Installing New FP - Can't Lower Pressure?

DaveyX87

Member
I am going to drop in my new Racetronix 340 fuel pump and ss sending unit. I was reading that some people could not get their fuel pressure low enough with this setup. One person had to mod the return line. Is this a common issue? I just want to know what I am up against. Thanks.
 

TType85

Well-Known Member
I am going to drop in my new Racetronix 340 fuel pump and ss sending unit. I was reading that some people could not get their fuel pressure low enough with this setup. One person had to mod the return line. Is this a common issue? I just want to know what I am up against. Thanks.
I have the same pump and can't get below 50psi. I have not modified the return line and am thinking of just replacing the pump with a slightly lower flow one.
 

TType85

Well-Known Member
A 340 is 255lph. Same pump. I think you are worrying unnecessarily.
Not the racetronix one.
FPS-G7RXP340M - Fuel Sender, G7 SS w/340LPH Pump is what I have. That is a 340LPH pump.

I checked the lines at the tank (put in new ones) but I think it just varies from car to car if it will work or not without modification.
 

precizion818

Well-Known Member
Mine did the same thing with that pump. I just changed my return line to a -6an line and now I can adjust it just fine.


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Nick Micale

Tech Advisor
Staff member
I have the same pump and can't get below 50psi. I have not modified the return line and am thinking of just replacing the pump with a slightly lower flow one.

Why would you do that? I prefer to have too much fuel supplied rather than not enough.

The typical setting of 44 psi is a general number, and it is NOT the optimum for most cars especially if the car has performance up grades.

We routinely use a higher number, as the 44 psi figure we consider a minimum number.

My street car runs best at 55 psi, and many others are 50 psi, and have gone up to 65 in a 500+ HP TR with a double pumper.
 

TType85

Well-Known Member
Why would you do that? I prefer to have too much fuel supplied rather than not enough.

The typical setting of 44 psi is a general number, and it is NOT the optimum for most cars especially if the car has performance up grades.

We routinely use a higher number, as the 44 psi figure we consider a minimum number.

My street car runs best at 55 psi, and many others are 50 psi, and have gone up to 65 in a 500+ HP TR with a double pumper.

I need to be able to lower it to be able to lower it down to 37-38ish for smogging the car. The alternative is to run a -6 return line which I may do. I am also going to try bypassing my hotwire and see where I stand (for getting the car through smog).
 

precizion818

Well-Known Member
FYI..... The -6 an line allowed me to lower my field pressure to acceptable ranges


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DaveyX87

Member
I got the new pump in with stock return and I believe my pressure is in a good range (45-46 psi vac line on). I cant go any lower than that but I think its fine. I read that 43 psi is the right number.
 

BMR

Bad Medicine Racing
Why would you do that? I prefer to have too much fuel supplied rather than not enough.

The typical setting of 44 psi is a general number, and it is NOT the optimum for most cars especially if the car has performance up grades.

We routinely use a higher number, as the 44 psi figure we consider a minimum number.

My street car runs best at 55 psi, and many others are 50 psi, and have gone up to 65 in a 500+ HP TR with a double pumper.
I was feeling like trying something new today, so I bumped mine from 43 to 50 line off. It seems to pull harder after it shifts into second now. It must have been a little lean down low.
 

Pronto

Believe nothing you hear and half of what you see.
I was feeling like trying something new today, so I bumped mine from 43 to 50 line off. It seems to pull harder after it shifts into second now. It must have been a little lean down low.
Instead of bumping the pressure, you could just bump the fueling in 1st and 2nd with the tt chip. Powerlogger and a wide band would really show better what's going on.
 

BMR

Bad Medicine Racing
Instead of bumping the pressure, you could just bump the fueling in 1st and 2nd with the tt chip. Powerlogger and a wide band would really show better what's going on.
I tried that before I took it apart and it didn't seem to make any difference. BUT it seems to run better now, so it may respond to the chip change.
 

Pronto

Believe nothing you hear and half of what you see.
Are you using a quality fp gauge? The cheap ones can be off by quite a bit.
 

BMR

Bad Medicine Racing
Its a no-no what I'm using. Its just a gauge intended for checking the pressure. Not intended to stay on the car, but I leave it there because when I got it the po had removed the Schrader valve from the fuel rail, and I have not rounded another one up.
 

dynoman

Well-Known Member
If you need a schrader valve and some back-ups I have a few . We use them by the thousands at work everyday . We make the fuel rails & injectors for GM . Sam
 

DaveyX87

Member
Why would you do that? I prefer to have too much fuel supplied rather than not enough.

The typical setting of 44 psi is a general number, and it is NOT the optimum for most cars especially if the car has performance up grades.

We routinely use a higher number, as the 44 psi figure we consider a minimum number.

My street car runs best at 55 psi, and many others are 50 psi, and have gone up to 65 in a 500+ HP TR with a double pumper.


My fuel pressure now wont go any lower than 46 psi with the line on. In any event, the car is idling and running much better than it ever has. It is mostly stock too.
 
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