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MG MGA - SU Fuel Pump Current Drain for fuse

I am installing a carburettor bilge blower for a summer trip to Europe and want to fuse it. I have added other fuses in my system and have the fuel pump on a 5A fuse.

The blower specifies a 4A fuse but draws 3A and I'm thinking of putting it on the same fuse as the pump. SU can't tell me what the current draw of the pump is. Does anyone know what the SU negative earth electronic pump draw is normally so I can size the fuse?
John Francis

Fuses are sized to protect the wiring, not the attached device.
Art Pearse

I think you should calculate the consumption of the fan and give a margin for the protection of the wiring. If you have an alternator, I think there is no problem, but if you have dynamo, the electricity consumption may drain the battery with the bilge fan on. You should assess this issue. On the other hand, Europe is very big. Denmark is not the same as southern Spain, where I live. Here we see temperatures some days in summer of 48º C can be normal 45º C. In my case I have obviated that solution because the outside air is too hot. I spray the lower area of ​​the carburetors with water spray to avoid the vapor look when stopped. When the car is in motion I have no problem.
Gabriel Martínez

I want to use the lowest value fuse that has sufficient capacity to cope with the normal load. That puts the minimum stress on any component part in case of a malfunction and gives a fast response to any problem. The fan draws 3A but I don't have a specification for the pump.

However, I have found the answer from Dave Dubois in 2010: - " If you are talking about the all electronic SU pumps, they will draw a bit over 5 amps if they are stalled in a current on condition. In actual operation, an ammeter attached to them (as I have on my test stand), they show less than 1 amp due to the short duration of the on pulse."....


Dave DuBois

So I think a 5A fuse for them both will be fine.
John Francis

This thread was discussed on 26/04/2018

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