Chevrolet Full-size Cars 1968-1978 Repair Guide

Fuel Pump

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The fuel pump is the single action AC diaphragm type. It is a non-serviceable type fuel pump. The pump is actuated by an eccentric located on the engine camshaft. On inline 6-cylinder engines the eccentric actuates the pump rocker arm. On V8 engines a pushrod between the camshaft eccentric and the fuel pump actuates the pump rocker arm.

TESTING



Fuel pump should always be tested on the vehicle. The larger line between the pump and tank is the suction side of the system and the smaller line, between the pump and carburetor is the pressure side. A leak in the pressure side would be apparent because of dripping fuel. A leak in the suction side is often only apparent because of the reduced volume of fuel delivered to the pressure side. However, fuel may leak out on the suction side when the engine is off.

  1. Tighten any loose line connections and look for any kinks or restrictions. Inspect rubber hoses for cracks or leaks and replace if necessary. Inspect the fuel filter for clogging and clean or replace it as necessary.
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  3. Disconnect the fuel line at the carburetor. Disconnect the distributor-to-coil primary wire or, on HEI systems, the distributor connector. Place a container at the end of the fuel line and crank the engine a few revolutions. If little or no gasoline flows from the line, either the fuel pump is inoperative or the line is plugged. Blow through the lines with compressed air and try the test again. Reconnect the line.
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  5. Attach a pressure gauge to the pressure side of the fuel line with a Tee fitting.
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  7. Run the engine and note the reading on the gauge. Stop the engine and compare the reading with the specifications listed in the Tune-Up Specifications chart. If the pump is operating properly, the pressure will be as specified and will be constant at idle speed. If pressure varies sporadically or is too high or low, the pump should be replaced.
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  9. Remove the pressure gauge.
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REMOVAL & INSTALLATION





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Fig. Fig. 1 Fuel pump mounting on inline six cylinder engines



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Fig. Fig. 2 Fuel pump mounting on V8 engines



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Fig. Fig. 3 The metal line secured to the fuel pump is the outlet line. The rubber hose, held to the pump by a spring clamp, is the fuel inlet



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Fig. Fig. 4 Using a flare nut wrench, loosen the fuel outlet line and remove it from the fuel pump



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Fig. Fig. 5 Place a clamp on the fuel hose. Using a pair of pliers, remove the spring clamp and the inlet hose



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Fig. Fig. 6 Remove one of the bolts which secure the fuel pump to the engine block



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Fig. Fig. 7 Remove the upper bolt from the right front mounting boss ...



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Fig. Fig. 8 ... then thread the first bolt you removed into the bolt hole to hold the fuel pump pushrod



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Fig. Fig. 9 Remove the last fuel pump-to-block bolt, then pull the pump off of the engine

When you connect the fuel pump outlet fitting, always use 2 wrenches to avoid damaging the pump.

  1. Disconnect the negative battery cable. Disconnect the fuel intake and outlet lines at the pump and plug the pump intake line.
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  3. On V8 engines, remove the upper bolt from the right front mounting boss. Insert a longer bolt ( 3 / 8 -16X2") in this hole to hold the fuel pump pushrod.
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  5. Remove the two pump mounting bolts and lockwashers; remove the pump and its gasket.
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  7. If the rocker arm pushrod is to removed, remove the two adapter bolts and lockwashers and remove the adapter and its gasket.
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  9. Install the fuel pump with a new gasket reversing the removal procedure. Coat the mating surfaces with sealer.
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  11. Connect the fuel lines and check for leaks.
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