You’ll first want to be sure that the fuel pump is defective. You’ll be surprised how many times I’ve encountered someone who changed out a fuel pump only to find that a clogged gas line or filter was the problem. I even ran into one fellow who changed out his pump and when that didn’t work he checked further and saw he had no gas in his gas tank. You can’t make this up. Even if the carburetor isn’t receiving gas you still might want to check that the lines and any inline or in carburetor filter(s) are free and clear. The problem doesn’t always lie with the fuel pump.
One obvious indication of a bad fuel pump is when gas is spitting from the weep holes which are located on the top of the fuel pump bowl. This is an indication the diaphragm is ruptured. If this occurs there’s a good chance that gas could have mixed with the oil. Smelling the dipstick and visually scrutinizing it for gas contamination will determine if this is a problem. If fuel did enter the crankcase, the oil and filter must be changed. Assuming the oil is okay we’ll continue with the installation procedure.
Handle the fuel pump with care. Make sure that no dirt gets into the ports. Make sure all protective plugs are removed. Make sure existing hoses and connections are in good condition. Replace any worn rubber or steel lines.
Disconnect the battery cable.
Disconnect the fuel lines from the old pump. Remove the two mounting bolts and pump from the engine block. Remove the old gasket and clean the mounting surface on the block. Keep in mind gas will probably leak from the gas line feeding the fuel pump and from the pump itself.
Check for signs of wear on the push rod. Replace if necessary.
Add grease to the rocker pad and rocker arm cavity to lubricate the internal parts.
Place the new gasket on the fuel pump keeping it in place by placing the two mounting bolts through the pump flange and gasket.
On push rod driven pumps, make sure the pump lever is positioned under the push rod; if not, damage usually results. Chances are that if the pump bolts up then the pump is positioned correctly; but not always. I like using a hacksaw blade to keep the push rod up while placing the pump lever underneath the push rod when the engine is at low cam. If the pump is properly positioned, you should hear an internal squawking noise with each movement of the pump.
Tighten the two mounting bolts evenly, from one side to the other firmly until completely tight.
Align and tighten fuel lines. Check for any leakage. Make sure all lines are in good condition and that all connections are tight and secure. Loose and leaking fittings, and lines in poor condition, can cause a fire when the engine is started or gets warm.
As I mentioned earlier, if the old pump had a ruptured diaphragm gasoline could have entered the crankcase. CHECK AND CHANGE ENGINE OIL if there is a smell of gas on the dipstick to prevent engine bearing damage due to poor lubrication. I change the oil and filter anyway.
If after installing the new fuel pump you find that the pump does not supply sufficient fuel there is a possibility of engine cam wear. This of course should be checked.
This is written intending to help you install a fuel pump. Installing a fuel pump should only be performed by someone with the necessary skill level to accomplish the task safely. I do not suggest this is the only way to install a fuel pump; only that it is how I would. I assume no responsibility whatsoever which may result from following the suggestions contained in this writing.