Refuses to start, where to start?

First.
If you flooded it, Pull the plugs and either replace them or dry them out with a torch on the end of the plug, let them cool and reinstall.

 

Next , make sure your battery is fully charged. With the vehicle sitting for three weeks, just the clock running will pull the battery down low enough where the vehicle will still have enough charge to turn over but not enough power to fire.
With plugs dried out and battery fully charged i’m betting she will start.

 

First thing to establish is whether you have any current running to the plugs. If they are all dead then its maybe something that's affecting the whole ignition system and not just one bank (which would seem to rule out coils, coil leads & ignition modules - unless you have a double failure). As above, I'd pull the plugs out first & check those but they are likely a mess anyway & not necessarily the cause. A couple of other things that could pull the whole ignition system down would be the crank sensors (in the clutch housing - white wires) or the ignition box in the trunk.

I'd also start by disconnecting & reconnecting every plug I could find in the engine bay one at a time & see if that reveals anything. Pull one apart, reconnect, try & start it & then move on to the next one. Do the obvious stuff like check the connectors to the ignition modules (had one of them come loose once) & also check for oil coming out the rubber boots bellow the distributor caps around the plug wires (in which case you'd go an oil seal failure and a distributor cap with oil in it which will tend to make it not work so well!

 

Well if you flooded, you are getting fuel. The car turns over, that rules out lots of things too. Did the car catch a bit and sputter while turning over, or no signs of life, just dead cranking? If one coil failed, the engine would try to start, but wouldn't, but there would not just be dead cranking. Two coils failing at the same would be unlikely.

The crank sensor is an oft overlooked item that in my view should be replaced as a service item, they do fail and can cause a dead cranking outcome, just like a skipped tooth on the timing belt would. Are the belts recent, or less than 5 years old?

Might be worn distributor caps, they are often not changed as frequently as in daily drivers. The carbon pin inside or rotors could be at their service life.

 

Did you put a full charge on the battery? If so.
There is also a large fuse, I believe it’s in the back of the car by the ECUs? 700 miles away from home at the moment so I can’t go into the garage and check location on my Quattrovalovle.

 

This was discussed about a month and a half ago.

Please see post #3: https://www.ferrarichat.com/forum/threads/dead-328-no-spark.573485/#post-145923625. In that thread I provide the link to the service bulletin (TSB 80-28) which reviews the electrical test procedure for Marelli Microplex systems. Best of luck.

 

Note that the microplex is a robust unit and they rarely fail without some sort of provocation, i.e. exposure to moisture. If I were a betting man I would put my money on the TDC sensor. This should easily be diagnosed by performing the microplex test procedure. In fact, I believe Mitchell's no start scenario noted in the thread referenced above was the result of the harness plug for the TDC and tach sensor not being fully seated.

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Good morning. I remember A conversation here a few years ago where some of the Quattrovalovle owners (Dr. Tommy and others?) reported a no start issue and it turned out to be a large clear fuse that was blown. IIRC, you could look at the top of it and see it had blown. Once replaced all was good. I’m in my mid-50s and short on sleep so my memory is probably failing me!
Agree with SeattleM5 and others who suggest checking all connections.

 

I have had a similar experience with my 1988.5 328. It revved well with the starter motor but no sparks on either engine part. Few hours later it started immediately and great drive. Few days later again no start but fuel smell anf after efw days again started immediatelt. I replaced the relays without any effect. This lasted for some time and finally replavced the 2 sensors (TDC and Tacho), see attached pic prior to change. In addition i replaced the vacuum tube as I read somewhere that these can also cause trouble. This I did do more than a year ago and never had the issue anymore.

 

if you proceed with the Microplex following will be handy to test and investigate

 

Below i liked as well. Hope it helps to enjoy your 328 asap!

I do have a manual how to test the Microplex, let me know if needed.

 

The vac hose goes to the left side of the plenum. Believe it or not this is the engine vac advance, there is a small diaphragm in the Microplex box.

Everybody should check that hose once in a while.

Some years ago (before my ownership) mine had a worn a hole in it down behind the LHS arch liner resulting in two things - no vacuum advance and secondly an air leak whereby additional air was being drawn in to the engine & then showing a low CO reading at idle. Needless to say somebody then cranked the mixture up to correct the idle CO level resulting in the thing then running very rich & drinking fuel.

The other thing to check is that the diaphragm in the microplex box is in tact. If the hose is sound and you can draw air through it from the engine end then you may have a hole in that - which means much the same as having a hole in the hose (see above).

As to your issue, my money would also be on a crank sensor.

 

ETA: the crank sensors are easy enough to test in situ. Just follow the white wires back & unplug them at the loom end . You are looking for a reading of 6-700 ohms across them. If they are open circuit then they are dead.

 

The testing procedure is in the link I provided in the prior post.

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see attached picture, it travels via the left rear wheel area (behind the wheel cover) through the bagage panel to the Microplex. Real easy to replace and cheap!
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open the pdf: