Technical 1.3Mjet not starting

[BenzinaBrera]

Hello all, i seem to have a issue with my doblo multijet, we replaced 2 injectors on it and coded them

problem is now she does not want to fire, seems like the injectors are not allowing fuel through, my natural conclusion is that the rail pressure might be too low due to a leaking injector and then the ecu does not allow the injectors to open

so i fired up MES and also my Launch X431 Pro V and both have me a bit puzzled, they show fuel pressure at 6bar with ignition on and when cranking it builds up to 20 bar and stays there until you stop cranking then it drops back to 6bar

from what i read even 20 bar is too low as most diesels seem to start at something like 180-200 bar but what is confusing me is the fact that the 20bar measured matches the desired parameter so by that logic the car is asking for 20 bar which does not make sense to me.....

so in conclusion i want to ask if anybody knows what their 1.3s desired pressure shows on their diagnostic tools?

 

[varesecrazy]

Hi

Yes you need hundreds..not tens

You are bleeding off pressure somewhere

 

[BenzinaBrera]

Hi

Yes you need hundreds..not tens

You are bleeding off pressure somewhere

Hi, thanks for the quick response, i agree with you but do you know why perhaps it is giving the desired pressure so low also? I would expect to see desired 200bar and my actual pressure at 20 then but for some reson both say 20... could both scanners be missing a zero or something?

 

[varesecrazy]

20 bar is still a significant pressure

Thing what you have changed..or disturbed

Maybe unplug some injectors..
Does pressure climb rapidly ?

 

[Goudrons]

As you've had the injectors off have you got air locked in the rail.
Did you bleed it, and if so, how?

 

[varesecrazy]

As you've had the injectors off have you got air locked in the rail.
Did you bleed it, and if so, how?

I would anticipate the tanks fuel input can still meet the HP pump..

Which SHOULD then raise hundreds of Bar in fuel pressure..

 

[chris3234]

As you've had the injectors off have you got air locked in the rail.
Did you bleed it, and if so, how?

Fairly sure the 1.3 is self priming with having a intank pump

 

[Goudrons]

Fairly sure the 1.3 is self priming with having a intank pump

That depends, I'm not totally familiar with the 1.3 MJ but it's quite common for diesels to send the spill off from the injectors back to the pump or the fuel filter.
Some diesels do this only does when the engine is cold and will send it back to the tank when it's hot.
This helps the cold engine as it's working with hotter fuel when cold.

Some will work on a totally closed loop, so won't vent back to the tank at all, the spill off just goes around the pump/filter and back to the rail.


20 bar (if it is measuring bar and not scrambling up 20,000 kpa) in the rail is less than 10% of what you'd expect when cranking, that's pretty poor if it is measuring fuel pressure. It's not so odd if if isn't actually measuring any fuel at all.

I would crack open the union on the furthest injector from the intake port on the rail and flick the engine over on the starter in very short bursts until fuel spurts out, retighten it and try again.