D5 (D5244T to 2005) Not starting

[doliver]

I have borrowed a code reder that can provide live values when connected to the car.

While cranking the engine I can see that the rail pressure quickly increases and stops at an exact value of 180Bar

The normal working pressure of the rail is 300 to 160Bar
I guess the pressure depends on the engine revs - the higher the revs, the higher the pressure is required to deliver the correct amount of fuel.

So, while cranking the engine I would expect to see a pressure around or a little higher than 300Bar as idling requires little fuel.

As the sensor reading is an exact figure of 180Bar just by cranking the engine via the starter motor, does this mean the sensor is faulty. I don't believe an true sensor value would be an exact figure.

Or, maybe the actual pressure in the rail has increased beyond the range of the sensor and thus it tops out at 180Bar.

The other question is; can the high pressure fuel pump actualy achieve 180Bar just by cranking the engine via the starter motor, or does it require higher revs when the engine is actualy working

any sugestions?

[doliver]

I forgot to mention in the reply above (#11)

the fault codes were cleared and the start of the test.
the re-appeared during the test after a few minutes.

[griston64]

I had similar problems with low fuel pressure and it turned out to be an injector fault.

It was the AA who first read the code but I cant remember what my pressure was at crank.

I seem to remember him plugging it into the AA Transit to find out what the pressure of that was and it came out at 270bar which was way above mine.

[5cilinder]

Originally Posted by doliver

I have borrowed a code reder that can provide live values when connected to the car.

While cranking the engine I can see that the rail pressure quickly increases and stops at an exact value of 180Bar

The normal working pressure of the rail is 300 to 160Bar
I guess the pressure depends on the engine revs - the higher the revs, the higher the pressure is required to deliver the correct amount of fuel.

So, while cranking the engine I would expect to see a pressure around or a little higher than 300Bar as idling requires little fuel.

As the sensor reading is an exact figure of 180Bar just by cranking the engine via the starter motor, does this mean the sensor is faulty. I don't believe an true sensor value would be an exact figure.

Or, maybe the actual pressure in the rail has increased beyond the range of the sensor and thus it tops out at 180Bar.

The other question is; can the high pressure fuel pump actualy achieve 180Bar just by cranking the engine via the starter motor, or does it require higher revs when the engine is actualy working

any sugestions?

Yes the pump (should)achieve 300 bar while cranking the amount of fuel needed idling is so small that the pressure is easily reached

I have a few clues now
If the sensor was faulty and transmitted a to high pressure value then the pump would counter react at the faulty ecm signal to inlfuence to the right value
Wich means lower the pressure but if the signal was false the TRUE railpressure would be to low
So i can make a safe guess that the pressure readout is the true value wich is 180 bar wich is to low hence the not running engine

So in this assumption excludes the sensor, the pressure regulator also seems to be ok according voltage and ohms
Faulty injectors could be a problem to leak pressure but since the engine cant be runned its hard to check the return flows (the cheap way)
You could try to measure the returnflow while cranking and if its excessive high thats suspect (Above 2ml/3 seconds pro injector)

Given the sudden presure limit of 180 bar a high suspect is the fuelrail safetyvalve
If you take it of and the spring is broken than its pretty sure the cause but maybe the defect isnt visible
Now i dont know what a pressure safety fuelrailvalve costs(second hand) and if secondhand obtainable refundable if placed and still dont solve the problem
If you can bring back a second hand one if it didnt solve the problem is the first thing to try/replace





The next thing to do is take out the injectors and test them at a bosch centre
(How did your engine run before the starting problem? injectors wear gradually)

If they are ok Next suspects are a broken piston(seal) in the high pressurepump

Im afraid its time to check/revise the high pressurepump internally wich if you take em of yourself not so expensive as the older electronic pumps
Commonrail pumps have no electronics beside the (replaceable fuel sensors) and few moving parts

Btw youre sure the intankpump works?
Just to be sure the smoke while starting is black or white?

[doliver]

Originally Posted by 5cilinder

Yes the pump (should)achieve 300 bar while cranking the amount of fuel needed idling is so small that the pressure is easily reached

I have a few clues now
If the sensor was faulty and transmitted a to high pressure value then the pump would counter react at the faulty ecm signal to inlfuence to the right value
Wich means lower the pressure but if the signal was false the TRUE railpressure would be to low
So i can make a safe guess that the pressure readout is the true value wich is 180 bar wich is to low hence the not running engine

So in this assumption excludes the sensor, the pressure regulator also seems to be ok according voltage and ohms
Faulty injectors could be a problem to leak pressure but since the engine cant be runned its hard to check the return flows (the cheap way)
You could try to measure the returnflow while cranking and if its excessive high thats suspect (Above 2ml/3 seconds pro injector)

Given the sudden presure limit of 180 bar a high suspect is the fuelrail safetyvalve
If you take it of and the spring is broken than its pretty sure the cause but maybe the defect isnt visible
Now i dont know what a pressure safety fuelrailvalve costs(second hand) and if secondhand obtainable refundable if placed and still dont solve the problem
If you can bring back a second hand one if it didnt solve the problem is the first thing to try/replace





The next thing to do is take out the injectors and test them at a bosch centre
(How did your engine run before the starting problem? injectors wear gradually)

If they are ok Next suspects are a broken piston(seal) in the high pressurepump

Im afraid its time to check/revise the high pressurepump internally wich if you take em of yourself not so expensive as the older electronic pumps
Commonrail pumps have no electronics beside the (replaceable fuel sensors) and few moving parts

Btw youre sure the intankpump works?
Just to be sure the smoke while starting is black or white?

Hi 5cylinder,

I made a mistake in quoting the pressure values in my last quote.
I have copied it below in blue text with the correct pressure values so that you can re-evaluate.

The smoke from the exhaust while cranking is white.
Tank pump unit is OK pumping at 2Bar and filter is new.

While the test below was being carried out, all fault codes where cleared.
After a few minutes during the test, the same 2 fault codes (as the start of this thread) appreared again.

Originally Posted by doliver
I have borrowed a code reder that can provide live values when connected to the car.

While cranking the engine I can see that the rail pressure quickly increases and stops at an exact value of 1800Bar

The normal working pressure of the rail is 300 to 1600Bar
I guess the pressure depends on the engine revs - the higher the revs, the higher the pressure is required to deliver the correct amount of fuel.

So, while cranking the engine I would expect to see a pressure around or a little higher than 300Bar as idling requires little fuel.

As the sensor reading is an exact figure of 1800Bar just by cranking the engine via the starter motor, does this mean the sensor is faulty. I don't believe an true sensor value would be an exact figure.

Or, maybe the actual pressure in the rail has increased beyond the range of the sensor and thus it tops out at 1800Bar.

The other question is; can the high pressure fuel pump actualy achieve 1800Bar just by cranking the engine via the starter motor, or does it require higher revs when the engine is actualy working

any sugestions?

[doliver]

By the way, the engine was running perfectly before this happend.

I happend immediately after re-fluing.
The car was running fine - fuel level was low, about 20 mile left in the tank.
I filled up to hlaf a tank and then it would not start and I was stuck at the fuel station until rescued by the AA

AA man thought is was low fule pressure but this could not be confirmed as his dianostic tools were faulty.

When I got it home, went through the fuel system item by item and the rest of the story you already know from the start of this thread.

[5cilinder]

Those kind of misquotes turns everything upside down ;-)

I doubt the pump can reach 1800 bar while cranking
Especially while you see fuel escaping trough the exhaust as white mist
Also wih too high real pressure the engine would probably be (rough) running
So this suspects to a faulty pressure sensor
But the AA man suspects according the symptomes low fuellpressure (wich there is in reality) but is misled that there is no "low fuelpressure" faultcode caused by the faulty sensor

If the sensor was faulty and transmitted a to high pressure value then the pump would counter react at the faulty ecm signal to inlfuence to the right value
Wich means lower the pressure but if the signal was false the TRUE railpressure would be to low

Because with those pressure readings the ECM tells the pressure regulator to lower the pressure as low as possible wich will be below 300 bar as TRUE pressure and isnt enough to get the engine running

Also there is a chanche (but lower) that the regulator is not functioning and that the exact 1800 bar is cut off by the safetyvalve

Whats the pressure readout before cranking ? 0 bar?

http://www.youtube.com/watch?v=85IP8eY1nXY

http://www.youtube.com/watch?v=niYW9pkPCH4

[doliver]

thanks for the video links they are very good

the rail pressure reading immediately after cranking goes from 1800Bar down to 4.3Bar after approximately 2 minutes

I will first test the pressure sensor / connection / voltage / ground to see if all is OK
then the regulator

thanks

[5cilinder]

The "slow" pressure drop to 4.3 bars (if the sensor functions ok) after cranking at least means you have no excessive internal leaking wich is good

[doliver]

the pressure has now dropped to 2.1Bar after 30min