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Having discovered a petrol leak from the S.U. (AUF214) fuel pump and/or hoses I noticed an electrical item attached to the fuel pump bracket (and probably the pump too?) on my 1970 MKIII Cooper S. Asking if anyone knows what it is, what it does and if I need it? I recently replaced the fuel pump and rotten hoses on my mini van which doesn't have such a thing.
Here's the obvious problem: The item in question: Thanks in advance...

Capacitor for radio suppression.

What's a radio? Seriously, thanks! Actually the car still has a Blaupunkt stereo radio with a cassette feature! It's circa 1990 when I restored the car which also still retains the original roof antenna... My guess from appearance it was some kind of condenser which looks similar to me but I'm assuming the capacitor's function is to suppress noise from the fuel pump which would interfere with radio reception. I plan to retain it for it's intended purpose... Thanks Again Ronnie!

Back in the days when your car was first put on the road it’s likely that radios fitted would have been only long wave and medium wave. They were more prone to interference from anything nearby that generated sparks, even very small ones.

With your current ‘almost modern’ radio cassette you would probably use only FM (used to be called VHF back in the sixties and was considered very posh). It would be less prone to interference. If you had a modern DAB radio, there wouldn’t be an issue with interference. That is, if you could get a signal at all once you’re out in the countryside! A modern radio would be totally out of place in a classic mini of course.

I think the capacitor is a nice period after market piece so I’d leave it where it is. It won’t do any harm.

Capacitors and condensers are the same thing incidentally. They haven’t really been called condensers since the Second World War, with the exception of the one connected to the points in your distributor. It is however, just a capacitor. Your latest TV or laptop is full of them, as with almost all electronic equipment. Often the size of a pin head.

Steve

minstix wrote: ↑Fri Jan 17, 2025 9:43 am Back in the days when your car was first put on the road it’s likely that radios fitted would have been only long wave and medium wave. They were more prone to interference from anything nearby that generated sparks, even very small ones.

With your current ‘almost modern’ radio cassette you would probably use only FM (used to be called VHF back in the sixties and was considered very posh). It would be less prone to interference. If you had a modern DAB radio, there wouldn’t be an issue with interference. That is, if you could get a signal at all once you’re out in the countryside! A modern radio would be totally out of place in a classic mini of course.

I think the capacitor is a nice period after market piece so I’d leave it where it is. It won’t do any harm.

Capacitors and condensers are the same thing incidentally. They haven’t really been called condensers since the Second World War, with the exception of the one connected to the points in your distributor. It is however, just a capacitor. Your latest TV or laptop is full of them, as with almost all electronic equipment. Often the size of a pin head.

Steve

Also sometimes referred to as a "Choke" when used for radio suppression.

A choke is a coil not a capacitor often used together
RGDS Stewart

Stewartp wrote: ↑Fri Jan 17, 2025 10:24 am A choke is a coil not a capacitor often used together
RGDS Stewart

This was the term used in 1972 when having a Radiomobile radio professionally fitted to an Elan Sprint. https://www.sjsportscars.com/parts-and- ... M0175F.htm

Thanks all, as others have said, this site is such a great source of knowledge, ingenuity and experience! I now recall putting in an inline capacitor when installing a 4 or 8 track tape player decades ago! The ultimate radio interference is the use of solid steel or copper spark plug leads, rendering any radio unusable! Whilst on the subject of fuel pump and hose replacements I should mention that there are problems when using the late style ethanol-resistant hoses, whether they be the stainless braided one's or plain style. I gather that most are made from high pressure fuel injection material and are very unforgiving to use in several ways. Unlike the hoses of yesteryear they are extremely hard to work with being so hard and inflexible. Using either the braided or plain they are fine for just replacing an existing hose of the same size. The problem is when trying to adapt to a larger or smaller fitting. I found out this recently when replacing the fuel pump on my mini van. The hose from the tank to fuel pump is 5/16" ID, no issue as the inlet and outlet on an SU pump is also 5/16 but the hard line to the carbs is 1/4" and using necessary 5/16" from pump to the hardline with the new style hose is the fact it can't compress due to hardness and even with double clamps, still leaks. The other issue is when installing an inline fuel filter such as the lovely glass one's from Mini Spares, the hose is extremely difficult to force on to the barbed ends of the filter to the point of squeezing the hose off on it's own, using the braided hose or the other. There is aftermarket hose to be found that is similar to the old type that will stretch enough, like having to force 1/4" hose on to a 5/16" fitting as may be needed. The only downside is if it isn't ethanol resistant you may have to replace it more often than once a decade and you may lose points at the local concour d'elegance, oh dear! Here is a picture of what I found useful recently and possibly soon which may be necessary when using 900 PSI hose when 7 PSI is all that's needed: The only problem may be that once the 2 hoses are connected to such, hope you won't have to pull one off anytime soon... Cheers

Yes, you’re right about fitting modern fuel hoses being difficult. I suspect that, added to the issues of slightly different size pipes you are trying to join, modern hoses are in fact metric. So the nearest metric size to the imperial size you actually want, even though sold as imperial. Possibly no one makes true imperial size pipes any more. So all in all, it creates a tricky job.

If the hoses are ethanol safe, they will have orange threads running through with the braiding. If they don’t have this, they will rot in a few years or even less. Trouble is, you don’t see the damage through the braid until you suddenly get a boot full of petrol.

Fitting the solid cross pipe between two tanks on. Cooper S is a real challenge with these new braided hoses. A process I went through a few days ago.

Like a lot of parts available for our cars now, it’s all a bit of a compromise and they may or may not fit properly.

Steve

Thanks Steve, absolutely right about the late style orange stripey braided hoses. Not only do the rubber ends slip off easily during installation (they always did before too) but they are also less bendable where needed. I spent the better part of the day yesterday in the garage replacing the hoses and fuel pump. I ended up using the ethanol resistant 5/16" plain hose I got from Mini Spares, the stuff you buy by the metre. Most difficult was feeding the hose through the angled hole in the boot down to the pump. Would have been nearly impossible with braided. I discovered one very important thing! Do drain the fuel tanks before removing the inlet hose to the fuel pump, will you! (it was the leaky bit) I didn't do that but fortunately there was only a gallon or so left in the tanks and the mess wasn't too bad as it could have been. Didn't have the same problem when replacing fuel hose and pump on the mini van, no fuel running out but then not too much fuel therein. In the process I discovered that the capacitor in question is not aftermarket but an integral part of the original wiring loom and serves as the ground/earth connection! Noting that the car has the original roof mounted antenna the wiring loom was designed to accommodate a radio, methinks. It seems the old FP was still functional, rewarding as it's one I rebuilt long ago. Since I had 2 new fuel pumps on hand, one original points style and another electronic one (I purchased in a while back in error) as I've had one fail prematurely. I installed the electronic one anyway, not sure why really. Haven't added fuel or tested anything yet as I ran out of daylight yesterday, hopefully the electronic wonder works, (hopefully compatible with the capacitor thing-afterthought) and no leaks anywhere. The only other fiddley bit was connecting the power lead to the pump body as the original loom terminal is a round one and trying to attach it in situ using that bloody tiny screw, taking more tries than I care to admit, fortunately the ground connection is the usual spade connector. As before I had installed a filter in the boot, old plastic one and replaced it with a glass one as seen in the photo to follow. Notable to purists is this car retains the original battery cable (and ground one) where you have to drill a hole in the battery positive terminal and insert a screw to make it work! One last tip I might convey for jobs such as this that makes things more comfortable is that I bought a 1" thick yoga mat just for working on cold garage floors and hot tarmac, lovely bit of kit!
Here's the photo of inside the boot: Cheers, Kirk