S1 1952 80" Generator tips

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Originally Posted by NobbyTD5

Thanks OF - yes I am quite sure I don't have the right fuel pump! - it suspiciously looks like a cheap ebay one and it does over pressurise the fuel system (I originally thought it was a float issue in Carby but you are right, overpressure is the real culprit) . Looking at a Lucas one now - back to original!

Pump is also wired negative earth and using JDNSW's guidance the car is positive earth - the ammeter indicated positive earth with headlights

I am still surprised that the motor runs happily either way!

I think prior owner was playing around with the fuel pump etc but never finished off the job - they did do up the brakes and they work well - which was good thing!

I will keep playing!

cheers Nobby

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I think the original pump was SU pos. earth. Now available in neg. earth. Not cheap but supremely reliable.
Cheers Rob S

I made a mistake (blame it on jetlag). The theoretical advantage is for positive earth!

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Originally Posted by LR1953

I think the original pump was SU pos. earth. Now available in neg. earth. Not cheap but supremely reliable.
Cheers Rob S

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The low pressure (1.5 PSI) SU pumps used on Series Ones were all originally hooked up to the standard positive earth system. If they still have points, they don't care if it's positive or negative earth. The later electronically switched pumps are polarity sensitive. Also some SU pumps may have some form of electronic assistance fitted to minimise the current flowing through the points to cut down on spark erosion on the contacts and may be polarity sensitive. If you have an old (Pre 1985) SU LP Pump an SU EPK700 rebuild kit will make it like new again and give years of reliable service. Kits cost about $135.00 last time I bought some from Classic Carburettors. The Solex 32PBI-2 carb can't cope with much more than 2PSI reliably, so don't waste your money on ebay cheapies that are nostly in the 4.5 - 6 psi range.
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