So I was tidying my shed and came across my almost unused Gunson's compression tester, and decided to compression test the box's engine - it's a 1119cc carb. The results are -

1- 14 bar
2 - 5 bar
3 - 13 bar
4 - 8 bar

Though it runs great IMO. Should be better than that at 33000 miles though - doesn't use any oil so it must be the valves. I would have thought that a 1993 enigne would be built to run on unleaded... Anyway let's see how it goes ....

I see what you mean.

Did you do the test with disconnected ignition, wise open throttle and an equal amount og engine turns for each cylinder?

DotMatrix wrote: ↑Sat Jul 15, 2017 12:36 pm I see what you mean.

Did you do the test with disconnected ignition, wise open throttle and an equal amount og engine turns for each cylinder?

Disconnected ignition - yes, wide open throttle - no, equal number of turns - no.

However - update - just went out on a run and then re-tested with a hot engine. Results were

1 from 14 to 12 bar
2 from 5 bar to 12 bar
3 from 13 bar to 13 bar
4 from 8 bar to 10 bar

When I did the first test, the engine had not been run and I wonder whether some of the inlet tappets were not "pumped up"...?
If I did this again, I would remember to open the throttle.
Took the opportunity to change the spark plugs from Bosch to NGK Iridium.

Now I'm going to forget the whole thing as there isn't really anything wrong. Cylinder 4 recovered the worst but who knows what's going on there.

those new numbers seems good. I wouldn't worry about it:)

DotMatrix wrote: ↑Sat Jul 15, 2017 8:48 pm those new numbers seems good. I wouldn't worry about it:)

Thanks - I've put the compression tester back in the shed.

Good idea:-)

I actually bought a new compression tester the other day as i recently found out that the one i was previously using was under reading. The one i bought was just a cheap £20 one. I haven't testet to see if it works yet.

**Update** - can't imagine anyone's interested ...but....I repeated the process with some changes.

1. I cleaned the spark plug seating areas of black gunk.
2. I screwed the compression tester well in and ensured that the sealing ring was well squashed into place.
3. I sat in the car and ran each cylinder test for 10 "cycles" with a fully depressed throttle pedal.

Result? - Couldn't be happier as the results are as follows -

Cylinder 1 - 13.5 bar.
Cylinders 2,3,4 - 13.25 bar.

The Haynes "minimum" is 10.3 bar so my engine is well up to par.

Torqued the spark plugs back in and started it up. The spark plugs look good since I changed the carb diaphragm and with my new timing belt my servicing and preparation of my Metro is complete. It's now a reliable daily driver from oast times.

that is a nice and strong result. now you can relax again