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MG MGA - SU fuel pump woes

Hi All!. I have a problem with the fuel pump on my MGA. The car is pos. ground and the fuel pump does not work. Pump is an SU AZX1331 put in by PO. I think it is a neg. grd pump. Is the pump "pooched"? The pump is new but does not work. I tried hooking it directly to neg ground and pos. to the contact....still no go.

Anyone familiar with these pumps, that can give me a little direction?

Thanks
C.R. Tyrell

I have replaced the fuel pumps in both of my MGA's. They were a new type (HP) and I have been told that the armature windings are now breaking down. One of the replacements is an SU (from an MGB) and the other is a Fuelflo (which I have also fitted to other MG's that I have). Both are perfectly satisfactory after many years of service.
Barry Bahnisch

Can't speak for the Fuel Flow pumps, but the SU pump armature coils are fine. CR - I suspect that the points in your pump are probably in need of cleaning. E-mail me at SUfuelpumps@donobi.net and I'll send you a procedure for getting the points completely clean (dragging sand paper through doesn't get the lower contacts very clean). When you take the end cover off, if there is a black cylindrical device with a red and black lead coming out one end. If the red lead goes to the power terminal, the pump is a negative ground unit and the black device is probably burned out, which in turn causes the points to burn prematurely. See the Article, SU Fuel Pump Services in the SU Fuel Pump Articles section of my web site at: http://homepages.donobi.net/sufuelpumps/ Cheers - Dave
Daved DuBois

Dave may well be right but I had my 1600 roadster in the UK and took it to a fuel pump "expert" and he (at Barnstaple, but was Irish) dismantled it and then went home! I went to a supermarket and bought a plastic fuel container and some plastic hose and proceeded to drive to Staffordshire with the container held on to the flat panel above the dashboard with an octopus strap, my wife judging the contents by the light of oncoming cars! We made it to Kings Bromley but not before our friend (the late Cyril Mellor, a vintage MG enthusiast) went looking for us! After that I fitted a Fuelflo.
Barry Bahnisch

The more I read about "SU fuel pump woes" the more I think there are two main contributing factors: 1. Cars are used much less than they used to be and the pumps do not adapt well to infrequent use; 2. Rebuilds by insufficiently skilled operatives (Let's say it's that DPO again!).

The pump on my 1600 Mk2 is working fine in spite of spells of idleness in the garage and I thank my lucky stars every time I turn the key and hear that reassuring tick-tick. However, the new solid-state pump installed in my Z Magnette caused me endless problems. Some of it was self-inflicted because of a faulty alternator that burned out the circuit board. Nonetheless, I concluded, after stripping the pump down and rebuilding it with new (expensive) solid-state parts, that for the pump to be reliable, the set-up of the diaphragm tension and the "throw-over" had to be very precise and maybe I wasn't that skilled. When the pump started to play up again, I decided that life was too short and fitted two Facet cubes in parallel, with a switch that allows me to swap them over in service. That way they both get regular use, but there's always a back up that can be switched in immediately. Belt & braces? Maybe but I get no more fuel pump problems.

If you want to stick to the SU pump, then tap into the wisdom on Dave's website, rebuild it very carefully and test it before you rely on it.

Malcolm
Malcolm Eades

I changed the pump to a spare that I had on the shelf that was waiting for service. I cleaned the points on that one and coaxed it to life. The "new" pump is electronic....so I am guessing no points, and no worky. It has a white thing with a small coil in the middle on the circuit board. I just can't tell if anything is burned out. No sign of a capacitor, or diode.

I will try and post a picture later.
C.R. Tyrell

Well thanks to Dave DuBois I have been able to determine that my fuel pump circuit board is "toast". My spare pump worked, but I was not able to adjust the throw as i have one seized bolt in the housing. ( currently soaking in AeroKroil). I "bodged together" my spare facet pump that I had as a back-up for my TD. Now I have fuel and car runs really well!

I will replace the facet with the SU points type and all will be well in the world... til next time!

Thanks again!!!!
C.R. Tyrell

Colin - If you want to send the all electronic pump to me, I may be able to fix it for you - there are only two components that could be causing it to malfunction and I have both on hand. Cheers - Dave
Daved DuBois

Dave, thanks for the kind offer. Currently trying to get a replacement credit. If I can't I will get in-touch. I am presuming that that the Halofect transistor is faulty. Are replacement circuit boards available for these pumps?
C.R. Tyrell

"Are replacement circuit boards available for these pumps?"

The only way to get a replacement board is to purchase the modification kit, which is rather expensive. Cheers - Dave
Daved DuBois

This thread was discussed between 13/10/2012 and 18/10/2012

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