Rising Sun Member Forums

Rising Sun Member Forums (http://www.risingsun4x4club.org/forum2/index.php)
-   General Tech Forum (http://www.risingsun4x4club.org/forum2/forumdisplay.php?f=17)
-   -   Compression Check Now what? (http://www.risingsun4x4club.org/forum2/showthread.php?t=18649)

azcromntic 10-18-2012 03:15 AM

Compression Check Now what?
I checked the compression as a result of my findings on my leaky advice thread: http://forum.ih8mud.com/80-series-te...oil-leaks.html I changed just about everything except rear seal. Seems sluggish in second.

Test was performed at 6000+ ft in elevation (if that matters).
I was not able to warm engine up to operating temp.
All plugs out.
C1 - 105
C2 - 105
C3 - 102
C4 - 105
C5 - 105
C6 - 105

Added some oil to C1 - C3 and came up with
C1 - 125
C2 - 110
C3 - 128

I'm guessing, even if it were +/- 10 psi for cold engine and other sundry things I'm on the bottom end of the scale.

Plugs for C4 and C3 had a lot of oil on the ceramic part. There's a lot of oil laying on top of the valve cover where the spark plug wires lay (before running the test). Throttle body has light residue of oil (just PCV probably). New PCV valve and hose. Plugs were not wet but had slight white residue on one side.

Uses 2 quarts every 440 miles.

I'm trying to determine what, if anything, I need to do to the engine.

SteveH 10-18-2012 11:12 AM

Yes - 6000' matters. Add 18% to the values for a sea level equivalent. The oil deposits on the plugs are likely a combination of valve stem seals and oil getting past the rings. I'd make sure your carburetor is working well and just drive it.

When doing a wet test, don't add a ton of oil, as it can affect the value by its volume. Your compression jump on cyl. 1 with the wet test seems high to me - that's more compression that I have ever measured on a 2F at this elevation. I use a pump oil can with ATF in it and use the same number of 'squirts' per cylinder to be sure I'm not careless with the oil. You might try another compression tester, too, in case yours is off one way or the other. I wonder how accurate mine is, for that matter.

A 2F won't be a rocket either way - it's a tractor motor. I'd just drive it and run at least 10w-40. Perhaps replace the valve stem seals to cut oil burning.

azcromntic 10-18-2012 01:49 PM

Very helpful info Steve. Thank-you.
I drive an 80 series so this is on a 1FZFE. I speculate I could just disregard your statement "that's more compression that I have ever measured on a 2F" and garner the 18% information to apply.

I only added about a teaspoon.

azcromntic 10-18-2012 01:52 PM


I was thinking of doing a leakdown but all I really want to know is if blow by is coming through the PCV, throttle body and possibly exhaust: If I can hear or see it that is.

I was thinking of doing the following:
1. put back 5 spark plugs
2. On sixth cylinder attach compression tester
3. rotate crank until compression deflects tester needle
4. slightly move crank back/forth to get highest reading
5. listen at PCV, throttle body and exhaust pipe for leaking air
6. swap to next cylinder I want to test and repeat

Do you think that would work? Thanks.

rover67 10-18-2012 02:27 PM

First, be careful pressurizing cylinders....

I have had a wrench on the crankshaft almost kick my ass when I pressurized a cylinder at TDC and it slung the thing at me. Make sure the motor is locked somehow. I usually find TDC on a cylinder by putting the hose in the spark plug hole and holding my thumb on it. Rotate the crank till it spits air out under pressure, then stops. Thats TDC on the compression stroke. you can stick a wire in the spark plug hole to see where the piston is and get it right at TDC. Then I lock the motor, hook it up to air and go for it. Sometimes it is nice to purposely let it go just beyond or before TDC so you know which way the motor is going to kick and can be ready for it with a wrench jammed against a frame rail or something.

When you pressurize the cylinders you shouldn't really hear any leakage if it is in pretty good shape. usually you only hear a ton of leakage when there is a problem. Either way look at the difference between the line pressure and the cylinder pressure to figure your leak down percentage.

Back to the compression test... your numbers are all very even. Surprisingly even actually... They did come up a bit with oil, which is almost always the case even on a healthy motor. Not knowing what that motor typically pumps up to (compression ratio is a big factor) I'd say it looks like it is in good shape but slightly worn maybe. Probably rings getting tired.

I'll go check out the mud thread in a bit.

rover67 10-18-2012 02:35 PM


Originally Posted by azcromntic (Post 220379)
Plugs were not wet but had slight white residue on one side.

so the spark plugs looked nice at the electrode then? They were wet all over the outer part where the wire hooks up?

I think you have an external leak. not burning oil.

Have you done the valve cover gasket yet?

azcromntic 10-18-2012 04:02 PM

I'm chuckling because you are like the fifteenth person to ask me if I've done the valve cover gasket yet. The answer is no but judging by 15 other people I'd better get on it eh?

The sparkplugs looked decent to me on the electrode side. Some of them had a lot of oil on the outside (sparkplug boot side). Others have said sparkplug gaskets are bad but I don't understand if that's something on the sparkplug or on the valve cover (or some kind of silly joke).

All I'm really hoping for on the "modified leakdown" test is to get enough pressure in the cylinder to cause me to be able to hear a leak if there is one. Use of the compression tester in this case would be to just allow me to recognize when to start listening (when compression is building or built). Once I determine if there is a leak or not will tell if I am going to spend money on a new valve cover gasket and sparkplug gaskets. If I have to do work on the engine I'd hate to do the valve cover gasket only to have to do it again.

I'll DEFINITELY heed your warnings!

SteveH 10-18-2012 04:56 PM

It sounds like you're being careful and taking the right steps. FWIW - The F(Z)J80 engine (either 1FZ-FE or 3F-E) will have different compression numbers than a 2F.

Between 4 2F engines - '76, '78, '83, '87, I've never seen more than about 123 dry for a compression value. Most were 116-118 for a healthy engine at 7000' elevation (my house). These were all stock engines with no performance mods and one was rebuilt.

azcromntic 10-19-2012 04:20 AM

Well I tried my "modified leakdown" test and it was pretty much a red, blistered, belly-flop. I installed the plugs in 5 cylinders and the compression tester in the 6th. I manually turned the crank, like 75, 1/5th turn, turns and could only get the guage to deflect like 1 or 2 psi.

I think I understand better why you put air into the cylinder on a leakdown test: you find the compression stroke and then pressurize the cylinder instead of relying on the actual compression because if you didn't you'd only get like 1 or 2 psi when crank is turned manually.

So, as I laid there under the steering stabilizer resting my arms I came up with a few questions. 1. Both cylinders 1 and 6 are on the compression stroke at the same time?

2. If I can pull the steering stabilizer braket into place with one hand to bolt it to the frame does that mean I need a new one?

3. Seems like the crank turns clockwise (if standing at front looking toward engine) Is that right?

Anyway, I could probably answer my own questions if I weren't so tired.

rover67 10-19-2012 10:05 AM

yeah you can't rely on the pressure building in the cylinders on the compression stroke for a leakdown test. you have to pressurize it with an air compressor. A lot of times the compression tester gauges have a quick connect fitting that will work with your air hose... you can just use the hose and hook it up to air. i thought that's what you were doing.

All times are GMT -6. The time now is 02:01 PM.

Powered by vBulletin® Version 3.7.1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.