Mitchell McNemar
Newbie
New to the page,I have a 1990 K5 blazer,swapped out the efi engine for a carberated engine,gas won't stay at carb,have to prime carb to get it started,would this have something to do with the electronic fuel pump in the tank?
CK5
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Fuel issues
- Thread starter Mitchell McNemar
- Start date
Carcinogen
1/2 ton status
It sounds like you have an air leak. Will it run at idle after you fill the carb bowl or does it die after a while(after the gas runs out of the carb)?
Mitchell McNemar
Newbie
Runs fine after I get gas to it,but after I shut it down and let it sit overnight,have to prime the carb again
First problem is :
If you have just hooked up the original in-tank EFI fuel pump to a carb,your likely getting way too much fuel pressure,a carb only needs about 5 psi,EFI can have anywhere from 12 to 50 or so depending on the application..you can still use the original fuel pump,but will need a fuel pressure regulator to knock the pressure down to 5-7 psi so the carb wont be flooding constantly..
The carb should stay full of gas at least overnight though, once it was primed..
If it is a Quadrajet it might have leaky fuel bowl well plugs,that will let the float chamber drain out after sitting awhile,and can also flood the plugs,making for hard starts..
Original fuel filters located in the carb itself had a rubber check valve that helped prevent fuel from siphoning out of the float bowl back towards the fuel pump and gas tank..also the mechanical fuel pumps used with carbs have built in check valves that are needed to make up pump,and they also serve to keep fuel flowing only towards the carb,not away from it..I'm not sure if an electric in tank pump might let gas just drain back into the tank or not..
If you have just hooked up the original in-tank EFI fuel pump to a carb,your likely getting way too much fuel pressure,a carb only needs about 5 psi,EFI can have anywhere from 12 to 50 or so depending on the application..you can still use the original fuel pump,but will need a fuel pressure regulator to knock the pressure down to 5-7 psi so the carb wont be flooding constantly..
The carb should stay full of gas at least overnight though, once it was primed..
If it is a Quadrajet it might have leaky fuel bowl well plugs,that will let the float chamber drain out after sitting awhile,and can also flood the plugs,making for hard starts..
Original fuel filters located in the carb itself had a rubber check valve that helped prevent fuel from siphoning out of the float bowl back towards the fuel pump and gas tank..also the mechanical fuel pumps used with carbs have built in check valves that are needed to make up pump,and they also serve to keep fuel flowing only towards the carb,not away from it..I'm not sure if an electric in tank pump might let gas just drain back into the tank or not..
Mitchell McNemar
Newbie
No power going to the pump in the tank,and it is a quad,I will have to check it out,thanks for the info
