A compression gauge can be bought for not too much - fits in the spark plug hole and you disable the ignition (in your case, unplug DI) and turn the engine over with the throttle wide open (don't know how to do this if you have TCS, but think you can work the throttle from under the bonnet). Read the pressure on each cylinder in turn.

On an engine in reasonable condition, the pressures should be within 10% of each other. If one is more than 10% lower than the others, you've probably isolated the fault to one cylinder (head gasket often blows between two cylinders, so if you get two that are low, you've got a good clue).

Usually, a "dry test" is followed by a "wet test". i.e. Do the compression test (the "dry" test) and if it shows a cylinder lower than the other, it could indicate a bore problem or a valve/gasket problem. Then squirt some oil into the cylinder and test that cylinder again (the "wet" test). If the pressure increases, there is a bore problem (scored cylinder, worn or broken ring, etc.). If pressure is still low, then the problem is a valve or gasket.

Alternatively, take it to a local garage, who don't need to know anything about Saabs, and will do it for you (just tell them how to disconnect the DI).

posted by 62.253...

• Timing chain Slipped?? (I need ideas!!!), Kyle, Wed, 12 Dec 2001 14:42:41
  • It's not the DI cassette..., Kyle, Wed, 12 Dec 2001 19:03:28
  • Does anyone think that it's impossible...., Kyle, Wed, 12 Dec 2001 17:15:10
  • I'm no longer convinced it's the timing chain...., Kyle, Wed, 12 Dec 2001 17:12:43
  • Timing chain would be the last thing on my list, how..., TKC, Wed, 12 Dec 2001 15:42:30
    • New DI cas. plugs and vaccum hoses., Kyle, Wed, 12 Dec 2001 16:05:30
      • that's a pretty long plug change interval, steve Ci n BC, Wed, 12 Dec 2001 16:41:46
        • Service interval for my Aero is 12K miles., BillJ, Wed, 12 Dec 2001 16:46:12
        • Re: long plug change interval (11,000 miles is long?), Kyle, Wed, 12 Dec 2001 16:45:57
          • Well...., TKC, Wed, 12 Dec 2001 16:53:53
  • Re: Timing chain Slipped?? (I need ideas!!!), Tim Goose, Wed, 12 Dec 2001 15:41:10
    • I have had both of these..., BillJ, Wed, 12 Dec 2001 16:41:46
      • Re: I have had both of these..., Kyle, Wed, 12 Dec 2001 16:51:50
  • Re: Timing chain Slipped?? (I need ideas!!!), Yaofeng, Wed, 12 Dec 2001 15:13:13
    • GOOD!...YES!...MORE IDEAS??...MORE, MORE!!!! n/m, Kyle, Wed, 12 Dec 2001 15:12:24
      • Have you tested compression?N/M, Yaofeng, Wed, 12 Dec 2001 16:49:28
        • How do you do that? n/m, Kyle, Wed, 12 Dec 2001 16:53:57
          • Well, with a compression tester, of course!, BillJ, Wed, 12 Dec 2001 17:24:02 <-- Viewing This Message
        • Re: Have you tested compression? (No) n/m, Kyle, Wed, 12 Dec 2001 16:53:12
      • Here's a few more, Jay K, Wed, 12 Dec 2001 15:39:23

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