The mechanical pump is sending 8 psi while running.. (360 Mopar w/Holley carb) pressure drops right away when engine gets shut off. Put a shutoff valve inline after pump to see if carb loses pressure, and it loses pressure pretty fast. Causing some starting issues. Carb should hold pressure, right???
It isn’t my car, but he was just here with it. Basically flooding, and I see fuel leaking from carb throttle shafts after shutoff. Tailpipes are black and running rich
Check the float level, also check the float itself for leaks. Change out the needle/seats. 8 psi is a bit high, but it should still not allow fuel passed the seat if there in good shape.
Carburetor's don't use pressure. They siphon fuel from the bowl so if it's leaking after shut off you have no fuel in the bowl to start the engine.
Nope! The carb should hold the pressure between it and the pump! A common “ hot start” problem. With today’s parts, it become a larger problem that before. Small leakage of the seat is absorbed by the engine going down the road. But when stopped, that pressure has to go some where if it disappears, causing flooding. A very little fuel leaking by the seat will relieve the pressure in the lines, but sometimes the pump is “ loaded” and will continue to add fuel , untill the spring is released. That can be a lot if fuel, causing flooding. One way to solve this problem,other than super quality needles and seats, is the way Chrysler , other OEMs, and a few racing pumps/carbs do it. Add a small return line from the pressure side of the pump to the intake side. How and where you do this will have different effects. Naturally the hardest to do has the best effects. That line needs to have a restriction in it close to .030 or so. Some pumps have this “ bypass” internally, some do not. Bones
Might also want to check your power valve, a very common problem on Holley carbs, even though they have made improvements, they can still be a problem. If it’s “ blown” fuel will drain directly from the bowel through the valve and into the vacuum source, that could show it self at the throttle plates, when the engine is stopped. But won't show while running, due to vacuum causing the atmosphere to push the fuel back into the carb. This would also drop the pressure in your fuel line, by dropping the fuel level , allowing the needle and seat to open! Bones
Just asking to see if your starting with a carb that has a spec base line from Holley or used with unknown specs.
Lower the floats so the fuel has some place to go when it heats up. It's running rich anyway according to the tail pipes, so lower floats will lean it out some. 8 psi is a little high but doable, 4-5 would be better and would probably run better, but lowing the floats should do about the same thing.
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