Best way to Compression Test the cylinders
#11
08-21-2015, 02:18 PM
Ok, the results are in:
1 - 170
3 - 125
5 - 170
7 - 170
2 - 185
4 - 150
6 - 175
8 - 185
I tried putting a plug in #1 and tested #3 no change, tried a plug in #5 tested #3 no change. Squirted some oil in #3 no change.
However, it didn't feel like the tester was screwing all the way in on #3, I tried several times. After the oil squirt I noticed some flowing out after cranking three times, so there may be an issue with the threads on #3, the plug did go all the way in as the rest.
1 - 170
3 - 125
5 - 170
7 - 170
2 - 185
4 - 150
6 - 175
8 - 185
I tried putting a plug in #1 and tested #3 no change, tried a plug in #5 tested #3 no change. Squirted some oil in #3 no change.
However, it didn't feel like the tester was screwing all the way in on #3, I tried several times. After the oil squirt I noticed some flowing out after cranking three times, so there may be an issue with the threads on #3, the plug did go all the way in as the rest.
Last edited by caymandrew; 08-21-2015 at 02:21 PM.
#12
08-21-2015, 02:25 PM
#13
08-21-2015, 02:31 PM
Recovery Vehicle
I would recommend getting a tap and cleaning out number 3 spark plug hole. Now, you need to get a shop vac and put the smallest end you can on the suction end and keep it real close to the hole while you are cleaning the thread, so you can vacuum any shavings that will be present when cutting the thread. This is important, so you don't get any in the combustion chamber. I have had to do this on aluminum heads before. they do make taps especially made for this.
#14
08-21-2015, 02:34 PM
You fixed it (numbers)!
Do you have any symptoms of a HG leak? If your 3 cylinder is a real figure I'd suspect that or a valve/valve seat messed up, or a weak valve spring. Wow, over my head but one other idea that occurs to me is that maybe the threads ARE the issue... they don't seal your tester then they may not seal your spark plugs. Hard to comment without knowing the extent of the thread issue. What did the #3 plug look like on the upper/outside part? If you had a HG leak with no mixing of coolant and oil, you should see some oil or blackness near that location, though it could be on the inside (under upper intake), but then you'd think you could hear it.
Do you have any symptoms of a HG leak? If your 3 cylinder is a real figure I'd suspect that or a valve/valve seat messed up, or a weak valve spring. Wow, over my head but one other idea that occurs to me is that maybe the threads ARE the issue... they don't seal your tester then they may not seal your spark plugs. Hard to comment without knowing the extent of the thread issue. What did the #3 plug look like on the upper/outside part? If you had a HG leak with no mixing of coolant and oil, you should see some oil or blackness near that location, though it could be on the inside (under upper intake), but then you'd think you could hear it.
#15
08-21-2015, 02:37 PM
I would recommend getting a tap and cleaning out number 3 spark plug hole. Now, you need to get a shop vac and put the smallest end you can on the suction end and keep it real close to the hole while you are cleaning the thread, so you can vacuum any shavings that will be present when cutting the thread. This is important, so you don't get any in the combustion chamber. I have had to do this on aluminum heads before. they do make taps especially made for this.
Joe, can you think of anything he could use to SEAL that thread for testing without contaminating the head? Like teflon tape or something? The thread has to be fixed, but he's also on a mission to eliminate the cause of the low figures and add up his needed repairs (haha, that's just sad... I'VE BEEN THERE, I ASSURE YOU)... anyway, maybe that would work, but maybe it isn't a good idea if you might booger your threads any worse trying it.
We posted at the same time.
Last edited by Charlie_V; 08-21-2015 at 02:39 PM.
#16
08-21-2015, 02:37 PM
#17
08-21-2015, 03:31 PM
Baja
Judging by the results #3 is down a lot but the adjacent aren't. My guess is that it's a decoke, valve regrind and new valve springs scenario. #4 also looks squiffy as well but again the adjacent cylinders look OK. Generally the drivers side bank with the exception of #4 seem good. You could try a retest with a copper washer or spark plug washer fitted but it's unlikely to render any differences. Regards cranking, max pressures are achieved no matter how many times you crank the motor over so no need to limit the cranking, max pressure = max pressure, but as someone mentioned earlier just ensure the fuel pump relay and ignition fuse/earth ground (if it has one) is pulled otherwise you'll end up either with white hair or even worse, in hospital with a cardiac arrest)
As I said, IMO the root cause would indicate valve let by or even piston rings but without further tests it's impossible to tell. If it were me I'd squirt some engine oil into each cylinder 20-30 minutes before a total compression retest which helps to eliminate piston ring bypass and repeat the exercise over. Good luck and repost the results if you try again.
As I said, IMO the root cause would indicate valve let by or even piston rings but without further tests it's impossible to tell. If it were me I'd squirt some engine oil into each cylinder 20-30 minutes before a total compression retest which helps to eliminate piston ring bypass and repeat the exercise over. Good luck and repost the results if you try again.
#19
08-22-2015, 08:19 AM
It does have the o-ring seal. I've over heated a valve before in and different car, a six cylinder, and although it drove rough, I was still able to start it and get it to a shop on the remaining 5 cylinders. This one is driving me crazy. It's starts and stalls. I can spray starter fluid and it'll rev to 2k on start up and stall. I've replaced the fuel pump and the fuel rail and injectors. Spark is good, air is good, I'm totally stumped. Let's say I have a ring issue in cylider 3, would start and stall be a normal symptom?