Technical Another Stilo preheat question

[lxrose]

Hi to all Fiat owners,

I am an old Fiat Stilo 1.9 JTD MultiWagon owner and I am a reader of this site when I need some information. This time I registered, because I didn't find the answer to my question. (Anybody here still own a Stilo? )
So last year I had my car mechanic replace all the glow plugs because of the preheat fault warning, but the problem is still there. I verified all the related fuses and the relay (it activates, if I apply 12V to it). What I cannot find and don't know how to check is the O20 preheat resistor, which must be somewhere inside the engine close to the diesel pipes. I have a guess, but I am not dare enough to remove the plug and it is not so easy to reach either. Can anyone post a picture of the related part (in its location) and some instructions how to be able to measure if it is functioning correctly. I mean where to put the wires of my multimeter where it is easy to measure if this part is broken? I have basic troubleshooting skills and some electric background too.

Thanks for everyone who replies.
lxrose

 

[Davren]

According to the Stilo eLearn workshop manual, O20 preheat resistor is a diesel fuel preheater on the side of the fuel filter head. It's a preheator, not a sensor.

Item 16 in the diagram below.

1 - Fuel tank
2 - Submerged fuel assembly complete with level gauge control
3 - Fuel filler pipe
4 - Reflux pipe
5 - Fuel filter element
6 - Water in fuel filter sensor
7 - Pressure pump
8 - High pressure pipes
9 - Single fuel manifold pipe
10 – Injectors
11 - Pipe from injectors to fuel return manifold pipe
12 - Fuel return manifold
13 - Pressure regulator
14 - Fuel temperature sensor
15 - Fuel pressure sensor
16 - Fuel heater
17 - Inertia switch

 

[lxrose]

According to the Stilo eLearn workshop manual, O20 preheat resistor is a diesel fuel preheater on the side of the fuel filter head. It's a preheator, not a sensor.

Item 16 in the diagram below.

1 - Fuel tank
2 - Submerged fuel assembly complete with level gauge control
3 - Fuel filler pipe
4 - Reflux pipe
5 - Fuel filter element
6 - Water in fuel filter sensor
7 - Pressure pump
8 - High pressure pipes
9 - Single fuel manifold pipe
10 – Injectors
11 - Pipe from injectors to fuel return manifold pipe
12 - Fuel return manifold
13 - Pressure regulator
14 - Fuel temperature sensor
15 - Fuel pressure sensor
16 - Fuel heater
17 - Inertia switch

View attachment 429885

Hi Davren,

Thank you for your reply. I am going to check this location. Do you know if this is the resistor that is feed by the relay T19 or is it a different one controlled by another circuit?

Cheers,
Sándor

 

[Davren]

Hi Davren,

Thank you for your reply. I am going to check this location. Do you know if this is the resistor that is feed by the relay T19 or is it a different one controlled by another circuit?

Cheers,
Sándor

Yes, O20 gets a power supply from relay T19 in the engine compartment fuse box B1.

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3360997 - E5050 DIESEL ENGINES ELECTRONIC MANAGEMENT - Wiring diagram​

Wiring diagram​

 

[lxrose]

Yes, O20 gets a power supply from relay T19 in the engine compartment fuse box B1.

Thanks for confirming. I will measure this resistor on the weekend. Hopefully I will find out something. I would like to fix it before winter, but things are going slowly on my side.

 

[skysword]

Thanks for confirming. I will measure this resistor on the weekend. Hopefully I will find out something. I would like to fix it before winter, but things are going slowly on my side.

Did you find any issues with the resistor?
I have a similar issue:
When I put ignition on, I get preheat failure few seconds after.
I tested with FES, setting the fuel heater on, and

• I can confirm that the relay is working (I can hear it and feeling engaging)
• the wire have voltage when relay is on
• the fuel temperature is increasing

However, when the ignition is turned on, there is none of the above, meaning that there is no command to turn on the relay.
What can be the issue here? ECU can give the command, because I can turn it on with FES, but it doesn't want to do it

Thanks

 

[lxrose]

Hello,

After a long time I could spend some time with my Stilo. It seems that the resistor is not broken, I can measure a couple ohms inside the fuel filter adapter. However I cannot measure 12V on the wires connecting to it. I need to find the reason why. Perhaps a broken wire? This could also be your problem. I had this problem with the ABS, when it was not working a couple years ago.

Regards
Lxrose

 

[lxrose]

Hello again!

I made some progress after a year.
A measured all the related wires and after all looked good, I found, that the voltage coming out of the ECU is only 8.5V after turning the key. Is it worth to open the unit and check the soldering of the connecting pin? Or is it too risky/complicated?

 

[lxrose]

Hello again. I opened the ECU a couple months ago, but I didn't find the reason why the voltage drops when there is a small load on the output.
I have the possibility to buy a used ECU, but I don't think it is as easy to replace it as removing the screws and the connectors. Am I right that it requires some programming?