Morris Minor Owners Club

I’ve got a reoccurring problem that’s getting me scratching my head. I’d love some thoughts please.

1967 1098 Traveller. Standard engine, distributor and carb.

When on a run the car is a pleasure and performs faultlessly...until after about 40 minutes when all of a sudden revs die down and engine stops. Restarts immediately and drives normal, then after 5 mins or so sometimes does it again.

Electrics seem fine, ignition warning light comes on when engine dying and starter works no problem. Starts on the button when cold (and after the fault occurs).

Not overheating, I went through the whole cooling system last year and is fine.

Puzzling. Anyone experienced this before?

I've never experienced it myself, but I know some people have experienced a vacuum in the fuel tank that can lead to fuel starvation, possibly giving symptoms like those you describe. It would be worth taking the petrol cap off the next time it happens to see both whether it hisses (indicating a vacuum) or indeed cures the problem. It's a long shot, but easy to try!

Thanks, will have a look at that next time.

If it is that, one would expect the fuel pump to be ticking away furiously?

oliver90owner wrote: ↑Fri Oct 16, 2020 11:09 pm If it is that, one would expect the fuel pump to be ticking away furiously?

Good question - as I've not experienced it myself, I'm not sure. I suppose it depends whether the (relatively weedy) SU pump is able to overcome the vacuum, as it 'pulls' the fuel rather than pushing as on many other BMC cars. I reckon that even a small vacuum could 'defeat' it, meaning that it wouldn't be ticking madly. I've no evidence to back this up with though!

Allthough its never the coil(as the old sage would say RIP) sometimes it is.If you can find an old known good one do a swap and see what happens .

First thing to check immediately after the car comes to a halt: Is the fuel pump supplying fuel? Does the pump have to tick a lot before the engine re-starts? Simply pull the supply pipe off the float chamber and briefly turn the ignition on to check. If that is working alright then check through the sparks. Coil, rotor arm and condenser can all give those symptoms when they begin to fail.

If performing the above test, be careful. The engine and in particular the exhaust will be hot, and you do not want to spray petrol on to it. A small container would allow you to return the fuel ejected to the tank.

Not for the faint hearted, but it is any spark, in the vicinity, which will ignite petrol vapour, not normal manifold and exhaust. Needs to be almost incandescent?

I know because my engine was drenched in petrol at a little over a hundred miles an hour - a long time ago (July or August 1976). Switched off the ignition Immediately the passenger compartment filled with petrol vapour. Petrol was still boiling off the head (after making a quick exit) after stopping.

Very likely, too, it was lucky that neither of us were smokers!

You state that “ignition warning light comes on when engine dying”.
Have I understood you correctly that the ignition light comes on whilst the engine is coming to a stop from speed i.e. on overrun. If that is the case then when the engine has stopped turning the light will go out when it should still be on.
The above would suggest you are losing the switched ignition supply.

oliver90owner wrote: ↑Sat Oct 17, 2020 12:13 pm
I know because my engine was drenched in petrol at a little over a hundred miles an hour - a long time ago

Wow! That's some Minor you have there!

StillGotMy1stCar wrote: ↑Sat Oct 17, 2020 1:11 pm You state that “ignition warning light comes on when engine dying”.
Have I understood you correctly that the ignition light comes on whilst the engine is coming to a stop from speed i.e. on overrun. If that is the case then when the engine has stopped turning the light will go out when it should still be on.
The above would suggest you are losing the switched ignition supply.

Yep, that makes sense now you come to mention it. I’ll have a proper look at the warning light next time. I can’t remember whether it came on when I stopped or before.

oliver90owner wrote: ↑Sat Oct 17, 2020 12:13 pm Not for the faint hearted, but it is any spark, in the vicinity, which will ignite petrol vapour, not normal manifold and exhaust. Needs to be almost incandescent?

I know because my engine was drenched in petrol at a little over a hundred miles an hour - a long time ago (July or August 1976). Switched off the ignition Immediately the passenger compartment filled with petrol vapour. Petrol was still boiling off the head (after making a quick exit) after stopping.

Very likely, too, it was lucky that neither of us were smokers!

Echo that, I had a Mini 850 in the 80’s and the petrol feed came off Of the carb, squirting petrol fleetingly from the pipe end into the carb, so the engine still ran (badly), and the petrol pump kept it squirting, also dripping onto the hot manifold. No spark, no fire.

Ok, an update. Haven’t been out on a long (ish) run for a while, but did that today.

Was running great, then as per usual the engine slowed and died after about 25 mins.

liammonty I checked the fuel camp, no vacuum.

This time the engine would turn over and restart but then die after throttle pressed a couple of times. No smell of petrol under the bonnet. I checked the carb dashpot, couldn’t see any oil in it, which was strange as I had filled it over Christmas. Got the Missus to find the top up oil (SU from ESM) in the garage and drive out to me with it. Filled the dashpot, started, ran, all good. Drove home.

So I think that’s my problem. Going to rebuild the carb and see if that cures it. More to follow when I’ve done that.

Cheers
Keith

Check that the short flexible lead inside the distributor is not fractured under its cloth covering...this can lead to intermittent ignition failure...as it can contact / disconnect as the advance mechanism operates...

Taupe

A few years ago my moggy would run perfectly for 25 minutes or so, then just die. After a few minutes, it started easily, then after another 20 odd minutes, just die. In the end, the fault was found to be the coil - even though it was a new Bosch one, I replaced it and (touch wood) the problem has not happened again. I pulled out a lot of hair trying to figure out the problem!

Good luck, I hope you find the issue causing the problem soon!

Pete Bags wrote: ↑Sun Jan 03, 2021 3:14 pm A few years ago my moggy would run perfectly for 25 minutes or so, then just die. After a few minutes, it started easily, then after another 20 odd minutes, just die. In the end, the fault was found to be the coil - even though it was a new Bosch one, I replaced it and (touch wood) the problem has not happened again. I pulled out a lot of hair trying to figure out the problem!

Good luck, I hope you find the issue causing the problem soon!

My recurring problems a couple of years ago, of suddenly cutting out, I eventually traced to an intermittent connection in the Coil....
viewtopic.php?f=11&t=69837&hilit=Coil&p=637860#p636467

Ok thanks. I’ll check the coil too. Daft not to take the advice of those who know what they are talking about!

Coincidence that the dashpot oil was gone and it ran fine when topped up? I had left the car to cool for 15 mins while the Missus came with the oil. I figured the mixture was too weak at revs with the damper not working properly?

Pete Bags wrote: ↑Sun Jan 03, 2021 3:14 pm A few years ago my moggy would run perfectly for 25 minutes or so, then just die. After a few minutes, it started easily, then after another 20 odd minutes, just die. In the end, the fault was found to be the coil - even though it was a new Bosch one, I replaced it and (touch wood) the problem has not happened again. I pulled out a lot of hair trying to figure out the problem!

Good luck, I hope you find the issue causing the problem soon!

Usually easily diagnosed by checking for an ignition spark at the king lead, immediately after the fault arises - before the coil can cool down.

"Coincidence that the dashpot oil was gone and it ran fine when topped up?"
Were that the problem I would expect issues to show up straight after firing up and trying to drive off, not after 40 minutes of 'performing faultlessly'. But you will soon find out when you next go for a longer drive!