Can someone elaborate on how the fuel delivery system works?

Here is what I think I know;

There are 3 lines under the car that lead to/from the tank. One is large and two are smaller.

The larger line is the main fuel supply. It is connected to the fuel pump and leads directly into a fuel filter and then the fuel rail. The fuel rail is where the injectors live.
The smaller line next to that line is the fuel return line. The purpose of the fuel return line is to return the fuel that was unused by the injectors to the tank. This creates a circuit that has a constant flow of pressurized fuel.
The third line, has something to do with vapors? maybe? I'm not really clear on the third lines purpose.

Tell me where I'm wrong and fill in the blanks.

 

Correct so far...

One line is the fuel supply from the fuel pump. That leads through filters to the fuel rail.

Another line is the fuel return. That one comes from the FPR at the other end of the fuel rail, and returns fuel to the tank. FPR operates as a back-pressure regulator by throttling the return flow.

Third line is the vapor-recovery line. It should go to the EVAP canister (charcoal canister) which I think is mounted on the firewall. While the car is parked, fuel evaporates from the tank and gets trapped in the canister. When you start the engine, it sucks a bit of air through that canister & burns the fuel that was trapped.

(In 1998 that EVAP canister moved to the underside of the car, below the left-rear seat.)

 

Awesome, thank alot.

That should be enough info to start diagnosing my poor fuel economy and gas odour. Is there anywhere else I might find fuel where I don't want it?

 

Check your FPR. The rubber vacuum hose (to intake manifold) isn't supposed to have any fuel. If it DOES, the FPR's diaphragm is busted.

Parts of the EVAP system disconnected?

 

I will investigate tonight.

Is there enough fuel in the EVAP system to seriously affect fuel economy?

EDIT: I suspect a leak in the line because I recently reran the brake lines and the fuel return line. The main fuel line wasn't looking too good at the time but i didn't replace it due to time constraints. That will be my first stop, if its sweating, thats probably where that smell is coming from.

 

Not SUPPOSED to be enough fuel in there... But if something's broken, open, leaking, whatever, then it all depends on what's wrong.

If there's any leaking, the fuel supply line is the only one that's operating at higher pressure. Return & EVAP lines are pretty close to atmospheric pressure.

I had a 95 Integra and the fuel lines under the car corroded through in a real funny way. They became almost spongy. They began leaking just enough to smell & become a little bit wet with fuel. I noticed them before it got bad enough to actually drip liquid fuel on the ground.

Every winter I think the roads/highways department has been trying to turn Lake Erie into the next great salt lake...

 

here's a nice shot of those lines pre-replacement...



The brake lines were not pretty, you may notice that one of them looks like the same size as the fuel supply line, they are actually smaller then the fuel return line... They more or less FELL off the car once I took the clips off.

 

Well I found the time to get under the car tonight. As I suspected, the main fuel line is sweating, but it doesn't seem to be enough to cause the terrible fuel economy I have been getting (I put in around $15 and I can drive about 40km).

I checked the FPR vacuum line and its clean as a whistle.

Any other ideas for what could cause poor mileage? Idles great and I'm very light on the pedal, I don't let the car see the other side of 3.5rpm.

On a probably unrelated note, while under the car, I noticed that the front engine mount is just about completely cracked through! I ordered a new one and I'll put it in tomorrow. Should I not be driving on it like that?

 

Sweating with gas or sweating because the line is cold?

 

Smelled like gas and looked like its been rusting in the ocean for years... Do you think that could more then half my fuel economy?