The Ultimate 2001 Buick Century Fuel Injector Replacement Guide (Step-by-Step)
Replacing the fuel injectors on a 2001 Buick Century is a moderately challenging but achievable DIY task, typically taking 4-6 hours for a careful home mechanic. The process involves relieving fuel system pressure, disconnecting the battery, removing the upper intake manifold plenum, accessing the fuel rail and injectors underneath, swapping out the old injectors for new ones, and meticulously reassembling everything. Success requires patience, proper tools, attention to detail regarding small parts and electrical connectors, and strict adherence to safety procedures due to flammable fuel vapor.
Before starting the fuel injector replacement process, gather all necessary parts and tools. You will need a set of replacement fuel injectors specific to the 3.1L V6 engine (GM part number compatible with 17113752 or equivalent quality aftermarket like Bosch, Delphi, or ACDelco). A basic mechanic's tool set (metric sockets and wrenches, extensions, ratchets, pliers), E10 Torx sockets (or external Torx), fuel line disconnect tools (5/16" and 3/8" sizes), a torque wrench (both ft-lb and in-lb scales recommended), and safety gear (safety glasses, nitrile gloves) are essential. Consider replacing related components while access is open: upper intake manifold gaskets, lower intake manifold gaskets if disturbed, throttle body gasket, injector O-rings (usually included with injectors), and possibly fuel pressure regulator O-rings.
Ensuring complete safety is the absolute first step in the process. Disconnect the negative battery terminal using a 10mm wrench to eliminate electrical risks and prevent accidental fuel spraying. Next, depressurize the fuel system. Locate the Schrader valve on the fuel rail near the rear of the engine compartment; it resembles a tire valve stem. Cover the valve with a thick rag and carefully depress the center pin using a small screwdriver or tire gauge, allowing trapped fuel pressure to slowly bleed off into the rag. Exercise extreme caution – pressurized fuel can cause severe injury. Have absorbent material and a fire extinguisher readily available.
Gain access to the fuel rail by carefully removing the upper intake manifold plenum. Begin by detaching various components connected to the plenum: the throttle body linkage/cable, the air intake ductwork and resonator box, the Mass Air Flow (MAF) sensor connector if routed through, and the Idle Air Control (IAC) valve connector. Use a T20 Torx bit to remove the throttle body position sensor retaining screws, allowing the sensor to be gently moved aside without disconnecting wires (risk damaging fragile pins). Disconnect any necessary vacuum lines and the brake booster hose, carefully labeling them for reassembly. Remove the bolts securing the plenum to the lower intake manifold using an 8mm socket or wrench (usually around 10 bolts). Lift the plenum straight up and off the engine. Inspect the old gasket surfaces and clean them thoroughly in preparation for reassembly.
With the plenum removed, the fuel rail becomes accessible on the driver's side cylinder bank. Before removing the fuel rail, disconnect the fuel supply and return lines using the correct size fuel line disconnect tools. Slide the appropriate tool (5/16" is common for supply, 3/8" for return) firmly over the line end where it meets the rail fitting, pushing it inward to release the internal plastic locking tabs. Carefully pull the fuel line off. Disconnect the electrical connectors for each fuel injector by pressing the release tab and pulling upwards. Use a 10mm socket to remove the fuel rail hold-down bolts. Carefully lift the entire fuel rail assembly straight up from the intake manifold. Older injectors might be stuck; gently rocking the rail side-to-side can help release them. Avoid prying which can damage components. Place the rail on a clean surface.
Replace the injectors individually on the removed fuel rail. Press the small locking tab on each injector's plastic electrical connector and pull the connector off. Extract the old injectors by carefully pulling them straight out of the rail sockets. Discard the old upper and lower O-rings. Lubricate the new upper and lower O-rings (included with quality injectors) only with clean engine oil. Never use grease or silicone. Firmly press each new injector straight down into the fuel rail socket until it seats with a distinct click. Ensure the injector electrical connector is oriented correctly for easy reattachment later. Reinstall the electrical connectors firmly onto each new injector until they click. Double-check all O-rings are seated properly in their grooves on the injector body.
Reinstall the fuel rail assembly with the new injectors. Carefully lower the fuel rail straight down over the exposed injector ports on the engine. Each injector must align perfectly and drop smoothly into its lower intake manifold port without binding. Ensure injectors are fully seated. Reinstall the fuel rail hold-down bolts and tighten them gently and evenly in stages using a torque wrench to the specified value (usually around 15 ft-lbs or as per factory manual). Reattach the fuel supply and return lines to the rail fittings. Push them on firmly until the plastic locking collar clicks securely into place. Pull gently on each line to verify they are locked. Reconnect all injector electrical connectors, ensuring they click.
Reassemble the upper intake manifold plenum. Place the new plenum gasket onto the lower intake manifold, ensuring perfect alignment. Lower the plenum carefully straight down onto the engine, making sure it sits flush without trapping hoses or wires. Reinstall the plenum retaining bolts by hand initially. Once all bolts are started, tighten them gradually and evenly in the crisscross pattern specified by the manufacturer, working your way to the final torque specification (typically 89 in-lbs - CRITICAL to use inch-pound torque wrench for precision). Reconnect all vacuum lines, the brake booster hose, and any electrical connectors moved aside. Reattach the throttle body position sensor using the Torx screws and reconnect the IAC valve connector. Reinstall the air intake ductwork and MAF sensor connection.
Before reconnecting the battery and starting the engine, perform a crucial leak check. Reconnect the negative battery terminal. Turn the ignition key to the "ON" position for 2-3 seconds, then back to "OFF". Repeat this cycle 3-4 times. This primes the fuel system, pressurizing it without cranking the engine. Carefully inspect all fuel line connections, fuel rail fittings, the Schrader valve, and around each injector base where they meet the intake manifold. Look and smell for any signs of fuel leaks. ABSOLUTELY DO NOT START THE ENGINE IF A LEAK IS DETECTED. Resolve any leaks immediately before proceeding.
After confirming no leaks, start the engine. It may crank slightly longer than usual initially as air purges from the fuel lines. Pay close attention to engine behavior. Listen for smooth idle and acceleration. Scan for any immediate Check Engine Light (CEL) illumination. A temporary misfire code might appear during the first drive cycle but should clear. A persistent CEL indicates a problem requiring diagnosis – potentially an injector connector not fully seated, a large vacuum leak, or an unrelated issue triggered during disassembly.
Adhere to these critical cautions for a safe and successful repair. Avoid disconnecting the throttle position sensor (TPS) electrical connector at the sensor itself due to fragile pins; remove the sensor from the throttle body by its screws instead if necessary. Take meticulous care with the brittle, aged plastic used in electrical connectors, vacuum fittings, and fuel line clips – these break easily. Never use carburetor cleaner on fuel injectors; use only approved fuel injector cleaner added to the gas tank. Pre-soaking injector tips with penetrating oil overnight can sometimes ease stuck injector removal but requires careful cleanup and prevents oil from entering the intake. If removing the lower intake manifold is necessary to access stuck injectors, this significantly increases complexity, requiring replacement of lower intake gaskets and much more disassembly – potentially beyond DIY comfort for many.
Performing this injector replacement yourself can save significant costs compared to a professional shop. A set of quality injectors costs between 250. Contrast this with shop labor rates (150/hr) plus parts markup. While demanding, success brings the satisfaction of repair and the assurance of using quality parts correctly installed. Following this detailed guide methodically greatly increases your chances of a smooth-running Buick Century for miles to come.
For optimal engine longevity and performance, adhere to recommended preventative maintenance practices. Use Top Tier detergent gasoline consistently to keep injectors cleaner longer. Replace the fuel filter every 30,000 miles to protect injectors from debris. Address engine misfires or running issues promptly to prevent damage to components like the catalytic converter. Regular visual checks for fuel leaks or damaged wiring can catch minor problems before they escalate into costly repairs requiring injector replacement again.