SU fuel pump (for MGA and other cars)
Burlen part number AZX 1331

Part received and installed Wednesday, 23 Apr 08. Ran immediately when installed. Stopped operating after about 5 miles driving. Tapping on the pump would not revive it. Towed car home. Called friend.

Barney Gaylord comes to help Thursday 24 Apr 08. Test on car. Good power and ground connections, but does not run. Tapping on pump does not revive it. Dismount pump and take to work bench. Ohm meter shows open circuit between power input terminal and ground on case. Call vendor to report and confirm it is okay to open cover for inspection.

Remove tape and cover. First glance reveals contact points are not level. Closer inspection reveals only one of the two contacts is touching at one edge while the other contact is still open (not touching). Pushing down points armature breaks and makes contact on one side only. With armature down (no contact) the blade lies flat. With armature up and making contact on one side only the blade is slightly cocked. Pressing down gently on other side of blade can make second contact but twists the blade considerably. Upon release of pressure the blade goes back straighter making contact on one side only. Photos below show misalignment of the contact points parts.

By this time an ohm meter check shows connection between power input post and case with about 2 ohms resistance (looks about normal). Applying power to the pump makes it run sometimes, but it is inconsistent, may run sometimes, but may not run at other times. Symptoms are similar to points being out of adjustment, possibly due to the significant tilt and misalignment of the moving contact armature. There is also a visible spark fairly often at the point of contact where the one contact is touching on one corner only. It appears to be making intermittent contact or a poor connection on the points contact parts.

Further inspection reveals that the hinge pin is cocked, slightly misaligned, not parallel to the end of the pump body. This pin is held by the molded end frame which appears to be FRP material (fiberglass reinforced plastic). I would not know if the hole for the pin mount was molded in the plastic or may have been drilled after molding, but the hole is definitely crooked, higher on one side than the other (photos below).

When the contact blade is pressed to tilt and make contact with both points, it appears to be twisted more than the misalignment of the hinge pin. This implies that the moving points armature may also be twisted some additional amount in the same direction. This fuel pump is hit or miss in operation, may work long enough to drive it out of the garage, then dies on the street a very short time later.

I had an urge to twist the moving points armature in attempt to make the contact plates parallel to see if proper operation could be achieved. However, I didn't want to risk breaking something or possibly making it worse. I also wanted to preserve the original condition so it could be returned to the vendor and/or manufacturer for their inspection and possible rectification of any production problem. This photo and notes page is being posted with immediate notice to the vendor, and the unit is being shipped back to the vendor on Friday 25 Apr 08.

NOTICE: There is a discrepancy between the catalog description of this unit and the instruction sheet packaged with it. The catalog states: "Currently available S.U. points-type pumps are not polarity sensitive". Indeed the unit has a metal oxide varistor (MOV) inside that would not be polarity sensitive (the small blue disc in the photos). HOWEVER, the instruction sheet states: "All pumps with part number commencing AZX are polarity conscious". The smaller part number tag on outside of the box says:
      AZX 1331
      ELECTRONIC FUEL PUMP
      12V DUAL POLARITY
      GRN No. 276269       Made in the UK
So the polarity reference between the instruction sheet and part number on the box does not match the non-polarity-sensitive pump inside the box.

Addendum 9 Sept 2008:
Last word is that Burlen is ignoring the issue and has given no indication that they are going to change the plastic piece. As such, let the buyer beware. Note that this is a single occurrence of a faulty part, not absolutely proven to affect a larger class of parts (but suspected to be similar for at least one production run). The parts will continue on sale "as is" if there are no further complaints or returned parts. If anyone else has a similar problem with one of these parts they should contact the vendor immediately. I would also appreciate a note to add to this web page to keep it up to date with any new developments.

Addendum 14 Dec 2010:
I now have verification that this is a batch manufacturing problem with multiple reports of the same misalignment.

At 03:31 PM 12/14/2010, Max Heim wrote:
"The replacement started giving trouble within 5000 miles. Examination shows that the point mechanism is built much less precisely -- as assembled, the moving arm was cocked and did not contact cleanly".

At 10:09 PM 12/14/2010, Paul Osborne wrote:
"Purchased a SU replacment from Moss, lasted 2 months. They replaced it, lasted about a year. Same problem with the points. Put in an electric universal pump from AC that I picked up from my local parts store. .... Adjusted pressure to 3psi and it has be running ever since".