Today I write about a problem we solved on Fiat Panda 1300 mjet 2008 4×4

Here is the description of the problem described by my Check Star Magneti Marelli workshop colleague:

The car arrives at the workshop and the owner complains that the engine does not start.

The problem, however, is occasional and occurs irregularly, i.e. without warning.

My colleague reports this: when the Panda does not start, I find that the revs signal in the diagnosis is alternating, the tachometer needle also jerks.

This also happens to the diesel pressure, which pulses and therefore does not reach the threshold for the injectors to open. Also, when it doesn't start, I can hear the glow plug relay going on and off.

I checked the cables going from the rpm sensor to the control unit and they seem OK (today I will try to replace them)

I replaced the rpm sensor

I replaced the phase sensor

I replaced the diesel pressure regulator

I disconnected the glow plugs

I checked the flywheel

checked injector recovery

checked the low pressure

replaced motor management relay

checked the power supplies in the control unit

checked the starter switch

PLEASE NOTE

when the car does not start, if you try to start it with a push, it starts immediately.

Diagnosing with the oscilloscope, I checked the signal at the diesel pressure regulator, and I see that the signal varies from a square wave to an abnormal signal.

I measured that rpm and the wave fades at times. I changed the wiring from the rpm sensor to the ECU, and also tried another ECU.

At the end of the checks, we discovered that the problem was caused by the starter motor, which had an absorption fault.

We changed the motor and the problem was solved.

See you at the next solved case

Best regards Antonio

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