HELP! - HELP! Citroen Berlingo 1.6hdi - fuel issues

[robertlaurenson]

Hi All,
I have a Citroen Berlingo 1.6hdi 57 plate, since getting it i have done the timing belt, water pump, crank seal, fuel filter and other minor maintenance.
It has had an issue for the past several months which i cannot seem to get to the bottom of i will explain.
To be clear this doesnt happen all the time and it happens worst when getting low on fuel.

When up to around 3k revs it starts spluttering, cuts out and the fuel pressure sensor alarm comes up. i have changed the fuel filters, took the fuel tank out to check the pump and found there wasnt one on this model and the tank was clean, bled the new filter and still its happening.
The next phase was to check the pump as best i could by monitoring the fuel rail pressure while driving, i purposely let the tank run down to about 1/4 full and tried again. watched the graph and the very minute the car splutterred the fuel rail pressure sensor spiked downwards and it was repeatable until the thing cut out completely each time.
I dont want to keep throwing money at this thing but what i am thinking is to try changing the fuel rail pressure sensor for a new one and see what happens. i think if i have to go down the route of a new HP pump the scrappy will be gettin a van.
Just thought i would see what any of your thoughts were before spending any more on this.
Thanks
Robert

[GraemeT]

Hi - I'd probably do what your suggesting - new pressure switch then bin it if that does not cure it (or drive every where at < 3,000 rpm ?). I'd not fancy faffing about replacing the pump - depends at what level your 'good money after bad' level is set at though.

If you have a 27mm ring spanner then you can get the old one off with ease after pulling all the air filter gubbins off. A 27mm deep socket may do but access to the drive end can be tight depending how deep it is.

About £30 for a new sender? Got to be worth a whirl as it's an easy swap.

[robertlaurenson]

Hi - I'd probably do what your suggesting - new pressure switch then bin it if that does not cure it (or drive every where at < 3,000 rpm ?). I'd not fancy faffing about replacing the pump - depends at what level your 'good money after bad' level is set at though.

If you have a 27mm ring spanner then you can get the old one off with ease after pulling all the air filter gubbins off. A 27mm deep socket may do but access to the drive end can be tight depending how deep it is.

About £30 for a new sender? Got to be worth a whirl as it's an easy swap.

Yes thats what i am thinking, might as well try it, save going around with a van acting like a bucking bronco

[geoff]

Is there a PRV on this model for the fuel HP line ?? Perhaps it blows off too soon / sticks open ??

Just a random thought without looking at the manual ( V&T in my hand lol )

[robertlaurenson]

Is there a PRV on this model for the fuel HP line ??  Perhaps it blows off too soon / sticks open ??

Just a random thought without looking at the manual ( V&T in my hand lol )

I have traced the fuel system end to end when i had the tank out and no sign of any PRV, so i would say no, but cannot be sure. will have a look in the manual i downloaded.

[Sol]

Has the fuel pickup pipe in the tank rotted and broken off maybe? Can the HPP get to the last 1/4 tank or is it inaccessible. Low head of pressure if it is that, i.e the fuel can be gotten at, would point to the HPP otherwise why would the fuel pressure be fine until the tank gets low?

Unless the pump can't physically get any fuel after it hits 1/4 tank, it has to be the pump. The FP sensor would act up all the time, not just when the tank is low so your fuel pressure must actually be dropping to zero.

[robertlaurenson]

Has the fuel pickup pipe in the tank rotted and broken off maybe? Can the HPP get to the last 1/4 tank or is it inaccessible. Low head of pressure if it is that, i.e the fuel can be gotten at, would point to the HPP otherwise why would the fuel pressure be fine until the tank gets low?

Unless the pump can't physically get any fuel after it hits 1/4 tank, it has to be the pump. The FP sensor would act up all the time, not just when the tank is low so your fuel pressure must actually be dropping to zero.

No ive had the tank out and checked everything, the fuel pickup goes into the sender unit into a well and its all plastic. i checked it all while it was out and couldn't find anything wrong.
Its not only when the tank is low, just seems to happen more frequently then than when its full.
I thought it would be the HP pump also but the trend on the fuel pressure seems to say different, its completely steady and then suddenly it drops off for a split second. if the HP pump wasnt right you would expect erratic fuel pressure all the time in my opinion. but i might be wrong. 
I will have a look again and try and see in more detail what is happening over a period, thought i may as well change the sensor as they are under 30 quid so it would rule it out.

[Sol]

Yeah all good points. My thinking was that the HPP was failing to pump properly when the incoming head of pressure in the tank was low. It is weird I'll grant you. 300 bar at idle up to 1800 at full load? (Can be as low as 280 at idle but shouldn't be much less. Of it's down at 260 I'd be suspicious)

Is there a little gauze filter in the sender unit? You know I'd be tempted to pull the sender and check it on the table.

[cancunia]

Is air getting into the fuel line?
When the rail pressure drops, maybe try the primer bulb with the engine running to see if it's full or if a squeeze puts the pressure back.

[Guanock]

Hi

You haven't mentioned the venting of the fuel tank, if air can't get in, then fuel can't get out.

Geoff