You still didn't say if you have one injector in the throttle body or four in the front of the engine. When you have four, the regulator will open a spring-loaded valve to bleed off excess pressure and the fuel will run back into the tank through the return line. The tension on that spring-loaded valve needs to vary a little. That's where the vacuum hose comes in. Higher vacuum is going to pull fuel from the injector(s) faster. To offset that excessively-rich mixture, the vacuum on the regulator makes the valve open easier, meaning to maintain lower fuel pressure. The net difference between the two forces working on the fuel remains constant. The point is, once the desired pressure is reached, anything higher makes the valve open and the fuel must be able to flow freely, under no restriction, back into the tank. That line can be restricted from being crushed or if it was disconnected and plugged.
The regulator can leak internally, then fuel will leak out the vacuum hose and get sucked into the engine. That has been a big problem with GM trucks. I've never run into that on any other vehicle, but I did read about it happening once here on a Chrysler product.
I worked on so few of your car model that I can't remember if they used a fuel return line, but they almost have to. Regardless, there should never be fuel leaking from anything on the regulator. My suspicion is the return line is blocked or the regulator is stuck causing fuel pressure within it to go too high and it's being forced out through a seam, or seal, or something like that. The throttle body injection system runs at 14 psi. The fuel pump will not cause too much fuel pressure, even if you had the fuel pump for the higher multi-port injection system in the tank. The pump is supposed to be able to build too much pressure. It's the regulator's job to set the pressure in the system. The pump can pump for all it's worth. All the fuel will flow through the regulator and back to the tank except for the very tiny percentage that stays in the fuel rail under pressure until it goes into the engine.
People have been known to cut a return line that is leaking from rust, and they plug it, then observe the engine seems to run fine. That can happen with multi-port injection systems that run near 50 psi. Some of those pumps can only build up to around 55 or 60 pounds, and that little extra goes unnoticed in how the engine performs.
Sunday, September 18th, 2016 AT 6:53 PM