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MG MGA - MGA Fuel pump

I'm doing some work on my 58 Coupé. When I purchased the car, the SU fuel pump was mounted in the engine bay wich is fine for me. As I do not have much confidence in the SU pumps, I want to change the pump. I bought an UGO pump, but this pump seems not to have enough power to feed the carbs (in fact there is not any fuel arriving at all). (Pump is ticking) I called Moss, Holden and the MGOC in order to buy a FACET pump. This pump is not longer available on positive earth. Holden recommends a SU pump mounted near the fuel tank. Is there an obvious problem when this pump is fitted in the engine bay ? Are there other more reliable (positive earth) pumps on the market ?

It's possible that a previous owner replaced the original high pressure SU pump with a low pressure type which was designed to 'pull' the petrol from the tank and to be positioned in the engine bay. The original HP type sited near the tank 'pushes' the petrol to the carbs. You really should not use an LP type mounted near the tank although I used one for a couple of years with no problems. I can't see any other reason why one would change from the original pump position except, perhaps, for ease of access.

You can tell which type of pump you have by measuring the strength of the diaphragm spring. If you place the spring on a set of scales the force required to squash it flat is 2 lbs for an LP spring and 6 lbs for an HP one.

If you've got an LP pump and can afford a new HP SU (around £70 from Burlen) then mount it in the original position near the tank. There will be less chance of you having problems with overheated petrol in the line. S/H HP SU pumps are far harder to find on Ebay than the LP types and even then you will pay around £40 for a decent one.

It's possible to convert an LP to an HP but it's an involved process and you will need to rewind the coil to give a higher current rating and increase the armature diameter.

Stick with SU - they are unfairly maligned!

Good luck Mike
m.j. moore

Henri - Regardless of where the pump is mounted, the fact that no fuel is being delivered to the carburetors is bothersome. I suspect that you have a logged line somewhere in the system - if that clog is between the tank and the pump, it will cause damage to a SU fuel pump. This may not be a problem with the UGO (HUGO?) pump if is is clicking away with no fuel delivery. The other possibility is that there is an air leak between the tank and the pump. For help in troubleshooting the problem see my article Fuel Delivery Troubleshooting Guide on my web site at: You will find it under the Fuel Pump Articles list.

The Facet pump should not care what polarity the car is as the electronics in it are isolated from ground and you just have a ed and a black wire coming out of it. It is hooked up with the red wire to the positive potential (ground in your case) and the black wire to the negative potential (power from the ignition switch).

To clear up the issue of "pusher" pumps vs "puller" pumps, there is no such distinction. Any pump can be installed as a puller (in the engine compartment) or a pusher (back by the tank). A low pressure pump is normally located in the engine compartment because it doesn't have sufficient output pressure to push the fuel from the tank up to the carburetors (it must be no more than 6" below the level of the carburetor). A pump located near the tank is a much better situation than one mounted in the engine compartment in that the fuel in the line going through the hot engine compartment is under pressure and thus less susceptible to vaporizing due to the heat. With the pump in the engine compartment, the fuel on the inlet side is under vacuum and will boil or vaporize (vapor lock) as a result. This and other issues are covered in my article SU Fuel Pumps Facts and Myths on my web site.

I am with Mike, stick with SU pumps for your car, they are as reliable as any other pump on the market. The pump that you want for you car is the AZX 1332. This is the points style pump and will work on either positive or negative ground cars. If you want an all electronic version of this pump, it is AZX1332EP for your positive ground car. You can order the pump through Burlen Fuel Systems or you can probably order it from Midel Pty in NSW Cheers - Dave
David DuBois

This thread was discussed between 17/04/2008 and 18/04/2008

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