Hot Start Issue

If the car isn't getting hot enough to vaporize the fuel then it's probably not your check valves. Not sure if the waiting allows the car to cool or allows extra gasoline to evaporate.

I would check a couple of things.
Are the fuel meters adjusted properly? They are often set way too rich. If the connector on one on the fuel meters (I'm thinking driver's side) is disconnected this will flood the hot engine (I suspect it is connected because the relay clicking you hear when the engine is cranking is being caused by the safety switch as it opens and closes).
You can roughly check this by pulling one of the injectors (one side of the engine at a time) and disconnecting the safety switch (I'm still thinking driver's side) with the key on you should hear the fuel pumps running. The injector should piddle out a little fuel at most.
If you're thinking thermotime switch then you can simply unplug the cold start injectors and see how it goes.

Anyway, there are two fuel systems you are dealing with. The first is a safety switch that is connected to one of the air/fuel meters. It turns on the fuel pumps when the air flap moves off neutral. For some reason these are often disconnected. If you hear relays chattering while the car is cranking, then this is probably connected. It's OK to have it disconnected if the air/fuel meter is properly adjusted.

The second system is the cold start system. It has a thermotime switch that controls two extra injectors that spray fuel while the engine is cold. These injector generally fail closed but you never know. If the thermotime is shot it might be calling for cold start enrichment all the time which is fine when the engine is cold.

There is also warmup regulators that adjusts the fuel meter control pressure but I don't think that would cause a non start.

And just to make this really fun, it might not be fuel related at all. You might not be getting any or a weak spark. The Ignition coil and amplifier (I don't know why they call it that) heat up very quickly. When you drive it for a while, is it missing a little or running strong? Also, is the timing set correctly?

I hope some of this helps.

 

My car had warm/hot start problems (after I sorted the cold start) & the culprit turned out to be the warm start relay. There is a relay that acts like a blinker flasher can but switches at about twice the speed & mine had a dry solder joint inside it. Once I resoldered it the warm start issue was sorted. To check the operation of the warm start relay disconnect one of the plugs from a cold start injector & check there is a pulsing 12v across the two pins while the starter is cranking. This is best checked with an automotive test light or analogue meter - a digital multimeter will jump around too quick to get a reading.

 

Trust me, just trust me...make sure the hot start relay (it is the tall one in the lower right of the board) is plugged in since they fall out all the time. If you are 100% sure it is then replace it.
Its the relay, just trust me.
By the way, only series 1 cars have this relay

 

You SURE it is plugged in and making contact?

 

Yeah, that's not good. Ok go double check it is the relay clicking and not current sparking across the contacts because they aren't making good contact (which is what mine used to do) and I'll check my spares box tomorrow or Thursday at the latest because I seem to think I have an extra relay.

 

Welcome back Dave. . Haven't seen you around in these parts lately.....

 

Yeah I'm like a bad penny...
I've been around just not posting as much, a lurker in the shadows

PS - I'll go look in my spare box today

 

I had similar symptoms with my 412. Eventually it was traced to failed check valves located at the top of the fuel pumps. These valves hold fuel pressure when the car is turned off. (The fuel system loops the gas back to the gas tanks and uses the check valves to ensure everything doesn't drain back to the tanks when you turn off the engine.) The cold-start system injectors will compensate for this when you start on a cold engine, but because they are deactivated when the engine is warm you are left with zero or low pressure. It is sometimes possible to generate enough pressure with the accelerator open wide, but this is at best an inadequate fix.

While the fuel pumps on the 412 are submerged in the gas tanks, I believe those on the 400s are positioned externally. I imagine, however, that the check valves are located together with them. In my case, it turned out the ethanol contained in most service-station gas had literally melted the rubber boots surrounding the fuel pumps and that residue had lodged itself in the check valves. Again, because you pumps are not submerged this may not be such a point of vulnerability. But I still imagine there are other rubber components in the fuel system that are vulnerable on a 400i, or that other residue may have become lodged in the check valves.

 

Crap, I'm sorry but I don't have a spare relay. Sorry.