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MG Midget and Sprite Technical - Fuel pump conundrum

I went to collect my 1500 midget from storage yesterday. Frustratingly it wouldnt start. It was last used in November and was running fine.

I had limited tools with me, and I was working outside on the farmers drive so there was only so much i could check.

Doing the usual checks:
There was spark at the plugs
The plugs were bone dry
There was fuel in the tank
The fuel pipe connections from tank to pump were tight (although I couldnt check one of them under the car)

I took the top off the (mechanical) fuel pump and it was bone dry. The diaphragm looked ok but despite lots of cranking I could not get any fuel to pull through. This is a new (cheap) pump fitted last summer so I suspect its the culprit.

I need to fix it with a better solution, I'm thinking Hardi electric pump. However I need to get the car home (5 miles) first. I'm wondering if I could engineer (cobble) a safe temporary solution. I would need to find a way of securing the pump to the underside of the car, and to get some power to it?

I'm loathed to waste £20 on another cheap mechanical pump just to get home. I don't fancy towing the car, and my breakdown insurance wont recover from storage.

Has anyone got any better ideas ?

Chris Madge

Are you sure there isn't a blockage in tge pipe or tank outlet? Even a cheap mechanical one should pump enough to get you going if the diaphragm is still intact. I would disconnect the inlet pipe from the pump and blow up it to clear any debris. You should hear it bubbling in the tank. Take a length of plastic windscreen washer tube to make this easier! The other check I would do is to slacken the nut at the pipe to tank connection and check that fuel runs out there.

Prop would have had you rig up a temporary gravity fed fuel supply with a plastic bucket next to you on the passenger seat!
GuyW

Thanks Guy, yes it could just be a blockage I suppose. I'll check the next time I'm up there.

I did consider the gravity fed tank option but I dont think my wife will be up for holding a petrol can above her head?
Chris Madge

Or, push the car out to the side of the public road and then call breakdown!
GuyW

Its odd that the pump was dry. In the UK climate I wouldn't expect fuel to evaporate out of what are essentially closed pipes and the pump body. Are you sure there is enough fuel in the tank? Perhaps it would help to take the pump top off and prime it with some fuel?
GuyW

The tank was low on fuel, but there was enough to run the car for 20 miles.

The last time I used the car it had been stood for a month, but started almost immediately - fuel hadn't drained back to tank.

Yes, this time its odd that the pump was bone dry. Maybe a leak somewhere?
Chris Madge

Are you sure there's fuel in the tank
William Revit

Does the pump energize?

If not - check earth and feed.
Oggers

Now you have me doubting myself William !

Ill take a can of fuel just incase.
Chris Madge

I agree
Add more petrol
Check tank supply by blowing back into tank - this is the problem I had before lockdown with a B - blocked tank filter. I rigged a foot pump with a bit of hose.
Prime pump - the little flap valves can stick a bit when dry.

Good luck

R.
richard b

All of above, I'd definitely take and add 5 litres of fuel to the tank (why not, might save a lot of embarrassment too).

Wouldn't sticking it in gear and pushing it a distance prime the pump and the carbs if there no over way.

Or being a farm you might be able to arrange a drag start.

I put a filter just before the carbs as a very quick and clean-hands check that the fuel is at least at that point or passing that point.
Nigel Atkins

The early mechanical pumps of that sort had a handy priming lever on the outside. Perhaps they were deemed to need help when left standing for a bit. You can prime them by taking the top of and pouring fuel directly in. But it may also help to unbolt the pump from the crankcase and prime it by manually operatig the lever arm that the cam normally operates on. At the least it would save your battery!

Also check you fuel cap vent is clear, or if in doubt at least just loosen the cap to eliminate that possibility.
GuyW

Put more fuel in Chris. I've found with the Frogeye that half a gallon doesn't seem enough for its mechanical pump. I've thought something was wrong when it wouldn't start and it just needed more fuel. Did get me wondering what the minimum tank level needs to be. Maybe you get an air lock in the pipe at low fuel level though I don't see why.
Bill Bretherton

Unbolting and re-bolting the pump on the 1500 is a pain, access is poor. So i would rather avoid that.

Ill definitely try some more fuel in the tank and pour some fuel into the pump.

I was wondering how I could pressurise the tank via the filler tube to help get the fuel to the pump. A mountain bike inner tube cut in half, with one end sealed and the other end stretched over the filler cap. Attach a pump and inflate. I used that method successfully to check the tank for leaks when I had it off the car........
Chris Madge

Replumb the screenwasher? :)
AdrianR

Chris,
I'm not sure I'd go with your pumping the tank idea especially as the tank isn't full of fuel but I expect you've got a stirrup pump, but if there's a blockage you want to an open end for the blockage to exit and depending what the blockage is forcing it along could wedge it more.

At one time I thought the pumps had an external priming lever, it'd certainly be a good idea.

Also beyond the pump you should now check if there's fuel in the hose to the carbs and carb fuel bowls and give the tops a tap with screwdriver handle to check the needle/seat/float are free(d).

ETA:
>>Replumb the screenwasher? :)<< Navigator would love the job of being the fuel pump. 😁
Nigel Atkins

2) Lawnmover tank secured under bonnet and gravity feed. Don't forget to bung up any disconnected pipes in case the blockage clears itself.
AdrianR

Chris, the inflated inner tube idea is how I used to pressurise the brake master cylinder for brake bleeding, before I discovered that Easibleed had already made a device to do the same!

Pump isn't that hard to remove! I once did so at the roadside when my 1500 pump failed. I found the diaphragm had split so I made another from a piece of a plastic carrier bag! It was on a trip around Scotland and worked well for the remaining 2000 miles of the holiday trip!

>>Replumb the screenwasher<< I was thinking that but decided that the sparks from the exposed electric motor weren't a good idea with petrol!
GuyW

I replaced the pump last year, and I remember access was awkward and a faff. But agreed Guy, its doable by the side of the road.

The washer bottle is a nice idea, and mine is a manual one so no electric motor to worry about. :)

Monday looks like the next decent weather day which will give me time to get a few bits together and tackle the problem...
Chris Madge

Have you tried starting it with the fuel cap off, just in case a weird breather issue?
A 5 litre can of fresh fuel on top is not bad idea too.

But before all that - sounds like you have poked your head underneath to see if my obvious fuel tank corrosion and leak, as well as check for crushed/corroded hard pipe or perished pipe leak at the tank end? And then engine bay from fixed pipe to carbs.

I do have an SU electric pump in the ‘wrong’ place in the engine bay near the carbs and water bottle which might be a way to get you home, then fit in properly under the car? Also fit a new fuel filter. Need a live feed wire plus make up an earth wire and perhaps have with you a portable drill, Stanley knife and some fuel hose, clips and tie wraps. Note the under car rear mounting bracket may be NLA, but secondhand ones are around (sorry if this is A Series only info).

Either that get a rebuild kit for the pump if you have the original that you had replaced before? I am not au faint with Triumph pumps, but if it is the AC Delco type rebuild kits are around, including via those who stock old tractor spares.

Cheers
Mike
M Wood

It should be an AC Delco pump and, if my memory is right, a type Y.
These were a very commonly used pump for decades back in the day, and are still used on assorted agricultural stuff as Mike alludes.
Not all variants are rebuildable though. It's easy to tell - if the top of the pump is secured with five (I think) screws it's super-easy and can be done in minutes in situ without removing the pump, unless you need to replace the mounting gasket.
If the top is crimped on, bad luck. But they're relatively unusual.
Rimmer Bros do the kit. Seals, valves, springs, diaphragm &c. I got one in 2019 for Don's GT6 (same pump) for about ten or twelve quid IIRC. It's probably still in the Shed somewhere I don't recall that he used it.
Greybeard

Surely when collecting a car from storage you always take jump leads and a tow rope. 😜



I'll get me coat ...
Nigel Atkins

Chris

The following old thread may have some useful info on 1500 fuel pumps, in relation to the in pump gauze filter:
http://www.mg-cars.net/mg-midget-sprite-technical-bbs/fuel-pump-2015102001283510263.htm

Cheers
Mike
M Wood

I suggested putting the gallon in the tank and perhaps leaving the cap of for a few tries at starting, and if required work on from there.

It'd never work for me in a million years but for others it might well and quick easy and harmless to try.

If it holds fire do not forget to put the petrol cap back on as you wouldn't want any airbourne farm debris to get in ands contaminate your fuel supply.
Nigel Atkins

Greybeard - the original pump had the top crimped on and thus not serviceable. It had started to weep fuel at the crimped edge so i replaced it with a new pump. Shame, as it was a good pump and always got fuel to the engine even when all the fuel and drained back into the tank.

Hopefully the new pump just needs priming and some more fuel in the tank to increase the pressure head to help the pump. That's a bit rubbish though really, it should be good enough to run the car even when low on fuel.

If that doesn't work Ill rig up an electric pump in the engine bay to get me home.

Nigel - yes I had jump leads and tow rope with me, but the tow rope was useless without a second person to drive the pulling car of course ! Towing with a rope is a last resort option though really.

Chris Madge

Chris, I was joking, I'm very saddened by your lack of faith in your vehicle that you would take a tow rope and jump leads (unless for the farmer to use as permanent repair materials for fences or something).
Nigel Atkins

I know you were Nigel, I'm used to your humor :)
I still cant help but respond though !
Chris Madge

Wrong response Chris. 😂
Nigel Atkins

Let us know how you get on, I was expecting it to be running by now, before the storm.
Nigel Atkins

Chris

Think I bought a modern replacement mechanical engine mounted fuel pump of the AC Delco type, only to find that LCB I had meant it would not fit so retained and fixed the POs installed SU electric pump in the engine bay. All A Series engine comments.

This is what I bought, but 1500 may be different, I give this weblink to a pump manufacturer’s website as seems that many of our car parts suppliers stock this brand so there may be handy technical info on this website in addition to what is on Rimmers etc:
https://www.ptzfuelpump.com/en/fuel-pumps/mechanical/cars/pn-3422

Nigel - was not trying to steal your thunder on fuel tank cap off and adding fresh fuel - I am not always the most diligent or careful reader or memoriser of all previous comments. And my typing, spelling and proof reading before posting is slapdash and rubbish. We are outside the realms of the ‘good book’ (BL Driver’s Handbook for the model) but fair play for not admonishing lack of round the year use to those of us that do a winter lay-up! (Or like me have not got my project car back fully on the road)

Cheers
Mike
M Wood

Mike,
you stole nuffink from me, I only echoed what Guy had suggested earlier, I've never had an original idea, or much of a clue.

Chris knows he's a naughty boy by leaving the car languishing but, wait for this - he's restoring another classic at the same time as owning the Midget, some sort of self punishment for I know not.
Nigel Atkins

<<Lawnmover tank secured under bonnet and gravity feed>>

I picked up a lawnmower tank at Newark autojumble a few years ago. I had intended to use it when balancing the carbs on my Honda, as the tank had to be removed to access the carbs.

It was never used on the Honda, but I did use it to run the B, although I'm struggling to remember why!


Dave O'Neill 2

After a couple of hours work this afternoon I got the car is running. I think it was a combination of needing priming and a possibly a dried out seal in the pump.

I ended up taking the pump off the car, taking it apart to check it, reassembling, and plumbing it into a can of fuel and manually pumping with my hand on the lever. It worked fine. I fitted the pump back to the car with the inlet still plumbed to a can. That worked. So reconnected everything nice and tight and it works now.

A bit inconclusive, and I don’t trust the pump. I don’t have the patience for unreliable cars. So I think I’ll Fit a Hardi pump and blank off the hole for the mechanical pump.
Chris Madge

Chris. Any fuel pump can fail, both mechanical and electric, and I have had both fail over the years. If absolute reliability is required (or, as close as it is possible to get), consider either adding an electric pump to your mechanical system or a series of two electric pumps. I am running an SU and a "box pump" on an MGB and have had good success for something over ten years with it. But, I have both an original SU and a box pump last over twenty years in the past. SU pumps need to be used on a regular basis, box pumps less so. Hence, I run the SU full time with my box pump as the back up, tested about once a month to ensure it is still working properly.

Good luck on your project, Please keep us informed as to what you do and how well you like the results.

Thanks, Les
Les Bengtson

Does anyone know why 1500's weren't fitted with SU's like most Spridgets?

Anyway, unless you are after originality, why not fit an SU pump now?

Easy to source, either new or old or rebuilt. Either points or solid state. I prefer points. VERY long reliable service life.

I took the mechanical pump off my webber(28/36dcd) equipped Ford 1500gt, and replaced it with an mgb sized SU pump, and in roughly the same position as the Spridget pump. The result is much faster starting, far less cranking the engine to get fresh fuel into the bowls, and no lack of fuel to the webber. So likewise I'm sure it would work on a 1500 Midget perfectly well.

I know some people seem to distrust SU pumps for some reason, but there is no good reason to at all. In 43 years with my Sprite, I'm on my 2nd SU pump, and I rebuilt the original (new points and cap) which lasted circa 30 years with no trouble, and keep it as a spare. I was going to do what was suggested above, and mount it in series or parallel, but can't really see the need, given how very infrequently they cause trouble.
anamnesis

Electric pumps are nicer, you get the reassuring priming noise when you switch on and if they do play up can usually be restored by thwacking with a stick to get you home.

If you knew where it was mounted this could be done from inside the car, I have memories of doing this in the Morris Traveller my grandfather used as a farm runabout - he liked to buy pre 1960s vehicles to avoid having to wear a seat belt, and there was the bonus that it still had a crank handle start for winter use.
AdrianR

>>Does anyone know why 1500's weren't fitted with SU's like most Spridgets?<<

US Fed safety regulations.
In the event of a shunt (the assumption is) the engine is most likely to be stopped/stalled and therefore so would a mechanical pump. In contrast the electric pump will keep going, especially if the fuel line is severed/damaged, as long as there is power to it.

(If it was working in the first place lol😁).

My personal experience of AC Delco mechanical pump is that it is generally highly reliable and cheap and easy to fix if it does fail. But I agree about it taking a lot of cranking. OTOH that's not necessarily bad. At least it means there should be a bit of oil pressure before the engine fires.
Greybeard

This thread was discussed between 09/03/2021 and 16/03/2021

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.