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MG Midget and Sprite Technical - Non working Fuel Pump

I guess this is a common one, but today I tried to start my Mk 3 1971 midget, on turning the key no ticking from the fuel pump. (Fully charged battery) I tried the usual clouts on the pump, still no clicking. No fuel at the carbs.
Whats the most reliable cure - clean/repair, new pump as origonal, update with a electronic version, get a more modern type or any other option?
100% reliability is what I am after - even on a 37 year old car!!

Colin
C Martin

get a fecet cube pump
it is noisy but it always works!
Onno Könemann

If you want "100%" reliability, replace with an SU "Solid state" pump - looks and does the same thing, but without the points.

Otherwise, it's a pretty straightforward job to remove the pump, dismantle and clean the points - which is what I reckon the problem is. Then you'll probably get many more years use (I carry a spare OE SU pump in the car)

But for complete peace of mind, replace with electronic.
Steve Clark

I put the "modern" Lucas type on my '72.
The fittment was easy and you get reliability, but dont have to give up the quaint ticking.
*Bonus* You'll still know when your out of petrol!
Phil
Phil

Just a thought - Is it definitely the pump that's failed? Probably worth checking for 12v at the pump before you replace it.

Ant
Ant Allen

Ant- that thought occured to me late yesterday just in time to stop me ordering a new pump!
I will further investigate may be this weekend.
My thoughts at the moment, assuming the pump is non working, is to replace with a facet cube but also renovate the existing SU to keep as a handy spare and to enable me to revert to origonal should I feel the need.
Thanks for all advice, many heads always better than ones own in isolation.
C Martin

Ant- that thought occured to me late yesterday just in time to stop me ordering a new pump!
I will further investigate may be this weekend.
My thoughts at the moment, assuming the pump is non working, is to replace with a facet cube but also renovate the existing SU to keep as a handy spare and to enable me to revert to origonal should I feel the need.
Thanks for all advice, many heads always better than ones own in isolation.
Colin
C Martin

Here's a really good video on rebuilding the original pump, one of many posted on YouTube by John Twist of University Motors in Michigan:

http://www.youtube.com/watch?v=_VGQPg15-8E&feature=channel_page

-:G:-
Gryf Ketcherside

Collin - If you get one of the little, square run all the time make a lot of noise and build your SU pump, reinstall the SU and use the Facet pump as a backup. A points style SU pump carried in the trunk as a spare won't work when the time comes to press it into service. The points in a SU pump film over in a relatively short period of time and unless it is used on a regular basis to burn the film off, it will build up to where the contacts will no longer conduct current. The Facet pump is electronic and doesn't use points so it can sit unused for years without any ill effects. See the article, Backup Fuel Pump in the SU Fuel Pump section of my web site at: http://homepages.donobi.net/sufuelpumps/ for information on how to install the Facet pump as a permanently installed backup pump such that it can be switched in when needed. While at my web site, also see the article, Fuel Delivery Troubleshooting Guide for help in determining where your present problem is. Cheers - Dave
David DuBois

Great vid; this is one job I've never done!

A
Anthony Cutler

Fitting both pumps with a changeover facility appeals to me, and will be done. Perhaps using alternate pumps on a reqular basis, especially during periods of infrequent use will keep both happy and give the reliability I desire.

Colin
C Martin

If its been standing or in a damp environment the chances are the contacts in the pump have oxidised and just need a clean up with wet and dry
mike storey

Mine used to need the occasional clout with a wooden bar... then it would rattle away to its heart's content... make sure you clout the body of the pump, and not the fuel connections...

A
Anthony Cutler

I've got one of the Facet cube pumps on my aeroplane. It is somewhat comforting to hear it clattering away. When you run out of fuel (no quantity gauge except a stopwatch) it hammers loudly, like a 1500 bottom end without oil, just to let you know you're about to land whether you like it or not.

One moving part, so I'm told. It also has the useful feature of an ability to allow flow in the normal direction via gravity in the event that it did fail. This means that you can wire/plumb it in after the standard SU pump. Some run at higher output pressure. 1.5 to 2.5 psi is fine for us.
rob multi-sheds thomas

<<I've got one of the Facet cube pumps on my aeroplane>>

errr, just the one Rob? You'd think Boeing would have fitted a second one to the 757 just as a basic safety precaution, wouldn't you?
Steve Clark

Wrong aircraft. This one is more reliable than the 757.


rob multi-sheds thomas

"It also has the useful feature of an ability to allow flow in the normal direction via gravity in the event that it did fail. This means that you can wire/plumb it in after the standard SU pump."

The SU fuel pump (and all other impulse type pumps) work the same, with just check valves to insure that the fuel only goes in one directions, so the backup pump can be installed on either side of the primary pump and it will work equally well. Cheers - Dave
David DuBois

I've never worked out the difference between the Minor and Midget pumps. One is a 'sucker' and the other is a 'pusher'. Anyone know what the mechanical difference is?

You need a minimum of 16 inches head of pressure to overcome the valve on the Facet Cube pump. Since the tank is below the carbs on the midget you cannot use gravity feed for 2 reasons. My tank is about 30 inches above the carb (Stromberg CD150) so it will work even if the pump is dead.
rob multi-sheds thomas

"One is a 'sucker' and the other is a 'pusher'. Anyone know what the mechanical difference is?"

That distinction is bogus. Both the low pressure SU fuel pump used on the Morris Minor and the high pressure SU pump used on the Midget are mechanically the same the only real difference is the volute spring that determines the output pressure. While the high pressure pump has a higher output pressure, it also has a higher inlet vacuum than the low pressure pump, so to call one a pusher and the other a sucker is a misnomer. See the article, SU Fuel Pump Facts and Myths in the SU Fuel Pump Articles section of my web site at http://homepages.donobi.net/sufuelpumps/
Cheers - Dave
David DuBois

I think I have found the cause of my non working pump - points shot to bits and no condenser in place. I shall fit the Facet next week and then decide whether to overhaul the SU or fit another Facet, the costs of either don't seem a lot different.
Colin
C Martin

This thread was discussed between 22/02/2009 and 01/03/2009

MG Midget and Sprite Technical index

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