Running ropey, engine management light, and cutting out.

[dexyowl2]

Hi. I've read many posts concerning these problems, but I've never seen a definitive answer.
There are so many 'iffs' and 'maybes' and many spurious cures and remedies.
My (2004, 74k miles) 406 runs fine for 30 or so miles (sometimes a lot more) then it starts 'holding back' when I ask for a response. Sometimes, it mends itself and runs brilliantly for the next 20 minutes, then starts 'holding back' again. More often than not (but not always) the engine management light comes on, the car goes in to limp mode, and gets me home. On 3 occasions, when slowing for a roundabout or junction etc, the car has cut out completely, and refuses to start again. After a few embarrassing minutes, and with help, I get the car going again by pumping the rubber bulb under the bonnet whilst someone turns the key. Air is/was present in the small pipes to and from the fuel filter etc. As the car had been recently serviced by another garage, my mechanic checked to see where the air could be coming from. The fuel filter housing cap was removed and refitted more tightly, and this reduced the amount of air, but a small amount remains. They inspected the in tank sender unit for any problems. Was something floating around and intermittently being sucked in and blocking the fuel feed? The inlet pipe (which was clearly not the original pipe) was sticking out of a hole in the side of the housing. The mechanic removed the pipe from the hole and placed it fully inside the housing. he figured that this pipe must always be immersed in diesel at the bottom of the housing, thereby not being exposed to the air as the diesel swilled from side to side. I've not really tested the car to check if this move has improved things or not? Anyhow, the mechanic seemed to think that the now empty hole, which the pipe WAS going through, maybe should be fitted with a non-return valve. Does anyone know if this should be just a hole in the housing, or should there be something in it?
There's plenty of talk about fuel pumps (unlikely cause) fuel regulators and other such remedies. We think there are two unrelated causes, one for ropey running, and one for the cutting out, but what they are is a mystery.
There is one remedy for each of my problems. Please, which components are needed?? I/we can speculate for weeks on this subject, but someone out there knows exactly what the problems are, and how to fix them? Many thanks for reading my diatribe. I'm pretty peed off with this long, long ongoing problem, and I need a fix before I drive the thing over a cliff.

[rwb]

Hi & welcome.

Since you have a priming bulb this must be a HDi 90 with the Siemens injection system.

Here's the diagram for the in-tank not-a-pump.

No sign of any pipes inside the tank.

And the fuel lines:


(Never knew there was a fuel cooler!)


For comparison: I have the same engine and also have bubbles in the clear tubes and I think this is normal. The bulb on mine will not go hard (whereas on my previous 1.9 it would go solid).

Need the fault codes reading really: find a member near you with PP2000 -- there are quite a lot of us now, and if it's helpful then I'm travelling from Basingstoke to Huddersfield on Friday.

[dexyowl2]

Hi rwb and thanks for the reply. There were originally 3 codes came up. I don't remember the numbers as the mechanic (not my own) was not very forthcoming, but he did tell me one was the Coolant Temp Sensor (done, no difference) 2/ Fuel quantity regulator and 3/ Fuel Pressure Regulator. The CTS 'fault' has now gone from the code reader.
The pipe I was on about? I don't mean the pipe went in to the fuel tank, (well, not by much) I meant that it fed the inlet fuel connection on the in tank notafuelpump, but the other end poked through a hole in the side of the notapump housing and into the main fuel tank. The bit sticking through the hole was about as long as my thumb. Should this inlet pipe be poking out through this hole and in to the main fuel tank, or should it be contained wholly inside the notapump yellow housing? My mechanic thinks it should be contained, as allowing it to feed straight from the main fuel tank leaves it exposed to the air in the tank as the diesel swills around, which consequently sucks air in to the engine causing the cut outs? If the pipe should be contained inside the yellow housing, should the remaining small hole just be a hole, or should there be some sort of non return device in it? I reckon if diesel is fed in through this hole, then diesel can spill out through the same hole as I turn a corner etc, thereby inviting the 'pump' to suck air in through that opportunity? How close to the bottom of the housing should the pipe be? ..... 2mm? 10mm or what? we can only guess at this stage. I'm so frustrated with it all.
My mechanic is convinced that the ropey running is probably a simpler mend than the code reader is suggesting, so is trying all the cheaper options first. If you were to tell me that it was DEFINITELY the Fuel Pressure Regulator, then I would change it without a thought, but I don't want to spend money on money with a trial and error approach. Is changing the FPR a straight forward swap job, or are special tools, bleeding, calibrating etc. needed as well? Is the FQR' a straight swap job as well? Should the ''poke through' pipe have some sort of filter on the end of it? I did say it was clearly not the original 'proper' pipe, so my mechanic is very suspicious of the maybe bodged repair some one did previously? There are severed electical wires on the notapump set up, so my mechanic is convinced that someone has converted a 'normal' in tank pump, and not done a great job on it. Thanks for taking the time

[dexyowl2]

Update. The car has not cut out since the fuel pipe was contained wholly inside the yellow housing.
The engine management light has not been on since either.
A change of fuel filter and air filter has greatly improved the running. I feel I can trust the car again.

There is a 'holding back' problem (it's like driving in to a 200mph headwind) below 2000 revs, but when that figure is
passed, the car picks up nicely and runs like a Rolls Royce.

Anyone know why it's struggling at below 2000 revs? ........................ Thanks in advance.