🔧 GS350 - Fuel Pump Replacement

On your GS350, the fuel pump is inside the fuel tank as part of an in-tank pump module. The job is mostly about safely relieving fuel pressure, accessing the pump through the rear-seat service cover, swapping the module, and resealing everything so there are no fuel leaks.

Difficulty Level: Advanced | Estimated Time: 2.5-4.5 hours

Assumption: Your GS350 uses the under-rear-seat access cover to the in-tank pump module (common on this platform).

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⚠️ Safety & Precautions

• ⚠️ Work outdoors or in a very well-ventilated area; fuel vapors ignite easily.
• ⚠️ No smoking, flames, heat guns, or incandescent work lights near the car.
• ⚠️ Disconnect the negative battery cable to prevent sparks.
• ⚠️ Relieve fuel pressure before disconnecting any fuel line to avoid spray.
• ⚠️ Keep a Class B fire extinguisher nearby and clean spills immediately.
• ⚠️ Replace the pump seal/gasket; reusing it can cause leaks and fuel smell.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 10mm ratchet
• 6-inch extension for 3/8-inch drive
• Phillips #2 screwdriver
• Trim removal tool set (plastic)
• Needle-nose pliers
• Fuel line quick-disconnect tool set (specialty)
• Brass punch set (specialty)
• Small hammer
• Torque wrench 5-60 Nm range
• Shop towels
• Catch pan
• Permanent marker
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• In-tank fuel pump module assembly - Qty: 1
• Fuel pump module seal/gasket - Qty: 1
• Fuel line retaining clip(s) - Qty: 1

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📋 Before You Begin

• 🅿️ Park on level ground, set the parking brake, and keep doors open for ventilation.
• ⛽ Aim to have less than 1/4 tank of fuel; it reduces vapor and slosh.
• 🔋 Disconnect the negative battery terminal using a 10mm socket.
• 🧯 Set a fire extinguisher within reach and keep rags ready for spills.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Relieve fuel pressure

• Remove the fuel pump/fuel system fuse or relay (usually in the engine-bay fuse box) using needle-nose pliers.
• Start the engine and let it run until it stalls, then crank for 2-3 seconds to remove leftover pressure.
• Turn ignition OFF and reinstall the fuse/relay.
• Tip: This prevents fuel spraying at disconnection.

Step 2: Remove the rear seat cushion

• Move the front seats forward for space.
• Release the seat cushion clips and lift the cushion out using a trim removal tool set (plastic).
• Set the seat cushion aside where it won’t get fuel smell on it.

Step 3: Open the fuel pump service cover

• Find the metal service cover under the seat and remove fasteners using a 10mm socket and 10mm ratchet.
• Peel back any butyl sealer carefully with a trim removal tool set (plastic).
• Clean dust around the pump top with shop towels so dirt can’t fall into the tank.

Step 4: Disconnect the electrical connector(s)

• Unplug the pump module connector by pressing the lock tab and pulling straight off.
• If the tab is stubborn, gently assist with a trim removal tool set (plastic) (do not pry hard).

Step 5: Disconnect the fuel line(s)

• Place a catch pan and shop towels under the line connection.
• Disconnect the quick-connect fitting using a fuel line quick-disconnect tool set (specialty).
• A “quick-connect” is a spring-lock fuel fitting that releases when the correct tool pushes the internal retainer back.
• Cap or wrap the line end with shop towels to reduce fumes.

Step 6: Mark and remove the pump lock ring

• Use a permanent marker to mark the relationship between the tank, lock ring, and module so it goes back aligned.
• The “lock ring” is the large ring that twists to clamp the pump module to the tank.
• Tap the lock ring counterclockwise using a brass punch set (specialty) and small hammer.
• Lift the lock ring off and set it aside.
• Tip: Use brass to reduce spark risk.

Step 7: Remove the fuel pump module

• Carefully lift the module straight up; angle it as needed to clear the float arm (fuel level sensor).
• Let fuel drain into the tank for a few seconds, then move the module to the catch pan.
• Remove the old seal/gasket from the tank opening using a trim removal tool set (plastic).

Step 8: Install the new seal and pump module

• Install the new fuel pump module seal/gasket onto the tank opening (make sure it sits flat and isn’t twisted).
• Lower the new in-tank fuel pump module assembly into the tank, keeping the float arm from binding.
• Align the module to your paint marks.

Step 9: Reinstall and tighten the lock ring

• Install the lock ring and hand-seat it.
• Tighten by tapping clockwise with the brass punch set (specialty) and small hammer until fully seated at the marks.
• If your setup uses lock-ring bolts instead of a twist ring, install and tighten using a 10mm socket and torque wrench 5-60 Nm range to Torque to 6 Nm (53 in-lbs).
• Tip: Even pressure prevents leaks.

Step 10: Reconnect fuel line(s) and electrical

• Reconnect the fuel quick-connect until you hear/feel a click, then pull back gently to confirm it’s locked.
• Install any new fuel line retaining clip(s) if your connector uses them.
• Reconnect the electrical connector(s) until fully seated.

Step 11: Reinstall the service cover and rear seat

• Reinstall the service cover using a 10mm socket and 10mm ratchet.
• Reinstall the rear seat cushion and press down firmly to latch the clips.

Step 12: Restore battery power

• Reconnect the negative battery terminal using a 10mm socket.
• Torque to 5 Nm (44 in-lbs).

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✅ After Repair

• 🧪 Key ON (engine OFF) for 5 seconds, then OFF; repeat 3 times to prime the system.
• 🧼 Start the engine and inspect the pump top and fuel line connection for leaks for 2-3 minutes.
• 🛑 If you smell fuel inside the cabin, shut the engine off and recheck the seal and lock ring seating.
• 🔎 If a check engine light appears, scan and clear codes after confirming no leaks.

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💰 DIY vs Shop Cost

Shop Cost: $900-$1,600 (parts + labor)

DIY Cost: $350-$900 (parts only)

You Save: $550-$700 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 2.5-4.0 hours.

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🎯 Ready to get started?

HowToo makes it easy: same-day/2-day shipping on every part, plus all the tools and specialty tools you need! Check out the parts and tools sections below to add everything to your cart.