Fiat Dino Forum (FDF)

I did a compression test today...eeek! r/h cylinders all read 90. l/h cylinders all read 120. Couple this with the noisy r/h top end, I guess i have an problem there. Any suggestions??

Did you keep your foot on the gas pedal fully when you did the test? Do not forget...
It should read 180 or more than 12 (depending on which scale)

no I didnt....Also, should the engine be warm or cold and all plugs out or just one at a time?

The absolute reading is not that significant, but the difference between the individual cylindes is important. Therefore, all plugs should be out and the engine must be cranked for the same amount of time for each measurement that they can be compared. You should not have a runaway value. It is OK if all cylinders are within a variation of 1 bar. With the measuring device on the photo the most important thing is to have the same conditions to get proper results.

great, thanks Tobi. Warm or cold?

It's the same with the temperature. First of all, it must be constant for each measurement, i.e. cylinder, to get comparable results. The temperature itself is not that important. If one or more cylincer(s) show a significantly lower pressure value than the average, you must have a closer look on this/them. There may be issues with piston rings, wear or valve setting. The absolute pressure value itself is not that significant since it depends on many factors like cranking time, measuring device, connection, temperature, etc.

Like Tobi said.
Cold engine is fine. One plug at a time or all plugs out does not matter much either. And the value of the measurement is not that important, but they have to be close to each other.

But you have to fully depress the gas pedal!
Not doing that probably caused your readings. Your readings are typically what you expect when you do not depress the gas pedal fully.

Good luck!

Out to the garage later and retest the compression Thanks Tobi and Leo!!
I will report back...

So....all up around the 120 +-5 except number 3 which is at 90. On the end of the compression nozzle, there was oily fuel in that one too.

Put a bit of oil down the spark plug hole of that cylinder and test again. If the reading is higher it might be the piston rings. If not, then open up the camshaft cover (easy job but just be sure not drop any nuts down the carburettors or down hy the famshafts. Work like a surgeon and count if there are no nuts in your patient. Do not rush.)
Check if your cam shaft lobes are not worn. Sharp edge or worn off lobe.
Check valve clearances: put car in 5th gear. Move car until lobe on a cam points fully upwards. Measure gap between cam and valve plate. Note down reading. Do this for all lobes on the cams. And compare if you 'bad' cylinder has a different reading or anything out of the normal range.
If all it all checks out, then it may be time to pull the head on the side with the bad cylinder...
Unless any body else has better ideas?