Engine Stalling

[jon schapiro]

Unfortunately this may be a rather long note. I had posted about two weeks ago that my 1973 stalled and took a while to restart after I opened it up. Since then I have been driving it conservatively on the primary side of the carburetor and it ran flawlessly. Well today I took it out for a short ride it didn’t go above 30 miles an hour when it stalled as if running out of fuel. It restarted but didn’t take the gas evenly like it normally does. I drove it another quarter mile that around 20 miles an hour and it stalled again and this time it was harder to start (multiple tries). I rebuilt the carburetor about two years ago myself and have been rebuilding carburetors for 50 years. My neighbor look down the carburetor throat to see if the accelerator pump was working and indeed it was squirting gas. He followed me home and the car stalled in my driveway and would not restart. My initial thought was it is a clogged fuel filter so I changed it even though that filter was not that old. I could blow through the old one easily. Anyway I got back in the car and it started immediately and takes the gas beautifully now but I am not sure I have fixed anything. When I remove the rubber hose from the old filter there was no gasoline dripping. It was bone dry leading me to think that either the fuel pump was shot or the line from the gas tank was clogged. I let it run for a good five minutes in the garage and every time I reved it it took the gas immediately. The car has 62,000 miles and the fuel pump is still the original one. I don’t want to start changing out parts randomly. Since the car ran beautifully for five minutes in the garage I am assuming the carburetor is fine and have to believe the fuel pump and gas line are not a problem but the car was starving for gasoline and stalling. I have ruled out vapor lock as the car didn’t even reach operating temperature and since it was gas starvation, I have ruled out ignition. I should add I took it for a 30 mile run last week and it ran as new. Anybody else experienced a similar problem or have any thoughts???

[tomo]

Check the Shop Manual for specs on fuel pressure and fuel delivery. As a general rule, pressure should be around 5-PSI and deliver about 1 pint of fuel in 20 seconds at 500 rpm.

If you don't have a shop manual, here is a link to the 1965 Ford and Mercury shop manual procedure to check fuel delivery. Your 1973 should be similar.

[Dan Szwarc]

This is definitely a fuel delivery problem. Replace all of your online fuel filters and maybe put a low restriction paper filter between the pump and the carb or the tank and the pump.

[jon schapiro]

This is definitely a fuel delivery problem. Replace all of your online fuel filters and maybe put a low restriction paper filter between the pump and the carb or the tank and the pump.

Agreed. The only fuel filter is the factory screwed in filter on the 4300 Motorcraft carburetor. I just started the car six minutes ago and let it run for five minutes revving the engine occasionally and everything seemed as normal. It didn’t even crank starting up but started immediately. It is very strange but has me concerned if I should take it out for a ride again.

[action]

If a fuel delivery issue it is during high or at least higher demand.

You stated when you removed the hose to the fuel filter it was bone dry. I am assuming this was an exaggeration as bone dry would imply zero gasoline has passed through the hose. Which would be impossible if the engine did run. So I get it that there was not liquid fuel present. Which is a clue to the issue.

The above suggestion for a fuel pressure test is a good one. Checking both pressure and volume.
The pump may be delivering fuel and under sufficient pressure, just not enough of it.
And low volume with close to enough pressure would support the symptoms you are experiencing.

The other issue could be rubber hoses. The one at the fuel filter and it is under pressure. Should it leak, that leak would be mostly visible.
The other two hose are at the tank and to the fuel pump. These hoses are subject to negative pressure because the fuel pump is pulling fuel from the tank. If those leak is is going to allow air to enter the fuel line. If it ever has an external leak it would be when the engine is shut down. Then the leak would be for a very brief moment until the pressure subsides. Do inspect those hoses. If it has been a long time since they were replaced (like you do not remember when it was last replaced) do replace them as a maintenance item. It is cheap and not difficult to do. Just awkward for the tank hose because you will have to get under the car.

Then post fuel pressure readings and fuel volume readings.

Action

[jon schapiro]

Pressure test and collapsing hoses next thing to check. Hose to filter seems fine. Hopefully I will get this sorted out.

UPDATE: I am out of the car now but cannot see any gas lines from the tank while the car is on the ground. I suspect I will have to have the car put on a lift?

[jon schapiro]

I am sitting on my sofa thinking I had a similar problem with this car 35 years ago when it died on the road and wouldn’t restart. For the life of me I could not remember what the problem was so I called my ex. She immediately said you picked up a thimble-sized fuel filter and the car ran fine thereafter. I do remember buying an extra fuel filter and placing it with a wrench on top of my spare tire under the tire cover in case it ever happened again. The filter and wrench are still in the trunk. I am hoping that is my problem.

[action]

UPDATE: I am out of the car now but cannot see any gas lines from the tank while the car is on the ground. I suspect I will have to have the car put on a lift?

There is nearly no way to see that short hose without lifting the car. The fitting from the tank is part of the sender which is positioned very high on the tank. The hose makes the jump from the tank to the metal fuel line.
If you have a set of car ramps that would do it to back up onto those.

Action

[TonyC]

Hopefully that is the cause of your problem. I say follow the others' advice and verify your fuel system's condition first: Hoses and lines, filter, carburetor, pump... If everything is confirmed to be in prime condition and the problem persists, well...

Anybody else experienced a similar problem or have any thoughts???

I do have a thought, which does not involve the fuel system, based on similar symptoms I faced with a different make of car. First, rummage through your fuel system; if that doesn't cure the problem, I'll elaborate on my own guess.

---Tony

[Dan Szwarc]

Pull the sending unit and check the filter sock. Inspect the inside of the tank or just drop it and flush it.

[tomo]

The fuel pressure and delivery test will tell you if you need to check the filter sock and hoses that are not easily accessible. If you have insufficient fuel delivery it could be caused by the sock on the tank pickup, the rubber hoses leaking vacuum, a metal fuel line that has internal rust, a weak fuel pump and all of the other things posted.

If you have sufficient fuel delivery and pressure, it is time to check the ignition system for weak spark and spark advance.