Compression Test - Don't Know What To Make Of It

ASSISTANCE Stock Engine-Bay Components
1

Hi Guys/Gals,

I have a 1993 Integra RS with 190K miles, and it’s been doing some weird things lately. For instance, coolant has been disappearing from the radiator, but I can’t find any sign of a leak. Also, it has this rainbow-like tinge to it, like when water mixes with oil. Also, it’s been running pretty rough lately, so I figured I would do some diagnostics on it, since I’m thinking my head gasket is on its way out. I did a compression test today, and I really don’t know what to make of the results. Just to ensure that I did it correctly, here’s what I did:

  • Made sure my engine was warm when I did the test
  • Disconnected ECU Fuse to disable fuel pump
  • Depressurized the fuel system
  • Disconnected the distributor
  • Took out all the spark plugs
  • Did 5 cranks for each cylinder at WOT

Here were my results:

#1 45
#2 40
#3 50
#4 50

That’s obviously way too low, so I did again, but this time with 10 cranks. The results were roughly double, which is still really low. Eventually, I just kept cranking it until the needle stopped moving, which took about 20 or so cranks. Here’s what I got:

#1 160
#2 155
#3 155
#4 170

I also did a wet test and cranked it until the needle stopped moving. Here’s what I got:

#1 180
#2 180
#3 190
#4 215

Any ideas as to what’s going on? Any help would be greatly appreciated.

Thanks,
-Alex-

2

compression looks fine to me

3

Do a coolant system pressure test if you’re experiencing coolant loss.

4

So the fact that I had to crank it ~20 times to get the compression numbers isn’t a big deal?

Thanks for the suggestion. I didn’t even know you could do that!

5

5-10 cranks is usually all it should take. you should get roughly half the end reading on the first stroke. are you sure the gauge is accurate? and pressure doesn’t bleed back any if you let it sit there?
you have any white smoke on start up after cold soak?

6

It could also be the gauge itself, if you are that worried rent or buy a new one and see if it behaves differently. Your compression seems fine. Try doing a leak down test, it could be the HG.

7

or if you have another car in the household, try it on that one. if 5 strokes still only nets you around 50psi, something wrong with tool, or the procedure. the number will vary depending on the vehicle of course. but it will be obvious.

8

I rented one from Autozone and it looks fairly brand new. It doesn’t bleed or anything like that, but I’ll rent another one and try it again in the near future. I’ll post my result when I get the chance to do it again. Thanks again for the suggestions.

9

Thanks for the suggestions guys. I ended up renting a cooling system pressure tester, and I found a leak from the hose that goes to the FITV, which probably explains why it’s running so rough. As for the weird compression test(s), I think the reason why my compression test results were so low is because my battery is 9 years old, so it probably wasn’t giving out enough juice to make it kick properly. Would that be a reasonable assumption?

10

Makes sense to me! Good find.

11

coolant lost

Hi I have a 91 integra loosing coolant. I believe its going into the combustion chamber where the sparkplugs are getting wet with fuel and water. Car doesn’t want to start. Any ideas would help.

12

pull the spark plugs out. pressurize the cooling system. look for external leaks. if none found, let pressure tester sit for a couple hours pressurized. relieve pressure. have someone crank engine. if you see coolant spit out of spark plug hole(s), pull the head and inspect.

or run a compression test instead