Presurizing Fuel Line
Thread Starter
Burning Brakes
Joined: Dec 2014
Posts: 1,038
Likes: 44
From: Pensacola Florida
Presurizing Fuel Line
I have a leak in my 89's fuel system somewhere causing the pressure to bleed to zero in less than 10 seconds after shutdown. It also takes some time to crank after it's been sitting for a while. Obviously fuel is escaping the system somewhere/somehow. No leak can be seen.
I've replaced everything from the injectors to the fuel pump w/new except the lines and this car has had this issue since I bought it last Sept.
I already did a pressure test on the check valve, held 40lbs of air for 15 minutes with zero leak.
If I pressurize the fuel line at the tank with 40lbs of air can I expect it to hold if there's no leak in the line? Or would the injectors allow it to leak down even if they're all good?
I know taking it loose from the rail and plugging it would be best but it's a PITA to get to.
Rick
I've replaced everything from the injectors to the fuel pump w/new except the lines and this car has had this issue since I bought it last Sept.
I already did a pressure test on the check valve, held 40lbs of air for 15 minutes with zero leak.
If I pressurize the fuel line at the tank with 40lbs of air can I expect it to hold if there's no leak in the line? Or would the injectors allow it to leak down even if they're all good?
I know taking it loose from the rail and plugging it would be best but it's a PITA to get to.
Rick
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
When you replaced the fuel pump, did you use the same Fuel Pump Pulsator, replace it with a new one or replace it with fuel line hose? IF you did not use hose to replace it, there is often a problem with the fuel line slipping off the inlet or out of the Pulsator which would allow your fuel to flow quickly back into the tank.
••••• TESTING FOR LOSS OF FUEL PRESSURE
... Here are the sure fail tests for the fuel system to save you time and money.. Take a fuel pressure gauge attach it to the Schrader valve.. Turn the key on and off a few times to build up the pressure in the system... If you are having starting trouble the pressure will probably drop as soon as it hits 38 or 40 and the pump turns off it will probably leak back to zero within a few minutes. Ok now right after you prime the system pinch off the return line near the tank if the pressure drop stops it is a bad fuel pressure regulator.... Next pinch off the feed line if the pressure holds then the leak is before the point where you pinched the line IE fuel pump check valve..hole in the metal line on the sending unit caused by it rubbing on the inside of the tank you should visibly be able to see this if you pull the pump and the sending unit...(this was my problem) or the pulse dampener which is the piece between the pump and metal line on the sending unit.. the diaphragm tears.. and last if you pinch both the feed and return line near the tank and the leak down of the pressure continues then a fuel injector is your problem.. This is the GM test.. saves time and money..
•• disconnect the vacuum line from fuel pressure regulator
••••• TESTING FOR LOSS OF FUEL PRESSURE
... Here are the sure fail tests for the fuel system to save you time and money.. Take a fuel pressure gauge attach it to the Schrader valve.. Turn the key on and off a few times to build up the pressure in the system... If you are having starting trouble the pressure will probably drop as soon as it hits 38 or 40 and the pump turns off it will probably leak back to zero within a few minutes. Ok now right after you prime the system pinch off the return line near the tank if the pressure drop stops it is a bad fuel pressure regulator.... Next pinch off the feed line if the pressure holds then the leak is before the point where you pinched the line IE fuel pump check valve..hole in the metal line on the sending unit caused by it rubbing on the inside of the tank you should visibly be able to see this if you pull the pump and the sending unit...(this was my problem) or the pulse dampener which is the piece between the pump and metal line on the sending unit.. the diaphragm tears.. and last if you pinch both the feed and return line near the tank and the leak down of the pressure continues then a fuel injector is your problem.. This is the GM test.. saves time and money..
•• disconnect the vacuum line from fuel pressure regulator
