Engine back firing and cutting out.

[mike9009]

Hi

The on-going poor running of my 2.0 litre AC engine is annoying me. I have been relying on garages/ specialists to solve, but now willing to have a go myself.

It seems to start fine, run for a few miles but then completely cuts out whilst running. Just before this, I get a couple of back fires. So I am presuming the fuel is getting through and I have an intermittent electrical problem?

Once cut-out it will not immediately restart, but a couple of minutes later(five maybe?) I can start again with a bit of cranking. Revving the engine seems to keep things running better. I presume the engine is slightly flooded at this stage hence the turning over clearing the system?

Any pointers (in BASIC) I can check to try and solve myself?

Thanks

Mike

[kevtherev]

On the contrary it may well be running out of fuel.. does your fuel pump work ok?
To find out what is working and what isn't you must never assume.
always make sure.
Start with fuel delivery, include fuel filters in that.

[mike9009]

Hi Kev

The fuel filter has been changed recently (five weeks ago) and I still have the issue.

Can you describe the easiest way to check the fuel is not suddenly cutting off (or the pump, which I believe is mechanical?)

Thanks

Mike

[kevtherev]

Hi Kev

The fuel filter has been changed recently (five weeks ago) and I still have the issue.

Can you describe the easiest way to check the fuel is not suddenly cutting off (or the pump, which I believe is mechanical?)

Thanks

Mike

Hi Mike
I think you need to tell us what you have done.
this will stop any pointless posting.

The fuel will not be suddenly cutting off
A faulty pump will simply be not able to keep up with the demand from the carb..hence it'll run for a while then the floatbowl will empty quicker than the pump can provide it.
A leaky diaphragm will do that, or weak return spring, or a worn cam follower that actuates the pump.
However this may not be the cause of your issue it is just a suggestion.
Equally an air leak will supply the same symptoms, as the engine warms, the choke comes off, and you get a leaner mixture, with an air leak it'll get too lean to tick over...and backfire.
And also..
A blocked idle jet will cause poor running/stall/backfire at low rpm

[mike9009]

Hi Kev

So far, I have not touched the thing.... but have had several garages take a look (with varying degrees of success). This is my frustration - no one seems to have solved my running issues completely.

I have had different diagnosis from new carbs needed to low compression.

So the last guy I took it to (the one I have trusted the most!), changed the fuel filter, reset the timing and found an earth strap from the gearbox to be suspect. This, he thought, was the main issue with my running problems. All seemed good after taking it from him. He also compression tested the engine and it was fine (135?) on all cylinders. He also said one carb needs refurbing soon (still running the original twin Solex), but should be okay until the autumn.

The stopping can happen at any stage in a journey (except when going up a hill!). I would have thought fuel starvation would happen whilst the engine was under load (high demand for fuel?) - but the last two times, it has happened on the flat and on a slight downhill stretch.

Again, I am a complete novice - but prepared to have a go with some guidance of where to look. After the engine has stopped, is there a quick/ dirty way to determine whether fuel is the issue?

Thanks

Mike

[kevtherev]

Lots of information there..thanks
Others will no doubt be able to offer their thoughts.

[mike9009]

Hi

The saga is on-going...

I have found another loose earth - which I have reattached myself.

I am getting the same symptoms - from cold, the engine starts fine. I will drive for a mile now and everything suddenly cuts out. At the same time the 'battery' light comes on.

Sit there for ten minutes and it will restart. It will drive for a similar distance and then stop again. (so at the moment I average 4 - 5 mph )

Now, it is sat around the corner with a flat battery.

Can someone give me a simple guide of things to check (and how to check).....

Thanks

Mike

[123-jn]

I had similar symtoms on an austin allegro once, The car woiuld run fine for a while then all of a sudden it would miss fire and stall, it would then refuse to restart for a while then suddenly all would be well. It turned out to be a faulty coil but took a long time to diagnose . The ignition amp can also cause an intermittant miss fire? I believe as thye coil heats up it shorts internally and the output reduces. (that is what I was told)

[kevtherev]

I had similar symtoms on an austin allegro once, The car woiuld run fine for a while then all of a sudden it would miss fire and stall, it would then refuse to restart for a while then suddenly all would be well. It turned out to be a faulty coil but took a long time to diagnose . The ignition amp can also cause an intermittant miss fire? I believe as thye coil heats up it shorts internally and the output reduces. (that is what I was told)

What he said.
I agree the coil is a suspect.
Does it get hot to touch when it cuts out?

[sarran1955]

Hello,

135 on all 4 cylinders is fine....

These engines are simple and reliable..

When they are properly set up...

For the ignition system..They use a 'Hall effect' electronico-mechanical system..

with complex plugs..

all 30 + years old..

This may be of help:

https://www.youtube.com/watch?v=KkyBAMMHpa4" onclick="window.open(this.href);return false;

Check and clean till shiney the 2 red cable terminals going to the starter..

..and the 'spade' terminal..

Hope this helps..

Cordialement,

[blacky]

I would be tempted to rig up (with great care ) a gravity feed from a sealed small container with vent hole to prevent vacuum forming, to the carbs thereby establishing the condition of the fuel pump which would then be bypassed.

[mike9009]

Hi

Firstly, thanks for all the suggestions. I have now removed the battery and got it on charge at home. I will try to start again after work tomorrow evening.

It 'feels' like the coil could be the issue (obviously based on my huge experience with these engines ) So I will check how hot the coil gets once it cuts out. Should it be too hot to touch or simply warm, if it is potentially failing? Do the coils slowly degrade over time once they start failing? The reason for asking is the distance I can travel before cutting out is getting less and less. Plus it seems to be getting more and more difficult to start after cutting out. (hence the flat battery )

It sounds like a case of trial and error. Hopefully I might learn something!

I will update with the latest instalment soon!


Mike

[123-jn]

sounds very coil like, mine eventually played up from the off and then didn't want to start much at all!! what you need is a friendly local garage with a spare to try, most coils will do just for a test.

[300CE]

The coil will be very hot to touch (as mine became when it started to break down). I'd also check the connections going onto the coil as these can go green over time - clean these up as well as the earths. See if there is anyone near to you who might be able to swap their coil to test to see if it makes a difference.

[blacky]

when it won't start why not check for spark. take coil ht lead out of dist cap and hold close to an earth whilst someone cranks the engine