Joined: Aug 2017 Posts: 2,748 Threads: 31
Reputation:
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Location: Auckland, NZ
Springs do vary. Makes with crankcase vacuum had heavie. 2.5 psi was a typical max, with. 1.9 psi recommended. This corresonds a column of petrol 5ft 6 if you have some tube and hours to waste. Check on crank handle not priming lever. The spacing from crankcase determines stroke and max spring compression and max presure and can be packed out. Must preserve reasonable output operated from engine or crank handle.. Variants fit and may not have ideal Seven arm. Contact should be inear middle of pad. Beware fitted correct side of camshaft. A bypassed pump would overwork itself. Decades ago very cheap vacuum guages were popular and many included a low pressure range for pumps.
Frequent reference in Forum to U and t type but how do owners recognise?
Joined: Jan 2019 Posts: 1,571 Threads: 20
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Location: Bala North Wales
Car type: 1933 RP Standard Saloon
20-06-2019, 11:07 PM
(This post was last modified: 20-06-2019, 11:13 PM by David Stepney.)
John,
On re-reading my previous post, perhaps I should have mentioned that the pump operating lever is articulated in such a way that it can only pull the diaphragm down. If the pump is idling, there is a separate spring in the very bottom of the pump which bears on a lug on the part of the arm in contact with the camshaft to ensure that it always bears on the cam, so that the pump is not noisy in operation.
The handbook gives a good if somewhat prolix description of the pump with a detailed drawing of its internals. If you haven't got a handbook, the A7CA archive site has several to cover most models.
David.
Bob.
The 'T' type pump has a bell shaped top cover. The 'U' type pump has a fatter body and a slightly domed top cover. I would put photos up but it is too dark in the garage for successful photography!
Joined: Aug 2017 Posts: 53 Threads: 11
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Location: Surrey
Quick update. Thanks to loads of helpful advice above, and after much searching, I managed to source an old pump spring (thanks to Henrik in Sweden!).
30 mins to remove the pump and replace the spring that came inside the Seven Workshop new replacement pump, and Jane is running as smoothly as I'd expect with no drips after switching off. OK, I've only driven 1 km so far, but the improvement is remarkably clear.
Standing the two springs side-by-side on the bench there was a huge difference, very easily discernible pressing down by hand without any gauges !!!
Joined: Aug 2017 Posts: 53 Threads: 11
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Location: Surrey
Yes, its all still working beautifully. No drips.
But in fairness, longest run has only been 10 miles or so. My 2 seater tourer needs a new hood for driving in England.
Joined: Sep 2017 Posts: 175 Threads: 66
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Its been a few months since I fitted a old spring in a new pump and it's been great since, no leaks , idles well and best bit it has a primer that works !!!
Joined: Sep 2018 Posts: 255 Threads: 67
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12-11-2019, 03:27 PM
(This post was last modified: 12-11-2019, 03:31 PM by Rpm.)
Did the same with my incontinent carb, no more drips, replaced with old spring in the pump.
RPM
Joined: Oct 2019 Posts: 24 Threads: 6
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Location: Wakefield
Car type: Austin 7 1934
Thanks guys I shall be changing my spring , once I've managed to drain and clean all the crap out of the fuel tank.
Andrew
