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Stromberg float valve issues


oldbury863

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I had a strange problem whereby my 13/60's engine would start and run perfectly, but then totally die. I checked for a spark (ok) and removed the petrol pipe from the carb and proved there was fuel when I cranked the engine. I reconnected everything and after a bit of turning over, it burst into life and ran perfectly! Many weeks later I went to start the engine and the same thing happened. It started perfectly, then died after about 30secs and refused to fire at all. I suspected that no fuel was getting through after the float chamber had emptied. When I removed the carb and tried to blow into the fuel inlet it appeared blocked until I blew harder and it cleared. After removing the float chamber, I was able to lift the float manually to check it's operation and found that every time I lifted the float and then let it drop, the valve stuck shut unless I blew very hard. Having decided that I had been victim to yet another poor quality pattern part, I ordered a brand new 'genuine' zenith float valve from Rimmers. Even before I had fitted it, I discovered the brand new valve behaves in exactly the same way! I would not have expected a float valve to behave like this. Is this in fact 'normal' and does it mean that its actually my pattern part fuel pump thats the cause of the problem? The operating plunger on the float valve does not appear to be spring loaded by the way. My only previous experience is with S.U. carbs and I have never encountered this 'sticking' effect with them. It is also Considerably easier to access and check the float valve on (non HIF) S.U's too!  Anyone else shed any light on this please? As I am sure most of you out have already discovered, there is just no way of sorting the 'good' from the 'bad' on pattern parts these days.  Oh for an S.U. conversion.

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  • 1 month later...

Just an update to this issue, I fitted an electric pump to the car instead of the mechanical one. Started the car and (as usual) after it had been running for a couple of minutes it died. One gentle tap on the side of the float chamber and hey presto I could instantly hear the note change on the pump as it filled the chamber with fuel. One turn of the key and the car started immediately. Now I know the pump wasnt to blame! It still leaves me scratching my head as to why it is doing this. Is it the 'modern' fuel causing the issue? Do I just carry a hammer with me in case it fails again?! Its crazy that out of sheer frustration I'm now considering a total and expensive change of setup with SU carb(s) because I cant find a <£20 item that works properly.🤬

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It is strange because Google says the pressure you can get with your lungs is usually a couple of psi and I would have thought either pump could exceed that. Ive noticed that the valves can have a bit of liquid stiction when blowing through them but this should disappear with fuel. Recently with pattern pumps theres been problems of excess output pressure reported but I think you need to get a pressure gauge plumbed into the supply line to see exactly whats happening...

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What fuel do you use? Are you still on the original steel fuel pipes or has it got copper ones?

There were reports a few years back that unleaded fuel combined with copper pipes and occasional use can result in the formation of a varnish-like goo that will stick things shut. The advice then was to avoid supermarket fuels and only run high octane stuff from recognised brands like Shell or Esso.

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