compression test - no vacuum event

Kudugar · Post by **Kudugar** » Wed Jun 13, 2018 1:35 pm

Hi, after engine overhaul non start condition persist. doing compression test it appears that the intake event is not as expected. from my understanding of the waveform it seems no vacuum is being created by intake ivent. Timing has been double checked and spot on using factory timing tools.
your advise will be very much appreciated

liviu2004 · Post by **liviu2004** » Thu Jun 14, 2018 1:45 pm

There is no vacuum during compression test, as throttle body is wide opened to atmospheric pressure, correct?

I see a bit of exhaust pressure, remove lambda 1 and start.

Technician · Post by **Technician** » Fri Jun 15, 2018 4:51 pm

Can you complete a cranking vacuum test using the WPS500x. Disable ignition/fuel to prevent start up so we can see a good record of the vacuum achieved.

Post by **ben.martins** » Wed Jun 20, 2018 7:30 am

Hello Kudugar,

Thank you for posting and what you are seeing is as Liviu has said, you're not seeing a change in pressure during the intake stroke as the throttle butterfly is open. If you wish to see more detail from the intake stroke you could trying restricting the inlet opening. This will prevent peak compression but it will highlight inlet valve opening as during the intake stroke there is a restriction which will create a vacuum.

If you were to open the automotive tab and select Pressure Transducers>WPS500X Pressure Transducer>In-Cylinder>Cylinder Compression (Cranking) you will notice that the capture is very similar to the one you have captured.

If it's a non runner I would be focusing on fuel and ignition to begin. I see you have a 4425 which means we can make use of the extra channels. You could keep Cyl 4 compression on and then add ignition (depending on coil pack type) and injection for cylinder 4 and maybe fuel pump current.

I know you have added in the notes that these are ok but by adding all these together will get a better picture of what is happening during cranking.

Hope this helps and please keep us posted with how you are getting on.

Kind regards

Ben

Kudugar · Post by **Kudugar** » Wed Jun 27, 2018 2:38 pm

Hi afetr scoping crank, cam, cyl no 1 pressure using wpx transducer and cyl no injector it appears that the cam signal is not correct. it is a magnetic sensor 2-wire unit. please see waveform and comment pls are welcome. the camsensor measure 440ohm resistance between two connectors

Technician · Post by **Technician** » Wed Jun 27, 2018 9:22 pm

The injector trace does not look good either!

Kudugar · Post by **Kudugar** » Wed Jul 04, 2018 10:26 am

HI Gents

i have now replaced camshaft sensor as i could default once getting no signal.
i added trigger from ecm to coil pack on cyl no i.
i have secondary voltage clamp over spark adapter on cyl no 1 sparkplug.
fuel pressure seems very good.

what i am perhaps seeing is that the trigger to spark and ign trigger lines up but my question is, is it not to far retarded to get proper btdc firing and ignition stroke, as the vehicle start up for half second and stumble within 1 sec of start attempt. no start event after that then for at least 5 minutes?.
alarm led checked and alarm functional as should be.

kona · Post by **kona** » Wed Jul 04, 2018 4:25 pm

Hi,

It seems you have a problem with timing (+30°) ...

Look at this:

liviu2004 · Post by **liviu2004** » Wed Jul 04, 2018 4:40 pm

Plugged exhaust, catalyser.

kona · Post by **kona** » Wed Jul 04, 2018 4:56 pm

liviu2004 wrote:Plugged exhaust, catalyser.

It seems that the exhaust pressure is a consequence wrong chain installation .
The catalyst can be working well.

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