[targa80]

When the engine is cold and there is no pressure in the fuel line it would not take too long for the cold start valve to provide a large dose of fuel in the manifold to start the engine. Once the engine is warm the start valve is no longer involved in starting the engine. You said that it will start after being shut off for 5 min. but not 15 min. After 15 min there is no real fuel pressure and the engine is still hot enough to prevent the start valve from helping to dump fuel into the maifold thats why it cranks for ever and doesn't start. What would happen if you caped off the line to the start valve with a pressure guage and started the car to build up the pressure and check to see if it drops off dramatically without the start valve in the circuit. I would suggest the Bosch fuel injection manual to help troubleshoot the problem. I used it and a fuel injection pressure guage kit to troubleshoot my starting problem. I ended up adding an external check valve to my fuel pump to prevent loss of pressure and subsequent warm start problems.