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MG MGB Technical - mitsuba fuel pump

Dear All,

My SU-pump needs replacing and I was adviced to go for a Mitsuba solenoid pump instead of the SU for reliability reasons. The existing SU pump has worked for 30 years (with the occasional blow of a hammer), so it can't be too bad either. Is there any first-hand experience how the Mitsuba compares with the SU? Its dimensions are not unlike the SU's, but I am not sure it is meant for horizontal or vertical fitting in the car? And I wonder if the supply pressure is not a little high for the SU carbs (the Mitsuba pump I saw has a label reading 0.3 bars max. pressure)
Your views on this matter are appreciated!

Thanks and regards

Huib
Huib Berger

Reliabilty? SUs don't have a reliability problem. Many after-market pumps put out too much pressure and cause carb flooding, and/or are very noisy, and/or need the fitting to be butchered to install them. I'd stick to an SU and get another 30 years. Chances are it only needs the points cleaning anyway. SUs put out about 2 psi which according to one conversion site is .14 bar i.e. less than half what you quote for the aftermarket pump.
Paul Hunt 2

Huib - I am with Paul, 30 years life time hardly qualifies as unreliable. The SU fuel pump, Mistuba, Facet, Walbro, Moprod, etc. are all electro-mechanical devices and as such have a finite life time. Any of hte pumps that use open contacts (including the SU, Walbro and probably the Mistuba) are further prone to having the points film over during long periods of disuse (such as laying up for the winter), which can be a bother. The one big thing in favor of the old, points style SU fuel pump, is that all the necessary parts are available to restore the pump is you are so inclined and have the requisit skills and patience. This is not true of many of the other pumps available. If you are going to replace the pump instead of restoring it, I would recommend the SU all electronic pump. It is the same output as the original (2.7 PSI), is the same size, mounts the same way and looks and sounds like the original (it is, in fact all original except for the circuitry under the end cover). Being all electronic, it does not suffer from the problem of the points filiming over. You will hear about problems with the all electronic pumps, but those have been resolved over the years and the pump is perfectly reliable and will remain so for many years (I have had on in our MGB, which is our primary transportation vehicle, for 5 or 6 years now and it has never missed a beat - based on the life time of your original pump, I still have 24 or 25 years left on it). If you decide that you want to rebuild your pump, e-mail me and I'll send you information about getting parts and a assembly/adjustment procedure. Good luck - Dave
David DuBois

I just pulled the fuel pump out of my '65 B and it's says 'AC' on it. I plan to replace it with an SU pump.

Dan D
Dan DiBiase

Huib,

The Matsuchita is o.k. when fitted with a pressure regulataor as it usually delivers 3.4 PSI, too much for a HS / HFI setup.
I think, the SU pump is not as bad as its repuation meanwhile sounds.
If you do a rebuilt to the SU you can fit an electronic contactless breaker as offered and can be sure to have fun for another 30 years.

Ralph
Ralph

I'd not even bother with contactless (otherwise and aptly known as 'pointless' pumps). Electronic pumps, like ignition triggers, and more likely to fail without warning and totally, whereas points in both cases usually give you fair warning. Pump point problems usually respond to a sharp rap - at least to get you home, not for long term, ignition points can usually be tweaked at the roadside and it is cheap and easy to carry and fit a spare. My V8 came with a contactless pump and it was alright for a while, but then intermittently started short-stroking and causing fuel starvation. I would be stranded until it decided to start working properly again. After a couple of bouts of this, including one at home when I had the time and facilities to investigate, I could find nothing wrong and small adjustments to magnet etc. made no difference. I fitted a old pump from my other MG where I had refaced and adjusted the points and so far (several years now) have had no further problem.
Paul Hunt 2

Paul is correct regarding all electronic pumps (or anything else for that matter) failing completely when they fail (the only time that I have been completely staranded in a car was whent he electronic ignition failed). That said, I believe that the all electronic SU pump has been perfected to the point, like some of the modern electronic ignitions, where the failure rate has become so small that the risk of being stranded with htem is truly minimal. That said, a pump that is rebuilt with a fresh set of points and is properly adjusted (and assuming that the internal swamping resistor is intact) will certainly last another 30 years with faultless performance. The only place where the all electronic pump will out perform the pump with points in it, is if the car is not driven regularly and spends long periods of time in the garage. In that situation, the points will film over and cause intermittent operation until the hammer is applied (gently please). Cheers - Dave
David DuBois

Ya know, this board is amazing. 30 years ago when I bought my first B, this type of community didn't exist. Well, it did, but things were truly Balkanized and it was tough to get good advice.

I learned about giving the fuel pump a tap from a young guy in Alameda, CA, who had a barn-like garage with a dirt floor and who was an absolute wizard with all things British. Called his place "Marty's Mechanics" or some such. He loved British cars - called them his little quirk-mobiles.

Today, more and better information is available with a few minutes at the screen, with valuable time left over for doing what counts: Tinkering and driving - sometimes at the same time.

IMHO.

Rick
Rick Stevens


An answer to a question like this always has most people responding that something has worked fine for the last 30 years so there is no need to change. Other people like to try new things like iridium spark plugs, etc. Most of us driving a modern car would not feel safe having to jump out and beat the fuel pump to continue on the freeway. I owned a Mazda 1800 and after pulling the points cover off the fuel pump, it was easy to see how much better the mechanism is desigined than the SU assembly. So I found a model of car that had the similar size motor and it has work flawlessly for the maybe eight years. The pump even had the same size banjo fittings and dropped into the mount. Good luck.

Jeff Pintler
Jeff Pintler

Jeff - You are correct, there are numerous electric or all electronic fuel pumps on the market that will work fine in the MGB. When you say "Most of us driving a modern car would not feel safe having to jump out and beat the fuel pump to continue on the freeway", I would have to answer that most people would not feel safe driving a low tech car like the MGB on a freeway, but some of us do and enjoy doing so. As I stated earlier, a properly repaired and adjusted, points style SU fuel pump will work flawlessly for somewhere around 75,000 - 100,000 miles, before one would have to start tapping on the pump to get it to run. At that point the pump should be restored or replaced with a new one. Having had experience with a number of other brands of electric or electronic fuel pumps, including the one used in the Mazdas, I have found that this is about the same life time of any of the pumps on the market. the SU fuel pump gets a bad reputation because when it starts to fail, people will continue to pound on it to make it work instead of replacing it, or they do a DIY repair with aftermarket parts (because they are cheaper) that are inferior, and they are not familiar enough with the pumps nor do the have a test stand on which to do a proper adjustment of the pump. After a few attempts to affect these half way repairs, they finally throw the pump out and replace it with a new "much superior" aftermarket pump. Replacing it with a new SU pump would get them the same results - the key word here is NEW. When competing on a level playing field and starting as a new pump, the SU is every bit as reliable as any other pump on the market. As for the superior mechanism under the end cover of the Japanese clone, yes it is a much tidier set up, so is the Harding pump made in Germany, the only problem with both of them is that it is impossible to get repair parts for either (I have tried, particularly for the Harding pump, because I feel it is a shame to throw away such a well built unit). Perhaps they have the better idea, don't supply repair parts so people have to buy a new pump and there won't be the problem with the pumps being improperly repaired. In regards to the Japanese clone on the Mazdas, I had one fail at around 100,000 miles and had to replace it. On a later Mada, the OEM Facet pump (another popular replacement pump for the SU) failed at about the same mileage, again replacement was the only option. As I stated before, all of the pumps are electro-mechanical devices and as such they have a finite life time. At that point, they have to be replaced or repaired by someone who knows what they are doing, can get good replacement parts and has the tools and set up to adjust and test the pump properly. There are a number of us in the USA who can and do repair the SU fuel pumps and will guarantee their work. Alternatively, as stated above, there are a number of aftermarket pumps and pumps supplied for other cars that will work well in the MGs. I would suggest that either of the above alternative be used over just beating on a dying pump to keep it operating. Cheers - Dave
David DuBois

I had a Saab Turbo, and have no doubt that the fuel pump was a better design than the SU in terms of (build) cost vs reliability. However, it packed up on me, and as the pump was cleverly built into the fuel tank I never got to see it, let alone attempt work on it. It cost me half a day of work getting it towed to a garage, where it stayed for two more days whilst a new pump was ordered and fitted. I was left with a £350 bill.

Soon after I made the leap to a BGT for work and pleasure. It's fuel pump packed up a couple of years later but a few taps with a large spanner got it going, and that weekend a couple of hours of cursing and a few grazed knuckles had it fixed.

If I hadn't have known what to do with the SU, each breakdown would have been as disruptive as the other, but if you are willing and able to "have a go", the old technology is a lot more responsive and accessible than a transistor. If you are not, I'd suggest solid state may be the better option.
Steve Postins

Prior to converting to V8, I used the pump from a 82 subaru that I happened to have. It worked great! I just wrapped a bit of foam around it and put it in the backcorner of the engine compartment out of sight. Didn't even have to screw in a bracket, it sort of wedged itself into that dead space back there. It was an quick emergency fix that just stayed. Took about half an hour (at the most) to do. I left the SU as a decoration right where it was and bypassed it.
I do not love the SU fuel pump. It has given me some very bad times, from time to time. The final straw was (after much rebuilding and point fiddleing) that it would not work (in the rain) on the (8 lane, very high) "West gate bridge" here in Melbourne. Every where else just fine, there, not at all. If the traffic was flowing OK I could get to the top (on the contents of the float bowl) and then coast. Once off the bridge, working again. Needless to say, my place of work was on the other side of the bridge!
Peter

Dear All,

Thank you for all your feedback. My current pump is beyond repair so a replacment is inevitable. A couple of years ago I installed a brand new, standard type SU pump, on my previous MG, but that quickly failed. Not once, but on several occasions within the second year from installing. I complained, got a new one and that failed too.
Hence my question about the mitsuba. I don't use my current MG very often , but when I do I want to enjoy it. The pressure of the Mitsuba is a concern and buying a pressure regulator means even more money while the mitsuba is already more expensive than the electronic SU.
So I think I will opt for an electronic SU

Thanks again!

regards

Huib Berger
Huib Berger

Huib,

not all is lost, try to contact a supplier for Eberspaecher or Webasto cabin heaters as used on sailbaots and motor yachts.
They have fuel delivery pumps made by Pierburg. I have one of these pumps fitted to the GT in 1979. It can be fixed into the SU bracked and is also an electro mecanical points operated pump, but it works absolutely trouble free and should be much more cheaper than all the other stuff, although it looks a little SU style.
BTW, you would not need a regulater for this pump too.

There are a lot of yacht service enterprises and service stations in the Netherlands, so just contact one of these and ask for details concerning cabin heaters.
The German parts list says 'Brennstoff Foerderpumpe'.

Hope this helps

Ralph
Ralph

i was at a uk moss supplier recently and they are launching a vw pump for the mgb rubber bumper range with a pair of hoses has any one seen it yet ? or did they get cold feet launching it regards steve
stephen curtis

Huib - Since you don't drive your MG regularly, you should definitely go for one of the all electronic types, be it SU or other manufacture. This will get you away from the problem of the points contacts filming over due to long periods of sitting idle. Good luck - Dave
David DuBois

This thread was discussed between 11/09/2006 and 14/09/2006

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