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Technical Crank, no start, no spark, no DTCs

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Technical Crank, no start, no spark, no DTCs

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Luke77

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My FIAT Punto 188 1.2 8v (end 2001) does crank, but doesn't start, due to no spark.

Therefore I replaced spark plugs, to no avail, still no spark seen when testing the sprak plugs.

Read-out with OBD2 gives no pending or stored DTCs.

Ignition coils checked and are within specification.

Tried with a different car battery and still crank but no start.

What could be the problem?
Thought it could be the camshaft position sensor (CPS) or the crankshaft position sensor (CKP), but there is no DTC seen for this sensor in the read-out.
 
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varesecrazy said:
Under a lot of circumstances.. you will NOT get a crank sensor error.

No signal.. but no other ECU input to say the crank is actuslly turning.
Click to expand...

You mean the crankshaft position sensor can be damaged, without a DTC (error) to be read?
 
varesecrazy said:
YES..
Without its input.. the ECU Is unaware at what speed the crank is spinning.

Hence no fault logged.

This VERY common with sick running diesels.

You have a CAM sensor too?
Click to expand...

As far as I understand, the problem could be a damaged CRANK sensor or CAM sensor or could also be the KNOCK sensor?

Do you have any clue what the normal input voltage from the ECU to the sensors should be, so I can check if it is correct?
 
I did, but can't find the right answer:

By measuring the wiring, with the CRANK sensor not attached, I measured (wire A) 1,46V; (wire B) 2,44V and (wire C) ground respectively.

By back probing with ignition ON and CRANK sensor attached I measured from A-C 2,04V and also B-C 2,04V even when moving the sensor along metal pieces the voltage did not change.

Did the same procedure with the CAM sensor and there the input was about 5V and I could see the signal voltage changing between 0.3V and 2.0V when moving along metal.

Is the CRANK sensor dead?
 
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Luke77 said:
I did, but can't find the right answer:

By measuring the wiring, with the CRANK sensor not attached, I measured (wire A) 1,46V; (wire B) 2,44V and (wire C) ground respectively.

By back probing with ignition ON and CRANK sensor attached I measured from A-C 2,04V and also B-C 2,04V even when moving the sensor along metal pieces the voltage did not change.

Did the same procedure with the CAM sensor and there the input was about 5V and I could see the signal voltage changing between 0.3V and 2.0V when moving along metal.

Is the CRANK sensor dead?
Click to expand...

Sounds like a faulty sensor but could also be wiring or ECU. What voltage are you getting at the plug with the sensor unplugged? You should see 5V to ground on one of them.


Robert G8RPI
 
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Re: Crank, no start, no spark, no DTCs - Crank sensor?

g8rpi said:
Sounds like a faulty sensor but could also be wiring or ECU. What voltage are you getting at the plug with the sensor unplugged? You should see 5V to ground on one of them.


Robert G8RPI
Click to expand...

With the sensor NOT attached and measuring at the plug I got (wire A-to-ground) 1,46V; (wire B-to-ground) 2,44V and wire C is the ground wire.

I find it weird :confused: getting respectively 5.16V and 5.19V to ground at both wires at the CAM plug (seems normal) and above measurements at the CRANK plug.
But maybe I am wrong and it is the normal voltage from ECU to CRANK sensor.

What do you think, Robert G8RPI?
 
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Re: Crank, no start, no spark, no DTCs - Crank sensor?

Luke77 said:
With the sensor NOT attached and measuring at the plug I got (wire A-to-ground) 1,46V; (wire B-to-ground) 2,44V and wire C is the ground wire.

I find it weird :confused: getting respectively 5.16V and 5.19V to ground at both wires at the CAM plug (seems normal) and above measurements at the CRANK plug.
But maybe I am wrong and it is the normal voltage from ECU to CRANK sensor.

What do you think, Robert G8RPI?
Click to expand...

The only punto 8v wiring diagram i can find shows an inductance crank sensor and a hall effect cam sensor. Different sensor types requiring different circuits.

Only the cam sensor requires the 5V reference voltage.
 
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Re: Crank, no start, no spark, no DTCs - Crank sensor?

judderbar said:
The only punto 8v wiring diagram i can find shows an inductance crank sensor and a hall effect cam sensor. Different sensor types requiring different circuits.

Only the cam sensor requires the 5V reference voltage.
Click to expand...

Thanks, I think I will buy a new crank sensor and hopefully the problem is solved... :worship:

The original sensor is the MAGNETI MARELLI - Ref: 11104021110 (FIAT OEM 46774532)

Let you know....
 
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Re: Crank, no start, no spark, no DTCs - Crank sensor?

judderbar said:
That part number is an inductive sensor so should have a resistance of 1100 ohms.


https://www.onlinecarparts.co.uk/oenumber/46774532.html
Click to expand...

Replaced the CRANK sensor with exactly the same, but new CRANK sensor MAGNETI MARELLI - Ref: 11104021110 (FIAT OEM 46774532).

But still no spark at any of the 4 spark plugs!! :cry:

Steps undertaken till now (Punto, 2001, petrol):

- read-out with OBD2 gives no pending or stored DTCs, but do get a red light (see picture, on my reader the <!> on the right is red)
- replaced all spark plugs with same type/brand
- fuel pump delivers fuel when I disconnect the fuel line close to the injectors
- ignition coils checked and are within specification
- tried with a different car battery and still crank but no start
- checked CAM sensor and seems to work normally
- replaced CRANK sensor (only weird thing is that I don't get 5V with the CRANK sensor NOT attached, but measuring at the plug I got (wire A-to-ground) 1,46V; (wire B-to-ground) 2,44V and wire C is the ground wire -> at the CAM sensor I do get a "normal" 5V at the plug)

What could be the problem?

- KNOCK sensor?
- wiring problem (see voltages at CRANK plug above; but I do get a voltage here and with a broken wire I would expect 0.0V)?
- other ideas?
 

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Re: Crank, no start, no spark, no DTCs - Crank sensor?

Luke77 said:
Replaced the CRANK sensor with exactly the same, but new CRANK sensor MAGNETI MARELLI - Ref: 11104021110 (FIAT OEM 46774532).

But still no spark at any of the 4 spark plugs!! :cry:

Steps undertaken till now (Punto, 2001, petrol):

- read-out with OBD2 gives no pending or stored DTCs, but do get a red light (see picture, on my reader the <!> on the right is red)
- replaced all spark plugs with same type/brand
- fuel pump delivers fuel when I disconnect the fuel line close to the injectors
- ignition coils checked and are within specification
- tried with a different car battery and still crank but no start
- checked CAM sensor and seems to work normally
- replaced CRANK sensor (only weird thing is that I don't get 5V with the CRANK sensor NOT attached, but measuring at the plug I got (wire A-to-ground) 1,46V; (wire B-to-ground) 2,44V and wire C is the ground wire -> at the CAM sensor I do get a "normal" 5V at the plug)

What could be the problem?

- KNOCK sensor?
- wiring problem (see voltages at CRANK plug above; but I do get a voltage here and with a broken wire I would expect 0.0V)?
- other ideas?
Click to expand...

As explained earlier the cam sensor requires a different circuit so has a 5 volt reference voltage to operate the digital transister technology in the sensor. The crankshaft sensor is just a coil of wire and a magnet. The teeth on the crankshaft disrupt the magnetic field created by the magnet and alter the electrical properties of the coil of wire.


On my car the crankshaft sensor produces sufficient power to operate a light emitting diode with no amplification required. Trace the crankshaft sensor to the ECU plug and confirm you can see the voltage fluctuation at the plug.

Previously you reported no fluctation in voltage from the crankshaft sensor.


Confirm you can measure a resistance of approximately 1100 ohms at the disconnected plug. Measure the voltage on those two wires at the disconnected plug when you crank the engine and then repeat the same procedure after tracing those two wires to the ECU plug and measuring them at the plug.

Earlier you reported identical voltages when the sensor was connected which could indicate a short circuit.

You need to be methodical and work it thru step by step.

Does the old sensor actually work??

Start with the basics and work it thru

Do you have a rev counter on the instrument panel? If you have a few hundred revolutions on that when the car is cranked then the crank sensor is being detected correctly.
 
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Re: Crank, no start, no spark, no DTCs - Crank sensor?

judderbar said:
repeat the same procedure after tracing those two wires at the ECU plug.
Click to expand...

You mean measuring the two wires as close to the ECU as possible (as close as possible to the yellow arrow in the attached picture)?
 

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Re: Crank, no start, no spark, no DTCs - Crank sensor?

Luke77 said:
You mean measuring the two wires as close to the ECU as possible (as close as possible to the yellow arrow in the attached picture)?
Click to expand...


I mean:

1 You test the old sensor and new sensor and determine you are able to demonstrate at least one of them is able to produce a signal

2. ***Then*** You remove the ECU plugs and trace which tiny connectors on the plugs has the signal that you have demonstrated the crankshaft sensor is able to produce.

You need a system here. A method.
 
Luke77 said:
My FIAT Punto 188 1.2 8v (end 2001) does crank, but doesn't start, due to no spark.
What could be the problem?
Thought it could be the camshaft position sensor (CPS) or the crankshaft position sensor (CKP), but there is no DTC seen for this sensor in the read-out.
Click to expand...


Hi. :)

Ok.. not a busy thread..so I will ask the obvious:

Had the car long, servicing history.?

How did the fault develop?

If it gradually became harder to start.. rather than 'just dead' one morning.

Is the KEY(s) being read ok?

Immob light coming ON.
Then once accepted.. going OFF


Charlie
 
Jusy to be clear, No spark out of coil aswell? Lift lead off a bit, no spark? Don't do this if you have a pacemaker!
 
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