Hi, recently watched SD video on carrying out compression tests using scope to ID faulty cylinder etc, I would like to know is there a diag tool/scope that gives ia readings in amps, I remember in the 80s we had a souriau diag machine that did this and we could print the results as diesels are a lot more complex to work on it made me think l maybe barking up the wrong tree any help would be appreciated thanks
Are you refering to relative compresssion? You would do so with an amp clamp to measure the cranking amps with a scope... Same procedure as with gasoline engines but the sync signal may be more challenging to get.
Typically you would sync to an injector as the pulse is close to TDC. As you don´t want the engine to start during the test an easy way to achieve this on common rail systems is to disable the HP pump. The resulting lack of fuel pressure would shut off the injector pulse. This you can overcome by "injecting" a valid signal into the fuel pressure signal wire to the edu.
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Last edit: 3 years 6 months ago by juergen.scholl.
The following user(s) said Thank You: glennlotus25
If you haven't an amp clamp you also check relative compressions by simply checking voltage although the wave form is inverted ie lower voltage = higher compression.
Some oscilloscopes such as the automotive Pico scopes have built in compression test.
Autoditex do a hand held tool specifically for this they have very recently extended it it with additional functions for checking common rail diesel injection issues.
autoditex.com/carscope-i-tester-basic-kit-106.html
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Last edit: 3 years 6 months ago by Andy.MacFadyen.
The following user(s) said Thank You: glennlotus25
