Fuel pump pressure experiment

[sujitroy]

I've been trying t sort out a hot starting issue that has been plaquing my car for may years. Terry suggested to regulate the pumps pressure. I bought a cheap 20$ regular and set the dial to 1 PSI. The car has been running OK at this rate. Today with the temp being almost 90 F here. I took the car for a run. I got stuck in slow traffic for about 10-15 mins. During this time, the engine temp. went up. As soon as I could speed up I noticed the car not going beyond 50 mph I got to my destination and increased the pressure to 2 PSI. I drove home and the car behaved normal at speed. I'm wondering if the under bonnet temperature would do anything to the fuel flow to the carbs?
Sujit

[KOY 23]

Good to see that you're back to 3 new questions a day, I was getting worried about you

1 psi is very low should be around 2.5psi.

I heard that there were some cheap fuel regulators that leaked and caused fires, bit more research needed.

IMHO there should be no penny pinching with fuel, ignition, brakes and tyres, your life and other road users lives are at risk.

[sujitroy]

I was busy gardening these days. Just got Stag no. 1 out after some time as I have to pick up my mini van from a mechanic 20 miles away and 500$ cheaper to replace a steering rack. Anyone thinks changing a rack on a stag is a pain, try changing it on a mini van. Back to Stag, the regulator is a good brand. I want to rule out the pump from over pressure. Yes. I recall the pump should be about 3 psi. It has a replacement SU pump but can't recall the part no. it may from an MGB.

[MikeParker]

Agree with KOY. 1 psi is too low. Even 3 psi can be too low at high temperatures and E5 fuel. The fuel vaporises and then the carb is running on vapour. Weirdly the engine does still seem to work in this mode but I have have never understood how. I have a clear plastic petrol filter and that generally is vapour filled when the engine and outside temp are hot. Perhaps someone can explain how this can work?

One advantage of fuel injection is running at 45psi. At that pressure petrol stays liquid!

[Lingen]

Mike.
The vapour has only collected in the upper part of the filter body, and there is still a continuous supply of fuel through it. Any small quantities of vapour that pass through will be released via the float chamber breathers. If you mount the filter vertically, it will stay full of fuel.
Mike.

[StagJonno]

Interested in your findings, Sujit. Have recently replaced a dead SU with an Ecco electronic version which I know some have found overpressurises. No problems so far . Nice to know what works.

I don't think I've ever seen a plastic underbonnet fuel filter that was much more than half full and this includes many shows and my own pre-drive checks at temp down to ~7C

[sujitroy]

As mentioned these are experiments. For a 30$ and not 20$, regulator, I cant' really believe the dial gauge is accurate so I'm try trying the settings. This was the first time the car was sitting in traffic, and the gauge was happy sitting on the 1 PSI setting up until this point.. The pump was replaced with a spare SU pump from a parts car. I just just changed it and didn't take note of the part no. The regulator is sitting in the engine bay just before the plastic fuel filter. My filter is sitting horizontally and is usually half full.
Here is a link to the regulator I bought: https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

Sujit

[mjheathcote]

My electronic 'moprod' su copy fuel pump runs at 5 psi according to the fuel pressure gauge before my Holley.

[MikeParker]

Mike.
The vapour has only collected in the upper part of the filter body, and there is still a continuous supply of fuel through it. Any small quantities of vapour that pass through will be released via the float chamber breathers. If you mount the filter vertically, it will stay full of fuel.
Mike.

Mike

I will try running it vertically, and it is true that I cannot see the output feed from the filter as that is obscured by the filter material (the input is flowing into the outer part of the filter body) but the whole outer volume is vapour when hot.

Mike

[brett_smith]

Hi Sujitroy. I trialed one of those fuel pressure gauge. I started the car about a week later and fuel was pouring out and under pressure. It was quite a scare. I replaced it with a King and have no more trouble. They are adjustable but come out of the box preset at 2.5 psi.

[jbuckl]

Recently fitted a no-name dial type regulator to a stag.
Tested it with a gauge.
None of its settings affected the pressure at all. (!)
Swapped it for a sytec one which worked.
Modern fuel has a very low boiling point… as low as 36 degrees (C) in the U.K. this causes issues with many engines with carburettors.
The sytec regulator is neater than the filter king imho.
Anyone had issues with the sytec regulator ?

[KOY 23]

The dial type regulators are universal and are supplied with no name or with a sticker with any name you want. There are far too many bad reviews on the link you provided Sujit, mainly for leaks and not working.

The gauge, if reasonably accurate, is useful for setting up but should be removed afterwards.