuel flow stops? Also (and I know this sounds weird), but try temporarily removing the gas cap and see if that makes any difference (vacuum can build up in an improperly vented tank and cause it to go lean and then die).

-Bryan

[FordPrefect]

Electrical fuel pump. I did open the fuel cap a while back, that didn't seem to change anything. I tested the battery, next I'm gonna check the voltage regulator. The fuel pump was pumping last I checked, but I'm starting to suspect electrical issue.

[18Fiatsandcounting]

Electrical fuel pump. I did open the fuel cap a while back, that didn't seem to change anything. I tested the battery, next I'm gonna check the voltage regulator. The fuel pump was pumping last I checked, but I'm starting to suspect electrical issue.

This could be important. Certain years of Fiats with the electric fuel pump had a relay that operated the fuel pump both when the car was cranking, and then switched to a different circuit when the car was running and there was oil pressure. So, maybe your fuel pump is running when you crank the engine, which fills the float bowl with fuel, but the "running" circuit of the fuel pump isn't working so when the bowl runs out of fuel, the engine dies. As it is running out of fuel, the mixture starts to go lean, which causes the idle to momentarily increase until the fuel is gone. If you try to start again, the cycle repeats.

Try (temporarily) running an electrical jumper to your fuel pump all the time whenever the ignition is on, and see if that cures the problem.

-Bryan

[FordPrefect]

I checked some voltages and it looks like the alternator isn't charging.

How does the charging circuit work with the charging light again?

[18Fiatsandcounting]

If the alternator charging indicator (red light at the bottom of the tachometer) doesn't come on when you turn the ignition to "on" but before starting the car, then it's possible the bulb is simply burned out.

Each model year has some differences, but at least on my older spiders, the positive for this light is through Fuse L (#10), and the negative is through a relay on the firewall near the voltage regulator. When the engine is running and the alternator is charging, the relay opens up, thus breaking the ground connection for the charging light and so it goes out. If the engine dies or the alternator isn't charging, the relay connects the ground again and the light goes on.

However, I have heard that in some models the alternator will not work right if that charging bulb is burned out, although I never did fully understand this myself. But, checking the bulb would be a good place to start.

-Bryan

[FordPrefect]

Oh boy, I fixed it!

I traced the exciter wire from the non-functioning alternator to the relay. It had power at the relay, but not the alternator. I followed it to the connector near the firewall, and the dang wire on the opposite side was purple. The orange and white connectors were plugged in to the wrong corresponding connectors.

After that, I popped the correct relay into the 128 fuel pump relay and the dang thing has been purring along.

I need to dial in the mixture now and a few other tweaks, but I'm thrilled.

Also, the horn works now, lol. What a dumb thing.

Thanks for your help everyone.

[18Fiatsandcounting]

Awesome work, Prefect!

Yes, those alternator wires get switched sometimes and then things go awry. The way I understand the 3 leads to the alternator is that the large black (sometimes green) wire is the high current lead to charge the battery, the grey (depending on model year) wire is the field excitation winding (from the voltage regulator) for the alternator, and the third lead (sometimes yellow or white depending on model year) senses whether the alternator is working. You can't measure whether it's working just by looking at the battery lead because the 12 volts from the battery would make the system think that the alternator was putting out the 12 volts when really it's just the battery. Hence the separate yellow (white) lead.

-Bryan