Only for the brief time period before the solenoid plunger movement closes the internal switch to run the starter motor. When the starter motor "pulls" the battery voltage down, it also pulls the terminal 50 white wire voltage down (and that's what you measured). You already know that cold initial starts work well so no surprise that the (cold) bench tests were also OK. To get to the next diagnostic level, add a wire to the terminal 50 at the starter solenoid, and run it into the passenger cabin so that you can measure it when the problem occurs: If terminal 50 doesn't get close to +12V when nothing happens = wiring or ignition switch problem If terminal 50 does go to +12V, but nothing happens = new solenoid (for example, you can have a micro-crack in the fine coil winding of the solenoid that is small enough to arc over at +12V when cold, but expands to a larger gap when warm). Good Hunting!
Something to consider.... 1. Check resistance from ignition switch to solenoid for bad wire or termination. It should be near an ohm. 2. Check across ignition switch contacts for continuity. If intermittent or resistance greater than an ohm or two, then consider replacing the switch contact block and install a flyback diode on your ignition lead to the solenoid to prevent any damage to the ignition contacts in the future. They will last forever with the diode. You should have close to full battery voltage at the solenoid coil. I learned this with my 246 Dino, Alfas and other 308s, I have owned. I got stranded at a restaurant because of destroyed contacts with my former 66 Duetto which uses the same Bosch contacts. I had 40k miles on it. Took apart the contacts and saw the damage. I am in instrumentation instructor and we use flyback diodes to protect from the coil field collapsing on equipment. My BmW M3 has this problem with the SMG power relay, so I keep a spare in the trunk. It goes bad in about 50k miles.I am on my second one. Something to consider for all 308/328 owners as you put on the miles.
I've reinstalled the starter. I checked to voltage at the solenoid with the spade connector disconnected so there was no load. It was only 11.6 volts when I turned the key to start (starter not turning engine over so it's no load voltage). The hot line on the solenoid reads 12.7 volts so I'm getting a volt drop somewhere in the line. I pulled up the carpet to have a look at the connectors and also to check the wire resistance from there to the solenoid. I figure I can check every one of them with an ohm meter to find the right one and get a reading. I'll get to the ignition switch after I check the connector. I like the idea about the diode that passes current in only one direction to protect contacts. Also, sometimes the starter will not operate when the engine is cold. At times it takes 3-4 turns of the key to engage the starter motor. Other times it works perfectly.
https://www.ferrarichat.com/forum/threads/dino-saga-050911-_-ignition-switch-alternator-regulator-starter-flasher.74532/#post-136791738
Update: My Fluke multimeter resistance portion went on the fritz so I cannot measure resistances at the moment. I pulled up the carpet and opened up the two connectors. It all looked OK but I sprayed all of them anyway with contact cleaner and reassembled. Also I put a little engine assembly lube in the solenoid where the movement occurs. It was a little sticky inside so it was cleaned with carburetor cleaner before adding a little lubricant. Tech at the starter/alternator place said I should not have done that due to problems in cold weather. This car is in basement in winter where temperature never falls below 60 so that is not an issue. I measured the no load voltage (Fluke volt portion of meter works fine) at the solenoid spade and am now getting 11.8 volts. The hot pole on the solenoid read 12.7 volts. I am in the process of making up some leads so I can measure the voltage just to see what happens when I only get a click and am in the driver's seat. Yesterday I started the car 4 times and it worked properly each time. Today I added 8 more making a total of 12 starts in a row. The last few today were after the engine was hot so the starter had to be hot as well. Oil temperature was up to normal levels. Twelve starts in a row is getting into recent record territory.
That should tell all -- but the "click" you get when it doesn't work, is it a strong mechanical click (indicating the solenoid plunger actually moved) or a very soft click? I think this is normal. The difference is caused by the hot pole being a very large wire connected directly to the positive battery terminal, but the wiring to the solenoid spade goes: positive battery terminal -to- ignition switch -to- things run in pos II and things run in pos III (when you are in pos III). This wiring is not huge and the current being drawn by the stuff of pos II when you are in pos III will result in a small voltage drop appearing at the ignition switch input -- so, even with the solenoid spade unplugged, the voltage appearing on the solenoid spade will be a little less than the battery voltage. In any case, 11+ V should be plenty to actuate a health solenoid.
"That should tell all -- but the "click" you get when it doesn't work, is it a strong mechanical click (indicating the solenoid plunger actually moved) or a very soft click?" It's a definite click I get when engine does not turn. It is not as loud a click as when I had the starter on the workbench and was tapping a wire to the solenoid directly or when the tech did it at the shop. I could also see a dimming of the interior lights when I only got a click that remained until I'd return the key to position II. But since then I have thoroughly cleaned and tightened the battery terminals. The negative one had somehow loosened. And I was the installer of the new battery last winter...….. I have started the engine 15 times in a row now without a failure. "Just wanted to toss this out there: have you done a VAT test on the battery? " The battery is less than a year old. Vehicle has a little over 31K miles on it. I am also going to attach a diode to my solenoid wire.
The starter has worked properly 18 times in a row which is a record since the trouble began a few months ago. Today I installed a diode, 1N4004, in the system in the vicinity of the starter switch to protect against potential future damage to the ignition switch.
