What is the Theoretical Cause of the HOT START issue?

[Bitsyncmaster]

The pump prime during starting is not enough to restore rest pressure. If you jumper the RPM relay and run the pump longer that can restore rest pressure but depending on how bad it loses pressure the car may not start. That is why the plug swap is so good. If it starts right up withe the plug swap then it confirms you are not holding rest pressure. Doesn't tell you why it won't hold but at least you know what system and what part of the system (fuel) is the problem. Actually the only way you will know what the problem is, is by the process of elimination. Starting with the accumulator. Next would be the fuel pump check valve and then the PPR. This is assuming you have no leaks but you would smell that!
David Teitelbaum

My testing showed about 1.0 seconds to bring the rest pressure from zero PSI to 45 PSI on the control pressure. Did you find your testing was different?

[Citizen]

The pump prime during starting is not enough to restore rest pressure. If you jumper the RPM relay and run the pump longer that can restore rest pressure but depending on how bad it loses pressure the car may not start. That is why the plug swap is so good. [SNIP]

David Teitelbaum

I read this thread with great interest, and I appreciate all the expert knowledge here, but let’s step back from theory for just a moment please, and go to the real world. I’m out stuck somewhere with apparently the hot start issue. What do I do to get started again?

1) Prime the fuel system by jumpering the RPM relay, not by using the ignition key.
2) Execute the “plug swap procedure” AND/OR manually press the meter plate open while starting (latter must require two people).

Is that it?

For us fuel system novices, would you elaborate on the plug swap procedure? What plug is this referring to, where is it, and what tools do I need to carry with me in the car to effect this successfully out in the wild?

...

[David T]

Every owner should know how to do this. You remove the plug from the Control Pressure regulator and the plug from the Cold Start Valve. You take the plug from the CPR and put it on the CSV. (You do NOT have to put the CSV plug on the CPR). You start the car and as fast as you can you remove the plug from the CSV and put it back on the CPR. Then you put the plug back on the CSV and you can drive away. You do not have to push the air sensor plate, prime the fuel pump, remove the air cleaner, etc. It is VERY IMPORTANT you DO NOT leave the CPR plug on the CSV. That will make the CSV run constantly filling the motor up with raw fuel. You can imagine for yourself what can happen. It is better if you have 2 people do it so you can get the plug off the CSV quickly but 1 person working fast can do it. A common quick fix by DPO's (Dreaded Previous Owners) is to wire a switch up to the hot start relay plug near the fuse box so you can fire the CSV from in the car. If you do it at least use a momentary switch so it can't stay on. This is just an emergency procedure, the problem causing this condition should be fixed.
David Teitelbaum

[Bitsyncmaster]

Or you can get my HOT START relay. It bypasses the thermal time switch and energizes the CSV after 1 second of engine cranking. It stops the CSV when you stop cranking the engine so it may not clear the lines as quick as the plug swap.