Electric Fuel Pump to suit SU Carb

[arceye]

Hi Chaps,
Can anyone tell me the optimum and maximum / minimum psi output for an electric fuel pump to be used with a SU carb on a BMC A Series 1098 engine set up.

Trying to avoid the traditional pump if possible and save a few quid at the same time and was looking at Facet style pumps that mount near the petrol tank. Trouble is they all seem to be rated about 4 - 6 PSI which I think will overwhelm the float needle?

I have seen a pump intended for motorcycles and rated at 1 - 2 PSI with a flow rate of 60 litres an hour, would this be sufficient? I have also found a universal car pump rated at 3 to 4.5psi with a flow rate of 80 litres per hour but again I suspect this may overcome the float needle valve?

Thoughts please, should I really just bite the bullet and buy a Moggie type SU pump at about £60 or £70, these other pumps are going for about £20 give or take and I'm notoriously tight

[megadethmaniac]

60 l per hour, against a 1098cc engine that does 30 ish mpg. Suspect you would need some form of return system unless it is limited to delivering upto 60l? After all that`s what 11 gals?

[arceye]

Yes mate, the flow would be plenty, that is (hopefully) limited by the output psi not being able to overcome the float valve needle. Thats the bit I really need to know, is say 1 to 2 psi output suitable for a standard SU as fitted to a Moggie Minor engine

[JPB]

Correct fuel pressure for a Minor is between 0.5 and 1.5psi, but the float needle seat should be able to cope with up to 4psi, beyond which it would possibly leak even without a contaminated seat at the float valve..

If fitting an electric pump to an A30, just make sure that it's fitted in the same place as the pump would have been fitted in its native application, IE; on the bulkhead "pulling" in a Minor or under the boot floor by the spare wheel in an A40 "pushing". The difference between these types is more significant than the maximum measured output at the pump.

[arceye]

Cheers John, that's great

Think I may try the smaller pump then,Hopefully the sellers can tell me if its a puller or pusher. The only concern now with that one is if it can keep up under load if real world use drops those figures dramatically (losses from head height etc).

[suffolkpete]

Huco do a fuel pump rated at 1.4 psi suitable for engine bay mounting. The Facet pumps need a pressure regulator, SU carbs should have a pressure of less than 3 psi.

[arceye]

Cheers chaps, I've ordered a small pump at 1.5 to 2 psi and will see how it goes. If that doesn't work out I'll get the proper thing. I've always preferred mechanical pumps as if the engine stops so does fuel flow but as you know most 1098's have no place for a mechanical pump unless you drill the block.

If I remember rightly the Minor set up would just carry on pumping if the fuel lines were damaged in the event of an accident? I'm thinking if this works out an inertia switch on the power supply may be a prudent way to go.

[Luxobarge]

If I remember rightly the Minor set up would just carry on pumping if the fuel lines were damaged in the event of an accident?

Technically, yes, but as the fuel pump is in the engine bay on the firewall, the most likely scenario is that the damaged pipes would be the ones between the tank and the pump (as beyond the pump they are all flexible hoses in the engine bay), in which case the pump would simply draw in air and become ineffective. I know this, as we had a split pipe on our Moggie, I wondered why it wouldn't start....

Cars that have a "pusher" pump on the other hand, down at the bottom near the tank would indeed be a bigger risk. However, with copper or kunifer pipes I'd be very surprised if they split in an accident? Still, if it's an issue that worries you then yes, an inertia switch would do the job. Just let us know how far you go with troubleshooting the first time the car won't start before you remember about the switch and find that it simply needs resetting - Lol! Been there, done that....

By the way, just out of interest, why don't you want to use an original-style SU pump? Expense? Both my Midget and Moggie have contact-less versions fitted many years ago and they have proved to be fit-and-forget, totally reliable and no problem at all. At around £35 a pop I didn't feel that they break the bank? Just curious, that's all.

Cheers!

[arceye]

Cheers Luxo, yes..... feeling tight at the moment, actually I'm just bloody skint because the house keeps robbing me of cash at the moment. All the new su type pumps I've found are about £70 plus vat as opposed to 25 notes for the one I'm going to try. If my plans work out I'll wait for a secondhand one ending cheap on a flea bay auction and do the contacts etc then I can either go over to that or keep it for a spare til the other plays up.

[Luxobarge]

skint because the house keeps robbing me of cash at the moment.

Oh man, talk to me about it.....

Fairy 'nuff - understand. I could have sworn that I paid around £35 for my solid state SU pump, but it was a LONG time ago and of course you're quite right, a quick search tells me that the going rate is indeed at least double that, so I totally get your point.

All the best and let us know how it goes eh?

As it happens fuel pumps are a bit of a (literally) sore point with me at the moment: came to drive my Jag XK8 last week, and no-start. Cut a long story short it was a failed in-tank fuel pump. The part isn't too expensive (relatively - it was around £86 delivered) but the official method is to remove the tank, the labour for which is £££££. So I did it myself, and by taking the rear speaker out of the rear parcel shelf (mine is a coupe) I managed to do the job without taking the tank out. My body is still sore though, you need to lie across the boot in the shape of a granny knot, and have the arms, hands and general dexterity of a gynaecologist. The whole job is done with your arm in the tank and therefore totally blind, just doing it by feel alone. I'm proud (and more than a little better off) for doing it though!

Cheers bud.