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MG MGB Technical - Standby fuel pump

Because I am a worrier and see myself in the desert on the I-10 with a malfuncioning fuel pump I ask this question.
Do any of you run an aux. or standby fuel pump on your MGB? It looks like there is room to install one of the electronic units in the line under the hood ahead of the carbs. Will this cause a restriction that will starve the existing fuel system? Any thoughts about this?

John
John King

John - Check your e-mail, I just sent you some information on installing a backup fuel pump. While it is not a real good advertizement for a guy who restores SU fuel pumps, I installed a backup pump on our MGB (there is nothing like having to lay on the side of the road of a major interstate highway in the freezing cold with the wind blowing 90mph trying to swap out a pump that stopped pumping to convince that a preinstalled backup pump was a really GREAT idea). Good luck - Dave
David DuBois

John,
Are you using an SU pump? If so, the biggest favor you can do yourself if you are worried about it is to install one that has a record for NOT forcing you to lie on your back in some Godforsaken place. By all means carry all of the spares that you feel necessary, but if a stronger link in the chain is available, why not use it instead of carrying a spare weak link? I've been in, under and around MGs for a lot of years and I see the Great SU Fuel Pump Struggle as our hobby's equivalent of continually hitting one's thumb with a hammer yet reusing to move it.
Cheers,
David
David

John,
Are you using an SU pump? If so, the biggest favor you can do yourself if you are worried about it is to install one that has a record for NOT forcing you to lie on your back in some Godforsaken place. By all means carry all of the spares that you feel necessary, but if a stronger link in the chain is available, why not use it instead of carrying a spare weak link? I've been in, under and around MGs for a lot of years and I see the Great SU Fuel Pump Struggle as our hobby's equivalent of continually hitting one's thumb with a hammer yet refusing to move it.
Cheers,
David
David

Some of the folks in our club, who have less than reliable cars, have fitted those noisy little square things as a backup pump. Kind of a belt and suspenders (braces-- for those on the eastern side of the Atlantic) approach, if you ask me. It's not altogether impossible to have a reliable fuel pump, although it may (or may not) be an SU. If you're a total, rivet counting, originality type, adding a second pump would not be an option, if you're not, why cling to a more than half century old technology. There are lots of reliable modern pumps out there. Just mind the fuel pressure and use a reg if necessary. An additional alternative is to give the SU pump regular maintenance, just like the oil, points, coolant and all those other things we're always cleaning, lubing, changing or checking. It's reliability goes way up with a little attention.
R. L Carleen

I've been running a solid-state pump in my GT for over
10 years. I have one in my roadster as well. It fits fine where the SU did, you may want to put 90 degree elbows on it. I see Moss is now selling it as an 'emergency fuel pump'. But it is a reliable pump and puts out 30 GPH for our cars and really QUIET too.
Made by (imported) Walbro, make sure you specify the one for Imported cars.
JC Whitney, part number 74JE9423W, at least from my old catalog. I bought a spare to carry in the boot as well. E-Z installation. Nobody sees it but you unless you are a stickler for originality.
Samuel Sullivan

The points based SU pump can be pretty reliable. The factory one ran fine for me for 29 years with one disassembly to clean the points after it sat unused for about 17 years. 6 more years then one of the check valves gave out so I replaced it with another SU that has worked perfect for the last 5 years or so (daily driver).

Maybe it's the local weather or something that makes a difference?
Mike Polan

I suspect that if anybody having problems with their SU fuel pump, were to buy a new SU pump, they would find that it would last every bit as long as the Facet, Walbro or the Japanese pumps that others have found to be so reliable when they are purchased new. Let's face it, whe one purchases an MG they are buying a car that is at a minimum, 24 years old and so are all the components in it. When electro-mechanical parts get to be that old, they start to fail regardless of who makes them. I have owned 2 Mazda trucks over the years, both of them used before I purchased them. The first one had a Japanese clone of the SU fuel pump and it failed at close to the 100,000 mile mark. The next truck had a Facet pump in it and it failed at about the same milage. Of all the SU fuel pumps sent to me, very few have been anywhere near what one would consider new, some of them looked to have arrived on these shores on the Mayflower and it still worked after a fashon, just not well. It is my feeling that the SU fuel pumps, when purchased new will hold up just as well as any other pump on the market that is purchased new. My 2 cents worth - Dave
David DuBois

Back in the olden days, I bought a nearly new '64 B. By 1970, the fuel pump had started being recalcitrant, and needed a tap every now and then to remind it of it's function. That's when I learned that a bit of point cleaning and general upkeep on things like electrical connections went a long way towards keeping me out from under the car on dark and generally damp nights--that's when they like to quit, when the environment makes it the hardest for them to do their job. SU's built today are probably a lot better, material wise, than they were forty years ago, but they still are not a "use it and forget it" component.
R. L Carleen

RL - The points, as we all know are the Achilles heel of the SU fuel pump (and all the other pulse type pumps that use points to drive them). Shortly after buying our 53 TD back in 74, I arrived home from work one evening to be met at the door by my wife whose first words were "FIX THAT DAMNED THING!" pointing at the TD (it was at that time her everyday car and is still her car of choice). It seem that the fuel pump had quit 13 times coming across town (a distance of about 6 miles) and she would dutifully get out and hit the thing to make it work for a few more blocks. That was the point where I started looking seriously at the pumps. Being a techno geek of that day, I saw that the point were burning and figured that a transistor would solve all the problems that ever beset the SU fuel pump. What I found out over the years, was that tungsten contacts develop a film on their surface that needs to be removed for the contacts to continue to function properly. When properly adjusted and in a pump where all the arc suppression circuits are working 100%, the points will self clean as they wipe across each other on closing and opening and by the small amount of arcing that still occurs when the points open. My transistor did a supper job of stopping the points from arcing by reducing the current through them to a fraction of what it normally was, to the point that there was no longer sufficient current density to burn the film off and the pump would stop working. Even with the wiping action, the build up of the film was sufficient to stop the pump after an extended period of time (looking at the contacts under magnification showed the film having been pushed to one side and piled up like snow in a driveway after the plows have come through (those of you in Florida will have to use your imagination here).

As I stated, a properly adjusted set of points and a working arc suppression circuit will keep the contacts working for many years on a car that is used daily. IF the car sits unused for long periods of time, the film will build up to the point that the contacts will not conduct. The points, over the years will start pitting from the arcing that does occur and in both cases will require manual cleaning with some kind of fine abrasive to keep them working correctly. I have also found that the replacement obtained from Moss and Victoria British are ones made by Intermotor and appear to use a different alloy of tungsten. These points seem to build up the film at a much greater rate that the original points do, which just exaggerates the problem.

One further item, if the pump quits, we all know that it is usually possible to get it going with some taps from a screwdriver handle. I would like to say that if the pump doesn't start running after 4 or 5 taps with the screwdriver handle, then it is not going to start by beating the living s--t out of it with a ball peen hammer. That only serves to make a mess out of the pump housing (and maybe releive some inner frustrations). I have gotten my share of pumps with hammer markes all over them and they are not pretty!
Cheers - Dave
David DuBois

This thread was discussed between 06/06/2004 and 07/06/2004

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