Compression test results, and spark plug ?

[unik5]

UPDATE, I think we got the compression portion figured out, thanks to "davidch" Please see below for the spark plug question..

Also, all of the spark plugs on the coil side (passenger) looked pretty good at the contacts, minimal wear. But all of the drivers side plugs had more wear, although even. Is this a common thing? I'll attach a picture. The plugs have about 25k miles on them.

The truck itself is pretty clean, and has 4.88's and electric e-locker (non- actuating atm). I just wanted to know if this is something I should worry about, or if I should be in the clear, motor wise.

Thanks for any info!

 

[brillo_76]

More even is important and the valves could just need adjusted.. how many miles on the engine itself?

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[Bad Luck]

You ideally want all cylinders within +/-5% of the average compression.

 

[unik5]

More even is important and the valves could just need adjusted.. how many miles on the engine itself?

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By more even, you mean that the numbers are all close?

And exact mileage is unknown. It had a tag on the timing cover that said 118,000 miles but my friend said the cluster was dead or missing (i dont remember), when he pulled it. Said it looked good on the inside.

Could the valves get out of adjustment on one side of the motor, and not the other?

 

[unik5]

You ideally want all cylinders within +/-5% of the average compression.

Average compression of the test we ran? Or average compression of what Toyota spec calls for? ... I guess both technically.. but should I be worried about the 150 number?

 

[davidch]

Location, Location, Location.

Altitude Correction Factor Table for Compression Testing | TW200 Forum

 

[unik5]

Location, Location, Location.

Altitude Correction Factor Table for Compression Testing | TW200 Forum

Interesting! Thank you for the link.. So basing at 175psi, between 5,000 and 5,500 feet would put me right at about the 150psi today :fro:

 

[Bad Luck]

Average compression of the test we ran? Or average compression of what Toyota spec calls for? ... I guess both technically.. but should I be worried about the 150 number?

Average compression of the results you have. There are a lot of factors that can change compression test results: all spark plugs out vs 1 at a time, throttle body held open or not, battery state of health, starter state of health, cold or hot engine, altitude, etc.

 

[unik5]

Average compression of the results you have. There are a lot of factors that can change compression test results: all spark plugs out vs 1 at a time, throttle body held open or not, battery state of health, starter state of health, cold or hot engine, altitude, etc.

Gotcha, thanks for the clarification!

 

[Romeo1]

Air density loss happens at roughly 3% of standard day of 14.7 psi per 1,000 feet gained in elevation. Barometric pressure plays a role also.

Does that 3% transfer directly to cylinder psi? I’m not sure. The chart on the Yamaha forum says it does from the looks of it.

Test cylinder psi with the throttle held open, and all the plugs removed. I also do a cold vs hot test usually as that can help determine wear. If your test is low, you have to verify that your valve clearance is good first.

 

[brillo_76]

By more even, you mean that the numbers are all close?

And exact mileage is unknown. It had a tag on the timing cover that said 118,000 miles but my friend said the cluster was dead or missing (i dont remember), when he pulled it. Said it looked good on the inside.

Could the valves get out of adjustment on one side of the motor, and not the other?

Most likely your exhaust valves might need adjusted.

I see BadLuck got your answer on psi being even..

They will run if the cylinders aren't just not a good and you lose power and efficiency.