Cold compression test

The Oily Bits S1 Specific Topics
1

Hi all,

Just done a cold compression test (I know it’s more relevant and important hot but gotta go out so may do it when I get back), and my car has had a hard life and will contineue to do so.

Current at 26000 miles it reads:
Cylinder 1: 14.8 bar
Cylinder 2: 14.6 bar
Cylinder 3: 14.5 bar
Cylinder 4: 14.6 bar

I’m pretty happy with that as at least they’re all even

Hope this could be of use to someone

2

For us old timers thats…

Cylinder 1: 214.6559 PSI
Cylinder 2: 211.7551 PSI
Cylinder 3: 210.3047 PSI
Cylinder 4: 211.7551 PSI



Good results on a cold engine Mark - how many engine cranks to reach that value?

3

Phil

Could you translate BAR to PSI for us duffers ??

4

IIRC 1bar=14psi

ya old duffer


actually I just re-read Phils post – he’s done the calc for you (and me… )

5

Good results on a cold engine Mark - how many engine cranks to reach that value?

That was about 4 each time… Didn’t get time to do a hot one this weekend but will do so next weekend

Yeah I’m pretty pleased with that too breathes sigh of releif!

6

RL

How did you stop fuel injection - pull the injector connections off ??

7

RL

How did you stop fuel injection - pull the injector connections off ??

I didn’t bother Just had all the plugs out and the leads off, also unplugged the coil pack (little 3 wire plug near the expansion bottle). There’s so little fuel to worry about really and any excess is just blown out the top on the compression stroke.

Thinking about it the box didn’t mention disconnecting fueling so you may need it to get a accurate compression figure as the fuel will add to that surely? shrug

8

How did you stop fuel injection - pull the injector connections off ??

Is that not how you’d do it Andy?

Ian

9

IIRC 1bar=14psi

ya old duffer


actually I just re-read Phils post – he’s done the calc for you (and me… )

Now I get it !!

10

Ahhhh thats the difference between a wet & dry test, to check it correctly, you do it dry, i.e. no fuel or oil.
Than take the readings, next add a teaspoon full of oil down the spark plug hole and retake the readings again.

This will shown you if you have any leakage past the rings as the oil will mask that and give a higher reading the second time round, the same goes for having fuel in there aswell, it will mask readings.

11

Ah gotcha, cheers Phil, I’ll do a hot dry test and hot wet test this weekend if it’s sunny.

Should be getting another wheel speed sensor again so it’ll be running right!

12

Mark, have you got a leakdown tester as well?
Well worth doing to get the overall picture of how your engine really is

13

Ian - yes and Phil explains why

14

Phil,

Never heard of a leak down tester

Is it expensive? I had the compression tester from my MR2 and is now just that extra bit of toolage.

What does a leakdown tester do?

15

mark,
Its a guage you screw into the spark plug hole at tdc and then supply a constant amount of air pressure into it via a regulator, but you do need a air compressor to use one.
The guage will then measure the amount of air being lost either by the valve seat seals or past the rings.
It can also check if the hg is leaking.
I cant remember exactly how much mine cost but i think it was in the region of �50.

HTH