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  #11  
Old 10-19-2012, 12:50 PM
azcromntic azcromntic is offline
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rover67,

Now why didn't I think of that. That's awesome. Only problem I have is that I have to turn the crank to position cylinder at TDC on compression stroke from _underneath_ the vehicle. I can't see what the heck is going on upstairs. For instance if I stuck a pencil in the spark plug hole and watched it go up and down to find approximate TDC. I'll have to recruit the wife to be the pencil watcher.

That brings up a couple questions. If I found TDC on compression stroke for cylinder 6 then I could jump to cylinder 1 and be at the same position right? Also, how many rotations of the crank would bring cylinder 2 or 5 to TDC on compression stroke (if starting from cylinder 1 on TDC compression stroke)?

I thought the crank went 4 times around per "cycle". Once for Intake, once for compression, once for exhaust, once for ??? good measure? Or maybe it is just three times around?

Thanks for the help!!!
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  #12  
Old 10-19-2012, 01:13 PM
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On a 4 stroke engine it works as follows:

piston goes down with intake valves open/opening - Intake stroke - 1st stroke (1/2 revolution)
piston comes up with intake valves closed/closing and exhaust valves closed - compression stroke- 2nd stroke (1 revolution)

just before TDC, spark plug fires and compressed charge burns. The piston is at TDC - ON THE COMPRESSION STROKE - right here. Both exhaust and intake valves are closed.

piston gets pushed down by burning fuel air - power stroke - 3rd stroke (1 1/2 revolutions)
piston comes up as exhaust valves open - exhaust stroke - 4th stroke (2 revolutions)

One thing to note is valves are opening and closing as the piston is moving, and there is overlap with intake and exhaust valves open. it's not all instantaneous.

Also, another thing to note is that the piston passe TDC twice, only once being TDC on the power stroke. That's the point when you can pressurize the cylinder since both valves are closed. When one cylinder is at TDC on the compression stroke, another can be at TDC but with valves open.

So, to do a leak down, you need to identify TDC on the compression stroke of the cylinder you are interested in. having a helper see the pencil move up and down is helpful if you can't see it..
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Old 10-19-2012, 01:15 PM
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http://www.youtube.com/watch?v=NNqmNqaZlKA

http://www.youtube.com/watch?v=2Yx32F1cncg
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  #14  
Old 10-19-2012, 02:41 PM
azcromntic azcromntic is offline
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That's quite different from what I was thinking.

You are a HAM. What frequency do you talk on?
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Old 10-20-2012, 01:02 PM
azcromntic azcromntic is offline
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I was able to pressurize all 6 cylinders with 70 psi of air and found the following:

Cylinder 2 and 5 seem to be okay. Maybe a teensy-tiny leak but I could not feel, hear or see a leak.

Cylinders 3 and 4 have an intake valve leak. I could feel air out of the throttle body. I could tell when I was on compression stroke because it was one revolution from TDC exhaust stroke and when I charged the cylinder the crank would turn CC and then I'd move the crank an 1/8th of a turn and charge the cylinder again and the crank would turn Clockwise. I turned it half way between those two points and locked the crank and did my test.

Cylinder 6, when charged with air, the air leaks around the Cylinder 1 hole even with the spark plug in Cylinder 1. Same thing happend with Cylinder 1 charged with air.

So, now I see why there is oil on top of the valve cover, on the spark plugs and in the area where the spark plug wires lay. I curious though what symptoms I should see from and intake valve leak.

What does that mean to the experts?
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Old 10-21-2012, 09:30 PM
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From reading your initial post and compression readings, it is very doubtful you have "bad" valves. Depending on how many miles the motor has on it, you may be losing a little compression from worn valve seats but nothing serious. Adjusted for the altitude you are getting 125 psi compression average and all of the cylinders are within 10% of each other. This motor only had 150 psi brand new from the factory, so you are still well within the normal range, especially since the readings were taken cold.

Chasing compression issues is what you do if you're burning serious oil, losing radiator water and/or have compression readings of 20 psi or 0. Unless you have oil in your water or water in your oil, I don't see anything to indicate a head gasket leak. As stated above, it doesn't sound to me like your valves are bad or your piston rings are seriously worn.

Before I do anything else, I would change the valve cover gasket and get the motor cleaned off. Oil on your spark plugs wires/boots can cause them to short and you will lose power.

Next, check what type of plugs are in the rig. You should replace them if you don't know how old they are and look at the heat reading. If you are seeing any signs of fouling step up one heat range.

Next, check your timing. If that is set correctly and you still feel down on power, it is most likely a fueling problem. If that motor has injection on it then there are several sensors that may need to be checked to make sure it is fueling correctly.
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  #17  
Old 10-22-2012, 01:11 PM
azcromntic azcromntic is offline
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Thanks Randy! It is consuming 2 quarts every 440 miles.

I think I'll take off the valve cover, do valve PM per Service Manual, replace spark plug gaskets and valve cover gasket, replace spark plugs and install an oil seperator so I can get an idea of how much oil is going through PCV.

Plus, I could maybe run something through the fuel to clean out buildup on intake valves?
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Old 10-22-2012, 02:31 PM
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Be sure to use Nippondenso or NGK plugs (or whatever your Toyota dealer has). IMO, you don't want to run Champion/Autolite/domestic-type plugs in a 2F. Glamor-plugs like Splitfires also don't belong in this truck.
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  #19  
Old 10-22-2012, 02:53 PM
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Quote:
Originally Posted by azcromntic View Post
Thanks Randy! It is consuming 2 quarts every 440 miles.

I think I'll take off the valve cover, do valve PM per Service Manual, replace spark plug gaskets and valve cover gasket, replace spark plugs and install an oil seperator so I can get an idea of how much oil is going through PCV.

Plus, I could maybe run something through the fuel to clean out buildup on intake valves?
There really are no additives that are going to clean your valves, most of that stuff is just snake oil and is a waste of money.

Fix your oil leaks first, then lets see what your oil consumption is. If you are burning 2 qts in 440 miles due to bad rings, then you should see some blue smoke upon hard acceleration and the plugs should show signs of oil fouling. Bad valve guides typically give you a puff of smoke upon start up and under hard deceleration like coming down a long hill. But, your compression numbers dont obviously indicate either of those being the case.

IMHO spark plugs are like oil. If it makes you feel better to spend more money on NGK's or whatever, then it's money well spent. The truth of the matter though is your engine doesn't care what brand of spark plug is used and as long as you use the correct type of plug there is not really any difference in them. What does matter is that the the plug is the correct length and depth into the combustion chamber, thread type and most importantly the proper heat range. If you look up an NGK XYZ plug and cross reference it to a Champion equivalent, they will work fine. There are minor differences in electrode design so one plug may last a little longer than the other but usually the differences are really small.

If you use the factory recommended heat range it will work OK but may not be optimal. The factory plug was recommended based on a new engine operating at sea level. Ethanol wasn't common in those days and now you get a steady dose of it all winter long plus you are operating at higher elevations here. As you can see your compression is down a little from the factory specification. Take the part number of the plug that was in the engine and look it up online to see where it falls in the heat range. If it is towards the bottom or middle of the range, you may want to go up one notch. A slightly hotter plug will help minimize plug fouling if you are actually burning a little oil. Run the plug for a few hundred miles then pop them out and check them. You can get a lot of good pictures online that will help you learn what a plug looks like if it is running too cold, too hot or somewhere in between.
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  #20  
Old 10-22-2012, 03:17 PM
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I agree that if it were burning oil, you'd see it. I think you need to be looking for and addressing leaks first. Your motor, as stated above, seems to be in decent shape internally.
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