Progressive cylinder failure

[kerm63]

Hi All. I jointly own a 1958 two door saloon with my father. We have been completely stumped by an engine problem that first occured a couple of years ago. The car will start on the button and run sweetly for anywhere between two and ten miles, then when the engine in under strain e.g. climbing a hill, we get the odd cough or misfire. This situation rapidly deteriorates, with first one then two then three cylinders failing followed by complete engine failure. At this point the engine will not re-start. However, five minutes later the engine will re-start fine and run for about half a mile before failing in the same way again. Leave the car for an hour or more and you'll get about another ten miles down the road before getting a repeat performance!!

The car has been in and out of several modern local garages and an older classic car specialist who is still working on the problem. A list of ideas from fellow members would be a great help, especially if someone has encountered this problem before! Our favourite guess is fuel starvation, but should we be trying other things first?

Thanks in advance for your help

[autolycus]

Sounds like the contender for "fault of the year" - coil.

Tell us what you know about the coil. Has it been replaced? Have you tried swapping it for a known-good one? Is it so hot you can barely stand your hand on it when the engine misbehaves?

If you do try replacing it, you must measure the resistance of the new one, and it must be around 3-3.5 ohms.

Kevin

[linearaudio]

My conclusion exactly! Put another coil in (not a ballast type) and all your troubles will be over!

[d_harris]

Thirded.

Just by way of an explanation of my logic. When coils get hot they can start to fail - they start to fire erratically or not at all. In this instance it sounds to me like its desperatly trying to make a spark but just doesn't have the oomph to meet all 4 and it gets progressivly hotter - exacerbating the problem.

By stopping for 10 mins you let it cool down and off you go again!

Incidentally, coils do get warm in use - try to replicate the problem and if the coil is uncomfortably hot then you have a definate answer

[bmcecosse]

Or - it could be fuel starvation. I would do a flow test on the fuel pump - into an empty gallon can - which it should fill in less than 8 minutes. Don't just pump a pint - go for the gallon to test it's staying power! The pump could be struggling to deliver through a choked filter (in base of pump) or there could be a vacuum developing in the tank. Check by removing the filler cap next time this happens - in-rush of air tells all!
Can also be the ignition condenser failing - for me this is far more likely than coil failure which in my experience either works fine - or doesn't work at all! But as already suggested - they are both easily tested by substitution!
Wild and highly unlikely senario - the valves may be sticking open when the engine heats up due to lack of lubrication. However it's even more unlikely for this to bring the engine to a halt - since extremely unlikely to happen to more than one valve !

[kerm63]

Hi all, thanks for the suggestions. The coil was replaced last year and seems ok, but on closer checking the earthing screw in the distributor was very loose. This apparently also earths the coil! The garage have tightened the earthing screw and so far have taken the minor on four ten mile runs without incident. Could be problem solved ..... but will keep you posted!

[bmcecosse]

Thanks for coming back - but 'earthing screw in the distributor' ? Hmm. Do they mean the two little screws one at each side - that clamp th base plate to the body - I wonder ?

[linearaudio]

Thanks for coming back - but 'earthing screw in the distributor' ? Hmm. Do they mean the two little screws one at each side - that clamp th base plate to the body - I wonder ?

I imagine they would be referring to the screws holding that naughty little earth braid on? That would make sense!

[kerm63]

Hi All, it was I believe the little earthing braid screw that was the culprit. Without changing anything else, we now have a fully working Minor again!! Thanks for all the suggestions and advice. Hopefully it will be a while before we are faced with another tricky problem!!