Diesel engines misfire analysis using USB Autoscope


Test CKP
Diesel engines The CKP test also allow you to identify cylinders
in diesel engines in addition to gasoline. To perform tests on diesel engines, record
the signal from the CKP (CranKshaft Position) sensor and a signal from a current transducer. The transducer, must be installed on one of the electrical wires from one of the injectors. The engine of a Peugeot Boxer performs well at idle. However, during driving conditions, the engine
is running very rough with low power. The efficiency graphs obtained with the CKP
test shows that the efficiency of cylinder #1 gets worse with increasing engine speed. There were no misfire codes stored, probably
because the engine is not misfiring at idle. The CKP script was used to determine if the
engine had a dynamic compression problem. On the color graphs can be seen that the compression
in all the cylinders is the same. Therefore, it was decided to replace the fuel
injector for cylinder #1. Retesting after the injector replacement showed
that the engine now operates much better, with good power. However, re-run the CKP test showed that cylinder
#1 now has better efficiency than the others. This is to be expected, a new injector will
perform better than one that has been in service for a long time and the main reason why manufacturers
recommend replacing all the injectors in these cases. The engine of an Opel Vivaro 2.5 dCi displayed
a very rough running condition while driving. Additionally, the idle was very unstable until
the engine had warmed up. Performing a CKP test on the engine while
cold showed poor efficiency of cylinder #3 at idle and under load. As the engine warms up, idle becomes stable. But under load, it was misfiring. The “Compression” tab, provided by the CKP
test script, showed lowered compression in cylinder #3, compared to the other cylinders. This type of deviation in the “Compression”
graph is specific for a reduced compression ratio. Engine disassembly revealed a bent connecting
rod in cylinder #3. Most likely caused by hydro-lock from the
engine ingesting a non-compressible fluid, such as water. When replacing diesel fuel injectors, the
sealing washer must also be replaced. Since this sealing washer affects the nozzle
location in the combustion chamber, it is important that the washer has the correct
thickness. This is the result of testing on a Mercedes
Vito 112CDI engine. On this engine, too thick sealing washer was
installed under the injector for cylinder #1. For that reason, the fuel injected in to the combustion chamber
did not swirl and mix properly with the air, causing poor combustion. Replacing of the sealing washer eliminated
the problem.

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3 Responses

  1. Paulo Rogerio says:

    muito bom, poderia mostrar as ligações é a configuração, como ligar as sondas etc?
    sou novo quero aprender as ligações.
    obrigado por compartilhar.

  2. Tashfeen Azhar says:

    An other good video but show how to connect and work thanks

  3. HVT Valencia says:

    Muy bueno 👍🏼

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