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Mechanical fuel pump pressure

15K views 22 replies 14 participants last post by  RealZ 
#1 ·
I have a 350 with a Rochester 2 jet. My problem is that it keeps flooding my engine. I believe the float and needle seat are set correctly. I have verified the gas cap is venting. I am looking at my fuel pump now because the fuel pumps you buy at the local auto parts store are set at 7psi to 9psi. The book calls for 5psi to 6psi fuel pressure. What are your thoughts?
 
#5 ·
According to the Chassis Service Manual an AC-Delco SBC V8 fuel pump should out put one pint of fuel in 30-45 seconds at 5 to 6-1/2 psi pressure (pretty wide range considering the pressure is dependent upon a spring). The fuel pump sucks fuel up and compresses the spring on the up stroke. As the arm falls back it is the spring that pushes the fuel up to the carb at a constant pressure.

Big Dave
 
#9 ·
I started having driveability problems a few years after putting a new fuel pump from NAPA. It was was suppose to a stock replacement pump. After about 5 years I checked the pressure to the carb (Holley 650 dual inlet vac. sec.) the pressure was almost 9 lbs. I put a regulator in the line between the carb and the pump. Then adjusted the pressure down to 6 lbs. No problems since.
 
#11 ·
Well I am going to try a fuel pump rated at 6.5 psi before I do anything else. If that don't work I will go back to the carb and check my float adjustment and any debris that may have gotten under the needle/seat.
 
#18 ·
I had this exact problem. Never had a problem with my pump from the 80's. When the car got "unparked" 2 years ago I replaced it and the carb. It would run ok for a bit but then flood out. This was an eldebrock carb. I read up on all the problems with these carbs and fuel pressure. My new pump was putting out 9 psi. Too much. I thought about a regulator but read about how thy can leak and cause a fire so I found a pump with the correct pressure, 5.5, and have had no problems since.
 
#19 ·
What Model number Carter pump did you buy ? I have looked on the Summit web-site and found 2 that look like they will fit the M4685 is 40 GPH at 5.5-6.5 PSI Outlet and the M4530 is 30 GPH at 5.5-6.5 PSI I am having what sounds like the same problems you had with flooding.
 
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