Faulty fuel pumps are an all too common fault, but to be fair to the little guys, they work very hard and often under difficult conditions. Fitting a new pump isn’t that difficult for most models, finding them however can almost be a bigger challenge.
Modern gas engines will have a fuel pump located inside the gas tank. To replace the fuel pump, an access port is usually fitted on the trunk floor or under the rear seat. Diesel-fueled engines will likely have two fuel pumps fitted: a lift pump fitted inside the fuel tank and a high-pressure pump fitted at the engine.
In this post, you’ll understand where your fuel pump is fitted and how to access it. You’ll also learn some secret insider mechanic hacks for fitting, sssshhh!
Is It Safe To Work On Gas Tank?
Gas tanks live under your vehicle and it may be necessary to climb under your vehicle. A good quality hydraulic jack and axle stands are needed. Never trust a jack, always use axle stands to support the vehicle weight.
I’m a mechanic for twenty-plus years, I won’t take a chance and you shouldn’t either. If you intend to open the gas tank, you’ll need to use caution. Gas is highly flammable, striking tools, wearing polyester clothing, or a hand lamp is enough to ignite the fuel. Don’t be fooled by an empty tank, it’s equally dangerous as it’s filled with highly combustible vapors.
Use a quality LED lamp, wear cotton clothing, and don’t strike tools together. Check out my favorite tools on the Mechanics tools page.
Locating The Gas Pump
All cars since the mid-1990s have had a gas fuel pump submerged inside the gas tank. The gas tank is located under the car. Many vehicles employ an access port on the floor of the car, usually in the trunk or under the rear seat floor.
To remove the access port cover, remove its fasteners, (usually three or four rough thread screws). In addition, the cover is likely fitted with a flexible sealer to prevent water and fumes access the cabin area.
It’s worth noting, on some rear-wheel-drive vehicles, the gas tank may straddle the prop shaft hump. In such setups, twin gas pumps and sender units (fuel gauge sensors) may be fitted. The second pump is used to balance the fuel between the two halves of the gas tank.
Now you have access to the fuel pump housing, but before you can access the gas pump, you’ll need to remove the gas lines and the electrical connector. I cover that process below “Removing The Gas Lines”.
How To Remove A Gas Tank?
It should be noted, not all vehicles will have an access port. If your vehicle doesn’t have one fitted, you’ll need to remove the gas tank from the car. Removing the gas tank is a pain in the jacksie, especially if the gas tank is full and you don’t have access to a vehicle hoist. In addition, if your vehicle has a few winters under its belt, the tank fasteners can be a touch rusty.
Your tank will likely be fastened to the vehicle chassis with the aid of metal straps crisscrossing the tank. The straps are usually bolted to the chassis at one or either end.
You’ll need to support the gas tank using a jack and flat plank of wood (helps spread the weight) before unzipping the bolts. Gas tanks are made from plastic and are robust, but really rough play can rupture them. A damaged gas tank can’t be repaired, you’ll need to replace it.
The top tip here, apply plenty of penetrating oil in advance (24 hrs. +) of attempting to remove the strap bolts. Breaking the bolts can ruin your day. Grinding and naked flame can’t be used to aid removal for obvious reasons.
With the straps released, lower the jack just enough to get your hands in, two fuel lines and an electrical connector will need to be released.
Removing The Gas Lines
Vehicles more than twenty years old may require a screwdriver to release the fuel lines. More recent vehicles will be fitted with toolless gas line connectors. To unhook the gas lines, push the connector towards its fitting, pinch the tabs and pull firmly. You’ll need a rag, residue fuel will flow from the line.
Repeat for the second line, don’t worry you can’t mix them up, the lines are different sizes. We’re not done yet, your fuel pump and sender unit electrical connector needs to be removed. It’s a toolless removal, pinch the tab, and pull.
Note: depending on your vehicle tank design, you may need to remove EVAP pipework.
How To Remove The Fuel Pump Housing
With the gas tank in the vehicle or on the ground, extracting the pump housing from the gas tank is an identical procedure. You’ll first need to remove all the dust and crap from the top of the unit. Compressed air works great, or with the aid of a clean paintbrush. Allowing grit to drop into the tank risks damaging the new fuel pump.
The fuel pump housing houses the fuel pump obviously but also a unit known as the sender unit. The pump housing unit is held firmly in place by the locking ring. There is a special tool to remove the ring but a large flat screwdriver and rubber mallet are perfect for unscrewing the locking ring.
Tip: It’s worth counting the number of turns to release the ring, this is helpful info later when refitting.
Some are threaded and others simply lock on tabs, all unlock in a conventional way. Anti-clockwise to loosen. With the ring removed the housing is free. The sender unit is connected to the fuel pump housing and is responsible for gas level information. It utilizes afloat on a dogleg rod which rises and falls with gas level.
As the rod is connected to the housing it can’t be lifted straight up, the complete unit must be maneuvered through 90 degrees when removed. You need a little patience here, removing can be a bit of a puzzle, but you’ll figure it out.
You may be tempted to bend the rod. Fight that temptation, bending the rod will cause incorrect fuel level readings.
How To Remove Fuel Pump From Housing
To remove the pump from the housing first move to a workbench for comfort. The fuel pump is located in the center of the housing, and the sender unit is usually tagged onto the side of the housing.
In some cases, the sender unit needs to be removed to allow access to the pump. A fuel line from the housing to the pump will need to be removed as will electrical connections. Finally, we get to remove the pump, the pump may be clipped or fastened to the housing with screws. With the fasteners removed the pump is now free.
- Before fitting the new pump, be sure to clean the pump gauze filter or replace it
- Clean the grit from the pump housing reservoir (bottom of housing)
- Be sure to fit the pump and sender unit wiring securely
- Lube the housing ring and locking ring threads, helps prevent pinching and binding
- Tighten the locking ring clockwise using the screwdriver and mallet to the number of turns you counted earlier
- Check fuel lines for leaks
- Reseal access port using automotive sealer
Where Is My Diesel Lift Pump Located
The diesel lift pump is located in the fuel tank and removal is identical to a gas fuel pump setup. Diesel is much less flammable and therefore less of a danger, on the downside, if you need to remove the tank, they tend to be much larger.
Where Is My Diesel High Pressure Pump Located
The high-pressure diesel pump does all the heavy lifting, any problem with the pump and you’ll quickly know about it. The high-pressure pump is mechanically driven and most are integral to the timing gear.
Most smaller automotive diesel engines are belt-driven and larger diesel engines tend to be chain-driven timing gear. Replacing the pump requires removing the timing gear and is, therefore, best left to a skilled mechanic. Setting the timing incorrectly will likely cause the engine internals to collide, Ouch! that’s expensive.
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John Cunningham is an Automotive Technician and writer on Rustyautos.com. He’s been a mechanic for over twenty-five years and has worked for GM, Volvo, Volkswagen, Land Rover, and Jaguar dealerships.
John uses his know-how and experience to write fluff-free articles that help fellow gearheads with all aspects of vehicle ownership, including maintenance, repair, and troubleshooting.