Compression test making me worry.

1105 · Dec 17, 2004

I did a test tonight and all my numbers were really low (below 60). Found out from my dad that the gauge might have a small leak in it, but almost all of my numbers were consistant except for two... 1,2,3 all read 60psi, and 4 read 10psi but the plugs all looked OK. 6,7,8 all read 50psi and the plugs looked OK, but number 5 didnt give me a reading at all, even after doing it 3 diff times, and the plug was pitch black.

Anyone have any ideas why number 5 didnt even give me the slightest reading? I know the reason why number 4 is low, but I'm stumped by number 5 and the black plug where the others were a light grey.

I'm going to try tomorrow to do another compression check at work using his gauge to get a 2nd reading, but that one plug is making me worry. Either that cylinder isnt firing, or the injector is stuck open, or something else. Got any ideas?

Stock block and internals, almost 130k miles.

WhiteDevil · Dec 17, 2004

When did it start running like crap?

1105 · Dec 17, 2004

WhiteDevil said:
When did it start running like crap?

Hitting the gas at any RPM in 2nd gear and the tires will still get blown away Running better than it ever has right now.

wytstang · Dec 17, 2004

I think it's the gauge itself. With #'s that low would mean the rings are so worn so bad you would burn a quart of oil a day if not more. Does it smoke at all?

1105 · Dec 17, 2004

no smoke at all, doesnt burn oil. I think its the gauge, but even so, number 5 would have to have been real low for it to have leaked out by time I got to it, and that was the only plug that was completly black... I had my g/f watch it one time for #7, she said it hit 100, which is still low, but when I got there it was at 50 and just barely creaping down.

I know that the gauge is leaking, but from 60 on down, the needle barely moves, maybe 1 psi every minute so I should have got at least somewhat of a reading for #5.

WhiteDevil · Dec 17, 2004

Well i would say as long its running good dont worry about it. But i know how things like this can bug you.

wytstang · Dec 17, 2004

Go to autozone and but there cheap testor it $25 and change and retest it. The fact that the gauge can't hold pressure at any point I would just disregard those #'s completly.

1105 · Dec 17, 2004

But then why is only one plug black? I think I'm just going to test that one tomorrow at work and see what I get.

wytstang · Dec 17, 2004

When you say black black how? oil,fuel,ie. My # 8 cylinder has a bad injector it sparys the fuel right at the plug soaking it and turning it black. It may be just a bad injector on that clylinder.

OinkAodeOink · Dec 18, 2004

hey zach, if you really need to, i have a new compression gauge i can borrow or come over and use..

You know... Your valves could be leaking the compression out.. What you need to do is get someone to look real close at the gauge while you give it like 5 rotations or so, over.. Let the gauge settle and watch its peak. If it drops quickly, this could be a valve/spring/seal problem..

I once had a rocker too tight, and lost almost all compression on that cylinder, so you might wana check the rockers, if you come back with wacky readings.

As far as the plugs go.. If its a dry black, thats most likely a rich condition.. If its a wet greesy black, thats most likely an oil burn condition, either from worn valve guides/seals, or worn rings (oil ring usually)

BTW, im guessing you were holding the throttle wide open? and letting the engine rotate over for atleast 3-4 seconds?

Lemme know if you need to use the gauge, no problem man..

Slow5.0 · Dec 18, 2004

Zach 31st this month in morning I will be in Florida and I will stop by you like I told you, I can help you out with compression test OK

BTW tell Oink that I wanna see him and his Stang and if you have some other members here around your neighbors

1105 · Dec 18, 2004

Earnie, me and Mike are about the only SN95 members around this area that I know of. What day do you want to meet? I'm probably going to be busy on the 4th. But everyother day after that I should be free after work.

The plug was a dirty black, not a shiny clean looking black.

Mike, maybe my valves are adjusted a little to tight because I did a compression check on my car when I had the stock E7 heads on and it was holding pressure at 120-135. I might go ahead and take the valve covers off today when I get home from work and readjust one and see if I get a higher number.

Rootus · Dec 18, 2004

With an honest 60 psi of compression, I don't think it would even start. Time for a different gauge .

Dave

Slow5.0 · Dec 18, 2004

1105 said:
Earnie, me and Mike are about the only SN95 members around this area that I know of. What day do you want to meet? I'm probably going to be busy on the 4th. But everyother day after that I should be free after work.

I said December 31st, not 4th , I will stop by and see whats going on
I will let you know where and what time

BlueOvalStangGT · Dec 18, 2004

Ernie are you driving your car there? Les have a little meet at OSW if its still open.

Slow5.0 · Dec 18, 2004

BlueOvalStangGT said:
Ernie are you driving your car there? Les have a little meet at OSW if its still open.

No man i driving my buddys '96 Cadillac Seville SLS, cheapper on gas ,plus I have no good rear tires (Nitto DRs are bold) , and right now my stang is on V6 rims and tires you know for snow
BTW me and my teo buddys going in Jacksonville FL for New Years eve ,we Bosnians have big party for New Years eve
Next summer I will come with my Stang down there

Compression test making me worry.

1105

I AM the random post master...bow down

WhiteDevil

New Member

1105

I AM the random post master...bow down

wytstang

Mustang Master

1105

I AM the random post master...bow down

WhiteDevil

New Member

wytstang

Mustang Master

1105

I AM the random post master...bow down

wytstang

Mustang Master

OinkAodeOink

Slow5.0

Active Member

1105

I AM the random post master...bow down

Rootus

Officially Addicted

Slow5.0

Active Member

BlueOvalStangGT

Active Member

Slow5.0

Active Member

Similar threads

Compression test making me worry.

I AM the random post master...bow down

New Member

I AM the random post master...bow down

Mustang Master

I AM the random post master...bow down

New Member

Mustang Master

I AM the random post master...bow down

Mustang Master

Active Member

I AM the random post master...bow down

Officially Addicted

Active Member

Active Member

Active Member

Similar threads

Privacy & Transparency

Privacy & Transparency