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Fuel Pump Polarity
Posted: Tue Nov 25, 2008 5:52 pm
by PSL184
I would have thought that the SU electric pump would run either positive or negative earth.... but, I have seen them advertised for sale by our usual suppliers and they list both types and the positive earth versions are more expensive - anyone know why ??
Posted: Tue Nov 25, 2008 6:18 pm
by alanworland
I changed from positive earth to negative earth a while ago and all seems fine!
I think that the 'pip and crator' that gets burnt on the contacts will now occur the other way round - so in 40 year time my contacts will be returned to new!
Posted: Tue Nov 25, 2008 6:23 pm
by PSL184
Thats the same as I thought Alan - just doesn't make sense as to why I need to specify pos or neg earth and the pos earth type cost more !!!
Posted: Tue Nov 25, 2008 6:58 pm
by Leo
The electronic SU Pumps are supplied either as Negative or Positive earth and they look identical to the traditional points type apart from a small alloy tag with electonic embossed on it.
In my experience they are not as reliable as the points type and prone to sudden failure.
Leo 69 Travellewr
Posted: Tue Nov 25, 2008 7:19 pm
by PSL184
Aha - that might explain it then.... I guess what it doesn't explain though is the difference in price? Cheers Leo.
Posted: Tue Nov 25, 2008 8:09 pm
by bigginger
'cos not many people are going to buy a positive earth one, I imagine
Posted: Tue Nov 25, 2008 8:28 pm
by polo2k
I was thinking of the extra insulation but thats a good point!
Posted: Tue Nov 25, 2008 8:49 pm
by bmcecosse
Yep -it's only the electronic versions that are earth sensitive. But if you do change polarity - you should at least stone the points - or fit a new set. Same applies to ignition points !!
Posted: Tue Nov 25, 2008 9:26 pm
by bigginger
polo2k wrote:I was thinking of the extra insulation but thats a good point!
Extra insulation? Eh?
Posted: Tue Nov 25, 2008 11:19 pm
by Onne
to insulate it from the body of the car, if one were to run a positive earth pump on a negative earth vehicle.
Which is impossible anyway as there is the matter of the fuel line.
Posted: Wed Nov 26, 2008 9:10 am
by alanworland
Rubber section in it?
Doesn't sound a very good idea though.
Posted: Wed Nov 26, 2008 11:29 am
by bmcecosse
Seems a long way for a short-cut!
Posted: Wed Nov 26, 2008 9:12 pm
by bigginger
Onne wrote:to insulate it from the body of the car, if one were to run a positive earth pump on a negative earth vehicle.
Which is impossible anyway as there is the matter of the fuel line.
Now why didn't I think of that? Must take more stupid pills tomorrow...
