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MG MGB Technical - SU Fuel Pump life expectancy

I have a 1977 MGB with a SU fuel pump that was replaced with new in 2002. What is the typical life expectancy of the SU pump? Is there any service that should be done to the pump?
JCH Hibbard

JC. Dave DuBois, one of the most experienced people in this area has some technical information on the SU fuel pumps listed on my website, www.custompistols.com/, along with a hot link to his e-mail. He would be one of the most informed people to be able to answer your question.

From my own experience, which is far less than Dave's, the expected live of an SU fuel pump is in excess of ten years. But, things have changed, significantly, over the years that I have been using them. Back when things were made in North America and Northern Europe we had some standards--they had been made there for quite a number of years. Today, with much of the manufacturing being made in "Third World Countries" things have changed significantly. If Dave does not respond within a day, drop him an e-mail and ask your question of him. He should be able to answer your question in light of the parts currently available.

Les
Les Bengtson

JC The points style SU fuel pump should be good for approximately 100,000 miles, depending on how the car is used. A car that is driven regularly, year around should get 100,000 trouble free miles. If the car is not driven regularly, or is put in hibernation over the winter will start experiencing problems somewhere along that time period. The alloy in the points tend to film over and if not driven regularly, the film will build up enough to keep the points from conducting and the pump will fail (as opposed to the car that is driven regularly so that the arcing of the points keeps the film burned off). if your car falls in this class of car, you should pull the pump each spring and clean the contacts of the points with some 400 grit sand paper and solvent to get rid of the film. Now, if you have an all electronic SU fuel pump, there are no points used to trigger the pump's solenoid and therefore there is no such problem. Cheers - Dave
David DuBois

Dave,

If the film bulds up until the pump quits, does this cause permanent damage, or will cleaning the points after it quits restore the pump? I ask this because I am driving the BGT regularly now, but it sat for three years previously.

Thanks, Charley
C R Huff

Charley - You are probably ok at this point. If he pump starts acting up, the first thing to do would be to clean the points. To get a heavy build op of the film off, it is necessary to remove the upper contact blade from the pedestal and scrub the contacts well over the sand paper or a medium grit sharpening stone, then wash them off with solvent. The lower contacts present more of a challenge to get clean and is why people often fail to get the pump to working well. One needs to remove the two pedestal mounting screws and carefully fold the pedestal back to completely expose the lower toggle with the contacts on it. A small sharpening stone comes in handy here to scrub the contacts and then wash them with solvent. If you have a high power magnafying glass, it is interesting to look at the contacts before cleaning them. You will usually see, what looks like a waxy build up on the contacts and often it will look like it has been pushed into a pile (not unlike snow pushed into a driveway by a snowplow) on one side of the contact - this is what you are trying to remove when cleaning cleaning them. A combination of the current flowing through the contacts and the small amount of arcing that occurs as the points open will keep this build up burned off when the car is driven regularly. Cheers - Dave
David DuBois

The film builds up when the pump is not used, cleaning it off removes it and restores full functionality. New SU pumps come with (or came with when I bought mine) a slip of paper saying to clean the points before returning a non-operational pump as faulty.

"Now, if you have an all electronic SU fuel pump, there are no points used to trigger the pump's solenoid and therefore there is no such problem." My V8 came with a Moprod version of the electronic SU. Worked fine for many tens of thousands of miles, then suddenly started short-stroking causing fuel starvation. Even though I was able to get into the guts of the pump (on a rubber bumper where they are accessible from the boot/hatch area) on a couple of occasions no amount of fiddling and tweaking would correct it, until it just decided to start working properly again. After the third occasion on what was then my daily driver I replaced it with the refurbished pump from my roadster, and since then I have had no more problems. When electronic types go wrong you are stuffed. With points types at least you stand a chance of getting them going again.
Paul Hunt 2

Thanks Dave, Paul, and Les,

Since mine is working reliably now, I guess I'll leave it alone and then maybe inspect it when I get the car home. I am carrying a spare of unknown quality, so even if it doesn't work I will have some extra parts. I'm pretty sure mine is the points type.

Charley
C R Huff

Paul's experience with the Moprod pump (also sold as Auto Pulse) is typical of that pump and any other all electronic pump. When they work they are a very good pump, but when they fail, that's it. That is the reason that I advocate a permanently installed back up pump (although to have some assurance that the back up will work when needed, it has to be an all electronic - kind of a cache 22). Of course I advocate the permanently installed back up pump even with a points style pump,since I have an aversion to trying to make a pump work or changing it out at the side of the road (you haven't experienced absolute, abject terror until you have had to lay under a MGB on the shoulder of I5 in the freezing cold, changing out a fuel pump with cars and trucks racing past at 75 mph and wondering which of those idiots is going to slam into you because they are looking at the car). Cheers - Dave
David DuBois

Thank you Dave, Les, Paul and CR...what a great response and help. I had just filled up the tank yesterday, started the motor and pulled out of the gas station and the the car died for a brief minute or two which prompted me to start thinking. However the fuel pump was replace in 2002 with probably 10,000 to 15,000 miles on it now.
JCH Hibbard

Good thought Dave,

In fact I do know the feel of being under the car in break down lane, maybe not I5, but seen one you've seen 'em all.

When you install the second pump, do you do it in series or parallel? In other words, will the backup pump work through the dead pump or does it need its own fuel path?

Charley
C R Huff

Charley - The pumps are plumbed in series. All of the pumps, SU or after market only have check valves in line between the inlet and the outlet so they will all pump straight though the disabled pump. This is the nice thing about this installation - you can even make up a jumper line so the car can still be driven while the primary pump is removed for repair. See my article on this subject at: http://www.custompistols.com/cars/dave/BackUpFuelPump.htm for installation instruction. With a switch in the power line where the driver can reach it easily, one doesn't even have to pull off the road to switch from one pump to the other. Cheers - Dave
David DuBois

This picture shows my experience with a two-year old points-style pump. This is in 100-degree heat on the infamous US 50 ("The Loneliest Road in America") in Nevada last July. No problem, just lost a couple of hours. While Florrie was busy with the camera taking this picture, the rest of the time, she held an umbrella over us while I installed the new electronic pump.

This is a typical "hibernation pump" - and it went over 2000 miles last season before this failure. I am now a firm believer in permanently-installed back-up pumps!

Cheers,
Allen


Allen Bachelder

Thanks Dave,

I scanned and bookmarked your article for future use. At the moment it will have to fall into the luxury category. I’m glad to see that there are so many low pressure pumps available.

Allen, Yes, I know US 50 well. I’ve been using some or all of it since the mid 60s between Kentucky and California. In the last few years I only use the Utah, Nevada, California section. In fact, if the temps aren’t too cold and the snow is not too heavy I might pick it when I return to KY from CA around the 20th this month.

Charley
C R Huff

Les-
Thank God, the SU fuel pumps are not made in a third world sweatshop. They are made in Merrye Olde England by Burlen Fuel Systems, the same people who make SU carburettors.

Paul-
In my boot I have a magic talisman that keeps my solid state SU fuel pump from burning out and leaving me stranded. It's the old points-style SU fuel pump that was original to the car, fully rebuilt. So far, no probems!
Steve S.

Allen - wimp - I changed mine with the car standing on its wheels! :o) When the pump died I was on a country lane and just managed to roll into a field gateway i.e. soft ground so wouldn't trust a jack. Even though I had never done anything to the clamp and hoses they came straight off, didn't even get any fuel running out. Had the Navigator standing at the back of the car on the drivers side to hopefully make sure no one came too close, and give me a bit of warning if they did. The irony was that we were nearing the start of one of the biggest MG runs on the calendar, a dozen other MGs must have come past while I was groping underneath and not one stopped!

When I got back home I decided to change the hoses as they were pretty ratty. Removing them in the garage fuel dribbled out the whole time. I came to the conclusion that driving had developed a small vacuum in the tank due to the valve in the petrol filler cap and that had stopped it running out. I do get a small 'gasp' from the cap when I fill-up after running a while.

Steve - I'd been carrying a spare in the boot for some years after a bought it for a (relatively) long-distance trip to France. I also bought a spare water pump for that trip as the (not long replaced) one on the car had a dribble during warm-up. That's still in the boot, 10 years later :o) The old pump is still dribbling the same amount.
Paul Hunt 2

The easiest way to keep the fuel line between the tank and the fuel pump from siphoning fuel out of the tank when changing out a fuel pump is to loosen the fitting on the side of the tank sufficient to cause an air leak at that point. Cheers - Dave
David DuBois

This thread was discussed between 11/01/2008 and 13/01/2008

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