The Ford Barn

Gino · 08-25-2023, 07:58 AM

Hi, Is it possible for a mechanical fuel pump to continue pushing out pressure after the engine has been turned off? 68 mustang, 6 cylinder, 200 ci, single barrel. Can fuel pump pressure force fuel past a float in the carburetor? IÂ’m unable to stop flooding. At this time IÂ’m using a 1904 universal carburetor, how ever I had the problem with a remake autolite 1100. IÂ’m told that the boiling and expansion of gas is not likely on a non high performance vehicle. Please keep in mind I owned three or four of these same engines and cars when I was young with zero problems. If there is the over heating of fuel taking place, where does it occur? In the fuel line or float bowl? As alway appreciate any help. Also just know IÂ’m a novice mechanic so slow down. Thanks again

BW · 08-25-2023, 08:41 AM

Your needle and seat controls the fuel going into the carburetor. You could have a bad or sticking needle and seat, or your float may be too high. Is the fuel line laying on the engine anywhere? This universal carburetor your using, what fuel pump pressure is the needle and seat rated for? You also could check your fuel pump pressure to see if it's in specifications.

cadillac512 · 08-25-2023, 12:51 PM

Gino, yes it is possible for the fuel to expand after the engine is off and heat is increasing under the hood. The outlet of the fuel pump has a check valve that prevents fuel from flowing back to the tank. The carburetor needle/seat are supposed to close when the fuel bowl of the carb is full to keep it from overflowing. BUT...when the fuel in the line and fuel pump expands, the pressure trapped in that line overcomes the needle/seat and fuel is forced into the carb, flooding it. It's a more-common problem with modern fuels and higher vapor pressures. One remedy is to install a tee fitting in the line going to the carb and route the excess back to the inlet side of the fuel pump. The tee portion returning the fuel should have a restrictor in it....030" or so has worked well for me. Returning it all the way back to the tank is even better but extra work is obviously needed for that.

Terry

cos · 08-26-2023, 08:15 AM

Hello The 1957 Thunderbirds with superchargers had to route fuel back to tank because of this problem (mention above) more a problem with vapor lock than flooding carb.

KULTULZ · 08-26-2023, 08:52 AM

Sponsored Links (Register now to hide all advertisements)

And then there is the never ending problem with CHI-COM carbs and pumps along with service replacement parts.

You will need a fuel pressure test gauge to diagnose the problem(s).

08-25-2023, 07:58 AM	#1
Gino Senior Member Join Date: Oct 2011 Location: Falmouth, Ma. Posts: 313	1965 ford fuel pump question Hi, Is it possible for a mechanical fuel pump to continue pushing out pressure after the engine has been turned off? 68 mustang, 6 cylinder, 200 ci, single barrel. Can fuel pump pressure force fuel past a float in the carburetor? IÂ’m unable to stop flooding. At this time IÂ’m using a 1904 universal carburetor, how ever I had the problem with a remake autolite 1100. IÂ’m told that the boiling and expansion of gas is not likely on a non high performance vehicle. Please keep in mind I owned three or four of these same engines and cars when I was young with zero problems. If there is the over heating of fuel taking place, where does it occur? In the fuel line or float bowl? As alway appreciate any help. Also just know IÂ’m a novice mechanic so slow down. Thanks again

08-25-2023, 08:41 AM	#2
BW Senior Member Join Date: Jul 2011 Posts: 259	Re: 1965 ford fuel pump question Your needle and seat controls the fuel going into the carburetor. You could have a bad or sticking needle and seat, or your float may be too high. Is the fuel line laying on the engine anywhere? This universal carburetor your using, what fuel pump pressure is the needle and seat rated for? You also could check your fuel pump pressure to see if it's in specifications.

08-25-2023, 12:51 PM	#3
cadillac512 Senior Member Join Date: Apr 2019 Location: Kansas Posts: 925	Re: 1965 ford fuel pump question Gino, yes it is possible for the fuel to expand after the engine is off and heat is increasing under the hood. The outlet of the fuel pump has a check valve that prevents fuel from flowing back to the tank. The carburetor needle/seat are supposed to close when the fuel bowl of the carb is full to keep it from overflowing. BUT...when the fuel in the line and fuel pump expands, the pressure trapped in that line overcomes the needle/seat and fuel is forced into the carb, flooding it. It's a more-common problem with modern fuels and higher vapor pressures. One remedy is to install a tee fitting in the line going to the carb and route the excess back to the inlet side of the fuel pump. The tee portion returning the fuel should have a restrictor in it....030" or so has worked well for me. Returning it all the way back to the tank is even better but extra work is obviously needed for that. Terry __________________ "It don't take but country smarts to solve the problem" (Smokey Yunick) '41 Merc Town Sedan / 260" 8CM engine '66 Fairlane four door / "warmed up" 302

08-26-2023, 08:15 AM	#4
cos Junior Member Join Date: Sep 2022 Posts: 16	Re: 1965 ford fuel pump question Hello The 1957 Thunderbirds with superchargers had to route fuel back to tank because of this problem (mention above) more a problem with vapor lock than flooding carb.

08-26-2023, 08:52 AM	#5
KULTULZ Senior Member Join Date: Aug 2012 Location: IN A 'GALAXIE' FAR FAR AWAY Posts: 6,485	Re: 1965 ford fuel pump question Sponsored Links (Register now to hide all advertisements) And then there is the never ending problem with CHI-COM carbs and pumps along with service replacement parts. You will need a fuel pressure test gauge to diagnose the problem(s).