C5 Reserve Fuel
Tech Contributor
Joined: Dec 2003
Posts: 19,384
Likes: 87
From: Horncastle Lincolnshire, England
2023 C5 of the Year Finalist - Unmodified
How the Fuel System Works
02 Fuel System Description
Two fuel tanks containing 9 gals each store the fuel supply. An electric fuel pump attaches to the fuel sender assembly inside the left fuel tank. The fuel pump pumps fuel through the fuel feed pipe (6) and an in-line fuel filter (9) to the fuel rail. The rear fuel feed pipe (6) has an integral check valve (4) in order to maintain the fuel system pressure in the feed pipe. The pump provides the fuel at a pressure greater than what is needed by the fuel injectors. The fuel pressure regulator, part of the fuel filter (9), keeps the fuel available to the injectors at a regulated pressure. A fuel return pipe (7) returns the unused fuel to the left fuel tank. The fuel pump also feeds the fuel through a tee (5) with an orifice in the fuel feed rear pipe (6) and through the auxiliary fuel feed rear pipe (2) in order to supply the siphon jet pump inside the right fuel tank. The siphon jet pump transfers the fuel from the right fuel tank to the left fuel tank through the auxiliary fuel return rear pipe (3, 8).:
(1)Fuel Feed Pipe (2)Auxiliary Fuel Feed Rear Pipe (left tank to jet pump) (3)Auxiliary Fuel Return Rear Pipe (jet pump to left tank) (4)Fuel Feed Pipe Check Valve (5)Fuel Feed Pipe Tee with Orifice (6)Fuel Feed Rear Pipe (to fuel filter/fuel pressure regulator and siphon jet pump) (7)Fuel Return Rear Pipe (8)Auxiliary Fuel Return Rear Pipe (jet pump to left tank) (9)Fuel Filter/Fuel Pressure Regulator
Two fuel tanks containing 9 gals each store the fuel supply. An electric fuel pump attaches to the fuel sender assembly inside the left fuel tank. The fuel pump pumps fuel through the fuel feed pipe (6) and an in-line fuel filter (9) to the fuel rail. The rear fuel feed pipe (6) has an integral check valve (4) in order to maintain the fuel system pressure in the feed pipe. The pump provides the fuel at a pressure greater than what is needed by the fuel injectors. The fuel pressure regulator, part of the fuel filter (9), keeps the fuel available to the injectors at a regulated pressure. A fuel return pipe (7) returns the unused fuel to the left fuel tank. The fuel pump also feeds the fuel through a tee (5) with an orifice in the fuel feed rear pipe (6) and through the auxiliary fuel feed rear pipe (2) in order to supply the siphon jet pump inside the right fuel tank. The siphon jet pump transfers the fuel from the right fuel tank to the left fuel tank through the auxiliary fuel return rear pipe (3, 8).:
(1)Fuel Feed Pipe (2)Auxiliary Fuel Feed Rear Pipe (left tank to jet pump) (3)Auxiliary Fuel Return Rear Pipe (jet pump to left tank) (4)Fuel Feed Pipe Check Valve (5)Fuel Feed Pipe Tee with Orifice (6)Fuel Feed Rear Pipe (to fuel filter/fuel pressure regulator and siphon jet pump) (7)Fuel Return Rear Pipe (8)Auxiliary Fuel Return Rear Pipe (jet pump to left tank) (9)Fuel Filter/Fuel Pressure Regulator
Pro
Joined: Dec 2009
Posts: 719
Likes: 2
From: Columbia South Carolina
It is my understanding that the fuel sending unit is relying on some fuel to keep it cool. Our mechanic says that running any new car below 1/8 tank is tempting fate and an expensive fix. It's simple enough thing to keep that much gas in the tank, whether he's right or wrong.
I agree with you, I have also been told that the pump is normally cooled by the fuel, running on a regular basis down to 1/8 and lower exposes the fuel pump and can cause it to overheat and fail..............Personally had the experience in my 1990 Ford Escort, after 2 failed fuel pumps and fairly expensive replacements, I learned my lesson and kept at least 1/4 fuel in the tank. Never had a failed pump for the remainder 100k miles....
Safety Car
Joined: Dec 2010
Posts: 4,820
Likes: 34
From: Ravensdale WA
You're correct as far the fuel pump being submerged in fuel to assist in cooling, but the electric fuel pump itself (which is what you're speaking of, not the sender) is enclosed in a container or "bucket", specifically to keep it submersed when the tank levels are low.
I agree with you as far as keeping fuel in the tank, but I prefer to do it because it minimizes any water (from condensation) in the tank. One other nice thing about plastic tanks too is that they "sweat" less than metal tanks, which also reduces water.
I agree with you as far as keeping fuel in the tank, but I prefer to do it because it minimizes any water (from condensation) in the tank. One other nice thing about plastic tanks too is that they "sweat" less than metal tanks, which also reduces water.
