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MG MGB Technical - Fuel pump and filter

I have been working on my new fuel system. The car has on it a small square box type pump and a pressure regulator. I have been trying to figure out where to mount it all. I was going to mount the filter and regulator in the engine bay but that looks kind of messy. I am thinking I would rather get a new fuel pump and lose the regulator (just another thing to fail and two more connections to leak). And I would like to put the filter between the tank and pump. I have a new tank and new lines so I figure that is the best way to keep the lines clean. Then the engine bay is nice and clean with just a simple hose from the hard fuel line to the front carb (through a little 5/16 to 1/4 adaptor I made from copper tube).

My questions are what pressure pump do I need? I don't mind a little tick-tick-tick type thing as my GT had that and it never worried me. I am running twin HIF carbs and no emissions control stuff so no return lines or vapour traps or any of that stuff.

And also how strong are those plastic filters. I have a Fram G2 I think it is? If I mount it between the pump and tank there only place I can fit it is on the side of the tank right near the pickup. Will it be alright in such an exposed location?

Simon
Simon Jansen

Simon, this is a relatively straightforward situation and i would suggest that you fit a completely standard fuel system meaning that you fit the original type of SU pump, no regulator and no filter on the tank side of the pump. I'm quite sure that David DuBois will pop up here and support that. There seems to be a problem in that when a suction filter is installed damage can occur to the pump when the filter chokes. In any event that filter would have to be installed in a very inaccessible position. I would install the original type of SU pump for the vehicle and preferably go for the points type as the electronic type in my opinion is of questionabe reliabibity. This pump will deliver the correct pressure of about 2.5/3 psi, correct for the SU carbs which will not overflow at that pressure. Additionally it eliminates the need for the further complication of a pressure regulator. Now the in line Fram type plastic filter is absolutely fine and should be installed in the line where the fuel line passes the front of the heater box which means that the braided fuel line will have an easy curve round to the T piece feeding the back carb.

This is the simplest solution and in my opinion should be fit and forget, it certainly is on my two MGs.
Iain MacKintosh

Simon - I will back up everything that Ian has said except that the all electronic pumps having a reliability problem. I believe that there was a problem when they were first brought out, but if that was true, the problem has long since been resolved. I converted the pump in our MGB to all electronic using the kit from Burlen Fuel Systems several years ago just to see how well they work (I already have my own method of converting pumps to solid state that is cheaper than Burlen Fuel Systems method, but wanted to test their set up). The pump has been working without a hint of problems since I converted it some three years ago and this is on a car that is driven daily year around. I have always recommended the all electronic pumps for people who don't drive their cars regularly because the all electronic pumps eliminate the points, which have a habit of filming over when the pump is idle for long periods of time. If your car is driven regularly, then the points style pump will work trouble free for many years.

Ian is correct in saying that the pressure should be between 2.5 and 3psi - The SU fuel pumps for the MGB has a nominal pressure of 2.7psi out of the factory. Thie issue with a filter between the tank and the pump only applies to any of the impulse pumps without a bypass valve in them. this includes the SU pumps, Autopulse pumps and various pumps made in Japan and Germany that are clones of the SU pumps. The problem is that a clog on the inlet side of the pump will cause them to stall ina current on condition. If power is left on for any period of time while this condition exists (for instance, while troubleshooting), the swamping resistor that is inside the coil housing will burn out. This burned out resistor does not cause any imediate problem, but since it is part of the arc suppression circuit fo the pump, it will cause the points to arc excessively and burn the contact material off of the points in a short period of time. Replacing the points with new ones will only result in their burning out in a short period of time. The ultimate result is that the frustrated owner installs a Mitsibusi or Subaru pumps and condems all things SU. If you must install a filter, put it on the output side of the pump (in the engine compartment where it is easier to access)

Going back to your little square pump, you might want to check the part number and see what the output pressure is. The Facet pumps put one out that has a pressure that is under 4psi and these work fine in the MGs. I have even permanently installed one in line with the SU pump in our MGB so that if the SU fails while we are on the road, I can just flip a switch and continue on home. I have instructions for this type of installation at: http://www.custompistols.com/cars/dave/BackUpFuelPump.htm
Cheers - Dave
David DuBois

Thanks guys, lots of good info there. If I had an original pump I would rebuild it and convert it to electronic points but unfortunately I am stuck with what came with the car for now. I will check the pump I have. I am sure it is a Facet type and it could be the low pressure one already in which case I can ditch the regulator. I guess I can live with the filter up in the engine compartment. That won't make things too messy looking and it more stock for a 78B. I will find out from my parts guy exactly how much a real SU is in the mean time.

Simon
Simon Jansen

Simon - Check the price for the fuel pump directly from Burlen Fuel Systems, You may find it cheaper to get from them plus there is a 5% discount for any on line orders. the part number you want is AZX 1307. Burlen Fuel Systems web site is: http://www.burlen.co.uk/. Also check with Midel there in Oz, their web site is: http://www.sumidel.com. Good luck - Dave
David DuBois

Simon,
I have a second hand pump that you can have for the cost of postage from Tasmania which shouldn't be too much, I have a new electronic pump which I'm about to put on, you will probably have to rebuild the old pump with new points or an electronic system if you decide to go that way but it is in going order.
Wayne
Wayne Styles1

Wayne, thanks very much fo the offer. Let me see what exactly I have on the car now then I will decide how to proceed from there. If it works out it is a low pressure pump I will just go with that I think.

Simon Jansen

This thread was discussed between 01/02/2006 and 03/02/2006

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