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MG MGB Technical - Fuel Pump servicing

1978 mgb roadster

Changed all the fuel hoses; rebuilt the carbs; new fuel filter.
Changed the distributor, coil, leads.

The only old component I've not changed in the ignition and fuel system is the fuel pump.

Is it worth changing the points on the existing pump or carry a cheap spare electronic unit (£23)in case of failure?

I know the pumps are generally reliable and I could probably get a failure of some of the new items I have fitted but feel I would like to do something to the pump to hopefully prolong its reliability.

Is there a guide for the overhaul of the fuel pump available?

Thanks for any advice

Adrian
AdrianS

Adrian. Google "David DuBois MGB Fuel Pumps". Dave has a tech article on adding an extra, in line fuel pump. I installed one on my 79 B and recommend it highly. If the SU pump goes out, all you have to do is throw a switch and the back up fuel pump comes on line. Great system.

Les
Les Bengtson

Adrian - e-mail me at SUfuelpumps@donobi.net regarding your fuel pump. Cheers - Dave
D W DuBois

Mine played up after 12+ years(but got me home!) so I used the "spare off the shelf" and rebuilt the one off the car. Burlen do a kit (?£50) but add a new diaphragm. Dave's excellent site plus Burlen's Tech pages give you step by step instructions.

I can see the attraction of adding an extra fuel pump, but given that these pumps tend to give you notice of imminent failure and last for 10 years, I decided against it. Be aware that pump left on the shelf will need the points "wiping" before fitting.
Michael Beswick

Go for the new set of points. It's cheaper and SU fuel pumps will run happily for a decade at least once set up properly. (correct adjustment is critical, but it is simple and outlined in the manual).

However, the points will erode over time and need attention, just like the points in the distributor do (would you ignore them for years on end?). We recommend to our customers that they get the points checked with every major service (that's 2-4 years, depending on mileage). It's not a big job and that way pump reliability is never an issue.

We have been using bi-directional diodes for very effective spark suppression. They present a short circuit to anything over the nominated voltage (we use about 25V) and open circuit to anything below - both in either direction. So the maximum back voltage the pumps ever see is 25V, which doesn't spark significantly at all, reducing the erosion rate substantially.

SU pumps are thier own worst enemy. When the points get old and tired, instead of simple stopping as the distributor ones do, the respond to a hit on the pump and carry on for a bit longer. Having thus "fixed" the pump, the owner then forgets to do the job properly - until the next time the points peg out. Owner then mutters about unreliable pumps, whereas its the unreliable owner that only has himself to blame. If the points had been replaced when they first faltered the problem would have gone away completely for another decade or more.

As for electronic pumps - they aren't completely trouble free either, I have seen the tricky bits burn out.

Paul Walbran

Burlen's description and procedure starts here http://sucarb.co.uk/technical-electrical-fuel-pumps, but when rebuilding one earlier this year I found some oddities and inconsistencies in the order of doing things. My rebuild is here http://www.mgb-stuff.org.uk/pumpr.htm
Paul Hunt

Adrian,
why carry a cheap spare of anything, why not fit a good quality part/component or do your repair properly and then test it works by using the car and then forget about it

are you also carrying spare dissy, coil and HT lead set, where does it end, spare pump, starter motor, alternator, engine!

I personally wouldn't fart about fiddling with points in a pump or have a pump with points in it but I know others enjoy fiddling with such things but I like fit and forget
Nigel Atkins

"the pumps are generally reliable" but the motors are not which is why SU invented a twin-headed pump for Rolls (which are generally reliable).

Best not to spoil a ship for a happorth of tar. Follow Adrian's advice and throw the pump out together with Alternator, starter motor and cooling hoses. You can then budget on a reliable car for six or seven years. R
Roger W

Roger, as a seller of such components I like your style :-)
Paul Walbran

""the pumps are generally reliable" but the motors are not which is why SU invented a twin-headed pump for Rolls (which are generally reliable)."

I have to disagree with this statement. The double ended pumps were designed for high capacity (or in some cases for a reserve of fuel, such as used on the Range Rovers) rather than greater reliability. In fact, with one end used only as a reserve, it would decrease reliability of that end since disuse of that end would result in the points filming over, thus not pumping when needed. Cheers - Dave
D W DuBois

I've had a points pumps fail once in my ownership on a car that had been 'previously owned', but never twice in my ownership despite a combined duration of 45 years and 150k. I have, however, had an electronic pump fail several times in the space of a few months that stranded me until it decided to start working again - binned. Pointless indeed.
Paul Hunt

The life of the SU points pump is variable; it makes sense to change them before they fail. More than 45 years on and four or five failures, I have given them six or seven years until my last which wouldn't work until I cleaned the points and then wouldn't pump at any sensible pressure. We all have to learn from our own experience, our three cars now use Ecco contactless.
R
Roger W

Ecco/Moprod was the one I binned :o)
Paul Hunt

We keep expecting these pumps to last forever. I'm sure that SU never dreamed that most of their fuel pumps would still be in service decades after the vehicles that they were installed in left the factory. The same applies to Lucas switches. Almost all of the electrical components on my '67B are original and still working perfectly. I replaced the original fuel pump in my B after twenty five years of trouble free service merely because Moss was having a sale on fuel pumps at the time and I figured that it was a good time to replace an item that was in constant use for a quarter of a century. The replacement points style pump lasted for ten years before giving me some problems, so I replaced it with the transistorized version in'02 shortly after installing a supercharger system. I've suffered no problems with it at all. RAY
rjm RAY

The SU pumps can be easily serviced and don't need to be thrown away on a regular basis. Changing the points is easy once the pump is out of the car, and the points are cheap. If you buy a new one I would also recommend moving to the electronic variety, which I have had for about ten years and have never had a problem with it.

Somewhere I have a spare kit to modify a standard pump from points to electronics, so if anyone wants to give it a go....
dominic clancy

"The same applies to Lucas switches"

When I restored my roadster 25 years ago I replaced all the switches as the logos were showing some wear. Some years later the 'new' headlight switch started playing up, and by then the logo on that was also showing wear as the engraving was nowhere near as deep as the original. I had kept the original (of course) and refitted that as wear-wise it was not really any different to the other switches, and it continues to function (so far!) perfectly.
Paul Hunt

So going back to my original question, it looks like its new points!
AdrianS

Personally I'd go for a rebuild kit as the other bits are old too! If you are just doing the points, You may be able to just polish them up, so then you'd get away with no cost! Might be worth a look before ordering anything.
Michael Beswick

Dominic,
I've upgraded one to electronics easy, peasy!

If you kit is going spare and incredible value (ie cheap ;)) I'll have room for another one soon.

email me pls.

Best of.....

MGmike
M McAndrew

If you do just replace the points as well as adjusting the two fingers to set the upper contact lift and the contact opening you will need to check the diaphragm 'throw'. This entails separating the solenoid and pump halves and carefully freeing the diaphragm from both so that it is free to turn relative to the solenoid.
Paul Hunt

90% plus of the pumps we service require only the points to be done. Why replace components which are in perfect working order? If they are doubtful, the certainly do so. If the diaphragm is sound and flexible it will be fine. Also check the valves are intact.

Paul's point about adjusting the diaphragm is critical, failure to do so is the reason for most refreshed pumps being faulty. The process is described in the workshop manual - if you don't have one I have the instructions in PDF form email me at paulatmgpartsdotco.nz.

And we get a lot of customers wanting to revert to SU after trying Ecco.
Paul Walbran

Thanks Paul

Found a copy of the manual for the pump!
AdrianS

This thread was discussed between 06/10/2014 and 14/10/2014

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