DIY Farm buggy

[Ricof4e]

I just found out that I can get a facet 40104 pump which has a range between 2,5 to 4,5 psi. What does this exactly mean? Can it be adjusted to the correct psi or does it simply pump at a rate of 4,5psi if needed. For instance, if the float needle on the carb closes the inflow of fuel, does the pump then automatically increase the pressure or does it stay constant.

I have also noted that it apparently has an internal pressure relief valve which prevents flooding after shut off. My current problem is (I think) once I turn off the ignition, the pressure is kept constantly at 0,3bar by the current pump which damages the float needle and floods the carb.

Will this facet pump make any difference? I could not find a facet pump with lower pressure capabilities in the whole of this kak place (or the rest of Nam for that matter).

[Wooky]

Are you sure the float level is correct?

it should close the needle valve at 3psi without any problem.

A return line with a restricted orifice will certainly help as Wooky says, but it shouldn't really be nessecary...

That's a good point....
Automotive carbs should be able to take 3psi.
I have been playing with a bike carb which has a very small float designed only to shut off a gravity fed fuel supply

[Ricof4e]

Are you sure the float level is correct?

it should close the needle valve at 3psi without any problem.

A return line with a restricted orifice will certainly help as Wooky says, but it shouldn't really be nessecary...

3psi is within the parameters of the carb. The problem is my current pump is pushing fuel at 4,5psi. With no pressure relief after shut-off, it eventually floods the carb.

I have seen small amounts of fuel leaking from the intake manifold which suggests to me the carb floods after shut-off. See the attached pic - it leaks at the rubber seal.

[Ricof4e]

It also struggles to start, runs rough for about 30 sec (with a lot of black smoke) and then evens out and idles perfectly. The black smoke may suggest flooding.

[Wooky]

I just found out that I can get a facet 40104 pump which has a range between 2,5 to 4,5 psi. What does this exactly mean? Can it be adjusted to the correct psi or does it simply pump at a rate of 4,5psi if needed. For instance, if the float needle on the carb closes the inflow of fuel, does the pump then automatically increase the pressure or does it stay constant.

I have also noted that it apparently has an internal pressure relief valve which prevents flooding after shut off. My current problem is (I think) once I turn off the ignition, the pressure is kept constantly at 0,3bar by the current pump which damages the float needle and floods the carb.

Will this facet pump make any difference? I could not find a facet pump with lower pressure capabilities in the whole of this kak place (or the rest of Nam for that matter).

The pressure range on these pumps is somewhat variable and dependant on flow rate. Dead-head the pump and it will only produce the high psi value.
At full flow it will be 0psi.
The internal pressure relief valve only really comes into play when the engine is shut off. Some have the relief valve and some have a non return valve.
depending on the application and where the pump is mounted in relation to the tank (height difference).

Not all the facet pumps are available locally. I think the one I got from the local spares place is the non return type and could over pressure the carb when shut down and hot. The fuel expands / percolates and could well get above even the 4.5psi in the supply line.

[Apocalypse]

An automotive carb will take over a bar and close the needle off.

Which carb is it? Have you checked the float level , needle and state of the float?

The brass floats can leak and then they don't.. erm... float.... the foam ones can also break down, absorb fuel and not float properly...

[Apocalypse]

Also a worn needle can stick and/or cause the float level to ride high. Is it the single barrel solex?

[Ricof4e]

Solex pict34 carb.

Seems Apoc was right. I took a washer off the old carb's needle and placed it on with the needle of the current carb. Floats a little lower now and it seems to have done the trick, for now at least.

[Wooky]

Glad you found the problem.
If it is shutting off now you should be good to go......

[Ricof4e]

Thank's Wooky.

I still think the pressure is too high, so it will only be a matter of time before I have the same problem again. The second washer is only a temporary fix.

Seems I have to import a pressure regulator from SA. Such a device does not exist in the whole of Nam

Do you have any recommendations as to a reputable auto shop where I can source one? Preferably in the Gauteng area - arranging with DHL there is much easier.

[henris]

Thank's Wooky.

I still think the pressure is too high, so it will only be a matter of time before I have the same problem again. The second washer is only a temporary fix.

Seems I have to import a pressure regulator from SA. Such a device does not exist in the whole of Nam

Do you have any recommendations as to a reputable auto shop where I can source one? Preferably in the Gauteng area - arranging with DHL there is much easier.

Make a t-piece. But on the one side you allow a 1mm hole. Then it can bleed off any excess pressure. Especially when you switch off the engine. Make that pipe a return line.

[Apocalypse]

Thank's Wooky.

I still think the pressure is too high, so it will only be a matter of time before I have the same problem again. The second washer is only a temporary fix.

Seems I have to import a pressure regulator from SA. Such a device does not exist in the whole of Nam

Do you have any recommendations as to a reputable auto shop where I can source one? Preferably in the Gauteng area - arranging with DHL there is much easier.

The fuel pressure isn't the problem.... you can blow at around 0,1bar (1,4 psi) ...

If you pushed the float level down by adding a washer and the problem has gone away, either the needle is worn or the tag on the float is bent or the float shaft has worn badly.... fax that and stop farting about with micro fuel pressure adjustments!

Hmmm... you could probably fart harder than that pump now I think about it....

[Apocalypse]

had to go and check!

[Wooky]

I hunted for a fuel pressure regulator when I had issues with no luck.
Most of the regs available are for fuel injection and not carbs let alone low pressure carbs
To find one that will work (and be stable) with very low pressures is almost impossible or very expensive.

That is why I went the T-piece route and restriction orifice. Was cheap and tunable to get where I needed.

As Apoc says your carb should run fine with the pressure you have.
Rather sort that out.

[Apocalypse]

https://www.cbperformance.com/product-p/3185.htm

these are the ones we always used on the high performance carb motors - large capacity with side draughts and so on - where you needed far more volume at high rpm than a beetle engine. the high volume pumps tended to ramp up pressure at low revs and could flood the carbs. These were pretty much standard on every European car with any kind of performance ambitions.

but you don't need one with a facet pump....