Su fuel pump overhaul

[Robmsharp]

I've recently overhauled the original SU fuel pump but after initally checking the pump worked by just pumping air, when it tries to pump fuel it struggles to maintain any sort of pressure and with a consequently poor flow rate.
I'm confident I followed the instructiions supplied in the Burlen kit carefully and was wondering if anyone could offer any advice as to where the problem might lay?

[Lingen]

Rob.
Was the test with fuel on or off the car?
Mike.

[jbuckl]

The reason it’s not that worthwhile to try fixing 50 year old su fuel pumps is that the valves do wear and cannot easily be fixed. (Staked in)

You can fix the points and diaphragm, then find the valves leak.

At least, that’s what I found, sorry to say.

Even if the valves were attended to, their security could still be suspect.

[nigele]

Did you replace the clear plastic valve discs? On mine these were starting to break up causing low pressure, and the pump never stopped ticking even when the carbs were full. I fitted a full overhaul kit from Burlen around 8 years ago and it’s been fine since. The valve assemblies are held in by 2 screws and are easily replaced.
Nigel

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[Robmsharp]

Thanks for your replies. The Burlen kit is quite comprehensive and included two new valve discs, I found these weren't staked in and pushed out once the square plate had been removed with only a little bit of finger pressure. I forgot to say I had checked the pumps performance before the overhaul and found it to be pumping 300ml in 30 seconds which is approx 1/2 the flow rate it should be doing, hence the overhaul.
My 'test bench' was off the car with the fuel tank being a 1 gallon fuel container and the pump depositing into a calibrated jar.

I've also contacted Burlen who suggested checking the diaphragm setting.

[jbuckl]

Afaiaa the su pumps on stags have no stroke adjustment.

only available on earlier su pumps for other cars.

could be wrong.

[Robmsharp]

Theres no stroke adjustment, the setting up process involves setting the diaphragm position in relation to the operation of the points, this I guess is the nearest to adjusting the stroke.