I have a small block Chevy with a stock mechanical fuel pump. Should the fuel pressure drop to zero when the engine is shut off? Mine is holding about 7 psi after shut off and when the engine is hot, it will flood the carb while the engine is not running making it hard to start back up.
2006-11-22 10:40:45 · 9 answers · asked by Stu 3 in Cars & Transportation ➔ Maintenance & Repairs
I had a pressure regulator set at 4 psi and that didn't help. SInce the pressure isn't bleeding off it increases after shut off due to the underhood heat causing the fuel to expand. I have replaced the needles and seats (Edelbrock carb).
2006-11-22 10:51:47 · update #1
OK more details, it's a 1977 Caprice. There is NO computer and NO electric fuel pump. It's mechanical. The floats are set up correctly, the needles and seats (yes there are two) have been replaced twice and the carb rebuilt twice. Everything is dead on. That's not the issue. Should a mechanical pump have pressure when the engine is shut off? Does anyone know with certainty? The carb does NOT flood when the motor is running, it runs perfect. Just floods when shut off when HOT.
2006-11-22 12:47:31 · update #2
You only need about 5.5-6.5 psi fuel pressure. It looks like your fuel pump is bad. There should be no pressure in the fuel line when engine is off in a mechanical pump fuel system.
Check your float setting. The needle valve may have debris in it.
2006-11-22 11:54:31 · answer #1 · answered by R1volta 6 · 0⤊ 0⤋
If the needle and seat inside the carb are working properly, fuel pressure in the line would not flood the engine. Either the float level is too high or something else inside the carb isn't working correctly. If the fuel system is operating correctly the line from the pump to the carb should have pressure in it. Another possibility is either a crack in the casting somwhere or a leaky gasket allowing the fuel to drain into the engine. Take a real good look at everything and try lowering the floats a little to see if that helps.
2006-11-22 12:01:56 · answer #2 · answered by Nc Jay 5 · 0⤊ 0⤋
Try new needle and seat on the float valve in carb, -- if this doesn't do it, you can put a "momentary interruption switch" on power lead to the fuel pump, just push the button for 30 seconds or so before you shut off the engine, and it will "bleed down the pressure as it burns out the gas! You can experiment with the time interval - or you could just hold the button down as you finish parking car! If it bleeds the system out and empties the carb.- the pump will fill it back up anyway when you turn the key back on! Using "momentary off" switch will insure that you can't have it shut off when you try to start,- and be confused about what is wrong!
2006-11-22 12:32:56 · answer #3 · answered by guess78624 6 · 0⤊ 0⤋
If the needle and seat interior the carb are working good, gas rigidity interior the line would not flood the engine. the two the pick the flow factor is in basic terms too extreme or something else interior the carb isn't working correct. If the gas gadget is working correct the line from the pump to the carb could desire to have rigidity in it. yet yet another hazard is the two a crack interior the casting somwhere or a leaky gasket permitting the gas to drain into the engine. Take a surely stable study out each and each element and attempt reducing the floats a splash to make particular if that facilitates.
2016-10-17 10:12:45 · answer #4 · answered by valda 4 · 0⤊ 0⤋
You have a problem with your float. It's probably set too high. Don't get angry with your carb. The edelbrock is actually a weber with a different name stamped on it and will give you little to no problems. Just bend the tab on your float up a little to allow it to close the needle fully. Good luck. OH, also make sure that the power valve needle is free of debris and can close all of the way. Very slim chance, but it may be allowing fuel up into the venturies.
2006-11-22 12:02:15 · answer #5 · answered by jeff s 5 · 0⤊ 0⤋
fuel pressure regulator?
wrong,,
is it a quadrajet or a holley?
whats most likely happening here is bad needle seat(S)
you say its flooding ? to start the car easier, hold it wide open while starting then as soon as it fires let off,
now what kind of pump is it? aftermarket stock? most aftermarkets have a bypass on them you may have to hook it up?? id have to know more about your setup. i tend to use regulators when im using a blue pump (electric) becouse of the high volume itll put out 14 psi
mechanicals wont there good for 7 or so untill high rpms when they become useless.
but the problem is most likely the needle seats in your carb, with holley there usually easy to replace, with q-jet youll have to take it apart (whitch sounds like a good idea in your case anyway.)
check float levels also,
2006-11-22 11:05:37 · answer #6 · answered by shadoburn 1 · 0⤊ 0⤋
i own a repair shop,and with a mechanical pump it wont drain off of It,and it will cause it to flood out,,you may have to install a pressure regulator on it to lower the pressure down some on it,this will help it a lot,but you might have a bad needle valve in the carb also ,it should hold back 7 pounds easy,,try the regulator it will help,,good luck,,i hope this help,s.
2006-11-22 10:47:41 · answer #7 · answered by dodge man 7 · 0⤊ 1⤋
You failed to mention the year which is important.
2006-11-22 11:53:14 · answer #8 · answered by Mikel 4 · 0⤊ 0⤋
it should not drop,you have a card problem
2006-11-22 10:45:04 · answer #9 · answered by Anonymous · 0⤊ 0⤋