coltonstewart

I did compression tests and I guess my cylinders or rings are bad - Around 120 - 130 psi each cylinder.

Im also having misfire problems after a HG rebuild. bad enough that it wont idle and sounds like a lawnmower. I really have checked the timing again and again.. and yes dist.rotor position as well.

I know Im not getting ignition cause the spark plugs and inside of my valve cover smell like gasoline.

Tomorrow Im gonna inspect my distributor and ignitor and cords resistance. But these were never causing a problem before I melted my HG's. (frozen coolant overheat). Its been sitting for the last 2 yrs

Please help guys

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3VZE 92 pickup 4x4 3.0

RJR

What's your location/elevation? Those numbers are normal for Denver (5000 feet), but way low for LA (sea level).

coltonstewart

NS Im actually in the rockies, near 5000 feet myself. Is that for real thats quite a discrepancy in psi?

RJR

Absolutely. You pull less air into the cylinders, so there's less to compress. I've never measured above about 135psi on any engine here at 5000 feet. No way you'll see the 150-170 that the service manual talks about. I don't know why they don't point that out in the FSM. I'm sure plenty of people have torn their engine down for no good reason because of this.

There's a formula for expected psi reduction on a compression test based on altitude, but I don't have it at hand right now. I'll post it if I can find it.

scope103

Atmospheric pressure at 5,000 ft above MSL is about 83% of what we rich people breathe. https://www.avs.org/AVS/files/c7/c7e...de54f87b9e.pdf Taking 83% of the Toyota-specified minimum (141psi http://web.archive.org/web/200611160.../6compress.pdf ) leaves us with about 118psi as a "minimum" compression result in Denver. (83% of 171 gives about 142psi as "standard," matching RJR's number).

This isn't exact; the 9.0:1 compression is probably adiabatic, and the whole thing is empirical anyway. But this calculation is well within the accuracy of any compression gauge setup.

robertd33

this is mine. still runs.

5=80 6=170
3=120 4=110
1=90 2=120

RJR

Thanks for the analysis, Scope. That 83% number was pretty much what I was thinking as I drove to Denver this afternoon.

coltonstewart

Thanks guys, that makes me feel alot better! Especially since I put new piston rings in a couple years ago