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Old 10-02-2007, 21:09   #1
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Compression Testing Diesel

I just bought a compression tester for diesels. It has adapters for almost any CAR engine you can name, but not one for a Perkins 4-108. Is the thread for the injector on the 4-108 like any known automobile?? If so which, maybe I have an adapter for that car.
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Old 10-02-2007, 21:48   #2
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Probably not. When we test, we often make up an adaptor usign an old injector. After awhile you build up a range of adaptors.
The other comment is, Why a compression tester?? This is not the best tool to use. A leakdown tester is by far the better tool. Is it a leak down tester you are using???
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Old 11-02-2007, 08:17   #3
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Why?....Well, for the main reason, the compression tester was $19 at Harbor Freight. At that price I can afford to have it in my tool chest. Otherwise I would have nothing.

Yes I know the value of a leakdown tester, I used to fly and that is all we used on aircraft engines. But when this is just for in the field diagnostics and it only cost $19, its worth while.

I could make a leakdown tester using this guage as a bassis and another one. But I dont know enough about the size of orfice I would need.
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Old 11-02-2007, 10:53   #4
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The compression tester does not tell you anything but a compression value. If the compression is down, the compression is down. And you most likely know that without the aid of the tester anyway, as many tell tale signs will allude you to a compression problem. Once you have tested the compression and established it is down, the only way to know why is to start stripping the engine.
A leakdown tester will help you with what the possible compression issue is being caused by. This can be a great help in determing a cause before you start pulling anything apart. It maybe a simple issue of Valve adjustment through to just top end work or you may have a major seriouse issue below the head level.
As for a fitting, I would suggest yu find a diesel guy and get him to send you an old worn out injector you can adapt to that you can keep in the tool box with your gauge.
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Old 11-02-2007, 12:44   #5
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A compression tester will tell you if it is a head/valve issue or if it is lower in the motor if used properly.Do a dry test as normal,then put motor oil into the cylinder and test again if the compression stays about the same it is a head/valve issue,if it has good increase it is a cylinder ,ring or piston issue.Greg
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