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MG Midget and Sprite Technical - SU fuel pump, how to limp home

My SU fuel pump failed last night about 5 miles from home and the car is sitting on the side of the road. It did not respond to tapping or cleaning the points. Having very few tools, I made it worse rather than better. Now the whole points plate has been removed from the pump, and the small red wire coming from the pump windings broke free from its terminal ring.

If I connect a wire to that red wire, route it through a toggle switch to the positive post of the battery, and flick the switch off and on, will it pump fuel? Would I need to add a ground somewhere, or would the normal ground take care of that?

Thanks
Charley
C R Huff

If by doing that if you have bypassed the contact breakers it may well get you home. The only thing I can say is try it but you will need a ground somewhere. It should be grounded through the loom somehow but that is prone to going open circuit anyway.

If you have a spare pump that works you can do what I did to get home. I jury rigged it in the engine bay, took off the pipes connected to the fuel filter, connected it to the spare pump with a bit of imagination, and connected it to earth and the live battery. It was able to suck enough even though the old pump was still in the fuel lines. This was easier than trying to swap the pump at the side of the road. I was about 25 miles from home when mine died, got a lift back home, collected pump, pipes and connections etc.

Rob
MG Moneypit

Thanks Rob,

The points are indeed off. It does still have the main ground, and the ground wire that has a ring terminal under the points cover is accessible.

And, good tip about rigging a pump under the hood. I do have a spare pump, but I'm not sure if it is here and if it still works. I will check to see. Dealing with the pump under the car is not appealing since it is wet here and the car is close to the ground, but under the hood would be good.

Charley
C R Huff

If you only have five miles to go, you could rig up a one gallon fuel can under the hood with a gravity feed to the carbs. No need for any fuel pump then. Just an idea!
DM Gibson

Hey charlie

This is really red neck advice but ive seen it work in a pinch...

Get a garden pump up bug sprayer...1gal

Put a 6 foot hose extrension after the sprayer trigger handle and hook it up to the carbs ...pump it up and pull the trigger slowly

That will get you home, just find an extra hole in the fire wall to push the hose thur

Prop
1 Paper

Hi Charley,
If you have knakered that pump in the process, why not just buy the replacement that you will now need to buy anyway, take it along and fit it?

No good to you now, But I once travelled 70 miles with a mis-behaving pump. It kept stopping every couple of miles, but would restart each time with a heafty thwack on the side with a trolly jack handle. Rather more vigorous than just "tapping" it ! Towards the later stages of the journey I could even get it restarted without actually leaving the driver's seat (RHD car) by leaning well out and flailing the jack lever arm around under the car until it made contact! Must have looked quite bizarre behaviour to anyone watching!
GuyW

"you could rig up a one gallon fuel can under the hood with a gravity feed to the carbs"

Or a fuel tank from a lawnmower.

I picked one up at an auto jumble for a couple of pounds. The plan was to use it on my motorcycle while balancing the carbs, as I needed to remove the bike's fuel tank to get access.
Dave O'Neill 2

Thanks guys,

I did think of the gravity feed, and have done it in the past, but at the moment, I don't have the hose to do it with unless I make a trip to the auto parts store. Same with the garden sprayer, but a good idea nevertheless.

I took the pump off of another one of my cars, and I'm heading out now to try doing what Rob suggested with an under-hood pump. I'll check back later.

Thanks,
Charley
C R Huff

Something I have wondered about for a while is this perennial issue of the SU pump. It pops up now and then and to the unitiated it looks like the pump is a weak point. Maybe it looks worse than it is because it results in a dead car.

I have a memory of 998 and 1275 Minis (and presumably other A series engines) in the early 70s having mechanical fuel pumps driven from the camshaft, like 1500s.

Is it realistic to convert to a mechanical pump, or would it mean a lot of work modifying the block and using a different camshaft? I have known very few failures of mechanical pumps over the years.

Please forgive my ignorance - I don't know A series at all well. Most of my knowledge is big diesels, just curious that's all.

By the way, as an historic curiosity, Prop's notion of the bug sprayer has precedent in a way. In the 20s Bugatti racers, especially Targa Florio and other distance racing cars, had a rudimentary cushion on the floor for a chap called a "riding mechanic" whose task it was to maintain oil and fuel pressure with hand pumps. Can't say I fancy that job much!
Greybeard

Some of those type of race cars used in historic racing still have that hand pump system, only the driver does it himself. Hard work on a circuit with not many straights.

Trev
T Mason

Frogeyes had mechanical pumps, as did the A35, whereas Morris Minors had electric pumps, so did the ADO16 (11/1300) and some Minis. The 1275 Marina also had a mechanical pump.

It would be easy to fit a mechanical pump to some 1275 Spridgets, as they have the opening in the block covered with a blanking plate, although some don't. The A-series camshafts generally all had the lobe for operating the fuel pump, with the odd exception. Some of the exceptions were competition camshafts that were designed to run a dry-sump oil pump, which had a skew gear in place of the lobe.

Perhaps the easiest option is to fit a Facet solid state pump.
Dave O'Neill 2

Okay, I made it back. The under hood pump pulled through the original just like Rob said it would. At one time I knew that from seeing it on Dave Dubois’ web site, but I had forgotten. I had to leave my daily driver where the MG was, and then get a ride back to pick it up, but both cars are now back home.

Thus ends the tough day yesterday. It started out well. I got my tractor fired up and ran my 80 inch mower down my country road to blow the leaves off of it. Then I blew the leaves off my roof and out of the gutters. From there the day went downhill.

I’m doing a rolling trans fluid change on my 99 Volvo V70 daily driver. I drained 3 qt out of the trans, and then went to replace it. I was surprised to find that the plastic tube that I stuck in the dipstick tube didn’t want to fit. I chalked that up to the hose swelling as I had used the same funnel and tube to drain the fuel from my tractor since the shut off valve leaks.

After adding the ATF, I jacked up one side of the car to elevate the wheel above the drive on ramp to check the control arm. It tipped the opposite side ramp, and the car landed with the tipped ramp jammed under it. That gave me the chance to see that the lower control arm was shot on the other side with the ramp stuck under it.

I got it off the ramps and found that it would not stay engaged in gear. I thought I might have crushed a trans line when it fell off the ramps, so I started looking. While looking, I noticed that all the lines were on the other side of the car near the trans dipstick. Wait a minute, trans dipstick? That’s not the one I dumped the 3 qts of ATF into. Yup, I had dumped 3 qts of ATF down the engine dipstick tube. I felt like I was in junior high school again.

That’s when I fired up the MG to go get more ATF plus motor oil to do a change. The MG crapped out on the way home, just as it was getting dark. That put the cap on a rough day. It was 11 before I got home, which included walking about 2 miles of it before someone stopped to pick me up.

Thanks for all your help and suggestions. It’s good to have the support after a day like that.

Charley
C R Huff

A Huco pump is a good reliable solid state alternative
S G Macfarlane

Thanks, Charley. I thoroughly enjoyed your day! Better than Hemingway.
Nick and Cherry Scoop

Glad to hear you're all sorted Charley but I'm sure we've all done similar things!

Talking of mechanical fuel pumps, I have one ready to put in the Frog's 12V 1275 when the time comes. What's the disadvantage over an electric pump?
Bill Bretherton

Glad you got home Charley.

I've had days like that. The world gets dark and life gets hard but the sun shines the next morning.

Rob
MG Moneypit

Some years ago I had the same problem with a fuel pump packing up on my Morris 1800 auto,this happened in a very bad place on a country road miles from anywhere, I could not leave it where it was, as it was in a dangerous position on the road, this was before the days of mobile phones, so I was stuck, I had no tools in the car apart from a pair of mole grips,after sitting there thinking what I could do,i came up with this plan, I took the washer bottle of the car, emptied it, took my mole grips, removed the tank drain bung, filled the washer bottle with petrol, refitted the washer bottle back in its holder, pulled the washer pipe out of the T piece pushed the washer pump a few times to empty the pipes of water, disconnected the flexible fuel pipe to the float bowl at the end that connected to the steel pipe from the tank, pushed the washer pipe up inside the flexible pipe, pumped the washer pump and started the car, I managed to drive home by just pumping the washer pump, I think I had to stop a few times to refill the washer bottle, when I got home I flushed out my washers cleaned out the bottle, fitted a new fuel pump, and never had any more problems,with the fuel pump or the washers,
Andy Tilney

Is it a new one, Bill? My engine came out with a mechanical pump, and it's going back in with the same one, which I've more or less just cleaned up and saluted. I find the mechanical pumping design satisfying: I suppose it came with the A35 engine and, being the standard fitting, was cheaper than going electric. When the Frog emerged, MGAs had had electric pumps for several years, so it can't have been a question of linear progress in BMC's design history.

On long trips - Le Mans for example - I always carried a spare fuel pump for the MGA, but I never carried a spare diaphragm for the pump on the Frog. Very easy to swap an electric pump, but I guess it's carbs off to get access to a mechanical one.

I'd love to hear from anybody who's had a mech. pump failure - why it happens, what fails, and how quickly.
Nick and Cherry Scoop

Nick, l had a mech fuel pump failure, though on a1500. Car ran fine until under load, as in going up a long hill, when the pump couldn't keep up. Turned out to be a split in the diaphragm. Stranded, roadside in Scotland, l made a replacement from a co-op plastic carrier bag. Lasted for the rest of the journey and the return trip - about 500 miles in all.
GuyW

Nick, not brand new, purchased from ebay seller but very clean condition. I think I'll try it. I remember having trouble with the SU pump on my mk3 Sprite in the 70's. I believe in keeping things simple as far as possible.

Great get-you-home repairs Andy and Guy. Does it need to be a Co-op bag Guy as I'll need to carry the appropriate spares?!
Bill Bretherton

Guy, how much dismantling to get at it? Though it's all the other way round, isn't it? The fuel pump must be on the left, because I can't imagine there's room for pushrods between all those ports. Please ignore my question.

I can't remember, Bill, whether you told us you were using a big engine. Are you going for front discs to cope with the huge power of a 1275?
Nick and Cherry Scoop

Charley,
yeah, I've had days like that, good to get passed them isn't it.

Unless the Volvo engine is different in some way why not run the ATF for say 50-100 miles as a flushing oil then when its hot drain it for as long as possible, refill with a cheaper oil than you normally use and change that oil twice as quick as you normally would or just put your normal oil in and not worry about it.

For the midget fuel pump I don't see the point (pun intended) of paying extra for the SU points type and I don't like the noisy square or barrel Facet ones, I've had an electronic type like the photo below on my Midget just after I got the car 10 years ago as a fit 'n' forget. I see no charm in getting dirty and carrying a stick to keep a fuel pump going.



Nigel Atkins

Charley,
just had a thought, I was assuming you'd emptied out the previous engine oil before adding 3 quarts of ATF but on rereading I'm not sure. Perhaps your day was even worse than I thought.
Nigel Atkins

Bill, when sourcing your carrier bag make sure its NOS. I dont think the modern biodegradeable type will last long because of the ethanol in the petrol!

Trev
T Mason

LOL Trev!
Yes, discs Nick. Disc hubs already acquired from a later Spridget and calipers rebuilt. The 1275 has been re-conditioned but is "stock" so not "huge" power. But enough I think!
Bill Bretherton

Nigel, Your second thought was right. The three qt of ATF were on top of a full crankcase. I did let it idle a bit to take advantage of the unintended flush.

Bill, The only disadvantage I can think of with the mechanical pump is that if your carbs are empty, you have to crank the engine until they fill. That is, unless you can get lucky and get one of the mechanical pumps with the hand pump handle on the side, but they seem to be a bit rare.

Andy, Good trick with the windshield washer. Years ago I had a friend with a Corvair Spyder who ran the washer output tubes to the inside of the car and then filled the reservoir with liquor.

Charley
C R Huff

Nice get-home tale Andy. Of course if you hadn't had the mole grips you could have used a length of the windscreen washer hose to syphon fuel out of the tank. ;-)

Bill, I believe the plastic bags to go for are now referred to as a 'bag for life'. Not sure if that is to do with durability, or some sort of exchange rate.
GuyW

Charley,
3 quarts, you must have filled the glove box too.

Last year's annual engine oil change I was refilling with my expensive high quality engine oil through the oil filler and I heard dripping, my mind flashed to replacing the sump plug which I always double checked(?), so I quickly looked under the car to see oil dripping at the back of the engine, looking up top again and I could see it had been coming out of the rear of the rocker cover, how I got it to run so much along the top I'm not sure.
Nigel Atkins

I carry a spare pump always with the thought that it would be a rotten roadside job to replace. It sounds as though an under-bonnet emergency measure would save the day so tomorrow I shall set about pre-engineering that so it can be carried out without too much hassle.
Graeme Williams

I had a fuel pump go on me in the middle of France.

My "fix" was to pull out the hazard warning flasher unit and wire it into the white power feed to the pump in the bullet connectors under the bonnet - the pump needs about 6 amps and the flasher will drive 7amps worth of lights.

The intermittent power feed ran the pump just fine - I did about 700 miles until I could get a replacement pump fitted.
Chris at Octarine Services

Graeme you just put that to wind me up! ;)
Nigel Atkins

Nigel: me? No!
Graeme Williams

I had a breakdown on the M25, a truly frightening experience, it was not the pump itself, but a leaking pump inlet hose,but I decided never to have that experience again, so fitted a back up pump.
Its easy to fit a Facet pump in series with the original SU, it just pumps through the SU. With a two way switch I can select either pump and the engine runs happily on either.
Just don't use a centre off switch, or you may loose both pumps.


Dave Barrow

For some reason i am thinking the SU double pump from MGBs was a popular racer toy trick for the midget back in the 1960s

If one side went down the other side kept pumping

Am i remembering correctly ?

Prop

1 Paper

The MGB didn't have a double pump.
Dave O'Neill 2

Hmmm but was there a SU double pump fuel pump that was used in the midget as a race modification

.
1 Paper

IIRC the double-ended pump is used on Jaguars?
David Smith

After a breakdown due to pump failure I plumbed a second one in line so the rear pump pushes fuel through the front pump, mounted under the bonnet. Should the rear pump fail, iconnect the earth terminal to the pump under the bonnet and it pulls fuel through the rear pump. The front pump has a live positive to it, same supply as rear pump, and I leave the earth wire off, every now and then I connect it up just to give the pump a workout. Never had a problem since.

Mike
M J Pearson

David...thats right, thanks now i remeber...i guess they just put a reghlator on them to drop the pressure.

I was planning on have (david ??) Dubois rebuild an old SU double pump, but just never got around to it, and i guess he moved onto greener pastures as i havent seen nor heard from him in about a decade ...he posted here quite a bit at one time.

I think its a good idea to run pumps back to back if you dont drive to often simple because of the crap we call fuel today...i had changed out to an electric faucit when i rebuilt the engine and i had a hard time keeping tbe inside of the pump clear as the fuel would turn to a white powdery crystal and i had to clean it out ... then last year it went out on me twice and had to be towed, so having a back up pump already installed ready to go is a smart move..like youbsaid just hook up a groud ... im going to make a by pass valve for the fuel so the back up pump will always be dry on fuel and no ethional issues to deal with

Prop
1 Paper

Prop

David Dubois posts fairly regularly on the MGA, T-type and possibly MGB boards.
Dave O'Neill 2

Dave,

Thank you... i did not know that. Small world after all

Prop
1 Paper

This thread was discussed between 23/10/2017 and 28/10/2017

MG Midget and Sprite Technical index

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