No Cylinder Pressure

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  #1  
Old 12-10-07, 12:21 PM
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No Cylinder Pressure

I have a 94 Grand Prix SE with a 3.1...i recently put all new gaskets from the head up due to overheating and no heat. I also had the heads checked out for warps and cracks and they were good. The car ran fine before just had an overheating problem, and now i have no cylinder pressure. I have checked and made sure i had all the push rods in the right places and i do...any ideas would be greatly appreciated!
 
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  #2  
Old 12-10-07, 12:37 PM
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Tell us how you are testing cylinder pressure.
 
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Old 12-10-07, 01:06 PM
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I'm testing the pressure by taking out the spark plug and putting in a pressure tester and rolling over the engine
 
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Old 12-10-07, 01:35 PM
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Make sure the tester works correctly.
 
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Old 12-10-07, 01:41 PM
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it does checked it on my other vehicle
 
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Old 12-10-07, 02:16 PM
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If you have NO compression, it's going to be a stuck valve most likely or the block is cracked.
 
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Old 12-10-07, 02:50 PM
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yeah it seems it would have to be the valves sticking but how could they all stick...i have no pressure in cylinders 2,4 and 6 haven't checked cylinders 1,3, and 5 in the back but the plugs were wet with gas so im assuming they don't have pressure either. The car had decent pressure before i riped it apart...so it had to be something i did...i did replace the valve seals i wonder if i could have did something wrong there...i did them one at a time so not to put one in the wrong spot and did them by the book. Its has to be the valves because its a big leak im not even getting a budge on the dial on the pressure tester. I guess i might have to tear it down again...any advise on what i should look for or should i just take the heads and valves in and have them looked at again...

thanks

james
 
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Old 12-10-07, 02:59 PM
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Is that a v-6 or a straight 6? If a V model, you need to check the other valves to determine if its a head problem or a valve problem.. Wet plugs are not indicative of a pressure issue..
 
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Old 12-10-07, 05:45 PM
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what torque setting did you tighten the rocker nuts to?

It could be you simply did not tighten them correctly and the valves simply are not opening.

Do not go and willy-nilly tighten them up. There is a correct setting.
 
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Old 12-10-07, 06:29 PM
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Do you even know that your valves are going up and down? A rotating engine does not guarantee the valvetrain is even working. You could have timing belt or chain come off even. Is it hard to take off valve cover?
 
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Old 12-10-07, 07:53 PM
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The first thing you have to do is a cylinder leak-down test to see where the pressure is leaking to. Might be the valves stuck open if you tightened the rockers too much, might be the head gasket leaking if not tightened enough, might even be cracked pistons or rings from the overheating.
 
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Old 12-11-07, 04:33 AM
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Head bolts properly torqued? Those are torque-to-yield bolts.

Didn't by any chance leave out the long spacer plate that goes under the rocker arms?
 
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Old 12-11-07, 12:36 PM
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Eveything is torqued right head bolts to 33 ft-lbs and then rotated 90 degrees....rocker nuts torqued to 20 ft-lbs...spacers are in...took out push rods and tested pressure and perfect pressure...so its nothing cracked...so it must be the cam or the lifters...timing is correct so its not that...guess its time to take off the upper and lower intake to check out the cam and the lifters...thanks for all the tips!
 
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Old 12-11-07, 12:57 PM
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Are you sure the chain/belt has not skipped out.


I still would have a quick check on the base valve timing to make sure that it did not skip a cog with that heat
 

Last edited by frankiee; 12-11-07 at 01:14 PM. Reason: Thinking of wrong engine: Im ok now; maybe!
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Old 12-11-07, 01:07 PM
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I was just reading something. It said the pushrods (intake v. exhaust) are different lengths.

the intakes are 6 inches long and the exhaust 6 3/8 inches long. Reversing them would surely cause some problems.
 
  #16  
Old 12-11-07, 01:15 PM
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Yeah the intake pushrod is shorter... there all in the right spot...i triple checked

thanks

james
 
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