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MG TD TF 1500 - Electronic Fuel Pump

I am attempting to rebuild my TF so it has a 1950s feel but is reliable enough for me to go on long journies. It has a beautifully engineered Mangoletsi tuned engine, a 5 speed gearbox, a Dynalite alternator and an electric fan. From experience of previous cars I know the SU fuel pump isn't the most reliable and doesn't cope too well with modern fuels (vapour locking). I am thinking about updating the pump but don't know if an electronic conversion of the SU's points or a swop to Facet pump is the best. If I install a facet what delivery pressure do I need for a rear mounted pump. The one I have been looking at is rated at 4/6 psi.


Jan T
J Targosz

Where did you get the information S.U. Fuel pumps are unreliable and subject to vapor lock? I have had my TD for over a decade, driven tens of thousands of miles in 100F temps and never had vapor lock while running or a break down..this is not a fleet wide experience, but I beg to differ on your description of the S.U. Pumps. Regards , tom
tm peterson

You really need something like 2-3 PSI at the carbs. Much higher, and it can push fuel past the float valve. I had one of those 4-6 PSI Facet pumps on my bugeye for many years and regulated it down to about 2 PSI with the Holley regulator. It worked fine. Here is the one I used:

I also have a similar setup on my Porsche 912. I use the same regulator, but a little higher pressure pump to minimize fuel boiling. I had no problems with vapor lock in either car, although I had some problems in the Bugeye before I created this setup.
S Maas

Jan - Electronic or points SU pump, either on puts out the correct pressure that is compatible with the SU carburetors - 1.2psi if the pump is mounted in the engine compartment. If you have a later TF, with the pump mounted in the rear, you need the high pressure SU pump that puts out 2.6psi. The choice between points or all electronic depends on how much you drive your your car. If it is an occasional driver, that get put into hibernation at the start of fall, you need the all electronic pump. If the car is a year around driver, the points style pump will work fine. Cheers - Dave
D W DuBois

After a six week lay up I tried to start the TF and once again I had to lie on my back under the car to give the SU pump a knock to restart it. I am once again thinking of a modern solid state unit and note there is a Facit PosiFlow 60104 available with a 1.5 to 4 psi pressure. They are inexpensive at 25. Only concern is the head of fuel they can cope with - 12". I will measure this today after I have cleared the snow from in front of the garage doors (you Aussies are so lucky) but am wondering if anyone else has fitted one of these. Apparently they will provide a steady flow of fuel , even in hot conditions, and are quiet.

Jan T
J Targosz

Jan have Dave rebuild your SU pump and convert it to electronic. They are trouble free once this is done. If you want you can add a hidden facit pump as a backup, lots of people do this. Result: original look, no worries, plus redundant backup!
Geoffrey M Baker

Jan I had a points SU fuel pump. Like Dave said I put my cars up for the winter. I bought a solid state one from Moss and have never looked back.

However, I did have Dave rebuild my old one in a solid state configuration. I will carry this as my spare on long trips.

In regards to vapor lock I live in what some would say is a hot climate and high elevation 7000' MSL so all my old cars have heat shields which really has stopped the issue. Honestly I do not know how scientific my results are but I seem to have solved the issue. No problems on restarting after a long drive, etc. Seems to have reduced the heat from the exhaust manifold which was boiling the gas. At least that is my story and I am sticking with it. LOL

This has worked in TR3, TR6 and TD.

JWP Policastro

Hi Jan,
you wont get vapour lock with a TF in this country. I have driven in France and Spain in summer and never had a problem. I have never had a pump fail in 40 years of TF ownership. I always put contact lubricant on whenever the car is up in the air.
Ray TF 2884
Ray Lee

I would be very happy to convert Jan's pump, but unfortunately, with the cost of shipping the pump in both directions would put the cost of doing the pump well above what the all electronic SU pump could be purchased from Burlen Fuel Systems there in England.

Jan - "there is a Facit PosiFlow 60104 available with a 1.5 to 4 psi pressure. They are inexpensive at 25. Only concern is the head of fuel they can cope with - 12" If you choose to go with the Facet pump, I can report (from personal experience - I use one as a permanently installed backup pump on our MGB) that it will work fine being mounted in the normal position on the TF. Cheers - Dave
D W DuBois

I strongly believe that Dave has a good system for conversion and he is correct that a properly rebuilt pump will give long life and does not contribute to vapor lock.

Having said that, there is another way to provide additional life to a pump by prolonging the life of the points. I have taken to installing a semiconductor device called a Transil across the points. The points arcing is caused by a high reverse voltage whenever the points open. The transil essentially shorts out whenever that voltage exceeds a certain value, so the arcing is prevented.
Transils are relatively inexpensive (under $1) and are dead simple to install. But note that you should have a fresh set of points to start with. The transil will not improve a pump already needing rebuilding.
LD Palmer

Lew Palmer's suggestion of installing a Transil (Transient Voltage suppressor) will stop or drastically reduce erosion of the points but it will not stop the film that develops on the contacts during the winter layup. The only thing that you can do to counteract the film buildup is to remove the pump and thoroughly clean the contacts - a rather onerous task on a pump that is mounted under the car.

Jan - another alternative would be to purchase the all electronic kit from Burlen Fuel Systems in Salisbury. That is a do it yourself kit with all the parts necessary to make the conversion. The only tricky part of the conversion is soldering the leads from the coil to the circuit board - due to the rather poor circuit board construction. That said, once installed and adjusted properly, it should last a lifetime (I have a pump that I converted with the BFS kit) in our TD some 20 years ago and it is still running strong (the TD is a daily driver in our household as long as there is no salt on the roads).

One other possibility - contact Peter Cole in London Peter has been installing the Transils for many years and the last time I talked to him, he was toying with the idea of converting the pumps to solid state. Cheers - Dave
D W DuBois

Hi David,

Thanks for the advice. Just out of interest I checked on the postage costs from Scotland to the States. It would cost me $110 return. From previous experience that's only half of the problem. Customs forms can be a nightmare. I will fit a facit if one is suitable (I have still to measure the head) but keep the original one in careful storage.

J Targosz

Hi Jan
If you fancy the trek south to Gaydon, Eric Worpe and Peter Cole are giving a talk on distributor capacitor and SU fuel pump upgrades at the T Register Rebuild event on 21 March -

David Wardell

Dave D,

In the past SU pumps have used capacitors then diodes as arc suppersors. For some years now Burlen have been fitting varistors instead.
What is the advantage of using a transil as opposed to a varistor?
The only reasons I can think of is maybe failure mode and/or ageing.


J Scragg

Jan - The following Facet pumps work fine in all MGs:
P/N 40171 40178 40217 All three have an output pressure of 2 - 3.5 psi and an output volume of 15 GPH. There is also a newer style P/N 60300 with an output pressure of 2.5 - 4 psi and an output volume of 20 GPH.

John - Yes, all the newer SU pumps use a varister, which is not polarity sensitive (it is possible to get Transils in a dual polarity - which I use in my optical trigger system). Originally SU just used a swamping resistor for arc suppression, later they used the resistor and a capacitor, then the resistor and a diode (which I have been told was, in fact a transil) and now the varistor. I have not come across sufficient numbers of pumps with the varistor installed to make any kind of a judgment on how well they work. The two things that I know for sure are that 1) regardless of the type of arc suppression, the points will erode over time as the result of even mild arcing and 2) the points in a pump that is not run on a regular basis, develops a film on the contacts that will build up sufficiently to keep the contacts from conducting. Quite frankly, I have not seen a great deal of difference in the points with any of the existing arc suppression systems - my feeling is that they are all about the same (my main competitor and collaborator swears by the capacitors).

There are only two systems that I have seen to cure the dual problem of points erosion and the film development over time are BFS's all electronic (Hall circuit) pumps and my optical trigger. Both eliminate the points completely and both appear to be quite reliable when properly adjusted (I would guess that there some other systems available that I haven't heard of yet. Cheers - Dave
D W DuBois

Hi David,

The pump I am hoping to use is a Facit 60104 Possi-Flow. The spec is 1.5 to 4.0 psi, 25 galls per hour and a dry priming height of 12 inches. The current SU is 18" from the floor and the float 30" so the lift height is OK. They are for sale in the UK for 25. Possi-Flows have superseded the Facit Cube

J Targosz

Jan - The Posi-Flow haven't superseded the cube pumps, but run concurrent with them. And yes, the 60104 will work fine. The one big problem with the Facet pumps is that if mounted hard to frame, their incessant chattering is transmitted into the passenger compartment, which will drive you up a wall. Get a pair of sound mounts and mount the Facet pump on them and it will nearly completely eliminate the noise in the passenger compartment. Moss used to carry the mounts that you need, but they no longer show up on their web site. You can see the mounts at: Cheers - Dave
D W DuBois

Here's a pump I'm considering for my TF. The SU has been relocated to the firewall and I'm inclined to leave it there. That leaves the original frame pad open for a backup pump. The one in the picture is a rotary design from Mr. Gasket and is pretty much silent. I happened upon it when the pulse type on my zero-turn mower broke on a Sunday afternoon after the regular parts stores had closed. The discount store had several different models and this one has a pressure, I think, of about 2+ PSI. I remember thinking that it's a little overkill for the Kawasaki 27 HP engine seen here on the bench after a ring job.

Anyway, it's had about 50 hours on it this past summer and is performing well. It's straight through so won't impede normal flow and is so quiet that I have to touch it to know it's running.

JE Carroll

This thread was discussed between 12/07/2014 and 26/01/2015

MG TD TF 1500 index

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