Fuel pump
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,460
Likes: 48
Fuel pump
Hello everyone,
I have an 89 6 SPD. I recently replaced the fuel filter, fuel pressure regulator and fuel pump. The fuel pressure will not go above 38/39 PSI. I am thinking of getting a better fuel pump. Do any of you have a suggestion with respect to what fuel pump I should buy. And is there a pump for this car I can mount outside the tank.
Thank you
I have an 89 6 SPD. I recently replaced the fuel filter, fuel pressure regulator and fuel pump. The fuel pressure will not go above 38/39 PSI. I am thinking of getting a better fuel pump. Do any of you have a suggestion with respect to what fuel pump I should buy. And is there a pump for this car I can mount outside the tank.
Thank you
Safety Car
Joined: Oct 2007
Posts: 4,203
Likes: 1,074
From: South Florida
The pump doesn't exactly make pressure, Regulators make pressure. The pump tries to send fuel to the rail, right? But on it's way back, the regulator clamps the line closed, which raises pressure, exactly as if you clamped the return line with a vice grip. The regulator uses a spring, one side is facing atmospheric pressure(or intake manifold pressure, or air filter tract pressure, you can run this side of the regulator to many places on the engine for different reasons) the other is fuel pressure, fuel pressure forces against the spring +/- the other side's pressure and that is how much fuel pressure you are set to.
When the engine is off the atmospheric pressure side is atmospheric exactly. The fuel flow through the injectors is 0%. This is how you can set and test the regulator and pump flow, since the engine is off it is easy. You can clamp the return line to see if that will raise pressure, this indicates the problem is with the regulator. Or, if clamping the line does not raise the pressure, then the fuel pump has some issue which is keeping it from making more pressure, such as, a leak between the pump and return line, sometimes there is a leak inside the fuel tank. Some pumps have regulator/returns in the fuel tank so more creative means of testing are needed, such as installing a (temporary perhaps) external regulator and return. A fitting or clamp un-tested or un-tightened. Or a hole in the hose. This can cause low pressure even while the engine is off. Or if the pump is very old and tired. Or if the pump has some manufacturing flaw. there is many ways a pump can fail. However, traditionally, the pressure end of things is usually perhaps 95 to 98% of the time focus with the regulation aspect, not the pump.
When the engine is off the atmospheric pressure side is atmospheric exactly. The fuel flow through the injectors is 0%. This is how you can set and test the regulator and pump flow, since the engine is off it is easy. You can clamp the return line to see if that will raise pressure, this indicates the problem is with the regulator. Or, if clamping the line does not raise the pressure, then the fuel pump has some issue which is keeping it from making more pressure, such as, a leak between the pump and return line, sometimes there is a leak inside the fuel tank. Some pumps have regulator/returns in the fuel tank so more creative means of testing are needed, such as installing a (temporary perhaps) external regulator and return. A fitting or clamp un-tested or un-tightened. Or a hole in the hose. This can cause low pressure even while the engine is off. Or if the pump is very old and tired. Or if the pump has some manufacturing flaw. there is many ways a pump can fail. However, traditionally, the pressure end of things is usually perhaps 95 to 98% of the time focus with the regulation aspect, not the pump.
Safety Car
Joined: Oct 2007
Posts: 4,203
Likes: 1,074
From: South Florida
Forgot to mention
The most desirable fuel system is minimum current flow through a sterile in-tank submersible, silent, reliable pump.
Find a way to keep the fuel clean, the pump clean in the fuel, and silent/reliable.
Aeromotive makes 'stealth' fuel pumps with 2000run hours at 58psi. Using less fuel pressure (30 to 40psi I recommend) can help extend pump lifespan.
Nothing wrong with 30 to 40psi if its set using regulator correctly and tuned at the ECU.
Lower and Lower fuel pressure is often desirable as performance demand increases and larger injectors are installed while keeping small in-tank fuel pumps that draw little current.
The most desirable fuel system is minimum current flow through a sterile in-tank submersible, silent, reliable pump.
Find a way to keep the fuel clean, the pump clean in the fuel, and silent/reliable.
Aeromotive makes 'stealth' fuel pumps with 2000run hours at 58psi. Using less fuel pressure (30 to 40psi I recommend) can help extend pump lifespan.
Nothing wrong with 30 to 40psi if its set using regulator correctly and tuned at the ECU.
Lower and Lower fuel pressure is often desirable as performance demand increases and larger injectors are installed while keeping small in-tank fuel pumps that draw little current.
