The heat soak on mine has been completely eliminated. All it took was to install an electric water pump...
The basic problem is the heat rising off of the exhaust manifold is cooking everything it can get it's pudgy little hands on. The heat must be moved somewhere else. Either run the fan for air cooling or run the water pump for liquid cooling. On my rig, the pump runs for two minutes after shutdown and, if the Heep is at 93C or above, both electric fans run as well. I have zero heat soak issues.
Yeah, both solid solutions that I've considered but again, they're workarounds - I'm after the root cause
Supposedly, the issue is caused by either a failing check valve or leaking injector that leads to enough pressure loss that vapor lock is possible.
Yesterday, I did as scientific a test as I could:
- Got the car nice and hot on the way home from work. Highway speeds, AC on, etc.
- When I arrived at home, I immediately popped the hood, connected the fuel pressure tester, and closed the hood. Started the car and ran it AC on (idling) for about 5 minutes and shut it off.
- I quickly popped the hood and clamped the fuel line connected to the fuel rail, and immediately shut the hood.
Upon doing so, I waited about 15 minutes (right when heat soak is guaranteed under these conditions) and went to check the pressure at the fuel rail... It was steady at 50 psi. At 30 minutes, it had dropped to 28 psi, but I assume this is due to the engine (and really the fuel in the rail) cooling off and pressure going down as a result of this. After an hour, it was below 20 psi.
If the same amount of fuel remains in the fuel rail, what kind of pressure drop can I expect as temperatures drop? Does the result of the above test indicate that my injectors are not leaking? I guess I just don't know the relationship between gasoline temperature and the resulting pressure it exerts.
*EDIT* (Follow-up thought) I'm going to do basically the same test again today, but without the pressure gauge... Get home, pop the hood, clamp the fuel line, close the hood, and wait 15 minutes... At the 15 minute mark, I'll remove the clamp from the fuel line and start the car to see if the vapor lock/heat soak issue is mitigated. If so, I'll turn my attention to the rest of the fuel system upstream of the fuel rail (i.e. the check valve).