Carb fuel pressure

[rustyrescue]

I am struggling stopping our carb flooding now we have a decent fuel pump.
The Mazda manual does not give a fuel pressure for it running....it offers a pressure of 3.7 to 4.7 psi to test a standard pump BUT with the supply pipe capped off so dead head test.
The car is a fuel return system as standard so I would assume the fuel pressure at the needle valves on a standard car with Nikki carb would be somewhat less than the pump can provide capped off because it will have a continuous flow.
Any ideas appreciated....I have tried several needle valves and float heights are correct.

[gt_james]

I have written down in my notes

For S1/2 its 4.5psi
For S3 its 3.5psi

Do you have a decent fuel pressure regulator and gauge?

[rustyrescue]

Hi, yes, currently have a filter/reg set up dead head though have a holly to try later on a return system if I prove the pump solves the coasting to a halt issue! The new pump flows double the acceptable measure according to manual whereas the previous pump was barely on acceptable and seemed not to cope at higher revs. (the standard pump died soon after getting the car back to life) I have two gauges to play with too
I am struggling to see how a capped pump test on a standard car of 3.7 to 4.7 psi acceptable can result in a running pressure on a return system of 4.5 psi? maybe I am missing something? The standard pump was always marginal I have been told.
I have tried several needle valves from spare carbs and with the carb lid off and inverted they seal ok if I blow into them gently so are sealing.
I may try winding back the fuel pressure a bit.....I feel if the float bowls can be kept full to the right level perhaps the pressure is a red herring.
Thanks again for thoughts.

[gt_james]

try adjusting the pressure down till the needles stop blowing by, and then try drive it. fuel pressure Gauges are never accurate anyway. Your gauges could be saying 3.5psi but actually at 5.5psi. I bet the two gauges you have don't read the same.

Remember pressure is just a measurement of the restriction to flow. A capped off return line just allows the pressure in the supply line to build up to the max the pump can generate, but in a full flow situation at high engine load the pump may not keep up and you'll get a pressure drop, even if it tested ok dead head. A capped test doesn't test flow, only pressure and is only a good test that the system doesn't have any leaks, tells you nothing about pump performance really.

[rustyrescue]

yes thats the plan, trouble is it floods whilst trying to adjust it I will play later! I do feel as long as the flow/volume can be met and the floats stay to the correct level then pressure is not important.