SU Pump rebuilding

Saloons
1

Looking for some info on rebuilding SU fuel pumps. I have three dead AZX1308EN (electronic) pumps.

Two were in the car with 2,500 miles and one was NIB but sitting in the attic for the last few years.
Last year, the pumps worked fine. I went to wake up the Mark X and not even a tick. I thought it was bad gas plugging them up. I pulled one out and it was clean.

I put power to it and I can hear a slight buzz but no movement of the diaphragm. I pulled it apart and the only thing wrong was a crack in the cork disk washer.

The diaphragm seems a little stiff. I tried to get it out but cannot figure out how to detach the rod from the motor. It looks like there is an Allen screw possibly holding it in but I feel as I’m going to break my little wrench trying to get it lose.

I pulled the new one out of the attic and it was just as useless.

Anyone have any instructions on rebuilding the electronic version of the SU fuel pump? Any hints why the two pumps died at the same time?

Thanks,
Micah

2

The electronic SU pumps are one ground only. A google search tells me that AZX1308EN is a negative ground pump. Therefore, connecting it to positive ground will kill it immediately.

To remove the diaphragm from the throw-over points, you simply unscrew the entire shaft from the points. You don’t remove the flexible diaphragm from the shaft. You buy a new shaft and diaphragm together. There are long and short shaft versions, so get the right one.

You can probably jumper past the electronics and just run power to the points directly just to see if it will vibrate. It won’t last long that way before the points burn up.

There is a scheme for making your own electronic version out of parts from Radio Shack or Frye’s Electronics. I have done about 12 of them. This was before the major vendors picked up on the idea. Search the XK forum for “Transistorized SU fuel pump” and my name.

3

Rob,
Thanks for the reply.

Car is negative ground and pumps were working fine for the last nine years.

One NIB is DOA also.

This pump does not have points, electronic version.

The diaphragms do not appear to unscrew like the points version of the pump.

I did the YouTube search but cannot find any rebuild videos for the electronic version.

Micah

4

Ah, ok I have only rebuilt old 1950’s pumps, not kept up on the latest improvements. How about posting a picture or two?

5

My only experience is with the mechanical points versions of these pumps. But from my experience with these type pumps on multiple British cars they can be quite “fiddly”. Rarely have I found problems with the diaphragms and the issue in my experience is usually with the points and the throw over mechanism. I would first clean the points with some emery cloth then try the pump dry with some current from a spare battery. Sitting around unused can cause them to refuse to work. When replacing the points and throw over mechanism the distance the trunion is screwed into the shaft connected to the diaphragm is very critical. There are instructions in the various WSMs but I find trial and error seems to work best to get it correct so the pump will continue to tick vigorously when tested dry for a few seconds. Once set correctly they seem to work well for a considerable length of time.

John Quilter
Eugene, Oregon

6

Thanks guys, but no points to deal with.

This is what is inside the new electronic pumps:
http://sucarb.co.uk/su-fuel-pumps-spares/electronic-conversion-kits/electronic-pump-conversion-kit-negative-earth-12-v.html

Micah

7

Hi Micah, can I ask a dumb question? Are you testing them in the car or on the bench? Seems odd to have three failed pumps! I have three pumps for our XJ6 - they tend to fail singularly - part of the beauty of two tanks. Having said that I did find this on another forum:
The electronic circuit in the all electronic pumps uses a Hall effect device (just like the Pertronics ignition system) to turn the current through the coil off at the top of the diaphragm stroke. The Hall effect mask is used to shade the Hall device from the magnet in order to keep it from shutting off prematurely. The mask is movable to adjust for optimum running speed - if it is adjusted too far in, the magnet carrier will hit the mask and the magnet will not release from the mask, stopping the pump dead in its track. 99% of the all electronic pumps that are dead on arrival are the result of that Hall mask being misadjusted or it was not tightened down securely after the adjustment was made at the factory (QA at Burlen was not as it should have been for awhile).
This might help with the NIB one, perhaps, Paul

8

Neither would operate in the vehicle. No electrical issues with the car. Both worked perfectly fine the last time I used the car, a little over a year ago. Pumps installed in 2007 but only 2,500 miles on them.

I pulled and partially disassembled one.

One still in the car.

One was new in box but in the attic for years. Originally, it was dead from new and was supposedly repaired by Burlen Fuel systems. I never tested it after I got it back from them.

Micah

9

Micah sorry I can not add anything–I never use them or electronic ignition for this very reason. Were they points I would suggest a whack with a hammer with the ign on–that almost always works. Best of luck but a new pump(s) are in your future. BTW isn’t your car an early one that had in tank pumps? Might be time to go back to them if that is true.

10

I am interested. By Paul’s description I understand the Hall effect, and I looked at the Burlen’s picture, but I would like to see what’s on the other side of the circuit board. I searched the web but did not find one.
Can you post a picture of it?

11

George,
Original pumps are made of unobtainium. I think there is a retro for E-types but not the 10. This is the exact set up used on later cars. Worked fine until recently.

Spoke with this shop regarding the issue. They think the diaphragms have hardened because of the modern fuel. He told me how to get them out. There is an Allen screw. Mine is just stuck and hopefully I can get it out. Then I will look at some new parts and will hopefully get them working again.

Micah

12

There is an alternative way to transistorize the SU pumps. This keeps the original points arrangement but adds some electronics to take the electrical load off the points. I’ve done a few. The plus is that the points will never need dressing, the downside is that the point mechanism will eventually wear out at the pivots.

Not much help to people like @Micah_Wellman who have a pointless Hall effect pump, but an easy enough mod to do while rebuilding an existing pump.

Here is a search to find the onsite posts:
https://forums.jag-lovers.com/search?q=transistorized%20fuel%20pump

13

Hi Rob, I could no find a reverse picture either. Our pumps are all points type - so I can’t offer any real assistance. Note that if the diaphragms are stiffened then a buzz (as noted) might be what presents with no proper reciprocating movement possible. Paul

14

Hi friends,

what about the very reliable Hardi-pumps ?

best regards
Lindi

15

I took out my propane torch and heated up the retainer that the diaphragm screws into, This broke free the lock tight. I was able to then remove the Allen screw and then unscrew the diaphragm.

It was stiff and cracked once out. I will order new ones and necessary gaskets for all three pumps. Hopefully, this will get them working again.

Thanks,
Micah

16

So, I got my pumps working again.

I contacted Mark, sufuelpumps@aol.com, at https://www.sufuelpump.com. He makes and sells SU parts from his shop in the San Francisco area.

Apparently, the original pump diaphragms don’t handle the alcohol mixed fuel sold in some places in the US. One of mine was so hard that it cracked. This is a 10 year old pump with 3,000 miles on it.

Mark got me new diaphragms but it took two tries since SU apparently likes to change things for no reason. The diaphragms, along with other seals, he makes up with new material that is supposed to be more resistant.

Disassembly and re-assembly was pretty easy. I had to use a torch on one to break the Loctite free. The other didn’t have it. I just took some pictures before I pulled them apart.

I had left some gas in the left tank. It went bad and plugged up the original SU pump that were still in the tank. I had to pull it, clean it and clean the tank. In the process I snapped one of the nylon fuel lines. This turned into a PIA in that it is no longer made in the correct size. Its too big. I ended up getting new hose, heating it and then tightening up a hose clamp to get a seal. It would be nice if they would still make the correct line.

The right pump went together with no problems. The gas in the tank did not get nasty like the left side. I have pump in but have not tested it yet.

So, to get ready for a show, I ended up redoing my manifolds, rebuilding two fuel pumps, replacing the steering box and having it aligned. She handles great and no longer bleeds puddles of fluid in the driveway.

I just need to swap out my large tube half shafts for the smaller solid ones. I’ll save that one for next year.

Only bad thing was losing one of my wrenches into the wheel well. Its gone. I tried everything to get it back. No rattle so far.

Micah