351 C wont start after sitting a week

Help Support 7173Mustangs.com:

1973MACH

Member
Joined
Dec 3, 2014
Messages
10
Reaction score
0
Location
Pa
My Car
1973 Mach 1, 351 2bbl, FMX automatic, dark green metallic/argent strips, dual avocado interior
I don't quite know what to check so I am asking if anyone has/had this problem. I have new carter fuel pump, Pony carburetor, electronic points distributor, after my car sits a week it will not start unless I pore gas into the carburetor, choke plate does close off. Then it will idle, run fine, no shutting off or ruff running but a week later same thing. Anyone have a suggestion?
 
Joined
Jan 1, 2012
Messages
8,177
Reaction score
932
Location
Springfield, OR
My Car
1971 Mustang Sportroof M code
It sounds like you might have two problems. Either the fuel is draining out of the carburetor or evaporating. The most likely suspect for draining out is a bad power valve, next would be a porous casting.

The other problem is the fuel pump not delivering fuel to the carburetor when you crank the engine. After it starts it has enough vacuum to pull fuel from the tank. The problem may be the fuel pump or a small hole or leak in the fuel line which allows air to be drawn into the fuel line. You'll need to check the draw vacuum, the output pressure, and delivery quantity when you crank the engine. A new fuel pump does not guarantee function.
 
Joined
Feb 17, 2018
Messages
62
Reaction score
29
Location
Cloverdale, CA
My Car
71 429CJ
After car has sat for a week and before you try to start it. I would take air filter off and with the choke plate open, look into the carburetor while you manually operate the throttle. You should see and hear fuel squirt into the engine. if you don’t see/hear fuel squirting the problem is with the carburetor.
 

1973MACH

Member
Joined
Dec 3, 2014
Messages
10
Reaction score
0
Location
Pa
My Car
1973 Mach 1, 351 2bbl, FMX automatic, dark green metallic/argent strips, dual avocado interior
It sounds like you might have two problems. Either the fuel is draining out of the carburetor or evaporating. The most likely suspect for draining out is a bad power valve, next would be a porous casting.

The other problem is the fuel pump not delivering fuel to the carburetor when you crank the engine. After it starts it has enough vacuum to pull fuel from the tank. The problem may be the fuel pump or a small hole or leak in the fuel line which allows air to be drawn into the fuel line. You'll need to check the draw vacuum, the output pressure, and delivery quantity when you crank the engine. A new fuel pump does not guarantee function.
It sounds like you might have two problems. Either the fuel is draining out of the carburetor or evaporating. The most likely suspect for draining out is a bad power valve, next would be a porous casting.

The other problem is the fuel pump not delivering fuel to the carburetor when you crank the engine. After it starts it has enough vacuum to pull fuel from the tank. The problem may be the fuel pump or a small hole or leak in the fuel line which allows air to be drawn into the fuel line. You'll need to check the draw vacuum, the output pressure, and delivery quantity when you crank the engine. A new fuel pump does not guarantee function.
I remember once it back fired on a lean mix and I thought about maybe the power valve could possibly be bad, I will look at that thanks.
 

1973MACH

Member
Joined
Dec 3, 2014
Messages
10
Reaction score
0
Location
Pa
My Car
1973 Mach 1, 351 2bbl, FMX automatic, dark green metallic/argent strips, dual avocado interior
I remember once it back fired on a lean mix and I thought about maybe the power valve could possibly be bad, I will look at that thanks.
 

1973MACH

Member
Joined
Dec 3, 2014
Messages
10
Reaction score
0
Location
Pa
My Car
1973 Mach 1, 351 2bbl, FMX automatic, dark green metallic/argent strips, dual avocado interior
After car has sat for a week and before you try to start it. I would take air filter off and with the choke plate open, look into the carburetor while you manually operate the throttle. You should see and hear fuel squirt into the engine. if you don’t see/hear fuel squirting the problem is with the carburetor.
I have done this and no, no fuel at the carburetor. I will check the power valve.
 
Top