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MG Midget and Sprite Technical - 1500 fuelling issues - where to start?

Today I finally got my wife's midget back together. It's not the prettiest but the parts which have been done are now done properly and should not need further attention for a long time.

The car was parked up in December 2020 and at the time had no known issues beyond the corrosion I have addressed. It was running fine. It was left with about 1/8 of a tank, today I added a gallon of fresh petrol. There are no visible leaks and there is no smell of petrol.

It is now not pulling fuel through the system at all.

I have taken the top off the fuel pump and the filter is clean, the pump is full and there is no fuel in the inlet or outlet pipes.

I have removed the pipe from the carb inlet and injected fuel with a syringe until the bowls are full. The car starts and runs perfectly until the fuel in the bowls runs out. Still no fuel being pulled through.

Clearly something has happened while it has been standing but what is the order of attack and, given that it is standing on a drive, what do I access and how?

Any thoughts/advice very welcome. I am hoping it is something simple as I would really like to use it on Thursday if possible.

Cheers

Alec
AG Gunner

Alec,
not sure what you mean with -"the pump is full and there is no fuel in the inlet or outlet pipes" but taking the pump off and checking that it works manually and doesn't need a repair kit would be a probable first step with the 1500 mechanical pump.

Also if you had E5 fuel from 2020 it might have gone-off and got water so check for that before putting it through your pump and carbs, the gallon of fresh may not help with that.

Personally I'd empty the tank of all its contents and put fresh fuel in, preferably the ones with the extra cleaning additives for the first couple of tankfuls at least and hang the cost.

You may also need to check any rubber hose for deterioration on the inside and out causing a collapse or blockage, and blockage in solid metal pipes.

If you are able to syphon through fuel to each connection on the fuel line starting at the tank and working forward it would check and flush through, you can save or dispose/use the fuel at each section/stage as required.

With the 1500 pump it's another reason to keep your battery well charged and in good condition (and all connections and earths) as even though the fuel pump isn't electric you can often need to have the starter turning to get the fuel through until the engine fires and continues to run.

Personally I'd recommend you fit a Hardi electric pump for fit and forget reliability and to save your starter and battery.

Good luck.

Nigel Atkins

Thanks Nigel,

Ref. 'the pump is full and there is no fuel in the inlet or outlet pipes' it is quite literal. I took the top cover off the pump and found it full of fuel, but inspecting both the inlet and outlet pipes they were completely dry, so I am presuming that the fuel in the pump is that which has been there since 2020 and no new fuel has pulled through from the tank, and no fuel has been pumped up to the carbs. Not knowing how the pump works I am unsure whether or not that itself can be used to diagnose that the issue is in the pump (I don't know whether it should be able to pump itself completely empty or works on a sump principle so you would always see it full of fuel but it will not pump out any more unless more is drawn in).

Not sure how the fuel line runs between the pump and the tank but I suppose if I can either drop it down at the engine end or find something to connect to the end and pull fuel through (big syringe?) I should be able to check that line without any dismantling. The line from the pump to the carbs is much easier as I can already access both ends to blow through. I know there is no issue downstream of that.

I couldn't immediately see how the pump attaches to the block. Hopefully it will be more obvious in daylight.

The battery is currently excellent, having been kept fully charged off the vehicle. We also have a spare, so that shouldn't be a problem. Just need to get it pulling fuel through one way or another!

Alec
AG Gunner

The pump should be an AC Delco type Y, which came in several flavours. If you're lucky it's the one with the top held on with 5 screws ( and it sounds like it since you've had a looksee inside).
The good news is there's a rebuild kit for these pumps which is inexpensive and laughably easy to fit.
Basically it's the poppets,springs, diaphragm and seals.
The pump is mounted on the block by two screws with hex heads. Sometimes there's an insulator block between the pump and the block, but not always - it's a bit of a lottery.
The pump can easily be rebuilt in situ but if you remove it be careful putting it back because it's possible to get the lever the wrong side of the cam then it's a sump off job to recover the broken lever.
Good idea to drop the fuel line down below tank level to see if fuel comes through. I like your thinking.
Greybeard

ETA: Grey posted whilst I was still typing

Alec,
sorry I misunderstood what you meant.

Suck out the fuel in the pump with a syringe and transfer it to a very small clear glass or plastic container and leave it stand (somewhere cool and shaded) to see if looks a bit cloudy/milky and separates out. Also smell it, does it have an overwhelming petrol smell (compare to fresh petrol if you can).

If you can also suck petrol from the bottom of the stilled settled tank you can also visually inspect that in the same way as above.

My concern is that you don't want to pull water through the fuel system causing you more problems, also you don't want to pull crud or bits of disintegrated rubber, or that hoses have collapsed or are sucking in air through cracks or poor/loose connection. You may not have any of these problems and it's just the pump (see Chris's quoted post later).

Any idea what the petrol was that you put in December 2020 (Tesco 95 or 99, Shell 95 or V-Power, other brands and supermarkets 95 or 97/98)?

The pump should pull the fuel up as the engine turns over trying to start as the pump is driven off the engine but it can take a while or not at all if the diagram or other parts of the pump are faulty. Hence the need for a good battery and connections as you churn the engine over by the electric starter motor. You don't want to churn the starter for too long and too many times in succession as there'll be heat build up and excessive wear.

You could try disconnecting the pump outlet hose to the carbs and feeding it to a collecting container and just try turning over the engine and pump with the starter to check if and when petrol gets through the pump. Obviously care must be taken with petrol in the engine bay. I'd give it about 6 attempts of about 5 seconds and then leave it a while before trying the same once more - others might know better.

Or -
Chris Madge, Bristol, United Kingdom, Posted 18 April 2021 at 20:17:24 UK time
"I recently had problems with my 1500 mechanical (new) pump. Now its sorted it happily self primes when turning the engine over even after being sat for a few weeks.

The problem was a dried out seal, and the screw at the top needed tightening up as it was sucking air rather than fuel.

With the pump off the car, you can hand pump the lever and it should draw fuel." - Note from me IIRC the problem with the new pump returned and was replaced with a Hardi, but that was a new made pump hopefully yours is old and better made.

It's just two 5/16" nuts (1/2" socket or spanner) on studs that hold the pump on, behind it, possibly a spacer, and a paper gasket. How awkward the pump is get at and take out and put back in I don't know.

See photos below of new pumps, it's (very, see Grey's post) important that the lever arm is put back into the engine the way it came out.

Others may be along with more and better ideas.






Nigel Atkins

An easy check at this stage is to disconnect the incoming fuel line at the pump. Push the end of a suitable piece of hose over the open end of the fuel line and blow hard down the pipe. You should hear air or air bubbles inside the tank, indicating that the fuel line that far is clear. If not then one of the lengths of rubber connecting hose may have decayed, swollen and blocked the pipe. Or some tanks had an internal gauze filter that can block with fuel sediment or varnish.
GuyW

I wouldn't try that in this weather you might pass out. 🤪

I think syphoning the fuel from the tank at the pump end would be better to save blowing any crud into the tank or to blocking a hose or pipe - but perhaps your lungs would have to be used to inflating rubber hotwater bottles to do that.

I put about syphon in sections to find at which points might be causing problems but Alec could skip to just trying at the pump inlet hose end. That way if the petrol is good and gets that far without crud he could squeeze/clip shut the hose to hold the petrol there and reconnect to the pump inlet and try starting the car.
Nigel Atkins

I hate any attempt at syphoning petrol. Even if you start the Syphon off properly so as not to get petrol in your mouth, you still get the taste of the fumes. Blowing is far better for clearing debris or partial blockages!
GuyW

Oh, no, I meant using a syphon pump, I thought I'd put that, forgot the word pump, even sucking on the petrol fumes would make me ill. I'd never suggest making yourself ill over a lump of metal!

If you had a big enough syringe type thing that might be enough if there are no faults in the line.

Nigel Atkins

This is getting more confusing.

1. Applying pressure to the end of the fuel line back to the tank with a bicycle pump produces a clear sound of air being pushed through the fuel, so that is completely clear.

2. The pipe from the fuel pump to the carbs is also completely clear (easily checked).

3. The original fuel pump is an AC sealed unit so not serviceable. It appears to operate fine when pushing the lever by hand - pressure is produced and held when pushing the lever with a finger over the hole. Holding for several seconds the pressure does not change.

4. The 'fuel pump repair kit' from MGOC is a complete new pump. It's the type which needs a spacer block, but it comes complete with one.

5. I carefully removed the old pump and found it was hooked upwards in front of the cam lobe, creating a sort of 'spring loaded effect' which tilted the pump body upwards when the nuts were off. I put the new pump unit on the same way (with spacer block) and felt a similar spring loaded effect.

6. Turning over the engine on the starter there is no pressure felt on the pump. Feeding petrol in to the short length of flexible hose on the inlet side results in nothing - it is not pumped out the other side.

So, the question is, why is neither new nor the old pump pumping when it was working fine when the car was parked up? Does this mean dismantling the whole cylinder block to take a look at the cam lobe or is there something less drastic I can do first?

Alec
AG Gunner

Alec, carefully inspect and check each of the lengths of flexible rubber hose between the fuel tank and the pump. They can split and allow the pump to pull air in rather than sucking the petrol through. Splits there don't necessarily leak out fuel, so can be hard to detect.
GuyW

Guy, I was fearing that would be the answer. The car is currently sat in a Carcoon. Getting it off by pushing it is extremely difficult and jacking it up is liable to damage it, and I can't fit underneath without doing so.

Before I do, I will run the pump with new lengths of hose in and out of a jam jar as that will confirm whether or not the pump is working. If it is, it looks like I will be pushing the car around in tomorrow's heat.

Oh what joy.

Alec
AG Gunner

Alec,
don't be offended just checking, you have the in and out the right way round (arrow mark is inlet I think) and I don't know what MGOC use as a mechanical fuel pump but I hope they didn't supply Chris with his, did you check it's correct for your model over the phone.

That's me out of ideas other than has already been suggested on the thread.

Below for general illustration only.




Nigel Atkins

Arrow is on the inlet of the Moss pumps at least.


Nigel Atkins

Hello Nigel, not offended at all. Always best to eliminate the easy ones first.

In practice, I can safely say yes, they are correctly connected up. The old one was of course connected from the start and the new one looks very much like the Moss one you have illustrated, with a big arrow to avoid any chance of confusion. In practice, the inlet is through the top in both cases so the fuel goes down through the internal filter first.

My wife went in and picked up the new pump in person on her way home. We are fairly close to MGOC and they have her car on record, so they know what we are asking for (and yes, it is correct, with the adaptor fitted).

Checking the pump with a jam jar will be the first move tomorrow. If that works then I will trace my way back through the fuel line renewing all the hose section (I think there should only be two unless it has been altered at some point). If the pump works fine when pumped by hand but doesn't work on the engine then I don't have a clue what to do next.

Alec
AG Gunner

Alec said...

"Does this mean dismantling the whole cylinder block to take a look at the cam lobe or is there something less drastic I can do first?"

Okay I know this is a bit left field but are you certain that the camshaft is turning? It's highly unlikely that the chain has gone or the drive key sheared but it has been known to happen.
Easiest check in the world - you can see a rocker or two through the oil filler.
Greybeard

I think there was an earlier post which indicated the car ran ok when the fuel bowls were filled??
Bob Beaumont

I presume you do have the correct pump? The pump bodies look much the same, so it's no good comparing that. The difference is in the length and shape of the actuating lever, and whether there should or shouldn't be a block spacer. If you fit a short lever arm pump with a spacer it won't work.
GuyW

Oops Bob, you're right of course.
Mea culpa - as you were chaps.

Sounds like the pump isn't sucking hard enough to self-prime. They can take a while at the best of times.
I have a priming bulb from an outboard engine in my project box for this exact reason. One day I'll try it.
Greybeard

Alec,
it's Sod's Law whichever end of the fuel pipe you start looking the issue will be the other end. If your fuel supply from tank is as shown on the Moss diagram there's only a couple of short runs of rubber hose to check and their clips, or just replace with modern fuel hose if not already done.

To protect the Carcoon base sheet you could perhaps use an old blanket and then wood to spread the loads from jack and axle stands. Or leave it until tomorrow when the weather is better.
Nigel Atkins

I expect the pipe inside the tank has corroded sufficiently that it's drawing air in from above the petrol level.
Rob
MG Moneypit

My original 1500 mechanical pump was the sealed type and worked great until eventually it started leaking. I replaced it with an after market pump which was garbage and I wasted time fixing it after a short period of time. In the end I ditched the mechanical pump and fitted an electrical Hardi pump which is a better solution in my opinion.


If the mechanical pump is not pulling fuel through there is either air getting in somewhere or the diaphram of the pump is damaged.
Chris Madge

Got it running.

Thanks everyone for the advice and comments - even when it turns out not to be that it is extremely helpful to have ideas to work from rather than just standing looking at it without a clue.

The fuel pump is working fine (actually both old and new). The problem turned out to be that the upper hose section that goes on the pump had a crack in it, hidden beneath the braid. It didn't leak under pressure with a bicycle pump jammed in it but was enough to let air through under low suction from the pump.

New section of hose and it's all good. I renewed the other sections too, except the one at the bottom as it would have meant draining the tank, and when I dropped the front pipe section down it was flowing well but not leaking. In time I will do it, but it's not urgent and is much easier done with the car somewhere easier to access.

The back section of pipe has been replaced at some point with a flexible fuel pipe of the same diameter. I'm not sure what exactly it is, spiral wound metal armoured I suspect as it is very flexible but not collapsible. It's a good choice and I have left it alone as it is in good condition, although again, once I have it over a pit or up in the air I will take a proper look as I suspect it hasn't got the proper upward bend in it.

I had flattened the battery yesterday so couldn't use that to pull fuel through. I primed the carb bowls with a syringe again and it started straight up, ran for a bit and suddenly stalled. However, it started straight up again and ran fine, including a quick trip to the roundabout a mile away and back. It's a bit odd getting used to the feel of it again - the suspension is so different compared to my Volvo estate! However, the engine, clutch, gears and brakes all work (the latter as much as they ever do), as do the indicators so I am good to go for Thursday if it isn't raining. Just need to set up the headlight again as that isn't working, mainly because the wiring is wrong as the labels fell off so I guessed! Might have to use the multimeter instead.

Ready just in time for the rain!

Alec
AG Gunner

Good spot Alec. Well done.
Greybeard

Alec,
well done on finding it.

Cigar to Guy for mentioning air getting pulled in via hose, I thought I'd put that and checking hose clips were tight but it must have been another of my visits to Fantasy Island and on another thread (perhaps one I read from the Archive looking for Chris's quoted post).

A couple of lesson to remember now you're trying to keep the Midget running, charge and condition of battery, and braided hoses over rubber can hide a lot of stuff especially modern made ones.

On the theme of rubber your brake may seem below par as probably the tyres have hardened through age and lack of use, same perhaps for the brakes. The tyres are part of the braking, steering and suspension systems so if they've not in good condition, regardless of tread left on them replacing them will good quality new tyres can make a big difference.

On the other hand regular frequent use of the car on reasonable length journeys, at least 15-20+ miles will help improve the whole running of the car, and find snags to get them out of the way. You'll also get more used to driving the car again and relearning how it could or should go.

Wiring diagram and colours are in the Driver's Handbook (assuming they remain as factory).

If you've not already done so, grease the 6 front suspension nipples every 3 months and just before MoT.

Enjoy the drive tomorrow.


Nigel Atkins

Well done to AG Gunner on finding the fault, and keeping everyone informed on the outcome.
Just my pennyworth (and possible red herring) . . cracked fuel hose . . . ethanol fuel . . . maybe related? Just me thinking out loud . . .
J Thomson

I have a few more things to sort out but at least the headlight now works properly, having figured that one out.

The new fuel hose sections are brand new. Not sure whether that means they are any better against ethanol but at least they have more years in them.

My wife has just taken it out for a run and filled up with petrol. It is running nicely, no issues and the brakes and suspension are settling down (or getting more familiar again). Tomorrow will be a 15 mile run to work, then back to pick up my daughter from school in the next village to us.

A few more bits and pieces that would be good to improve on (including how to grease up the suspension and getting the windscreen wipers to work on two speed again) but nothing that will stop us using it now until the winter. Next winter's work will be to sort out the front bumper (metal sections are solid but not great so will simply replace if I can get the parts) and the front valance which just needs a tidy up and painting satin black. I will also take off the driver's side wing and see what lurks beneath (and reinstate the satin black section), but all that can wait.

Alec
AG Gunner

This thread was discussed between 17/07/2022 and 20/07/2022

MG Midget and Sprite Technical index

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