Engine Compression
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Elder User
Joined: Jul 2010
Posts: 610
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From: Sequim. WA
Engine Compression
My 7.3 engines are getting old so I did a compression check on one.
The numbers came out around 400 psi.
Is this good enough for continued work?
The numbers came out around 400 psi.
Is this good enough for continued work?
Last edited by MauleOne; Aug 11, 2011 at 07:11 PM. Reason: spr\elling
Thread Starter
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Elder User
Joined: Jul 2010
Posts: 610
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From: Sequim. WA
Compression Test
I used a snap on gauge that reads up to 500 psi. It connects to a fitting that screws into your glow plug port.
You have to remove all 8 glow plugs. Then screw the fitting into one glow plug hole at a time. Be sure to put some anti sieze on the fitting that screws into the glow plug hole.
It is hard to reach all the glow plug holes becaue the injector lines are in the way. You may have to loose the injector lines as necessary.
Crank until the pressure stabilizes. My gauge held the pressure so I could look at it after cranking.
Mainly you are looking to see if one cylinder might be much different than the others.
You have to remove all 8 glow plugs. Then screw the fitting into one glow plug hole at a time. Be sure to put some anti sieze on the fitting that screws into the glow plug hole.
It is hard to reach all the glow plug holes becaue the injector lines are in the way. You may have to loose the injector lines as necessary.
Crank until the pressure stabilizes. My gauge held the pressure so I could look at it after cranking.
Mainly you are looking to see if one cylinder might be much different than the others.
Laughing Gas
Joined: Apr 2011
Posts: 1,002
Likes: 7
From: London, KY
I have one cylinder that concerns me more than the others. It's the number one cylinder. When I changed my injectors, it had alot more carbon build up than the others did. May be nothing, but it concerns me. The engine runs great now after the new IP and injectors so maybe I should just leave well enough alone! LOL
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Elder User
Joined: Jul 2010
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From: Sequim. WA
Compression Test
I have twin NA 7.3 IDI engines in my 21000lb boat. I run them at 2500 rpm all day long.
My compression test was 360,410,450,440,400,390,390,360
A coupla were a little low but these engines have 3500 hours on them. I expect them to last 5000 hours.
I have been working on the idea of adding turbo chargers to the engines and should have the project operational by next month. I will post pictures when I have it set up.
My compression test was 360,410,450,440,400,390,390,360
A coupla were a little low but these engines have 3500 hours on them. I expect them to last 5000 hours.
I have been working on the idea of adding turbo chargers to the engines and should have the project operational by next month. I will post pictures when I have it set up.
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Elder User
Joined: Jul 2010
Posts: 610
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From: Sequim. WA
Compression
LSO 1123
Fly it and watch it.
Put some miles on it and then check that injector again. If it continues to carbon up then it needs to be investigated.
Fly it and watch it.
Put some miles on it and then check that injector again. If it continues to carbon up then it needs to be investigated.
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Laughing Gas
Joined: Apr 2011
Posts: 1,002
Likes: 7
From: London, KY
I think that's what I'll do. I just put the injectors in last week so I'll check it in a month or so and see if it's starting to build up.
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Laughing Gas
Joined: Apr 2011
Posts: 1,002
Likes: 7
From: London, KY
John I can't remember, I know one of them was but I can't remember if it was that one or not. One of them only came out with half of the copper washer, I don't have a clue where the other half went but it wasn't in the bore!
Senior User
Joined: Sep 2008
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I would not think 3500 hrs is that much time I have seen 6.534 120 hp perkins run 18000 hours under full load and a 65 kw light plant on a boat go 72000 hrs and it was not burning much oil . But I allways do short changes 150 to 200 hours on the perkins it doubled the life of eng from 9000 to 18000
