ok i may be missing something but I'm still having problems with fuel!

recently changed my hard lines to 3/8 feed and return (stock tank inlets 8mm feed 6mm return and breather) I'm in the process of making a new inlet with 3/8 feed return and breather but i've seen people on hear running stock with no issues

I'm running a 51IDA extended fuel bowl on a 13b Street port

pump is a 4110 mallory and 4309 return pressure regulator (I'm not using the vacuum/boost compensation port)

when i first start the car i have loads of pressure, too much 7.5psi take it for a easy drive and all seems fine pull over after a couple of miles and pressure is around 4.5 perfect if i rev stationary i loose pressure down to 0! its the same under WOT no pressure ease of then it stablises again but slowly (tried it with tank filler cap off and same issue)

am i missing something?
i'm hoping the new tank feed and return will resolve but its sounds like a bigger issue
any thoughts welcome!

 

How/where do you measure the pressure at?

 

being measured at the regulator pre carb
even if the readings not right I'm getting fuel starvation

 

Since you have a new pump, hoses (assumed) and lines, these are the things to check:

1. Kinked line somewhere?

2. Filter clogged, replace with new if so.

3. Crud in tank, drain and drop tank and open it up to verify and then clean it out.

How about power to the pump, using standard wiring or have you done a relay mod
so it gets power directly from the battery? That can make a difference too.

 

stock power at the mo gonna pull the filters out and check them

 

ok so i have made a new pick up and fitted new lines for the spec on the 4110 10mm / 3/8" I'm still seeing some issues with variable pressure, I'm measuring pressure at the regulator now the lines do go larger after the regulator to the carb -8 1/2" would i need to increase the pressure to compensate this or would it be easier to go -6 to match?

 

Rig up a way to measure the pressure between the regulator and the carb. When I hook up the pressure gauge directly to the regulator it shows the pressure bouncing all over the place but when I put in inline with the hose going to the carb is shows stable pressure.

Not sure why that is but worth a try.

 

^^ this....





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cleaned out all the filters and carb, found a load of sand in the first filter (Pre pump) had the same problem before, the shell was sandblasted by a previous owner and the breather was pulling the sand into the tank, looks like with the bigger pump its doing the same thing so its a tank clean and plenty of cleaning of filters for a couple of weeks till it clears again