Parts of a Fuel Tank – Labeled Tank and Fuel Pump Diagram

All 16 parts on the diagram

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Tank and filler 4

Fuel cap It lets air in as fuel is used. But it keeps the fumes from coming out.
Filler neck Fuel from the pump nozzle runs down it into the tank.
Baffles They keep the fuel from sloshing and make the tank stronger.
Drain plug Taking it out empties the tank for draining and cleaning.

Fuel and vapor lines 6

Fuel line It runs forward under the car, through the fuel filter.
Fuel filter It traps dirt in the fuel on its way to the engine.
Return line It carries back the fuel the engine did not use. Some systems have none.
Rollover valve Stops fuel running out the vent line if the car rolls over.
Vent line It takes vapor from the tank to the charcoal canister.
Charcoal canister Stores the vapor until the running engine draws it in. The engine then burns it.

Pump unit 6

Fuel pump Pushes fuel from the tank along the fuel line to the engine.
Strainer It keeps dirt in the tank out of the pump.
Float It rises and falls with the fuel level and moves the arm.
Float arm It passes the height of the float to the sending unit.
Sending unit (fuel level) A resistor whose contact is moved by the float arm.
Electrical connector The car's wiring plugs in here to power the pump.

How this list was compiled: Every name checked on 2026-09-30, a name kept only where two independent sources use it: US Army TM 9-8000, Principles of Automotive Vehicles (https://archive.org/details/tm-9-8000-principles-of-automotive-vehicles-1985); Wikipedia, Fuel tank (text only); a parts maker's fuel tank and fuel pump installation sheets and a second pump maker's product sheet, read in Internet Archive copies (the first is https://web.archive.org/web/20240805224410/https://ecat.spectrapremium.com/documents/BOU-AVM-1-I-013B_Technical%20Notice_Fuel%20Tank%20Installation%20Instruction.pdf). No maker is named on the page. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; a schematic of no maker's tank or pump, nothing traced. Licence: own work

How it works

The parts of a fuel tank are shown on a car's tank cut open from the side, with the pipes that leave it. The second drawing lifts out the unit that stands inside: the pump, its strainer and the fuel level sending unit.

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Fuel in, fuel out, vapor out

Fuel goes in through the fuel cap and the filler neck. Baffles inside the tank keep it from sloshing. The pump sends it forward along the fuel line and through the fuel filter, and unused fuel comes back by the return line. Vapor leaves the top of the tank past the rollover valve, along the vent line to the charcoal canister.

The pump unit

The electric fuel pump stands in the fuel with a strainer on its inlet. Beside it, a float on a float arm moves the sending unit, which tells the gauge how much fuel is left. The electrical connector on top joins the unit to the car's wiring.

The parts of a gas tank are the same ones: gas tank and fuel tank are two names for one thing.

Questions and answers

What are the parts of a fuel pump?

An in-tank fuel pump unit has the electric pump itself, a strainer on its inlet, a sending unit with a float arm and float for the gauge, and an electrical connector on top. The fuel line leaves from it.

What do the baffles in a fuel tank do?

They are plates across the inside of the tank. They keep the fuel from sloshing about as the car moves and make the tank stronger. Openings in them let the fuel pass from one part of the tank to the next.

What does the charcoal canister do?

It stores fuel vapor. Vapor from the tank is led along the vent line into the canister, where charcoal holds it. When the engine runs, air is drawn through the charcoal and the vapor is burned in the engine.

How does a fuel gauge know how much fuel is in the tank?

A float rides on the fuel. Its arm moves a contact along a resistor in the sending unit, so the electrical signal changes with the fuel level, and the gauge on the dashboard shows it.