compression waveform help

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rburgy
OneWave
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Location: PITTSBURGH

compression waveform help

Post by rburgy » Thu Nov 23, 2017 2:01 am

I have a 2002 Ford Escape 3.0L engine. have a dead misfire on number 2 cylinder. found broken exhaust valve springs
on number 2 cylinder. replaced #2 exhaust valve springs. number 2 still misses constantly. checked for spark and fuel with no issues there. If i was out of time, at least the whole rear bank would miss. performed a relative compression test and found one cylinder with no compression.

next i performed an in cylinder cranking compression test on #2 and it showed 180psi??


lastly i performed an in cylinder running compression test on #2 cylinder and it looks like i found the issue. appears to be a burnt exhaust valve?
does anyone disagree with this diagnosis?
why would a cranking compression show good but relative compression clearly show an issue?

please let me know any thoughts.
thank you
Attachments
ford escape cylinder 2 compression.psdata
(190.06 KiB) Downloaded 153 times
escape 3.0 cylinder 2 running compression bad.psdata
cranking relative compression
(7.76 MiB) Downloaded 125 times
ford escape relative compression bad.psdata
running compression using wpx5000
(2.97 MiB) Downloaded 114 times

victor2k
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Re: compression waveform help

Post by victor2k » Thu Nov 23, 2017 8:08 pm

Hello,
Please look at the moment of opening of exhaust valve:look how fast the cylinder pressure decrease/compared to the cylinder pressure increase.Try to record also the pressure in intake or exhaust.Sometimes only the compression will not show the issues... :?
Regards
Attachments
Ford_Escape_2002_Petrol_20171123-0002.psdata
(82.32 KiB) Downloaded 114 times

rburgy
OneWave
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Joined: Wed Feb 26, 2014 3:07 pm
Location: PITTSBURGH

Re: compression waveform help

Post by rburgy » Sat Nov 25, 2017 1:00 am

victor2k wrote:Hello,
Please look at the moment of opening of exhaust valve:look how fast the cylinder pressure decrease/compared to the cylinder pressure increase.Try to record also the pressure in intake or exhaust.Sometimes only the compression will not show the issues... :?
Regards
just to clarify, are you saying to use wpx500 and measure exhaust pulses, and use it to measure intake manifold pulses as well?
if the exhaust valve is burnt, it would affect both waveforms. correct?
thank you

Technician
TwoWaves
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Joined: Thu Apr 24, 2014 8:32 pm

Re: compression waveform help

Post by Technician » Sat Nov 25, 2017 6:11 pm

Hello,

Victor2k might be asking you to record inlet manifold vacuum pressure?

victor2k
TwoWaves
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Posts: 245
Joined: Thu Jan 28, 2016 7:17 am

Re: compression waveform help

Post by victor2k » Sun Nov 26, 2017 7:21 am

rburgy wrote: if the exhaust valve is burnt, it would affect both waveforms. correct?
thank you
Hello,
Sometimes you can't see a burned valve/wrong free play of valves only measuring the compression...
Adding a new measurement of intake/exhaust pressure to the cylinder pressure you will see where is the problem,or you can perform a leak down test . :)
Regards

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