N47 Fuel Starvation Issue

[mbwoy84]

I picked up a 2009 120d Convertible (E88), which had been sat for a few months after being recovered after suffering High Pressure Fuel Pump Failure (RAC Diagnosis). The owner had bought a brand new fuel pump, and someone had started taking things off the car with a view to fitting it, before coming to the conclusion that it was beyond their capabilities.

So, I fit the pump and give the car a thorough service as it had been sitting for a while. The car fires into life after much cranking (expected with the fuel system having been apart so I thought). Drove the car a short distance on private roads around my workshop over the course of the next week. Still slow to start, but seemed to improve slightly each time, so thought with use it would sort itself out, and booked it in for MOT, which it passed. Drove it the 2 miles to the MOT station, not a problem, but then broke down on the way back.

With no towing eye in the car, I managed to limp it back in 3 stages with the help of easy start (hate having to use that, but it worked and got me back). Thought the next logical step was to change the fuel pressure sensor on the end of the fuel rail. Did this, and still the same. Further diagnostics showed no fuel pressure, but with some cranking and messing managed to get it to run, then a sudden drop in pressure after a very short drive and the car cuts out and won't start again without further messing.

The fault codes are plentiful (please see below) and return no sooner than clearing them.



Where should I be looking now? This is after a new HPFP, Fuel Filter & Fuel Pressure Sensor (the one of the end of the fuel rail)

[mbwoy84]

Not sure whether they could be in any way related, but based on that list of codes, I've just ordered a new set of glow plugs, glow plug module and EGR Valve. Dodgy glow plugs won't help with any starting issue, so they'll need changing anyway.

I've also just ordered a new Fuel Pressure Regulator Valve, as I think that's the only other thing on the fuel rail side of things that can be changed, and may cause such an issue.

[RUSSELLM]

I presume there’s a low pressure fuel pump located at the tank ?

[Touring442]

When the HPFP fails, all the steel swarf gets into the injectors and ruins them so you'll need four of those. Swarf is also pumped back into the tank and then comes around again for another go. When the pump fails, you need to replace that, the injectors, pressure regulators, the rail and in tank supply pump as well. Completely empty and wash out the tank and use compressed air and clean fuel to wash the fuel lines out with. Putting a couple of decent sized magnets in the tank (one each side) for a few hours collects a lot of the swarf. With the tank empty (you can do it with the tank still fitted), get a hose in there and really wash the tank out before draining it and drying it out.

Your car is dying because the injectors are shagged, basically. They are leaking off and unable to retain any pressure.

[Elliot2000]

I agree with touring442 - the old pump died and the swarf from the damaged internal cam has gone for a wonder around the fuel system.

The only thing I would add is I’m not sure the swarf will exit the fuel tank that manages to get back in there- the in tank pump has a gauze in it to stop most of the fragments leaving, and then the fuel filter should then collect the rest.

The biggest thing causing the loss and fluctuating fuel pressure after the pumps has been changed will be the control valve on the common rail and the injectors. A used set of injectors and fuel rail with the valve and pressure sensor attached is pretty inexpensive from a breakers on eBay. Just make sure you clean the high pressure pipes that you reuse and it might be worth taking off the control valve on the back of the high pressure pump to make sure there is no buildup of swarf as it’s been running

[mbwoy84]

Yes, I found this problem almost straightaway after my last post, and just came back on here and saw the posts stating the very same thing.

I should have checked everything over first really as I had exactly the same problem with a MK3 Mondeo TDCi some years ago, but I was hoping that the AA/RAC had misdiagnosed it as the fuel pump and it was just a sensor or something, but when removing the pressure regulator valve from the end of the fuel rail, that was full of swarf/tiny filings, so checked the tank and that was full too.

I've drained and cleaned the tank and all fuel lines front to back. Fitted a brand new in-tank pump, fitted another new fuel filter, sourced a used fuel rail fro a low mileage car with the sensor and valve still fitted, so I could check for any issues upon removal of those, but still cleaned it out as best I could even when it appeared clear. I wanted to reuse/clean as much as was possible to be certain of cleaning thoroughly, as I didn't want to fit used, untested injectors. Managed to buy 3 injectors from a guy who reconditions and tests them for just under half the price of new ones. Unfortunately, he wasn't expecting any more in for a few weeks, so I bought one new. The one thing that would really pain me would be to have to change the new pump again, so I ripped the old pump apart and cut it open to see exactly what had happened and where the swarf had got to, and am 95% confident that with removing the valve and stripping and cleaning it thoroughly, that it should be fine, fingers crossed!