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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Inline spare fuel pump.

I recall seeing a diagram of a fuel system using two fuel pumps in series with a switch that will allow only one pump to be on at a time. It requires the rear fuel pump to pump thru the front pump or the front pump to take suction thru the rear fuel pump. Has anyone used this system of spare fuel pumps? The advantage is of course that your spare fuel pump is already hooked up and ready to go.

John
John Progess

John

I fail to see the advantage of putting this system in series. Surely, if you want to go down this route of back-up systems you would have them in parallel so that one pump can by-pass the other. With your system, what if one of the pumps fails because of a blockage? What can the other do?

Steve
Steve Gyles

I use this system and have the standard SU pump in the normal position and an electronic facet under the bonnet. When the SU fails, as it usually does then the Facet simply pulls fuel through it and my car stops for as long as it takes me to flick the switch.
Bob (robert)

John. What you have seen is an idea of Dave Dubois, a very experienced SU fuel pump rebuilder. He has been kind enought to do a couple of tech articles for my website, www.custompistols.com/ and, if you go to the MG section, then articles, you can both read his articles and contact him through his hotlinked e-mail address.

Bob, I have had two failures of SU fuel pumps over a 35 year period. That compares quite favorably with any other fuel pump I have ever used.

Steve. Depending on where the blockage is, even splitting the fuel lines as they come off the tank might not be enough. But, Dave has a good head on his shoulders and has put a lot of thought into his dual pump design. The set up might not be perfect, but what is? Based on a very long period of testing, working with fuel pumps, designing the equipment to test his rebuilds, etc., he has come up with a system that works very well most of the time. The few times it might not work well are those rare instances which can always happen. The use of two in line pumps would reduce the number of hoses involved, themselves one item of upkeep which is often neglected. If you can come up with a better system, diagram it out and write it up. I will post it on my website, if you are agreeable, and see if Dave is willing to post his version. That would allow people a couple of alternatives.

Les
Les Bengtson

Yes OK Les I have messed with my original pump a number of times and thought that will not fail again but after a couple of weeks it does.
If only David lived in the UK I would give him my pump so he could make it work for ever. Please move to the UK David so you can fix my pump.
Bob (robert)

Bob. How old is your fuel pump? One of the two failures I had was with a brand new SU pump, installed about a year ago and lasted less than two weeks. I also bought a new "Made in England" radiator for my 68 BGT which lasted four years. I replaced it with a used, original, radiator which has done fine since then. I am not sure that the modern parts are of the same quality as the original parts. Certainly, many of the parts (very few) still made in the US are not of the quality of the ones made 20+ years ago. The radiator in my Ford Bronco lasted 20 years, then, needed replacement. The replacement lasted five years and had to be replaced again. I wonder how many of the problems we see are the result of an overall decline in quality, among the first world nations, when faced with competition from the third world nations?

For myself, I would be willing to pay twice the price for something that would mimic the quality of the OEM parts.

Les
Les Bengtson

Les

It is something I had not even thought twice about until last night. First Glen with his failed Facet pump and now John with his question. I put a Facet pump in my rebuild in 1997 on the advice of a local MG racer and I have never had a hint of a problem since. It just struck me strange to put 2 potentially dodgy items in series. To me it seems sensible to keep items apart that are likely to fail - it's called risk mitigation.

Steve
Steve Gyles

Steve. I am, by training a Sociologist, not an engineer. One British joke, from many years ago told about a fellow who, upon vetting, had his security clearance turned down because he was a socialist. He complained to the Higher Authority who appologised. It seems that the investigating agency had used a number of older, retired spooks to do their background and their handwriting was somewhat difficult to read. The granting agency had mis-read "Socialist" for "Sociologist". The security clearance was immediately granted after the misunderstanding was cleared up.

Dave's premise, as I understand it, is that both the SU and the Fawcet type pumps can be "pumped through". Thus, when the SU is the primary pump, with the Fawcet type plumbed in ahead of it, the SU will pump straight through without restriction. If, however, the SU should fail, the switch is switched over to the Fawcet pump and the in-line SU pump will not affect its operation. Once again, the best thing to do is contact Dave for the complete, and, perhaps, most accurate information. I will e-mail him about posting this design so that it will be available.

Les (Who got his Top Secret/SIOP security clearance inspite of being a Sociologist--but, there was a war on then.)
Les Bengtson

John, see this month's issue of MGA! magazine. On page 20 is an exact diagram of what you are referring to by Tom Ball who does restorations of the pumps in question.

Clayton
C. Merchant

John - You have mail.

Steve - You can plumb the back up pump in parallel if it makes you fee better, but you are just adding unnecessary complexity to the system. All of the fuel pumps that can be used to replace the standard SU fuel pump (there are a large number of them) use check valves and in some cases a bypass valve (to set the output pressure). The use of check valves, means that fuel will flow through them in the direction of inlet to outlet and any of the pumps will pump through any of the others. Further, the plumbing is much simpler with the pumps in series.

"It just struck me strange to put 2 potentially dodgy items in series. To me it seems sensible to keep items apart that are likely to fail - it's called risk mitigation." I would agree with this philosophy except for the fact that Glen's Facet pump has been in use for many years if I read his posting correctly. All of the pumps, regardless of make, are elsctomechanical animals and as such, have a finite life span. I have had Facet pumps fail in our Mazda pickup truck fail also - at 100,000+ miles. I expect that the SU pumps have a similar life span if they are in cars that are used on a regular basis (If the cars sit idle for long periods of time, the points develop a insulating film on the contacts and they fail prematurely). A new Facet or Carter pump, installed as a backup pump is an excellent choice as neither uses points in them, therefore there is nothing to burn or film over.

Bob (robert), England - My wife and I were over in England last summer. Too bad I didn't know at the time that you needed a rebuild, I could have brought my tools. If you can get some other people in need of SU fuel pump repair and can take up a collection to get us over there, we would be only too happy to come and spend time repairing fuel pump in your lovely country, we absolutely loved it over there.

Clayton - I suspect that, since Tom Ball and I have had a number of in depth conversations about fuel pump repair and spare fuel pumps, etc., that his installation may well have resulted from our conversations.

I will send my write up of a permanently installed back up fuel pump and the associated pictures to Les Bengtson to publish on his web site for all who wish to use the set up. In the meantime, below is a short story of how I came about installing a permanently installed back up fuel pump to give you all something to think about.

Backup Fuel Pump (the story)
Let me make the NAPA alternative look a bit more attractive. Consider the following scenario: You are traveling north on I5 and are just north of the Weed airport using airport transfers tunbridge wells (sounds remote, doesn't it? - it is). Weed is just about 50 miles south of the Oregon, California boarder. The temperature outside is low to mid 40s and there is a 45 - 50 mph wind blowing (as always). The *&@# pump quits!!! Oh well, there is a spare in the trunk, under the spare tire. Pull off on the shoulder as far as you can go without driving in the dirt, get out, unpack the trunk, remove the spare tire and get the spare pump. Jack the passenger side of the car up with the OEM jack, remove the right rear wheel and place it under the car in hopes that if the jack slips, the tire will keep the car from making you too flat as you work under the edge of the car in the blowing wind to remove the original pump, all the while hoping that some idiot doesn't come over on the shoulder and hit the car with you under it. Of course, you have not installed the shut off valve yet, so with the first fitting removed, you have gas running off your elbow as you watch the all important fiber washer drop to the ground and roll out of sight (the wife later finds it about a hundred yards in front of the car where the wind had finally deposited it). The spare pump is finally installed and all hooked up and your arm that was getting the bath in gas feels like someone lit the gas and you still have to replace the road wheel, and the spare tire and re-pack the trunk. You are finally back under way in about an hour and a half, feeling very fortunate that it wasn't raining (or worse, snowing as the altitude there is somewhere around 4000 ft.). Sound convincing? - Been there, done that - permanently installed the NAPA pump and the shut off valve shortly after getting home - NOT going to do that again!!!!
Cheers - Dave
David DuBois

Dave,
Thanks for the email and your senario is exactly why I asked the question. I have the square pumps installed on both my MGA's for a spare but not ready for use with the switch. I can imagine that the SU will fail at the exact worst moment in the worst of conditions and the thought of trying to connect the spare at night in the rain or snow does not sound appealing. Again thanks and have a good day!

John
John Progess

I surrender! Good arguments. I have learnt something out of this. I would also concede that I run 2 12 volt batteries, although I run them in parallel not series! Mind you, I only ever have one switched on at a time. Just occasionally in mid winter I will switch both on for first start of the day but isolate one as soon as the engine fires.

I was asked on this forum why I carried the two. Quite simply, I had a spare in the garage and I thought it better to keep it in a place where it could be readily used - on the car.

Steve
Steve Gyles

I am installing two fuel pumps plumbed in series, just as described in Tom Ball's article in MGA! magazine
I have not found a switch so far, the ones I have looked at are plastic with too long a toggle, as I intend to install it behind the passenger seat (along with a spare sweatshirt, gloves and an umbrella) I want a more substantial single pole, double throw switch with off in the middle.
Any sugestions?
Joe.
mgajoe

Joe - Forget Radio Shack or even Home Depot or Lowes (if you even have them in Canada and go to your neasest electrical contractor supply house. Here in the US we have CED, Stussers and Platt electrical. Another place that would carry suitable switches would be HVAC supply houses. All of these places will carry suitable toggle switches for use with your fuel pumps.

Good idea with the batteries, particularly in colder climates. As long as you switch back and forth ont he batteries so one doesn't suffer from disuse to the point where the plates wind up sulfating (and this would be a more commn thing to happen with one battery consigned to the garage until needed) you are in business.
Cheers - Dave
David DuBois

Dave, What are your thoughts on the new SU pumps with electronic switching instead of points? And what about those dual bodied SU pumps that were used for racing I believe? Gary
gary starr

Gary - The Burlen Fuel Systems all electronic fuel pumps eliminate the points so there is not the problem associated withthe points filming over if the pump sit unused for a long period of time. The pump works well (I have one on our MGB that I put the all electronic kit into to see how well it works) and it has worked flawlesly for about three years of everyday driving. They are somewhat more fragile if a clog develops on the inlet side, causing the pump to stall in a current on condition. This is because the circuit board will burn when overheated (When in England last summer, I talked to the people at Burlen Fuel Systems about modifying the pump with some kind of an over temperature protection - nothing yet on that score). They also told me that if the internal swamping resistor in the coil burns out (which is another result of the clog on the inlet side of the pump and why I discourage a filter between the tank and the pump), it will cause the circuit to cease to function properly. So far, none of those things have hapened tothe pump I modified.

I also modify the pumps that I restore so that they are solid state, using a different triggering method than Burlen Fuel Systems and is not subject to the same problem as their's. My modified pumps are sensitive to magnetic interference if large pieces of ferrous metal is brought in very close proximity to the end cover, so I guess you can say I traded one problem for another, but overall, both methods have proven very reliable over the years.

The double ended pumps, such as the AZX 1400 and AZX 1500 series are fine, but expensive. The AZX 1400 series pump has both ends working simultaniously and are designed to deliver high volumns of fuel and as such would be overkill for a stock MGA. The Twin Cams use a LCS style pump that will match the AZX 1400 series, so the AZX 1400 series would be appropriate for them, but more expensive than the LCS. The AZX 1300 series pumps are a single ended pump used on MGBs and provide nearly as much fuel volumn as the AZX 1400, so unless you are going for impressive looks, there are less expensive ways to go.

The AZX 1500 series pump is also double ended set up to work one end at a time, using the other end as a reserve. It is set up with two inlets, one going to a stand pipe in the tank that is several inches high. The other inlet goes to the very bottom of the tank. In use, the end going to the stand pipe is used normally until the fuel level drops below the level of the stand pipe, at which point, the driver switches to the other end o the pump and starts looking for a gas station. This could certainly be hooked up as a primary pump and a back up by plumbing both inlet ports to the tank and using a switching power between the two ends. While this would work, it would cost more than twice as much as using a normal SU pump for the car and a NAPA supplied Facet or Carter pump as a backup. Additionally, if the AZX 1500 double ended pump was not an all electronic style, the points of the backup end would probably film over from disuse and not work when you needed it (unless you switched ends with each tank full of fuel). Cheers - Dave
David DuBois

Dave:

Can you tell me about the operation and vehicle application of a AUF 411 SU pump? I acquired one on eBay sometime ago with the idea of rebuilding it for my MGA/B. I am particularly interested in knowing if it operates like the AZX 1500, which it appears to be most similar to externally, or the AZX 1400.

Also, I always thought that the square body LCS basically was a single ended pump with a higher volume pressurized reservoir (i.e., fuel ballast) for acceleration, but basically had the same pumping rate as the stock SU. Is that wrong? In your response, you seemed to imply that the pumping rate of the LCS was the same as the AZX 1400.

Thanks,
Steve
Steve Brandt

Steve -To get the exact specs on the AUF 411, you will need to contact Burlen Fuel Systems <http://www.burlen.co.uk/> as the AUF 411 is no longer a number they use, so it is not on their on line data base. I can tell you that it is either 2.7psi or 3.8psi output pressure at 30 gallons per hour and operates on 12 volts (whether it is negative or positive ground or non polarized, I don't know). By the way, you are correct, the LCS pumps are only 12.5 gallons per hour. I was thinking about something else when I said that they were close to the double ended pumps.

You could use the AUF 411 as a primary/backup pump set up just by switching the power between ends. The AUF 411 only uses a single inlet line to feed both sides, so nothing special is needed for the inlet plumbing. The same caveat applies as with the AZX 1500 series pumps that use points. The unused end will develop a film on the points over time and will keep it from working. To prevent this from happening, one would have to remember to switch power betweent he ends with each fuel fillup. Cheers - Dave
David DuBois

I have installed two Facet pumps on both my MGA (sadly now sold) and my MGB GT V8, as I did not want to be delayed by a failure when rallying.

In each case they were in series, although I accept that a more elegant solution would be to have them in parallel .

One point to bear in mind is that the power supply should be switched so that pump 1 or pump 2 is live; not pump 1 live or pump 1+2 live - which is how I first had it.

With pump 1 & 2 live if one pump fails you can get a wiring loom fire despite each pump being fused - I know it happened to me.

No great damage, but I would advise everyone to carry thick "work" gloves somewhere easily accessible; and (of course) a fire extinguisher - which I didn't have to use.
Nigel Steward

Nigel - It may be more elegant to plumb the pumps in parallel, but it would gain you nothing other than added complexity in the plumbing. And with my luck with plumbing (of anything), the simpler the better. My wife used to take the kids and leave the house any time I had to do any plumbing repairs. Cheers - Dave
David DuBois

This thread was discussed between 03/09/2005 and 07/09/2005

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