Servicing the SU AZX1307 points fuel pump.

The SU fuel pump is mounted near the tank in the Excel boot. I have bought a new one for my car- but I have an old one from my old Elite, and this has been stored since it stopped working. All nuts and screws on this pump are British Association (BA) except the two pump mounting bolt holes (on the bottom in this view) which are threaded to 5/16 BSF. There is an exploded diagram here.

The pump comes in three functional parts- the pedestal/rocker mechanism in the top that controls the solenoid  which operates the diaphragm pump, incorporating the valves governing fuel movement. I decided to try to renovate this pump as it seems likely a spare will be quite useful! This means at the very least changing/cleaning the points in the top of the unit. The first step is easy

Remove the tape and the top is removed by unscrewing the terminal nut.. 

Su pump from my old Elite. Bulge on top to accommodate capacitor, air vent pipe on top.

and removing the nut, terminal and shake-proof washer (note order)

Remove terminal nut, spade contact and shakeproof washer.

The top then pulls off the terminal pillar bolt to expose the points mechamism. This in in two parts mounted on a raised plate or pedestal; an upper blade or wishbone contact  on the top and a rocking contact mounted on the underside. The top of the pedestal has three screws, two large pillar screws that retain the pedestal and a small 5BA screw in between that retains the wishbone upper contact strip.

Remove cap to expose pedestal and upper contact strip

Unscrew the small cheesehead screw in the centre to release the wishbone contact and its associated electrical connections.

Small central screw retains blade contact strip

The connections are two fold- a green wire to the suppressor capacitor and a black wire to from the solenoid control circuit. At the bottom is the wishbone flexible contact strip itself which is revealed here in position, having removed the contacts.

Capacitor wire and black earth connection on terminal above contact strip

The wishbone contact pair then just lifts off- here its been turned over to expose some really nasty looking points- burned black and dirty. The lower points are visible in the slot and these are also dirty. 

Wishbone contacts removed.Note the small ridge on the lower edge of the square cutout. This props up the contact end of the wishbone to ensure a gap between upper and lower points. The wishbone has to be bent to adjust this gap which should be about 30 thou when the points are open. If you don't disturb the lower points and clean everything gently the gap may not need resetting.

In this case the two pairs of points, (upper wishbone and lower, rocking points) were both very dirty and pitted. It may be that cleaning these is enough to restore function. They can be wiped with fine emery and meths before reassembly. If you do this process carefully it shouldn't disturb the points settings very much. I find that resetting the gaps is a bit of a hit and miss affair anyway (see on) and best avoided, so I just reassembled the thing. In fact this did restore pump action and it started ticking as soon as I connected it. I was then able to check that there really was some sucking/pumping action so the diaphragm must be functional. This is quite expensive to change (£20 app) so it was good to know it was working. 

Given the state of the points on the other hand, they are not likely to last so I decided to order a new set and fit these anyway. At around £15 they are quite good value.

Removing the points

If dismantling further, then the pedestal has to come off to get at the rocking points. Since this is screwed to the diaphragm rod you must first remove the diaphragm pump section at the bottom. Unscrew the 6 x 2BA screws and washers that secure the diaphragm... including the pump name plate.

Diaphragm retaining screws

The lower section, containing the valves, then detaches with its gasket leaving the diaphragm stuck to the upper section.

Diaphragm in upper section

Lower section gasket with valves visible beneath

There is a rod from the diaphragm that penetrates through the solenoid and screws into the lower rocking points. This has to be removed before the points can be released so you need to peel back the diaphragm and then unscrew it and its rod anticlockwise.

This also releases the 5 nylon guide spacers which will fall out!

The diaphragm and rod detach once unscrewed and release with the underlying spring.

Unscrewing diaphragm rod

Rod diaphragm and spring

Note; spring fits small-end next to the diaphragm.

Its then possible to dismantle the top end and remove the points. There are a total of 4 wires making connections around the pedestal. The red and black wires are the power feeds to the solenoid section below. There is a green wire incorporating a small capacitor which connects the blade wishbone terminal screw on top of the pedestal to the 9 O'clock cheesehead screw and finally a naked wire which connects the points carrier to the same screw.  It is important to get these back on the right screw and in the right order, and to fold the wires and any associated components out of the way around the upper section so take careful note of how the thing is assembled before taking it apart!

Reminder of how the wishbone/blade contact was assembled, from the top, washer, black wire tag, green wire tag, blade contact

Removing connections from the terminal post- note insulating washer on top of lock nut

 

Lock nut and washers removed- Red wire tag (power pick up +ve) still attached to terminal post, the green and black also visible were removed from the blade contact.

The order on the terminal pillar is (from the top); rubber washer 2BA locknut, wiring tag (+ve power pickup)

Column screws:
If you position the contacts at 12 O clock (as below) then the screw at 3 O'clock has only a Thackery washer beneath it. That at 9 O'clock has two wires. Loosening the screws allows the top portion (or pedestal) to be removed without actually taking the screws out so that their fittings can be seen:

Loosening pedestal retaining screws

9 O'clock screw- Thackery washer, green wire tag (other end goes under the blade contact) and earth wire from rocking points unit.

Fittings and connections spread out but not removed.

The order of attachments on the LH column screw (ie at 9 O'clock) is from the top; Thackery washer. Condenser tag (green), points earthing tag (naked wire). The other column screw has only a Thackery washer.

The points are pivot on the underside of the pedestal upper section secured with a sliding pin. 

as above but note the pin which slips through the pedestal and points assembly.

 Push the pin out sideways to release the points.

Removing the pin to release the lower rocking points

The pin is apparently a hardened metal and shouldn't be replaced with anything else. There is a short wire that connects the points to the 9 O'clock column screw. There is a central trunnion that screws onto the diaphragm rod and triggers the pivot action of the points. 

Removing the rocking points unit

Threaded trunnion that accepts diaphragm rod

The books describe the action of the lower points as "throwing over" or "wiping" ... neither of which is very helpful... its simply a spring loaded pivot that tends to flick suddenly from one position to another- I guess that's the "throwing over"? However there is no  side-wise movement involved so I don't see why its described as "wiping"... ?

If you wish to go further, the pump base can also be dismantled for servicing. However, this is another case of bad pricing or poor economics. A rebuild kit (including valves and diaphragms, washers points etc.) will cost around £45. Of course you have to fit it, and get the thing back together with the confidence that it will still work and not leak! A new pump is only £75 so to my mind this isn't enough of a saving to make complete rebuilds an attractive route. The points however are the item most likely to wear and you can pick these up (Part no AUB6106) for around £15 so this is worth doing provided the rest of the pump is OK. I will therefore check  and clean the rest of the pump before I order the new points.

Pump base

The pump base carries two covers: a smoothly domed cover over a cork washer that forms a fuel space, and a square belled cover with a diaphragm beneath that acts as an air trap. Removing the smooth metal cover (RHS) exposes the cork washer underneath

Unscrewing the cover centre bolt

Cork washer

 Inside the fuel cavity the pump was remarkably clean! Very satisfying but probably indicating the base doesn't need a service.

I reassembled the cover and then removed the 4 screws that hold the air bottle cover onto the base.

Air bottle cover

Unscrew

 This reveals the blueish diaphragm beneath- I'm not sure why this is there but probably just as an airtight seal. Again this and the sealing rings around it looked clean and in good condition, so I reassembled.

 The valves are retained in the base by a cover plate secured with two Phillips screws.

Valve cover retaining plate

 When the plate comes off the valve covers can also be lifted off.

Valve covers

 ... and this reveals the valves beneath. Again these were very clean and blowing/sucking through the ports showed that they were both functional. Its not clear how the valves are removed because there is no access to the rear to tap them out- I suspect you just pull them up, but this will probably damage them and since they are both clean and functional I think I will leave them as is. I didnt remove the gasket and as it looks  undamaged and I am expecting it still to seal.

Cover removed, valve exposed.

Second valve- again clean and functional.

Replacing the points

Reassembly was pretty much as they say the reversal of dismantling.

Assemble the new points to the pedestal using the special pin

Lower points in position

Screw pedestal to solenoid unit with the two cheese headed screws- Thackery washer, earth wire and green wire under the 9 O clock screw, thackery alone under the 3 O'clock.

Assemble the terminal post contacts as from the bottom- red wire, Thackery washer, nut insulating washer

Fit the spring and screw in the diaphragm; mating the thread with that in the trunnion of the moving points. This is by far the hardest part of the rebuild. I used a rod to line up the trunnion hole before pushing the diaphragm rod in its place. Fiddly!

Having successfully inserted the diaphragm, (check that the blade contact not yet fitted) set it up by screwing it in until a point is reached where the contacts will no longer flick under gentle thumb pressure. Then back off by rotating anticlockwise for 4 screw holes and align with the next hole. 

Refit the blade contact and its associated wiring and check its in line and meets the moving points centrally. There is also a need to check the contact gaps.... I alluded above to this being very hit-or-miss! 

SU specify two gaps- The first when the points are closed (lower points raised), the lower arm should be 60-70 thou above the pump body. There is in fact no way of adjusting this distance so I'm not sure why its specified. However my new points came with a spacer that prevents the lower arm from getting too low anyway.

Spacer arm in  lower points  raised position

Spacer action when lower points are lowered.

Spacer ensures lower pivot arm must clear the pump body.

The second gap specified is that when the points are open (i.e. lower points lowered) then the gap between upper and lower points should be about 30 thou. This can be adjusted by bending the wishbone/blade contact up or down... but it can't be easily measured! Point-to-point contact occurs inside a small plastic frame and this blocks the use of any feeler gauge to check separation when the points are open. Slipping a feeler in simply alters the gap anyway! You might be able to check it with a dial gauge perhaps?? I just do the best I can and its going to be in the right ballpark- but not sure how close!

Insert the nylon spacer/rollers above the diaphragm and fit the bottom section to the solenoid section with the screws. I reused the gasket but a new one would be a good idea.

Finally, make sure the wires are folded out of the way and fit the plastic cap. Add the shake-proof washer, terminal, plain washer and brass nut. Tape the cap to the body of the pump with nice new SU tape if you have any!

Test the pump by hooking it up to a battery to make sure everything has gone back together correctly. In my case the pump sprang smoothly to life with suction and output from the right holes!