The fuel pump gets turned off when the engine is not rotating. Even if it did stay running, the injectors are not being pulsed, so the fuel would just get pushed through the pressure regulator and go back into the tank, just like when the engine is running.
It is possible for the fuel pressure regulator to leak through the internal diaphragm, then into the vacuum hose and get sucked into the intake manifold, but that would cause really poor engine performance with lots of black smoke from the exhaust. A better suspect is a leaking fuel injector. That typically will not be noticed while the engine is running, but once it is stopped, the fuel will leak into the intake manifold and usually into that cylinder.
The clue to a leaking injector is you will find that leaked fuel in just one cylinder. From there it will seep into the oil. To verify the fuel is going somewhere, connect a fuel pressure gauge to the test port on the fuel rail, then watch if the pressure drops when the engine is stopped. It should hold for days, if not weeks. With a leaking injector, pressure will drop within minutes to perhaps as much as an hour.
Once you have verified fuel pressure is dropping, use a small hose pinch-off pliers to pinch the fuel return hose where it is rubber between the fuel rail and the body. If the pressure is dropping because the regulator is leaking, it will not drop while that hose is pinched. The problem with this story is with a leaking regulator, the fuel will just go harmlessly into the tank. You are finding fuel in the engine. The regulator will not cause that unless it is through the vacuum port, but you did not observe the associated running problem.
The first thing I would try is a good hour-long run with fresh gas. Almost all brands of gas have plenty of detergents and other additives that may start to dissolve any varnish build-up in the injectors. Over time the injectors may start to seal better. I normally do not expect fuel system additives or cleaners to do much because they are just a quick shot of highly-concentrated additives already found in gas. Every time you fill the tank with fresh gas, you are getting the same cleaners at a lower concentration, but continuously.
If the car was parked six years ago because of this fuel problem, you have to look at the rest of its history. If it was driven regularly, an injector may have just decided it I is time to leak. That is not terribly common. If the previous owner drove in such a way that a tank of gas lasted for a coupe of months, there could be varnish built up inside otherwise good injectors. Replacing the injectors would solve that problem right now, but regular driving might also solve it in short order.
Friday, June 16th, 2017 AT 11:06 PM