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Guest Message by DevFuse

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EA82 with low compression after t-belt change

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5 replies to this topic

#1 nichzimmerman



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Posted 27 April 2014 - 07:17 PM

Hi folks, I'm the guy that started the topic called "1990 loyale engine problem" and since the scope of the problem has evolved so much I figured a new thread is in order. Before the timing belt change, compression on cylinders 1 and 3 was normal. After the t-belt swap everything was back to normal except cylinder 1 was reading 20 psi. Obviously the engine was running a bit rough.I checked and rechecked the timing belt configuration and even adjusted the right cam sprocket a tooth or two in each direction and switched the crank sprockets just in case I had them backwards. In every case, the engine ran the same and compression was just 20psi (needle just barely off the stop.) What next? I tightened the compression tester fairly tight to ensure air wasn't leaking past. Valves maybe? Thanks.

#2 ruparts


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Posted 27 April 2014 - 09:00 PM


 i had followed your issues but after all the try this and that you now have good compression on #3 , yes,   but not  #1?   if this is correct and the motor runs although poorly, and it doesn't cough back through the intake manifold,, it most likely is the exhaust valve on #1 , and the compression is passing out the exhaust.  low compression  can be broken piston,   bad rings, bad head gasket,   valve not closing to its seat, even a broken spring.   so if compression on 3 is back to normal  then the belt is ok , and you need to focus on why 1 is not.  my thought is the exhaust valve is not closing all the way, , either stuck or bent stem.  no reason to suspect the rings or the head gasket if they were good before this belt issue.  i have seen the little rocker get shifted to the side and not sit on the valve stem properly, and still run and stay in place, there is a notch in the rocker tip, the valve stem has to sit inside the notch or it can't close all the way, i've done it myself.  if this is it, close inspection you might see there  is not quite a straight alignment  between valve tip and  lifter tip, and the rocker might look tilted a little.  just a thought.

 second thought,  if the intake rocker on #1 has fell out of place and not opening the intake valve, the compression would be very low,  the cylinder would get some air during the exhaust valve closing after the exhaust stroke passes tdc,  but not enough to make proper compression.   ( i have personally had the rockers fall out of place before)   pull the right side valve cover and do a close inspection, , rotate the crank by socket and ratchet and look for anything different on 1,  from 3 ,  also stop  with #1  at tdc compression,, you can use the ignition  timing  "0"  mark on the flywheel, ( has to be compression, not exhaust,  since the mark will line up at both),   and see if both valves  on #1  look to be fully closed or if the spring retainers are  level with each other.  check the rockers to see if they are loose in place.   a collapsed lifter, something broken, something don't move when rotating the crank, close inspection.

Edited by ruparts, 28 April 2014 - 12:07 AM.

#3 jono


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Posted 28 April 2014 - 07:53 AM

or this :




gave me zero comp after it was 190 or 200 psi when I parked it four months ago.


Prior to parking it , I had it running nice after 8.5 years of going nowhere. I tried to start it on the stale fuel, blew the intank mesh clear of barnacles with 90 psi, got it running, drained barnacle urine and feaces out, fresh new fuel into barnacle lined  tank. Happy that it was running right for storage, went to restart and things got a little noisy, blamed dormant starter motor, got a miss, no power to even reverse the beast.


Putting it down to the black sticky, gummy crud on the valve stem of #3 inlet coming from stale fuel ?


Bent the push rod

Edited by jono, 29 April 2014 - 05:09 AM.

#4 MilesFox


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Posted 28 April 2014 - 08:54 AM

Possibly it could have a dropped valve seat. It would be worth the labot to remove the intake and inspect it. Just in case you have to pull the heads, you are already half way there, and are well versed in timing belts by now.


I have seen a dropped valve seat on an ea82, bot only one exmple of the many i had. It was dropped due to the cracks that form between the seats. It should be possible to re-stake the valve seat.

#5 nichzimmerman



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Posted 29 April 2014 - 12:44 AM

I tried blowing compressed air into the spark plug hole on cylinder 1 at TDC (the zero on the ignition timing scale), then rotated the crank 360 degrees and did it again. in both cases my wife told me she felt air out the exhaust. I put a bunch of oil in the cylinder and did another compression check and still got the needle barely off zero. are these tests generally adequate to diagnose a stuck exhaust valve? I would just like to be as sure as possible before committing to more disassembly. cylinders 2, 3, and 4 have compression in the 150s. thanks!

#6 jono


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Posted 29 April 2014 - 05:08 AM

sounds like stuck exhaust valve

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