synergie in tank pump

[mikeb49]

Hi i posted a problem 5/2/12 about our synergie hdi cutting out,will ocationally start for a few seconds to a few minuits, management light on, aa said fault code was low pressure at rail, has had new main filter, i have just removed pressure regulator and washed in white spirits looks ok can,t see a filter on or in it?, in tank pump is noisey and once did not run when ignition was on, i think it may be either breaking down when running or not producing enough pressure to feed hp pump?, is this possable?.
The garage disconected the fuel pipe after filter and because fuel pumped through when ignition was on they said the pump was ok?, they did'nt check pressure or continual running,the diesel ran out but did,nt realy squirt, should it?.
when the engine does'nt start i can still hear the tank pump running while the engine is turning over its that noisey.
My question is how can i tell if the in tank pump is ok other than replacing it?.
Does the in tank pump need to produce a certain pressure for the engine to fire?.
would an extra in line pump work or would'nt be able to pull fuel through the existing pump?.
could i rig up an external fuel reservior fed by gravity to prove everything after the in tank pump works ok?,if so were would i connect it to?.
i dont know were the electrical feed for the pump comes from but as i can hear it i assume its getting power.
any suggestions would be appreciated.
regards mike.

[Lighty]

The in tank pump only needs to supply up to the High pressure pump, seriously doubt that is causing your problem if its getting fuel up to the filter head.

[Old-Guy]

For once, your problem is probably exactly what the fault code says, "low pressure at (common) rail". Your problem is not the Low Pressure (in-tank) pump, but the the High Pressure pump not providing enough pressure at the rail for the injectors to be able to work.

[wheeler]

For once, your problem is probably exactly what the fault code says, "low pressure at (common) rail". Your problem is not the Low Pressure (in-tank) pump, but the the High Pressure pump not providing enough pressure at the rail for the injectors to be able to work.

You still need the LP pump to operate to get to the HP pump in the first place, This fault could still be caused by an LP pump, you can get the same fault code logged on cars that have simply ran out of fuel.

[Lighty]

For once, your problem is probably exactly what the fault code says, "low pressure at (common) rail". Your problem is not the Low Pressure (in-tank) pump, but the the High Pressure pump not providing enough pressure at the rail for the injectors to be able to work.

You still need the LP pump to operate to get to the HP pump in the first place, This fault could still be caused by an LP pump, you can get the same fault code logged on cars that have simply ran out of fuel.

Yes but he said fuel was coming out of the pipes under the bonnet, so the LP must be working even if its noisey.

[wheeler]

The LP pump is working but is it providing enough pressure ?? Probably is
What im getting at is just because there is a fault code logged with low pressre at the common rail doesent neccisarIly mean theres a fault on the high pressure side.