glenn_a

hi fellow MB friends.. I am new in here and need to pick your brain to solve this issue i am having,,,

I have a W251 2006 R320 cdi and having an issue for not starting, it cranks then it will start for a 1-2 secs then it will dies but then you can always start again and again but only 1-2 second enigine runs...

I have sent the Hi-pump to get it checked plus replaced the lo-fuel pump (in the tank) i have replaced fuel filter and the Glow Plugs even the module because it was showing that it was faulty but then still the same issue...

i am guessing it has a low pressure of fuel, the reason i said that... I loosen up the high pipe coming from the hi-pump and the fuel there was dribbling, i have checked the fuel pressure between fuel tank to fuel filter and showing 55-60psi and the i checked the between fuel filter to hi-pump and showing 55-60psi also..

i ran out of ideas please help, if you have same issues and sort out the problem... thank you!

kajtek1

Right now even $20 Bluetooth adapter for my android shows me rail pressure.
Get one and come back with data.

kajtek1

CORRECTION
It is $12

glenn_a

what is the normal pressure on the pressure rail?

thanks!

kajtek1

That is something that can be hard to confirm with manufacturer, but if I remember it correctly, at idle my 3l BT makes 5000 psi and goes close to 20000 at higher speeds.
Will recheck tomorrow.

glenn_a

the car been sitting for 4days now and just started today and the car runs a bit longer than usuall, it idles but cannot accelerate hard. only max to accelerate 1600rpm but after that it fluctuate and cannot go any higher but then soon it warmed up after 3mins on idle then it cuts off and back from the beggining ( it starts and run for few seconds then stalls again)

i gathered when its on idle @700 rpm i got 321(bar) = 4655psi

when i was revving it on @1600 rpm i got 653(bar) = 9470psi

kajtek1

I recheck it today and it is how I remember it.
Oscillating around 5000 psi at idle and hitting 18k under the load.
The high pressure jumps up and down in city driving very fast, but what I noticed it is related to load, not to rpm.
Meaning when I push the pedal, it will jump to 18k below 2000 rpm.
So my conclusion is that your pump giving max 9k is not performing.

glenn_a

you meant the hi-pump or the low-pump...?

just to let you know i sent out the hi-pump to get it checked but they said its all good but then we assumed the low-pump could be the issue because i thought the 55-60 psi fuel pressure wasnt enough but then we replaced it but still same pressure out put 55-60 psi so 100% it wasnt the low-pump....

marc hanna

I think you need to get a thorough diagnostic done before spending money on any more high ticket items.

It is not a normal thing for a diesel to stall out in the way you describe. It could be related to exhaust restriction, intake restriction, fuel restriction, faulty electrical, faulty injectors, faulty rail pressure sensors . . .

glenn_a

thank you for yourf reply...

as I mentioned before we checked the fuel pressure and got the hi-pump serviced plus checked airfilter and turbo charger plus checked the exhaust system... No Faulty codes showing on our scanner...

RAIL PRESSURE (Bar) 4
CURRENT INJECTED QUANTITY (mm^ 3/Hub) 23.9
PRESSURE CONTROL VALVE (%) 11.0
QUANTITY CONTROL VALVE (5) 0.0


when ignition ON:

RAIL PRESSURE (Bar) 13
CURRENT INJECTED QUANTITY (mm^ 3/Hub) 23.8
PRESSURE CONTROL VALVE (%) 29.7
QUANTITY CONTROL VALVE (5) 40.6


when cranking position:

RAIL PRESSURE (Bar) 193
CURRENT INJECTED QUANTITY (mm^ 3/Hub) 23.8
PRESSURE CONTROL VALVE (%) 36.2
QUANTITY CONTROL VALVE (5) 57.6


when its on IDLE: 700rpm

RAIL PRESSURE (Bar) 297 - 321
CURRENT INJECTED QUANTITY (mm^ 3/Hub) 15.6 - 16.1
PRESSURE CONTROL VALVE (%) 15.9 - 16.2
QUANTITY CONTROL VALVE (5) 27.4 - 27.8


revving 1607rpm:


RAIL PRESSURE (Bar) 653
CURRENT INJECTED QUANTITY (mm^ 3/Hub) 23.5
PRESSURE CONTROL VALVE (%) 23.4
QUANTITY CONTROL VALVE (5) 33.0