Hot start problem

[LarryH]

Hello, ‘02 4.0. Cold starts well, no fuel delivery shortage at 75 mph full throttle kick down. Hot start requires 3 on-off key cycles and starts well on 4th.
Doesn’t seem to clearly be a fuel pump fault. Is there temperature sensing functions and relays or switches that could cause this?
thank you!

 

[RonD]

What does the temp gauge show with key on before the "hot start"?

As far as I know there is no "high" temp/no start issue in the 4.0l computers

The key on and off 3 times rebuilds lost fuel pressure, but that is usually a symptom of hard Cold Start and loss of pressure over a few hours
Running pressure is 60psi
It should hold pressure above 30psi for many months just sitting

If you have an OBD2 reader have a look at the Computers ECT sensor degrees on cold start and then at hot start

Could be a Flooding issue as well, leaking pressure damper
It is at the end of passenger side fuel rail near the firewall, it has a vacuum hose attached, check that hose for gasoline smell or liquid gasoline

When you shut off the engine if damper was leaking then raw fuel goes into the intake via vacuum hose
Warm/hot engines are easily flooded
So no start on first crank and no fuel pressure
So key on and off builds up the pressure and engine can start
Long shot

 

[LarryH]

Thank you, I’ll look at that stuff. I think gauge was at normal operating temperature but I can check again.

 

[LarryH]

I started in on the damper idea, then discovered fuel pressure Schroeder port. Zero pressure to start up to 20 psi at third cycle, definitely bad fuel pump. Put in a new one, starts and runs great. ECT was working fine. Still don’t understand why started well cold with zero pressure.