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MG TD TF 1500 - Fuel Pump

Are the fuel pumps polarity sensitive? Also, is there a way to know if a pump is electronic or points without pulling the cover? PJ
P.S. Jennings

Early ones are polarity sensitive, later ones are wired to be both...easy to pull that cap?
Am sure the Daves will chime in with details.....
gblawson(gordon- TD27667)

Go to Dave's web page on SU Pumps. It's a great education on all aspects of the pumps. The specs page list what polarity applies to certain pumps. Study hard.
Mike
http://homepages.donobi.net/sufuelpumps/
Mike Hart (52 TD 16378)

PJ - Remove the end cover and see if there is a diode/resistor assembly (see attached picture) on top of the pedestal. Unless the pump was made after 1985 and has an end cover with an elongated dome on the top, there is probably no diode/resistor assembly attached and the pump is not polarity sensitive. If the pump is an all electronic unit, it will have an aluminum tag on the coil housing flange with the word 'ELECTRONIC' on it and will have a printed circuit board in place of the black pedestal under the end cover. Pumps with a diode/resistor assembly installed are polarity sensitive and can be damaged if hooked up improperly (although the damage will not keep the pump from working). All electronic pumps and the pumps that I convert to optical triggering will not be damaged by applying the wrong polarity to them, but they will not work at all unless they are hooked up properly. Cheers - Dave


David DuBois

Dave here's the pump with the cover off. Looks like electronic. So, is it polarity sensitive or do you need more information? PJ




P.S. Jennings

Doesn't PJ's pump look like the shorter TD/early TF AUF 25 pump intended to be mounted to the firewall, and not the longer-bodied AUA 54 that the TF with the rear-mounted pump needs? Or how can one tell the later shorter-bodied pumps apart?

Thanks. Tom
t lange

PJ - Your pump is definitely an all electronic pump. If you can tell me what the model number stamped on the aluminum tag mounted around 4 o'clock on the coil housing flange, I can let you know what th epolarity of the pump is.

Tom - The AUA 54 pump is no longer made (it was never the greatest pump SU ever made) It was replaced with the AUA 150/AUB 150 and numerous other model numbers, all of which were replaced with the AZX 1331 and AZX 1332 and all of which had the shorter (and more efficient) coil and coil housing. If there is no model number tag on the pumps, there is no way to tell if it is an AUA 25, low pressure pump or the AZX 1331/1332 pumps without disassembling the pump and measuring the OD of the coil core. The high pressure pumps will have a core of about 3/4", while the early low pressure pumps will have a core of about 1/2". Things get more confusing if the low pressure pump was made after 1985 as it used the same coil and core as the high pressure pump and there are only two things that are different. The low pressure pump will have a lighter volute spring under the diaphragm and the diaphragm will not have a stiffener plate under diaphragm material. Cheers - Dave
David DuBois

Dave, The number on the tag is, AZX 332. PJ
P.S. Jennings

I have a couple pumps that I believe are Hastings; one works one doesn't. Are these pumps as good as the SU units and can they be converted to electronic as well?

Thanks,
Rich
Richard Taylor TD3983

PJ - That would be AZX 1332, which would make it positive ground.

Rich - Is that Hastings or Harding? If it looks like a SU pump, it is Harding (or Hardi). Use the one that works and throw the other one away - parts are not available for them, so they can't be rebuilt. Cheers - Dave
David DuBois

Dave - is that Harding or Harting?

Thanks for all the clarifications as to the last SU pump numbers - all new to me.

Tom
t lange

Tom (and Rich) - It should be Harting, mistyped this morning. Cheers - Dave
David DuBois

Dave, AXZ 1332, Thanks for the info! I must have missed the 1 on the tag, thanks for the correction. Positive ground, all I needed to know. The pump looks like new and works the same. PJ
P.S. Jennings

I checked the pumps this morning and one is a Hardi and the other is a Harting.

The Hardi has a clear cap on the end so you can see the works.

The Harting has a black cap covering the points that has SU on it; maybe got put on when the original broke but it still has a cardboard cylinder around the body and the pump looks like it has never been used.

Richard Taylor TD3983

Richard - You can probably bring the Harting with the black SU end cover on it back to life by throughly cleaning the points as follows: Remove the upper set of contacts from the pedestal by loosening the 5BA screw at the back end of the upper contact spring. slide the spring out and scrub the contacts on a fine sharpening stone or some 400 grit sand paper on a sheet of smooth metal or a sheet of glass until the contacts are bright and shiny, then wipe them off with a solvent soaked rag and reinstall them.

To clean the lower contacts, you will need to remove the two 2BA mounting screws that hold the pedestal to the top of the coil housing and carefully rotate the pedestal back around the swivel pin that holds the lower toggle to the pedestal. Once the pedestal has been rotated back, clear of the lower contacts, you can scrub the contacts with a fine sharpening stone or 400 grit sand paper folded over a piece of flat metal until they bright and shiny. Finish up by wiping the points with a solvent soaked rag. Reassembled the pedestal and test the pump for proper operation. Cheers - Dav
David DuBois

This thread was discussed between 07/11/2010 and 09/11/2010

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.