See full version: Signs of a Bad Diaphragm in a Fuel Pump
A fuel pump with a defective diaphragm may be torn or have developed holes from wear. These tears or holes allow fuel to escape past the diaphragm and exit the fuel pump housing. A leaking fuel pump can be noticed as fuel droplets or puddles on the ground and a strong smell of gasoline when the car is running. Leaking diaphragms are likely to eventually fail completely and cause the engine to abruptly stop running. more
A badly damaged fuel pump diaphragm will be unable to pump fuel, causing a total loss of fuel pressure and no gas to be supplied to the engine. As a result, there will be no fuel to produce the proper fuel-air mixture and no combustion within the cylinders when the engine is turned over. The end result is an engine that will turn over but will not start.
Most modern cars are equipped with electric fuel pumps that are mounted either inside the gas tank or in-line with the fuel line. Older vehicles were typically equipped with mechanical fuel pumps that mounted to the engine and used a rubber diaphragm to pull gasoline from the gas tank and push it to the engine. Mechanical fuel pumps can fail to operate properly or not at all when the diaphragm becomes damaged or wears out. more
A bad fuel pump diaphragm will cause the fuel pump to produce less fuel pressure than is necessary for proper operation of the engine. This low fuel pressure causes less gas to be supplied to the engine, resulting in fuel starvation and a too lean air-fuel mixture at the carburetor. The end result is hesitation and stalling when the vehicle is driven. [links]
GM Applications – Fuel Pump Push Rod Info here
Mechanical fuel pumps siphon fuel from the gas tank. It then pushes it to the carburetor, when the engine is cranking or running. All mechanical fuel pumps used on inline six cylinder and V8 engines are diaphragm type. As a result, no adjustments or repairs are possible.
Mechanical Fuel Pumps Arm
Sometimes the hole in the front of the block can not be accessed. An alternative is to remove the spacer plate and push rod and put some heavy grease on the push rod. This grease will (for a while) hold the pushrod to the cam in the retracted position. Reinstall the spacer plate, use a new gasket. With the gasket on the fuel pump insert the fuel pump arm into the hole in the spacer plate. Once the pump arm is in position, you’ll have to push against the pump’s return spring pressure. This will get the pump’s mounting holes, close enough to the spacer to start the bolts. more
Now you will need to loosen the bolt, holding the push rod in position, so the push rod can move. Also, you may need to rotate the engine a bit, to let the fuel pump cam retract the push rod. Tighten the bolts evenly, until the pump meets the spacer. DO NOT forget, to remove the longer bolt holding the push rod. Replace the original bolt into the same hole, with a little sealer on the threads. Finally, reattach the fuel lines- do not use teflon tape. more
Pumped fluid in air exhaust muffler [links]
Air valve is stuck or dirty.
Check operation manual for correct part installation [links]
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Air valve cover or air valve cover screws are loose. more
Loose fluid side diaphragm plate more
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