Vapor lock is caused by super fine sediment in the fuel pump check valves. The fix is easy. A 10 micron fuel filter between the frame rail fuel line from the tank and the mechanical fuel pump inlet. I use either an 1984 corvette fuel filter for 3/8 or a 1994 ford probe 2.0l automatic fuel filter for 5/16 fuel lines. I disconnect power to the ignition system so no sparks are created. Disconnect the fuel line to the carb. Extend it with some fuel hose into a clean clear soda bottle. Get somebody to crank the engine for 15 seconds while you watch the pulses into the bottle. Each pulse full and equal to the other. Not diminishing do the 15 secong cranking full flow procedure 3 times. This is usually enough to flush the sediment out of the fuel pump check valves. Why. The sediment reduces the pumps ability to hold fuel pressure to the carb and reduces the ability to pull fuel from the tank. The engine heat causes the low pressure fuel to boil and create vapor. The expanding vapor pushes liquid fuel backwards thru the partially open check valves leaving nothing but fuel vapor coming from the carb vents.
Is the vacuum line normally from ported or manifold source? Also on a mid 70's 360 Ford there is a temperature controlled vacuum switch by the thermostat housing, would that be part of the air cleaner vac circuit or be for something else?
Exactly what I needed. So hard to find content on older model cars. 1984 Oldsmobile here.
Glad you like it! That's what we're here for.
Just got an 86 El Camino and have to say your videos have been extremely helpful on educating myself on the topic you have covered. Thanks!
Glad I could help. If there is anything you would like to know more about, please let me know.
Vapor lock is caused by super fine sediment in the fuel pump check valves. The fix is easy. A 10 micron fuel filter between the frame rail fuel line from the tank and the mechanical fuel pump inlet. I use either an 1984 corvette fuel filter for 3/8 or a 1994 ford probe 2.0l automatic fuel filter for 5/16 fuel lines.
I disconnect power to the ignition system so no sparks are created. Disconnect the fuel line to the carb. Extend it with some fuel hose into a clean clear soda bottle. Get somebody to crank the engine for 15 seconds while you watch the pulses into the bottle. Each pulse full and equal to the other. Not diminishing do the 15 secong cranking full flow procedure 3 times. This is usually enough to flush the sediment out of the fuel pump check valves.
Why. The sediment reduces the pumps ability to hold fuel pressure to the carb and reduces the ability to pull fuel from the tank. The engine heat causes the low pressure fuel to boil and create vapor. The expanding vapor pushes liquid fuel backwards thru the partially open check valves leaving nothing but fuel vapor coming from the carb vents.
Enjoyed it. Well done.
Thank you. I'm glad you liked it.
Is the vacuum line normally from ported or manifold source? Also on a mid 70's 360 Ford there is a temperature controlled vacuum switch by the thermostat housing, would that be part of the air cleaner vac circuit or be for something else?
It should be manifold. And I can't say for sure about the switch. It all depends on where the hose goes.