Morris Minor fuel problem - very confusing

[Mouseamy]

I have a 1960 Morris Minor 2 door saloon 948cc with an intermittant starting / stopping issue and wanted to see if anyone else has had similar issues.
Car runs for about 15 minutes then slows and stops as if there is fuel starvation, leave the car for a bit then she sometimes starts and runs for a while then stops again. When shes running she doesn't miss a beat and pull in every gear.
Replaced the following with new:
SU Fuel pump
Metal fuel line,
Contactless ignition
Spark plugs
HT leads
Air filter
Electric fan
Cleaned out the tank and lines.
Checked the float chamber, all operating as they should.
Have been running her on ordinary unleaded for a while, then premium unleaded, then a mixture of the two, not much difference between them as far as I can tell.
Read an article about fuel evapouration and heatshields one can fit over the float chamber but unsure if they really makes a difference.
Would really like to hear from anyone who has had the same or similar issues, thanks in advance.

[mad4amanda]

have you cleaned the vent in the fuel cap , my dads old mm used to suffer from this?
has the cap been replaced with a non vented one?

[littleredrooster]

I have a vague recollection of this fault - hope it helps you!

IIRC, there are two types of SU fuel pump - one needs a positive head of fuel (i.e. it sits under the tank like a Mini), the other one will lift fuel from a tank which is below it. I believe that they look identical, but are not interchangeable.

Again, IIRC, the Moggie fuel pump is on the front bulkhead, so needs to lift the fuel up from the tank, yes? A Mini pump will not do this and will produce fuel starvation symptoms.

Check that you definitely have the correct pump, or will someone with more knowledge pop in and tell me I'm talking bolleaux!

[Pothole]

mad4amanda said:

have you cleaned the vent in the fuel cap , my dads old mm used to suffer from this?
has the cap been replaced with a non vented one?

Definitely have a look at this. A telltale can be an obvious release of pressure when you open the cap.

[838HNK]

I had a similar problem and it was down to one sticking needle valve on one float chamber.

The car would run for a float chambers worth of fuel then cough horribly.

I would stop and the flow to the float chamber was very slow but enough to slowly refill it. Run it again and similar.

The car had sat for a while so think it was waxing up ..

Not sure if this helps but doesn't take much to pull both float lids and let some nice clean new fuel flow through...

[Huntsman]

Coil?

[gothatway]

838HNK said:

Not sure if this helps but doesn't take much to pull both float lids and let some nice clean new fuel flow through...

Single carb on a Moggie (originally).
Easiest thing to check first - as suggested - is that the filler cap is vented. Next time it happens, quickly get out and check to see if there seems to be a vacuum under the cap (hisses when removed).
Then yes, remove the float chamber lid to see if the valve is sticking, or if the pump is giving up (does it tick away merrily when the engine stops ?)
If you've got fuel in the float chamber then it's probably the ignition, so check if you have a strong spark.

[eldar]

Pothole said:

Definitely have a look at this. A telltale can be an obvious release of pressure when you open the cap.

A slightly concave tank is a giveaway! When the engine cuts out remove the fuel filler cap - does it suck in air?

[Mouseamy]

thanks all, new SU pump fitted by Morris Minor Centre, West Malling, Kent. so think that should be ok, vented petrol cap is a thought as it is a lockable type. mind you it ran for 6 -7 months without any probs so not holding out too much but will check tomorrow. will also check the float chamber needle, i cleaned it before and it seemed to be working correctly, i take it there is not any lubricant to use other than the petrol itself.

Edited by Mouseamy on Sunday 29th July 23:10

[davepoth]

As Huntsman said above, check the coil. If it is at fault it will likely be uncomfortably hot to touch when the car has cut out.

[bstark]

Another vote for the coil - these are exactly the symptoms you would expect. Dirt cheap on the A series as well...

[Skyedriver]

I'll forth the posts suggesting coil
Was reading this and recalling a Marina I had, did exactly the same thing

Only other thought was dirt in fuel tank, pipe sucks it onto the in-tank filter, blocks filter, engine off, ignition off, suction stops, bits fall off filter, car starts, repeat....

[anonymous-user]

I've had a problem similar to this twice over the years on my Morris van, both drove me nearly mad. First time it was one ancient wire to the distributer that looked fine but had broken inside the insulation but looked fine. When hot and moved around it would intermittently fail giving what felt like fuel starvation problems. Only found after replacing everything else. Same car a couple of years but few miles later. Similar symptoms. This turned out to be the new graphite-cored plug leads. I put back the ancient copper ones and the problem ceased. This again was after hours of mucking about thinking I'd fixed it several times.

Touch wood, it's been fine for years with only a clean of the points every year or so.

[Mouseamy]

Dirt in tank seems feasible as she is 58 yrs old, and has been on a rollover jig having some welding done recently.
What the best way to clean out the tank without removing it from the car?

[anonymous-user]

Mouseamy said:

Dirt in tank seems feasible as she is 58 yrs old, and has been on a rollover jig having some welding done recently.
What the best way to clean out the tank without removing it from the car?

That reminds me of a fuel starvation problem I had on another car. It would run fine for ages then without warning suffer fuel starvation. It would start again after a short wait. To cut a long story short after trying everything else I ended up removing the tank expecting to have to remove loads of silty, rusty crap. It was as clean a whistle except for a small waxed cardboard disc, the sort you get in a bottle lid to provide the seal. This must have fallen in when someone added some fuel additive and happily floated around only to be occasionally sucked onto the end of the pick-up tube thus blocking it. Hours of work just for that.


Getting the tank off a Minor is pretty easy. If it's cruddy either clean and seal or just get a new one, I think repros are available.

[Mags]

I vote for non-vented tank cap or coil.

[LuS1fer]

Sounds like the coil breaking down as it heats up.
The other thing that I had on my A40 was the wire from the ignition to the coil which was frayed and once replaced, ensured total reliability.

[Mouseamy]

Checked the wiring as far as I can without replacing, I am going to replace the coil and let you all know how I get on. Thanks for your help so far, great website.

[RicksAlfas]

Have you lubed your dashpot?!

[ARHarh]

Having owned a minor for 21 years I have fixed every fault. My first thought was coil. Second was wire from coil to dizzy. 3rd wire from dizzy baseplate to dizzy body. If none of these I would check the choke cable has not jumped out of its mounting on the carb you can here the pump working so that will be obvious. It could also be the rubber fuel pipe collapsing.