We know the compression test wasn't done correctly so those numbers weren't useful. Except for the fact that the car is not performing well, we know nothing about the problem at this point.

My experience with these late UK spec cars ( my assumption ) is they tend to have very old and/or cheap ignition parts in them and until the ignition system has been updated it's hard to tell what is happening with the car.

Kelley

Definitely don't follow the instructions (or the person) that said to leave the plugs in. That's a pretty fundamental error. A 4-cylinder motor will run on 3 cylinders and maybe even on 2.

Sounds to me at best you just need just adjust the valves or just go ahead and get a valve job. You'd be surprised at how crapped up exhaust valves get on a mini in a very short time, which impacts the sealing and hence the compression.

One min specialist will do a basic 3-angle valve job for $150 plus shipping, but they often "discover" you need new parts, like guides, valves or whatever bringing the cost closer to $300.

I checked them one at a time, removing one spark plug, inserting the compression tester, while the other three remained in place.  This is what the instructions said to do. I did not remove all four at the same time and did not keep the accelerator to the floor.  I have since returned the tester to my cousin.  Thanks for your help. I guess the next step is to find a competent British car repair person.

Anybody in Vermont to help out.

still not making sense

what the others are saying is that you cannot possibly be trying to turn over (start) if properly checking compression on any one cylinder because ALL of the spark plugs should have been removed

Cylinders 3 & 4 it acts like it's going to start, but doesn't.  It actually does turn over - start - when cylinders 1 & 2 are being compression checked. Sorry. I'm a statistician, not a mechanic.  I'm sure the hair doesn't help either.

Did you have all of the sparkplugs out and the throttle pedal to the floor when you checked the compression? If not that can cause low or inconsistant readings.

Kelley

"..It wouldn't start on cylinders 3 & 4."..."...along with only turning over when checking 1 & 2...."

Maybe I'm being dense ...but what on earth does this mean??

Cheers, IAn

The compression in your engine will most likly be affected by either a blown cylinder head gasket, warped or cracked cylinder head, burnt or mis-adjusted valves, or pistons rings.

With the readings you are getting it is possible that the cylinder head gasket has failed between #1 and #2 cylinder head. The distance between 1 & 2 and 3 & 4 are closer than between 2 & 3.

Remove all spark plugs so that the engine spins freely when cranked over. Take reading in each cylinder. Then skirt some engine oil in each cyclinder just priot to re-taking another reading in that cylinder. If your reading have increased by 10-20# and are uniform, then you may have worn rings. The oil will help seal the worn rings long enough to change the readings while taking the compression test.

If you have access to a CO2 tested that you can hook up to your radiator, do that and allow the engine to run up to normal operating temperature and see if there is any indication of CO2. The CO2 will indicate if any of the combustion gases are escaping by the cylinder head gasket. Also check your coolant in your radiator to see if the is any signs of oil. It may appear linke chocolate milk shake. This will indicate a failed head gasket and the oil passage is allowing the oil to mix with the coolant.

Check you valve settings to be sure that are not too tight. If you adjustment is too tight, it will allow the valves to open too early or remain open to long and thus dropping compression. Remove the valve cover and crank the engine and verify that all the valves are opening and closing properly.

If the tests indicate it is the cylinder head gasket, remove the head and inspect the gasket. Be sure to have a new gasket handy as you can not re-use the old one. You will be able to see any burn or ruptured areas of the gasket. It will most likely be between cylinder 1 & 2. While you have the head off, clean and inspect it. Do a dye penetrant exam or mag particle to make sure you have no cracks. Also take it to an automotive machine shop to have it surfaced to make sure it is not warped.

It can be burnt or worn valves as well and if you have the head off, a valve job is a good idea.

Good Luck and keep us posted.

Norm

Try all the "easy" tests first without removing the head to try to see if you can determine the cause

Squirt a little oil (one at a time) in the cylinders through the spark plug hole and check each cylinder again.  If compression increases rings are gone/going.  If no change maybe head gasket.

My Mayfair '88 is running weak so I borrowed a compression tester. It wouldn't start on cylinders 3 & 4. The compressions were (with #1 being closest to the radiator) : 75, 75, 100, 125.  I know they are supposed to have only a little variance between then, so I suspect this is bad along with only turning over when checking 1 & 2.  Any hints on what my bad news is?  Also, does anyone know a competent mechanic in the central Vermont/ Ft. Ticondergoga, NY area?

Thanks!