328 Hot starting problem

Can you describe the problem a little more ? Does it always turn over when hot but won't start or the engine won't turn over when hot ?

 

A little more info would be nice. Does the starter move in any way. Please post some more details.

I had kind of similar problem with my 1985 911 3,2. When the engine was hot, the starter ring (pinion / gear) would not jump in. ( I hope you get my point, just realizing how bad my english is if it comes to cars, in german we call it "einspuren" ). After opening and cleaning the starter everything was fine again. In the end it was a bad connection of the magnetic switch.

Just a little bit confused that the problem resolves when you disconnect the battery for a moment. Sounds strange.

Regards,

Dirk

 

Your description sounds like the magnetic switch/starter solenoid (sorry, i am not sure getting the technical terms right). And it definitely looks similar to the problems with my Porsche in the past, apart from that I never tried to disconnect the battery. Maybe i should have done ( i even have a quick disconnect). It was so embarrassing to look for a parking lot which you could roll out downhill or even worse, to push start the car

So i would dismount the starter (never did on the 328 or 308, but can’t be that different to other cars.) Open it, clean the contacts (especially the big copper one) and make sure that the (frustrating, again I lack the words) I just call it gizmo (it is initially a coil which pushes the starter in and by doing so, closes the big copper contact to make the starter turn) is working fine. You can check this outside of the car.

Based on your info I would guess if you do so there is a 99% probability that after that everything is running fine

Regards,

Dirk

 

The EE word you are looking for is a relay. Which is a big mechanical switch actuated by a small electrical signal.

 

Do you really just call it relay? Basically it is kind of a quite big relay with an additional feature. I am taking about the stuff attached sideways to the starter. In german we call it "Magnetschalter" (literally translated "magnetic switch", but given that the OP wants to change the "solenoid" i guess this is the right word. It is a coil with a pole inside. On starting the coil gets power and does two things: 1. The frontside of the pole pushes the starter pinion forward to engage the flywheel and the backside is pushed against a big copper contact, closing the power circuit (>>100amps) for the starter itself.

To eyeman: I have no experience with aftermarket solenoids. Did you tried to open and clean the old one. I had no problems with my 328 so far, but with the 911 (also from 1985) it was a quite common problem after 15-20 years that the big copper contact was burned/dirty and therefore no longer able to deliver the high current. Just cleaning it (sandpaper) did the job for me in 2002. Never had any problems since then.


Regards,

Dirk

 

Had the same thing with an 82 Mondial QV. Usual electrical gremlins. Refurbed the starter. A lot better. Fitted a direct 12v feed to the starter (adding a starter button), which worked fine, but I didn't like the fact the key didn't always work (Plus I never got round to fitting the inline starter into the console properley). Eventually removed the button and fitted a relay between the starter and the positive feed, using long wires (tie wrapped down the oil breather tubes/filter), the relay is earthed to the engine compartment surround and sits by the ignition system largely out of view. The car now starts fine every time (when the car isn't stripped down for refurb). Basically it prevents the starter motor solonoid sticking, which was preventing the Starter Motor from engaging (combination of resistance, heat, and a catch-22 cycle making it worse). Cost was minimal - thanks to a friend who sorted a wiring diagram- and saved my great (ex)independent service agent from replacing my fly-wheel which he claimed had lost teeth and so was failing to catch (I kid you not). I am also changing the circuit board, and sorting earths, including the battery isolation switch (see threads). Apologies for the non-tech answer, but I'd recommend a relay. I promise the wiring is even tidier now!
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The heat associated with a car up to operating temp can a) increase resistence in weak spots in the circuit (either main circuit to the starter from the battery, or, the actuation circuit from the key), or b) cause thermal expansion which can break continuity in the circuits where there is corrosion or other issues. My advice is to a) go through both circuits and make sure all connections are clean and free of corrosion or moisture, and b) examine all grounds in the area (including the main engine ground strap) and ensure these are also clean and free of corrosion. Lots of these types of electrical gremlins are caused by dirty/corroded connections.