Car losing power….where to start

[Andyhereford]

Any suggestions please as to what to look at.
I was driving my Minor home yesterday…1969 4 door saloon, all standard.
While I have not used the car much over the winter it always starts reasonably easily and goes quite well. Yesterday, while nearing the top of a not very steep hill, the car suddenly lost all power, came to a stop and the engine cut out. The car restarted first time of asking and continued down the other side of the hill as if nothing had happened however on getting to the flat at the bottom of the hill it started running very unevenly and again eventually came to a stop and the engine stalled. Again it restarted first time and I managed to limp home with the engine losing power and stopping when ever the engine came under any significant load.
Once home in the garage of course the car behaves as if nothing happened!
There is petrol in the tank.
The petrol pump, which I replaced a couple of years ago, appears to be working properly.
There are a few air bubbles ( always have been) on the tank side of the petrol pump but these “jump” around when the engine is running and don’t seem to cause any problem.
The engine is not smoking excessively.
I can not hear any misfiring in the engine.
The plugs are relatively new. Plugs 1,2 and 4 are covered in dry black carbon. Plug 3 is covered in wet black carbon.
Engine starts, runs and revs fine and there is no noticeable leakage of either exhaust or oil / water from anywhere in the engine.
The engine is old and no doubt quite worn but it doesn’t use any oil or water and I certainly don’t drive it hard. It normally pulls quite well and, while not the faster Minor around will do 40 / 50 mph in top gear.
My initial thought was some sort of intermittent fuel blockage. The tank is original and no doubt has some muck/ debri inside it. Looking at the plugs I imagine that the mixture is also too rich. I also have never looked at the cylinder compression…could this be factor.
I had the cylinder head off last year and at the time all the valves looked OK. A new cylinder head gasket was of course fitted and torqued down. It has run fine since then.
Any ideas as to where to start to solve this problem please.
Thanks

[KeithL]

How long has the petrol been sat in the tank, what petrol was it (E0, E5, E10) and how full was the tank? It is possible the fuel has gone off over the winter.

[svenedin]

As you have a 1969 car, does it have a PCV valve? My 1969 car does and so do a lot of 1969 cars I have seen. However, they have quite often been removed.

If it does have a PCV valve, check the diaphragm for a hole and also check the rubber pipework for splits. Any leak will draw in air causing the mixture to become weak and the engine to stall.

Just a thought!

Stephen

[oliver90owner]

I would start with checks. Colour of spark at the plugs, fuel delivery by the pump, any loose electrical connections.

Number three appears to have a compression problem - but not associated with the present problem. Yes, the mixture appears to be too rich, but unlikely to be the cause of this issue.

You say there is no obvious leakage - but is the cooling system at its normal level? Is the heater working normally?

Could be electrical or fuel related - fuel supply is marginally favourite without the checks mentioned above. If low on fuel and with debris in the tank, I might start there - again, if the checks don’t reveal anything untoward.

[les]

I once had an issue with a 944, although not a Minor, the same would apply, when under power it would cutout but start again, I suppose there are many possibilities but in my case it was eventually traced to a bad/thinning connection to the fuel pump. Maybe, although I don’t know, when pulling hard the pump drew more current causing the bad connection to break down. Could be a starting point !

[svenedin]

I once had an issue with a 944, although not a Minor, the same would apply, when under power it would cutout but start again, I suppose there are many possibilities but in my case it was eventually traced to a bad/thinning connection to the fuel pump. Maybe, although I don’t know, when pulling hard the pump drew more current causing the bad connection to break down. Could be a starting point !

I think that may be a very good call because the OP had problems with a failing connection to the dynamo I seem to remember. When the connection fails at the spade connector the wire feels abnormally floppy because most of the strands are broken. I'd suggest checking connections to pump, coil and distributor on that basis.

Stephen

[Andyhereford]

As always thanks to everyone for pitching in with suggestions.
To try to answer some of the points raised.
Keith….I only use E5 petrol, never keep too much standing in the tank and tend to top up with fresh as and when I take the car out. So I don’t think that the petrol is stale.
Stephen…Not sure what the PCV valve is…any help please and I will check as suggested.
Oliver…..Water level ( and oil level) are normal / static.
Les and Stephen…I will check the various wiring as suggested. Visually it all looks OK but I will check the connections as suggested and repair/ replace if necessary.

One thing that puzzles me is the fact that is that the loss of power / stalling only happened on the road when the car was under load that yet back in the garage….on the flat of course…the car will start and rev as you would expect.
One thing that I should perhaps have mentioned which has just occurred to me is that when the car was being restarted yesterday on the road I could hear the petrol pump was having to “ multiple click” each time as if it was having to refill the float chamber …..like it does when you have left the car for a while and go to restart it. Normally with my car if you stop the engine / the engine stops and you restart it again immediately the pump either doesn’t click or it only clicks once or twice.
Anyway…thanks for all your help

[svenedin]

PCV valve is a mushroom shaped valve on the inlet manifold. They are rare on Morris Minors.

What you describe sounds more like a fuel issue. Car under load would be using more fuel. Perhaps the pump can cope with the fuel demand at idle but not when under load on the road.

I would suggest you disconnect the fuel hose from the carburettor, place the hose in a suitable container and turn on the ignition (but do not try to start the car). Check that the pump is producing a good flow of fuel.

I do not understand what you mean in your first post that there are "air bubbles on the tank side of the pump"???????? Does this mean there is some kind of filter on the inlet pipe going to the pump? There should be no filter, there is a filter inside the pump (that can be removed and cleaned). There is a copper fuel line on the inlet side of the pump.

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[oliver90owner]

Quote One thing that I should perhaps have mentioned which has just occurred to me is that when the car was being restarted yesterday on the road I could hear the petrol pump was having to “ multiple click” each time as if it was having to refill the float chamber ….. Unquote

That was a serious omission, which should clearly indicate where to start your checks!

[Andyhereford]

Thanks Oliver for your helpful comment.
There is no PCV valve.
I will investigate the various fuel issues identified.
Thanks everyone for your help.

[svenedin]

I am still puzzled by these “bubbles on the tank side of the pump”. What is this? You can’t see bubbles inside a copper fuel pipe so what do you have there?

Your pump is fairly new so I would suggest the pump is drawing in air from somewhere on the inlet side. This could be anywhere from the fuel line connection to the tank right up to the union with the pump including the actual union of the metal inlet with pump body. As part of your investigations I would routinely remove and clean the pump filter. If it is clogged with rusty particles you have a rusty fuel tank.

I have had problems in the past with even new pumps where they weep petrol from the unions of inlet and outlet with the pump body and they still wept even when the unions were very tight. It was very small quantities but enough to make the engine bay smell of petrol and cause a dampness around the unions. In the end I resorted to thread sealant (Permatex) on the threads that go into the pump body which completely eliminated the problem. Don't use thread sealant on the filter thread because that needs to be easily removable to clean the filter.

I would start at the pump end but if this is unsuccessful then you will have to get under the car and tighten the union between metal fuel line and tank. There should be one continuous metal pipe from tank to pump with no joins.

I have seen cars where the metal fuel pipe from tank to pump has been shortened and a piece of plastic pipe with an inline filter placed in the last bit to the pump. This is what I think you may have. It is a bad idea and likely to cause fuel vaporisation problems. This is where when the engine bay is hot the fuel vaporises in the fuel line and then the pump is trying to pump vapour which results in frantic clicking of the pump and no fuel so the engine stutters and eventually cuts out.

Stephen

[jaekl]

What colour is your distributor rotor?

[myoldjalopy]

What colour is your distributor rotor?

I did wonder about the rotor arm as the symptoms mirror those I had years ago caused by a rotor arm breaking up. Most problems of this kind are ignition related but it doesn't quite explain why, when trying to re-start the car, 'the petrol pump was having to “ multiple click” each time as if it was having to refill the float chamber'. Still, I think it worth swapping in a spare rotor arm to check, especially if the old one is a black one.

[Andyhereford]

Stephen, Jackie, Myoldjalopy

The inlet fuel pipe is how you describe ….. the metal pipe has been cut about 6 inches from the pump inlet and the two are joined by a short length of plastic tubing. In this short length of pipe there is normally a couple of small bubbles. Up until now this has not caused any particular problem but perhaps I might need to think about replacing the petrol line from the pump back to the tank.
The rota arm is black, I will check it and if needs be replace it. I think that I have a spare. Just out of interest what is the difference between the black and orange rota arms.
Thinking about this more I feel fairly certain that this is a fuel issue and for some reason…blockage, poor electrical connection, ?, the pump was not delivering adequate fuel to the engine. It started happening when the car was going up a hill on a fairly rough country lane so any muck that there is in the tank would have been disturbed. Also I have a filter between the pump and the carburettor which I intend to change as I suppose this could have become blocked with any muck disturbed. I will try to get to the bottom of the problem and will let you know how I get on.
Thanks again for all your help / interest.

[myoldjalopy]

See here about rotor arms: https://www.distributordoctor.com/rotor_arms.html
I (and others) have had black ones fail suddenly in the past and one that caused on/off running problems before I cottoned on to the fact that the rotor was breaking up intermittently. It wasn't obvious looking at it though. For the last 15 years or more I have used the Dizzy Doc's red rotor arms without issue.
Of course, it might well be a fuel issue but if you have a spare rotor it only takes seconds to swap it in......

[svenedin]

See here about rotor arms: https://www.distributordoctor.com/rotor_arms.html
I (and others) have had black ones fail suddenly in the past and one that caused on/off running problems before I cottoned on to the fact that the rotor was breaking up intermittently. It wasn't obvious looking at it though. For the last 15 years or more I have used the Dizzy Doc's red rotor arms without issue.
Of course, it might well be a fuel issue but if you have a spare rotor it only takes seconds to swap it in......

Yes although most likely a fuel issue it is just good practice to use Distributor Doctor red rotors. The rotors are hand made by a small business in England and usually rationed to one rotor per order. I would also recommend Distributor Doctor distributor caps which are much better quality than alternatives. There is no online ordering, you have to phone but they are very helpful. Standard distributor on car of your age is Lucas 25D4 with anticlockwise rotor.

Stephen

[Andyhereford]

Stephen. Thanks I will give them a call.

[Andyhereford]

Just an update / additional question.
I have put in a new rotor arm …the old one had signs of wear / carbonisation around the edge….and will order a new red one from the Distributor Doctor on Monday.
I am getting a new “ in line” petrol filter…the old one is looking pretty dirty… and will fit that when it arrives.
I have cleaned the plugs and weakened the mixture slightly.
Car starts and seems to be running as it was.
HOWEVER…..I noticed that the distributor vacuum tube, where it is joined to the carburettor by a short length of rubber tubing, had somehow become kinked…not completely closing it off but certainly restricting the inside bore. I have unkinked, cleaned and replaced this short length of rubber tubing. Could this have been / contributed to my original problem?
The Haynes manual does not deal in very much detail with the function / purpose of the “ distributor vacuum system” but my understanding is that is in some way “ fine tunes the timing when the engine is warm / running under load.
Anyway..thanks for all your help/ abvice

[jaekl]

A section of clear tubing before the pump can be a useful diagnostic device. The most common occurrence of vapourisation occurs on the vertical run to the pump. This is where the pressure of the fuel will be the lowest allowing it to vapourise first. Bubbles just start appearing like a carbonated drink. With your section if the bubbles "return" after each stroke of the pump, then are just trapped is a local high spot. If there is an increasing stream of bubbles, that would be vapourisation and the pump would be pumping extremely rapidly for long periods of time if not indefinitely. Slower pumping indicates some amount of fuel is actually being pumped. Listening to the fuel pump will tell you a lot about what is happening. Running out of fuel (in the bowl) yet the pump sounds normal indicates a restricted supply line or not a good enough vent in the cap.

[myoldjalopy]

I don't think a little kink in the dizzy vac tube would cause the sudden and dramatic running problems you experienced.
Now that the car "seems to be running as it was" I would see how it goes for a bit.........a few local tests runs.