Fiat 1.3 JTD Intermitant Poor Start

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Fiat 1.3 JTD Intermitant Poor Start

Postby andygarv » Thu Feb 28, 2013 9:00 pm

Hi all, been looking at a 54 plate Fiat Panda 1.3JTD common rail diesel for intermittent poor start. Think I have found the fault, just looking for a second opinion really. Carried out basic checks, injector back leakage, fuel pressure supply and found no fault. Looking at the fuel pressure signal while cranking and poor start fault present, the pressure starts to build the drops off instantly before starting to build again, obviously the vehicle wont start until enough pressure has built up. Ive tried to attach this file to look at.

I then decided to look at the current for the fuel pressure regulator mounted on the fuel rail, at the same time the fuel pressure drops the current for the regulator drops, i then checked the supply voltage while the fault occurred, all looks well, which lead me to check the switched earth control for the pressure regulator. At the very instant that the fuel pressure drops and current drops the control switched earth goes to battery voltage. After much thought, I have come to the conclusion this must be a ECU fault which will require, removal, send for testing and possible repair. Only seems to happen during cranking, runs fine. Hope the attached files can be viewed, i would appreciate any feed back, kind regards, Andy
Attachments
Fiat 03' 1.3 JTD Fuel Pressure Sensor + REG Current...psdata
This is a capture while cranking and running, fault present at cranking
(132.12 KiB) Downloaded 225 times
Fiat 03' 1.3 JTD Fuel Pressure Sensor + REG Current....psdata
This Is the voltage supply to the pressure reg and current during cranking, although the fault didn't occur while taking this
(156.84 KiB) Downloaded 193 times
Fiat 03' 1.3 JTD Fuel Pressure Sensor + REG Current.... Fault.psdata
This is fuel pressure regulator control signal in blue and current in red, need to zoom in to see the detail, the vehicle did not start for the whole capture. Can see when the current drops the signal is not earthed.
(229.27 KiB) Downloaded 200 times
Fiat 03' 1.3 JTD Fuel Pressure Sensor + REG Current.psdata
This is Rail pressure signal in blue and pressure regulator current in red, can see the erratic fuel pressure as it builds and current dropping down
(103.02 KiB) Downloaded 196 times
Last edited by andygarv on Fri Mar 01, 2013 1:34 pm, edited 1 time in total.
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Re: Fiat 1.3 JTD Intermitant Poor Start

Postby Robski » Fri Mar 01, 2013 8:45 am

Only briefly looked at the captures, one thing jumps out .........nearly 4A on a FPR !!!!

You are happy to call the PCM without checking powers/grounds as well a volt drop during crank ??

Where were you taking these captures from PCM or sensor ??

Cranking current & volt drop ??

CMP/CKP signals during fault ??
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Re: Fiat 1.3 JTD Intermitant Poor Start

Postby KimAndersen » Fri Mar 01, 2013 12:44 pm

Hi

Don't condemn the ECU yet - the readings you get from your pressure regulator(DRV) looks suspicious - they should not be that high.

When your engine is at idle speed and the rail pressure are between 300 to 400 bar you should expect a reading around 450 to 550 milli amps.

The DRV valve could be stuck or short circuit periodically and don´t forget the basic measurements as Robski mentioned.

Regards
Kim
Last edited by KimAndersen on Sun Mar 03, 2013 10:35 pm, edited 1 time in total.
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Re: Fiat 1.3 JTD Intermitant Poor Start

Postby Robski » Fri Mar 01, 2013 6:58 pm

$ Million question ............ DTC's ?
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Re: Fiat 1.3 JTD Intermitant Poor Start

Postby andygarv » Fri Mar 01, 2013 8:01 pm

Hi guys, thanks for the input. I'm not happy to call the PCM at all, the last thing I want to do is get it wrong. That's why I've come here for some guidance. I've clearly not done so checks surgested, fairly new to this. Could you please explain what you mean by current and volt drop check? Would I do this at the component? Attached two more captures since the first post, when the engine idles, the FPR current is in the milli amps. The one that shows 4 amps was the worst I saw the vehicle fault, without looking I think it cranked for about 6-8 secs no start and the current increased half way through this. This is the only time I saw the current this high. My thoughts were with fuel pressure and FPR current dropping at the same time, this was the cause of poor starting. As the current drops out, I was looking for a supply or ground fault. As for DTC's, sorry but I carnt be too spacific as I didn't record them, that was a mistake. Initially one for pre heating circuit that was it, them I rechecked when the vehicle left the workshop and found one for FPR and one for fuel pressure, assumed these were set during the 6-8 sec cranking, non start and 4 amp current capture. Sorry I carnt be more specific with DTC no. Thanks for the interest guys, I'm learning from my mistakes, kind regards, Andy.
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Re: Fiat 1.3 JTD Intermitant Poor Start

Postby KimAndersen » Sat Mar 02, 2013 10:26 am

Hi

You didn't mention - if the vehicle were equipment with a dual-control system !!!

With a dual-control system you have a valve called MPROP or IMV that controls the inlet to the high pressure pump and as such controls how high the pressure should be.

If the rail pressure becomes excessive should the MPROP reduce this pressure. This MPROP is a vital component and should also be properly diagnosed to get the full picture of how the system are working.

Typical values for a MPROP are 0.8 to 1.5 Amps.

EDIT:
I forgot to mention that when the MPROP are fully open it draws no electrical current through the coil.

Regards
Kim
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Re: Fiat 1.3 JTD Intermitant Poor Start

Postby andygarv » Sun Mar 03, 2013 10:07 pm

Hi, it is a single control system, FPR on the rail, pressure sensor on the other end. Bosch system. Does any one know how much current the FPR uses while cranking on a known good vehicle? Is it possible that the ECU detects the FPR is drawing too much current, ie sticking, therefore switches it on and off whilst monitoring it? Regards Andy.
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Re: Fiat 1.3 JTD Intermitant Poor Start

Postby KimAndersen » Sun Mar 03, 2013 10:31 pm

Hi Andy

It depends on your cranking pressure - but typical cranking pressure are around 200 - 300 bar and that equals 325 mA to 450 mA.

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