1967 250SE cold start problem
 

My 250SE requires about 20 seconds of cranking before starting when cold. After starting, if ignition is turned off, it will start up again instantly. I have replaced the fuel pressure regulator and cold start solenoid but the problem persists. I would appreciate guidance in rectifying this annoying problem.
:confused:

Fuel Pressure regulator? It has a mechanical injection pump.

On to your problem. You have to check your cold start circuit. There is a starting solenoid on top of the injection pump. That moves the rack full forward during starting. Make sure there isn't a broken wire.

The start valve is controlled by a time delay relay on the firewall. It's got a heated bi-metalic strip to complete the circuit. Operate the starter, heat up the bi-metalic strip until it disengages. So, you have to adjust the set screw. Make sure the relays are operating properly.

I had to do this on my old 220SE and the 250SE pump may be slightly different.

Your car had a CSV energized by the thermo-time-switch .
Here is an easy test for both.

Hook a test light up to the Cold start valve teminal and ground. [put it where you can see it when you are operating the starter key]
Try start and watch for power. If power ,but no start , the valve is not opening. Chk valve ..
If no power while key is in start pos. , go to next step:

Pull the rubber cap on the TTS and run a ground wire from terminal "W" to gnd.
Turn key to Start pos and watch for power at light .
If you now have power and start , the TTS is bad .
If still no power , relay,fuse # 6 , or wiring should be checked .
If you need schematic, email me...