PR280z Posted June 11, 2013 Share Posted June 11, 2013 Hello all . I did a compression test last night on my L28ET. The results where as follow : cyl 1- 6. 125,125,125, 130,130 130. I was reading on this forum that the norm from factory on all six was 140. Am i due an engine refresh/overhaul ? Quote Link to comment Share on other sites More sharing options...
Leon Posted June 11, 2013 Share Posted June 11, 2013 No. Quote Link to comment Share on other sites More sharing options...
PR280z Posted June 12, 2013 Author Share Posted June 12, 2013 Leon, Thanks! I also found two spark plug wire tips broken off, maybe that's why at times i had a hard time getting it started. Well i`ll start replacing the tips and then do the COMP. test again . Quote Link to comment Share on other sites More sharing options...
PR280z Posted June 13, 2013 Author Share Posted June 13, 2013 Results of the compression test cyl 1-6,145,145,140 145 145, 145.Not bad for a 20 yr old engine. Quote Link to comment Share on other sites More sharing options...
OhBilly Posted June 13, 2013 Share Posted June 13, 2013 Leon, Thanks! I also found two spark plug wire tips broken off, maybe that's why at times i had a hard time getting it started. Well i`ll start replacing the tips and then do the COMP. test again . I'm confused as to why your spark plug wires have anything to do with the results of your compression test.....? Just how are you performing your compression test? Quote Link to comment Share on other sites More sharing options...
winstonusmc Posted June 20, 2013 Share Posted June 20, 2013 My engine tested like this, stock cam: From 1 -> 6 : 167 160 170 170 162 160 Quote Link to comment Share on other sites More sharing options...
levi3011 Posted June 21, 2013 Share Posted June 21, 2013 When doing a compression test there is no need to have spark plug wires connected. You supposed to take out all the plugs as well Quote Link to comment Share on other sites More sharing options...
softopz Posted June 24, 2013 Share Posted June 24, 2013 I read its ok seen both ways done with or with out plugs for compression tests. Although, you can take wires out and fuel inj clips so your not flooding it. I would do your test again, do a wet test squirt about 5-10 ml of oil in cylinder and see what your numbers are. Quote Link to comment Share on other sites More sharing options...
PR280z Posted July 6, 2013 Author Share Posted July 6, 2013 My first attempt i took gas pump rely off, but i did not wot when cranking. That`s why the low reading. On my second attempt, crank and WOT gave 145 all except piston #3 -140. 140 on all six for a turbo L28ET is good. Quote Link to comment Share on other sites More sharing options...
Milenko2121 Posted July 6, 2013 Share Posted July 6, 2013 (edited) Have you done a leak down test? It's a bit more important. Edited July 6, 2013 by Milenko2121 Quote Link to comment Share on other sites More sharing options...
Pyro Posted July 6, 2013 Share Posted July 6, 2013 Gages can vary. I have 2 gages, the same make and model, and one reads 20 psi lower than the other one. More important to see the differences between cylinders. A stretched timing chain can lower cranking pressure. Advancing the chain to the next position can increase cranking pressure by a large amount. Years ago on an old worn out 78 280z, my engine increased cranking pressure by 50 psi by advancing the cam from the 1st position to the 3rd. Check timing marks on the cam/sprocket to see if the chain has stretched. Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 7, 2013 Share Posted July 7, 2013 (edited) "I read its ok seen both ways done with or with out plugs for compression tests" From a CREDITABLE source? Or just someone on the Internet? Since doing compression tests starting some time around 1978 I have NEVER seen a directive to leave the plugs IN the engine while cranking a petrol engine. Can you site the location where you read that, and in what context? Having paid my good money to go to several schools (GM Tech School, Motech in Detroit, USAF GP Mechanic School, USAF AGE, and so on) I have never had a gasoline engine test specification that called for plugs to be IN the engine when cranking for compression. Universally, they are ALL removed and compression is taken on one cylinder at a time to maximise cranking speed to optimum. I have to agree with Leon's first answer: "NO" your engine is fine. Not even close to a rebuild time. Edited July 7, 2013 by Tony D Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.