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MG TD TF 1500 - Emergency In Line Facet Pump

Dave DuBois, Your recommendation on locating the emergency fuel pump. Before the SU or after? I installed one on the wifes B a couple years ago after the SU and the system has worked well, but fortunately never had to use the facet pump and fuel seems to flow through it ok, but I'd like to know your, or others input on this for the TF. PJ
P S Jennings

Fuel will flow through an SU Pump so it doesn't matter where you put it. Just put the filter (if you install one) AFTER the SU pump. I can see doing this if you have a rear mounted pump. On the TD (and early TF), it is much simplier because the pump is on the firewall.

After getting my current trouble-some SU pump on the bench at home and fixed up (for the cost of a set of points and some re-wiring) I decided to tackle the beat up pump which was the one I removed from the car when I installed the one that gave me so much trouble on the trip and is now repaired. I've had this pump with burnt points and frayed wiring and a broken pedestal since 1988 (yep, the broken pedestal was my own doing- stupid kit that I was). I epoxied the broken pedestal (although they are available) fixed the frayed wires and bad connections, enlarged the channel for the wires since I heat shrunk on some tubing while I was at it, and installed a new diaphram and armature, using the silly figure eight nylon pieces that center the armature. After adjusting it, it ticks like a clock, only faster. It cost me about $55 for parts, and I'll slip it into my spares box.

I'm not able convert them to electronic, provide dampening systems for the current, or test them like our friend Dave DuBois, but I do think that a person can rebuild one of the simple ones (like the TD or TF) pretty easily and keep it hanging around. Would I do an MGB one? Maybe, but I would want to know some of what Dave DuBois understands about the supression methods, and I'm not a sparky by any stretch of the imagination. I also think it is a safer bet to send them to Dave DuBois, but it is also kind of fun to try it yourself.

Dave Braun

PJ - Dave B. pretty much says it all, the Facet pump can go anywhere in the line. That said since Facet recommends a filter between the pump and the tank and since a clogged filter can cause damage to a SU pump, it would make sense to install the Facet pump after the SU pump if a filter is installed on the inlet side of the Facet pump.

Dave B. - If by 'damping system' you are referring to arc suppression, there are several ways to do it. You can just use a standard diode, such as a 1N4002 installed across either the points or the coil such that the end with the band on it is connected to the positive voltage (reverse polarity so it only affects the high voltage pulse generated when the points open). The problem with a plain diode is that it will cause the pump to run slower (not a problem on the pump for the MGB, but is a bit of a problem on the rather anemic low pressure pumps on the T series cars). A better approach is to use a bi-directional Transient Voltage Suppressor. It can be installed in either direction and doesn't slow the pump (e-mail me for further information).

As for epoxy to repair a broken pedestal, it probably won't hold very long unless you drill in install some pins across the fracture line. The early pedestals didn't have any support under the mounting screw holes and were prone to braking if the mounting screws were overtightened. You can also cut some tubes (I use aluminum arrow shafts) to provide support under the mounting screws on the older pedestals. Cheers - Dave
David DuBois

Which model Facet fuel pump will do the job in my 53 TD with pos. ground? I think I'll keep one as a spare.
Best regards, Daniel
D Desmond

Many thanks for the info, Dave D! As always you make many excellent points. I would like to try my hand at arc supression. But I probably lack the tooling needed to pin the pedestal. I may try to procure a new one. One of the things I disliked about this pedestal is that it lacked the slight ridge that better locates the blade bar to provide the contact distance needed.

Again, thanks.

Dave Braun

I'm sure you know my car is the later model 1500 and the pump is on the frame along side the right rear wheel. Not a friendly place to work on it, especially in clean clothes. So, I will install an emergency pump after the SU just in case. I will also install an in line filter between the SU and the facet pump. Thanks for the information on doing it right. PJ

Gotta get me a pair of "Safety Fast" cover-alls to keep in the car.(Grin).
P S Jennings

What is the reason to install the filter after the pump rather than between the pump and fuel tank? I think mine is installed between the tank and pump to protect the pump. Thanks and have a good day!

John Progess

Repeating Danial's question; Which Facet pump (if there is more than one model) and where is the best place to buy? Mine is a '53 TD that I want to convert to negative ground with an alternator.

Bobby L
B. F. Loughridge

You want the filter between the last pump(s) and the carbs....if it clogs up and is before the pump, it will run dry.....and self destruct?
gblawson(gordon- TD27667)

Any of the Facet pumps that have an output pressure between 1psi-4psi will work fine on any MG. P/N 40104 and 40254 in the cube style (there is a new style pump, called the Posi Flow pump, but I don't have the P/Ns on them - you can check on their web site at: The Facet pumps can be hooked up to either positive or negative ground vehicles,just hook the red wire to positive and black wire to negative.

As for a filter between the tank and the SU fuel pump, Gordon has the right idea, although the pump won't completely self destruct if the filter clogs. What happens is that a clog on the inlet side of the pump will cause it to stall in a current on condition. If power is left on in this situation (such as while troubleshooting), the pump will over heat and the internal swamping resistor will burn out. Since the AUA 25 low pressure pumps used in the T series cars through the early TFs ues only the swamping resistor for arc suppression and is half of the arc suppression system on all the later pumps, when that resistor burns out, the pump is left with no arc suppression and the points will burn out prematurely. Of course the owner doesn't realize that the lack of the arc suppression circuit caused the points to burn out and usually purchases a new set of points, only to have them burn out in a short period of time. Worse still, in the all electronic SU pumps, the swamping resistor burning out will cause the pump to cease working altogether.

PJ - if you install a single pole, double throw switch to switch power between the two pumps there will never be a need to get under the car to swap out pumps.
Cheers - Dave
PS. All or most of the questions about the SU fuel pumps are answered in my web site at:
David DuBois

This thread was discussed between 04/08/2010 and 05/08/2010

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