Ford Thunderbird/Cougar 1983-1997 Repair Guide

Mechanical Fuel Pump



See Figure 1

Before removing the pump, rotate the engine so that the low point of the cam lobe is against the pump arm. This can be determined by rotating the engine with the fuel pump mounting bolts loosened slightly. When tension (resistance) is removed from the arm, proceed.

  1. Loosen the threaded fuel line connection(s) with the proper size flared nut wrench, then retighten snugly. Do not remove the lines at this time.

Click image to see an enlarged view

Fig. Fig. 1: The mechanical fuel pump is driven by the camshaft

  1. Loosen the mounting bolts one to two turns. Apply force with your hands to loosen the fuel pump if the gasket is stuck. Rotate the engine, by nudging the starter, until the pump cam lobe is near its low position. The tension on the pump will be greatly reduced at the low cam position.

The outlet line is pressurized. Disconnect the fuel pump inlet line, the outlet vapor return line, if so equipped.

  1. Remove the pump attaching bolts, then the pump and gasket. Clean the mating areas well.

To Install:
  1. Install the attaching bolts into the pump, then install a new gasket on the bolts. Position the pump to the mounting pad. Turn the bolts alternately and evenly, then tighten to 12-15 ft. lbs. (16-20 Nm).
  3. Install the fuel outlet line. If it is a threaded connection, start fitting by hand to avoid any crossthreading. Tighten the fitting to 20-24 ft. lbs. (15-18 Nm).
  5. Install the inlet line and fuel vapor return line, if removed. Using new clamps, install the fuel hose. Inspect and replace any cracked or damaged fuel hoses.
  7. Check that all connections are intact, then start the engine and inspect for leaks. Run the engine for approximately 2 minutes.
  9. Stop the engine and check all the pump and fuel line connections for any leaks. Inspect for any oil leaks at the pump mounting pad.


See Figure 2

No adjustments may be made to the fuel pump. Before removing and replacing the old fuel pump, the following test may be made while the pump is still installed on the engine.

  1. If a fuel pressure gauge is available, connect the gauge to the engine and operate the engine until the pressure stops rising. Stop the engine and take the reading. If the reading is within the specifications given in the Tune-Up Specifications chart in Engine Performance & Tune-up , the malfunctions is not in the fuel pump. Also check the pressure drop after the engine is stopped. A large pressure drop below the minimum specification indicates leaky valves. If the pump proves to be satisfactory, check the tank and inlet line.

Click image to see an enlarged view

Fig. Fig. 2: Fuel pump pressure and capacity test equipment

  1. If a fuel pressure gauge is not available, disconnect the fuel line at the pump outlet, place a vessel beneath the pump outlet, and crank the engine. A good pump will force the fuel out of the outlet in steady spurts. One pint in 25-30 seconds is a good flow. A worn diaphragm spring may not provide proper pumping action.
  3. As a further test, disconnect and plug the fuel line from the tank at the pump, and hold your thumb over the pump inlet. If the pump is functioning properly, a suction indicates that the pump diaphragm is leaking, or that the diaphragm linkage is worn.
  5. Check the crankcase for gasoline. A ruptured diaphragm may leak fuel into the engine.