How to Replace the Fuel Regulator in a 3800 Engineby Robert Bayly
The General Motors 3800 engine is not to be confused with the General Motors 3.8-liter engine. The 3800 was introduced after the 3.8L and uses a balance shaft to enhance engine smoothness. The 3800 is not unique to any single General Motors brand; it is found in all GM offerings: Chevrolet, Buick, Pontiac, Oldsmobile and Cadillac. The fuel-injected, 3800 V6 has a fuel-pressure regulator mounted on the fuel rail. The regulator in non-adjustable and must be replaced as a unit.
Remove the gas cap to relieve the fuel pressure. Remove the fuel pump fuse. On early 3800 models, the fuse is located in the fuse panel on the left side of the instrument panel and marked "FP." On later models, it is located below the relay panel on the driver's side of the firewall, under the hood. Start the engine and let it run until it dies.
Disconnect the negative battery cable. Disconnect the positive battery cable.
Locate the fuel-pressure regulator, which is on the driver's side of the fuel rail (the pipe that is connected to the fuel injectors). It is at the beginning of the rail, before the injectors. It is round and has a vacuum hose attached to the top and a metal fuel line on the bottom.
Remove the vacuum line from the top of the regulator by pulling it off.
Use two wrenches to remove the fuel line from the bottom of the regulator. Place one wrench on the hex fitting on the bottom of the regulator. Use another wrench to unscrew the fuel line.
Remove the two bolts from the bracket that holds the regulator onto the fuel rail with a ratchet and socket. Pull off the bracket. Remove the regulator.
Place the new regulator in the bracket. Bolt it to the fuel rail. Install the fuel line by hand and tighten it using two wrenches as in Step 5. Push the vacuum hose onto the top of the regulator. Replace the fuel pump fuse.