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Non Starting Fiat Doblo 1.9 Multijet Diesel - Fuel Rail Pressure Low

Posted By chris1973 Saturday, December 01, 2018 6:39:44 PM
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Non Starting Fiat Doblo 1.9 Multijet Diesel - Fuel Rail Pressure Low

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chris1973
 Posted Saturday, December 01, 2018 6:39:44 PM
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Hi Everyone, just looking for a bit of advice as I have a Fiat Doblo 1.9 Cargo Multijet on a 55 plate, which refuses to start and of which i've now been trying to fix for some months. Up to the summer it was running fine starting at the first attempt, then suddenly it began needing longer cranking times in order to start, but it would always finally start after which it would run from the first turn of the key all day, even when cold, until the next morning when it would be hard to start again.

Then one Afternoon, it just cut out whilst approaching some traffic lights and wouldn't restart, and upon lifting the bonnet I found that diesel was leaking all over the engine. This was traced to a perished leak off pipe running between the end of the injector leak offs to the black fuel manifold box, from where fuel is returned to the fuel tank. The pipe had swollen and become too wide for the connecting barb. This pipe was replaced, along with the complete leak off pipe assembly running across the tops of the injectors, and normal running was resumed, and the starting issue disappeared.

However the normal starting and running only lasted for about a week, when the hard starting problem returned, and then one morning a few weeks later it just refused to start at all, eventually flattening its battery and a booster pack when attempting to get it going. There were no error codes logged, and no obvious leaks so I tried replacing the most obvious and easiest things first, replacing the fuel filter, Fuel pump relay and then the Battery, but the problem still wasn't solved.

The in-tank pump is running and there is a good flow of diesel being pumped through the filter and into the intake side of the HP pump, but according to the running parameters the rail isn't seeing the requested pressure it needs to open the injectors during cranking. The rail pressure seems to peak at the start of the cranking, then slowly drops away even as the cranking continues and the RPM is constant.


So I then replaced the following:-

Rail Pressure Sensor
Fuel Pressure Regulator Seals replaced (Green and white washers on the spindle)
Complete Fuel Pressure Regulator ( New Bosch unit)
All low pressure fuel lines
Replaced metal high pressure Fuel Line linking the HP Pump and Fuel Rail
Removed and cleaned EGR Valve Removed the in-tank fuel pump and cleaned the filter insert.
Cleaned the ECU Pins on its connectors

I've also done a physical leak off test on each injector using 4 bottles and tubes, and all fill slowly to within one mark of each other, there is no huge gush of fuel to indicate that there is an injector are stuck open.

(Cambelt was replaced and a Brand New set of Glowplugs fitted at the Start of the Year)

Non of the above have got it running, and there are still no fault codes logged, then I noticed this weekend that despite the Starter Motor sounding like it is cranking fast and the Battery being brand new and fully charged, the cranking speed shown on the Software never seems to go much above 220 - 240 RPM. So my first question is, whether this upper cranking speed is OK?, as I'm sure that I read somewhere that the Fiat Diesel's need to crank above 250 RPM before the ECU increases the fueling and activates the injectors?. Does anybody know if there is any Truth in this? or is it just internet pub talk!?.

I also notice that during cranking the Battery Voltage hovers around 10.5v and often dips under 10v, after a couple of starting attempts from being fully charged. The replacement battery was a cheap Calcium style battery to replace the one which was on the Van when I bought it, but it has the same Capacity (60AH) and CCA (540A) and is the same size and type (075) and i'm now wondering if its not up to the Job. I have charged and refitted the old battery and even tried them both together (linked via Jump Leads) but the results are around the same.

I've uploaded and linked to three screenshots showing the various parameters logged by the Diagnostic Software during start up and cranking sessions to see if anybody has any suggestions?

https://ibb.co/2tQYF55

https://ibb.co/qNWhQ8b

https://ibb.co/ZgWTjxv


Thanks in advance
Saturday, December 01, 2018 6:52:24 PM by chris1973
Robski
 Posted Sunday, December 02, 2018 4:19:25 AM
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^^^or is it internet pub talk^^^

Yes i agree, to all which i have just read is exactly that !
If you come to me & i spent all that on a whim i would be all the wankers under the sun.

^^^to see if anyone has any suggestions^^^

Certainly have, take it to a reputable garage or mobile tech because the problem is staring them straight in the face as long as that live data is from a believable source !


Rob.
Sunday, December 02, 2018 9:04:31 AM by Robski
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 Posted Sunday, December 02, 2018 5:03:39 PM
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I am not opening your links but CPS is the first place to start.
PicoScope
 Posted Sunday, December 02, 2018 6:52:13 PM
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Can't see how the Crown Prosecution Service could help him as he done all that himself BigGrin

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