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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - SU Pump Inspection/Rebuild

Following on from my fuel pressure saga from last week, I have my old SU pump laid out on my bench in a million pieces for inspection and possible rebuild. I have had a look at Barney's site and read a few articles in the archives.

First of all, it appears to be the correct HP pump, requiring about 6lb to compress the spring. Secondly, the diaphragm is shot; it crackles when I flex it! Thirdly, the points are well worn.

OK, a couple questions: Before I even think about a rebuild is there a check I can make to test the strength of the windings? If that part is gone, then the whole unit can be consigned to the bin/spares for someone. I am not great on electronics so please keep instructions simple.

Second, if it is recoverable, is it worth the outlay to convert to solid state? Other than trying to recover a piece of old equipment, I am unlikely to replace with my Facet pump with it, certainly in the immediate future, now that I have my fuel system working so well.

Steve

Steve Gyles

Two good questions. I will try and answer the second one:

The solid state conversion kit is £45.59 plus postage and then you need a diaphragm set at £25.81. A new electronic pump is £79.99 plus VAT and delivery. So there is a saving so long as everything goes well and you don't need any other bits.

I have heard that the electronic pump is currently unavailable due to quality problems with the supplier of the pump body, but that was a couple of weeks ago, so a quick phone call will confirm.

Above prices from sucarb.co.uk include current offers.
N McGurk

One of the winding wires was broken flush leaving insufficient left proud to effect a repair. Consigning to the bin unless anyone would like all the castings etc.

Steve
Steve Gyles

Steve, I went into Burlen 2 months ago and the electronic pumps were out of stock. I tickled the points on mine and it recovered. Other suppliers had them but at a significant mark-up.
Shane
Shanerj

Steve, Burlen do a repair kit (EPK605) which includes the diaphragm and points assembly as well as the rocker mechanism. Don't worry about the coil winding breaking off, just unwind a turn or two on the coil. You may find a few turns of very fine wire wired across the coil which I think is an energy shunt of about 30 ohms. You could remove this if needed before unwinding and resolder it afterwards. As far as I remember the coil resistance itself is around 3 ohms so if your coil measures this it should be good to go...............................Mike
m.j. moore

Mike

Thanks. I found that thin wire wrapped around with the paper wrappings. What does the free end attach to?

Steve
Steve Gyles

I gave up on SU pumps some years ago. Apparently the type fitted to MGA's (branded HP?) have reached their "use by" date . I have fitted a Fuelflo (originally made in NZ I have been told) to a number of MG's with complete saisfaction. They are light enough not to need mounting, the hoses will support them adequately! I still have the original brass-bodied SU pump on my (1947) TC.
Barry Bahnisch

The very thin, nichrome wire is a 100 ohm swamping resistor that works in conjunction with the capacitor (if one is installed) to serve as arc suppression. The ends of the nichrome wire go to either end of the coil wires. Nichrome wire cannot be soldered (solder will not stick to it) so it is just run along the ends of the coil wire and both wires are scraped of all the insulation, lied against each other and a length of shrink sleeving put over them. Cheers - Dave
Daved DuBois

Thanks Dave. That would tie in. The broken wire appeared to have a 'strand' attached to it.

Steve
Steve Gyles

Clausager lists my pump as AUA 54. However, this option does not come up in Burlens lists for spare parts. What model should I use? When I look at any model for the diaphragm replacement it lists the spindle length as 2 3/8". However, mine is 2 7/8".

David. Having unravelled the windings to get a suitable length exposed for a new terminal attachment, the small nichrome wire fell away. Is it just free wrapped in the paper cover with the one end attached as you describe?

Steve
Steve Gyles

Steve, In the SU catalogue the MGA (except twin cam) pump number is given as AZX1331.

I believe the fine wire 'resistor' is connected in parallel across the coil.......Mike
m.j. moore

Thanks Mike. I spoke with Burlen. The diaphragm spindle length they quote refers to its exposed length after screwing in to the diaphragm, not its overall length.

If I am reading my meter correctly, it reads 5 ohms. Is this okay?

Steve
Steve Gyles

I've just looked up some notes I made six years ago (where does the time go?) when I was working on my pump and I've got the coil resistance at 4 ohms not 3. All the better if it works at 5 ohms.............Mike
m.j. moore

Steve - You have, what is commonly referred to as a High Pressure Long Body pump. It was the first iteration of the high pressure pump and not a really great pump. A coil resistance of 5 ohms is not an unusual reading on the HPLB pumps. The later HP pumps were AUA 150 series, employing the shorter coils that have a resistance on the order of 3 - 4 ohms (note: When reading the resistance, be sure that the wires are cleaned down to bright copper or else the reading will be abnormally high). Today's HP pumps, the AZX 1330 series also use the shorter coils and have a resistance of 2.6 ohms. The shorter coils with the heavier wire (thus lower resistance) are a much more efficient pump. Cheers - Dave
Daved DuBois

Having made more investigations, my 'original' SU pump isn't. It's an AUF214. The inlet and outlet connections are different (see picture). Any idea what car used it?

Steve


Steve Gyles

AUF214 was used by later Magnettes, midget, 1100/1300, some of the Minis and Austins.............Mike
m.j. moore

I think that is a PD or a SD (not real sure) and was a forerunner of the AUF 214 (the AUF 214 uses plastic turrets with push on fittings instead of the threaded aluminum fittings - otherwise pretty much the same pump. Be real careful with the fittings on the turrets as they will crack fairly easily.

I will take back my identification of the pump being a high pressure long body pump (the 5 ohms reading of the coil threw me off). The coil resistance on this pump should be about 3.5 ohms. Cheers - Dave
Daved DuBois

Thanks David. As it's not MGA I am now wondering whether it's worth my effort and expense restoring it - unless of course if it has any rarity value. If any Midget/Magnette/Mini owners want it for spares give me a shout - free to a good home.

Steve
Steve Gyles

Steve - I doubt there is much value to them, they are a rather rudimentary pump. Cheers - Dave
Daved DuBois

This thread was discussed between 01/10/2012 and 04/10/2012

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This thread is from the archive. The Live MG MGA BBS is active now.