1955 fuel pump pressure problems

[fastman]

dear members. i have 55 t/bird which i have fitted a new airtek pump with vacuum. when driving the fuel pressure hold 2.5psi and when you excelarate the pressure reduces to 0 and when you take pedal off it goes back up. can anyone help and advise. regards gary

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[doug7740]

Gary,

Since the original mechanical fuel pump pressure specification is 4.0 to 5.0 psi at 900 rpm and your new airtek fuel pump only has a pressure of 2.5 psi, I would suspect you’re your new airtek fuel pump is defective or you have it mounted in the wrong place. Looking at the specifications of the electric fuel pumps that CASCO sells, both the 6 volt and the 12 volt versions have an output pressure of 2.5 to 4 psi.

Where did you mount your new airtek fuel pump? Electric fuel pumps are designed to push fuel and should be mounted as close to the fuel tank as possible. They are also designed to be mounted in-line with the original fuel pump.


doug7740
1955 Thunderbird Blue

 

[fastman]

Hello Doug 7740. the airtek mech pump is mounted to block. factory position. the strangest thing is when driving and you excerate the pressure drops off. thanks gary

 

[doug7740]

Gary,

Sorry my mistake, Airtek is the manufacturer of electric fuel pumps so I assumed that you had an Airtek electric fuel pump. That being said, are you having a drivability problem with your car? Does it seem like it is starving for fuel under acceleration?

According to the service manual, the fuel pump pressure specification is 4.0 to 5.0 psi at 900 rpm and you said that you only have 2.5psi, that would lead me to believe that you have a defective fuel pump.

Did you perform a fuel volume test on your new fuel pump? The volume specification is 1 pint in less than 45 seconds, at 900 rpm.

doug7740
1955 Thunderbird Blue

 

[fastman]

Gary,

Sorry my mistake, Airtek is the manufacturer of electric fuel pumps so I assumed that you had an Airtek electric fuel pump. That being said, are you having a drivability problem with your car? Does it seem like it is starving for fuel under acceleration?

According to the service manual, the fuel pump pressure specification is 4.0 to 5.0 psi at 900 rpm and you said that you only have 2.5psi, that would lead me to believe that you have a defective fuel pump.

Did you perform a fuel volume test on your new fuel pump? The volume specification is 1 pint in less than 45 seconds, at 900 rpm.

doug7740
1955 Thunderbird Blue

Dear Doug. yes i am having problems as the fuel pressure reduces to 0 psi when excelarating then when you reduce throttle pressure comes back to 2psi. its very frustrating .I have even fitted suction hose sraight from pump to 10ltr fuel can and no difference. thanks gary

 

[doug7740]

Gary,

As I said before, since the original mechanical fuel pump pressure specification is 4.0 to 5.0 psi at 900 rpm and your new airtek fuel pump has 0 psi under acceleration and 2.0 psi when you reduce throttle pressure, I would suspect you’re your new airtek fuel pump is defective. If the problem was in the float circuit of the carburetor, the engine would flood and stall out when the engine is running at idle speed and you are reading 2.0 psi fuel pressure.

Try doing this: Disconnect the fuel line from the carburetor and connect your fuel pressure gauge directly to the disconnected line. There should be enough fuel in the carburetor fuel bowl to idle the engine to perform this test. If the fuel pressure increases to 4.0 to 5.0 psi at idle speed, then your problem is in the carburetor. But if the fuel pressure is still at 2.0 psi, then your problem is with the fuel pump.

Since you said that you ran a hose directly from a fuel can into the fuel pump and the fuel pressure was still 2.0 psi, that would rule out a blockage in the fuel tank or a small leak in the fuel line causing air to enter the fuel pump.

doug7740
1955 Thunderbird Blue

 

[fastman]

Hello doug. i will try what you have listed and see what we have thanks gary

hello Doug well i have checked as you said. still no pressure. then i removed fuel pump the new one and compared it with the arm movement on old fuel pump. then i found that the arm had a 3rd of stroke movement prior to touching diaphram. that shows me that at idle i was getting some pressure and when i gave throttle it would drop of fuel supply. so i fitted the old pump that leaked oil from vent holes but the pump had good pressure fixed all my problems so i have sent the airtex pump back to supplier in california for a replacement.thanks gary

 

[doug7740]

Gary,

I'm glad that you found the cause of the low fuel pressure. From everything that you told me I thought the cause was the fuel pump. It just goes to show that new doesn't necessarily mean that the part is good.

I'm glad that I was able to help you.

doug7740
1955 Thunderbird Blue