Hdi fuelling problem, driving me to depression

[1Mozzy]

Where do I start,
2000 406 hdi estate, 90 bhp.
It's an old work commuter but has been fantastic until now , I am a hgv mechanic so no issues getting my hands dirty but this problem has left me at White end

Gave car a service, since then it randomly cuts out and throws up po230, primary fuel circuit malfunction so I narrowed it down to a dodgey Bosch high pressure fuel pump, then it was perfect, 2 days later it started again and discovered in tank pump was shot so fitted a brand new pump. I discovered the in tank pump was a vdo Siemens, the high pressure is Bosch, so I replaced in tank with a genuine Bosch unit, still no difference, I replaced the twin relay, still no difference

I then removed the fuel pressure regulator, cleaned and refitted, then it was perfect for app 20 miles, then the cutting out returned, still none the wiser I took it into my hgv workshop and used our hgv/lgv reader, a £7k bit of kit so not An eBay special which bought up multiple stored codes ( some caused by me whilst unplugging sensors etc) but the only one that will not delete is po380 glow plug relay, it's showing as an active fault.... But what's stumped me is that code will not clear, surely that won't cause it to just cut out, it's defiantly a fuelling issue as when it dies, it's very quick and abrupt, then you have to leave it like 5 mins before restarting.

The fuel rail pressure is good, 400ish bar. What's wrong with it, any ideas, me and my colleagues are all stumped so hoped someone hear might Have encountered it before.....I have a video of live readings from the car if it helps

[Hell Razor5543]

Well, first, welcome to the forum. Second, while I cannot help with your problem, I expect that somebody will be along soon with advise over what you have already done. Just a thought though. When you removed the regulator, did it have a fine mesh at the output end? Sometimes this is an issue. People have replaced the regulator and sorted out the problem.

Another question. What was the state of the in tank pickup sender? I have seen pictures where the pickup is blocked up with sludge from bacteria that live in diesel.

[1Mozzy]

Hi, thanks for the reply, what was odd was the original pumps FPR had the mesh filter missing, the new one had the filter in place, the low pressure pump came out clean but the brash bushings/bearings had worn sending swarf to the high pressure pump

[Peter.N.]

I have had similar problems with my C5 which eventually turned out to be the pressure regulator on the back of the HP pump, or rather a blocked filter on the regulator, is this the one you changed?

Peter

[BX]

Your primary circuit fault was almost certainly due to the in tank pump. The lp in tank pump brand is irrelevant. In all likelihood the vdo one was there since the car was manufactured. All that pump has to do is supply diesel at about 2.5 bar pressure. You probably let some of the dwarf through into the hp pump when changing the filter. Also I assume the replacement hp pump was second hand so you do not know what state the regulator filter was in when you fitted it. The filter cannot be effectively cleaned.
There is a typical fault caused by the regulator clogging. At certain engine speeds the rail pressure becomes uncontrollable. The ECU then stops the engine. It can be restarted as soon as the pressure drops. Some of these regulators, particularly the ones for Mercedes do not have a filter. However they can still clog or dwarf can prevent the needle from seating making starting unreliable. The only purpose for this filter is to protect the valve in the regulator itself. You can remove this filter without risk of damage to any other part of the injection system. If the cutting out ceases you have found the fault.
As regards clearing the fault on the glow plugs there are two possibilities. The most likely is that the circuit self tests immediately after clearing the fault and the fault is still there. The second is that the diagnostic system you are using might have an incompatibility. I think you can safely ignore this fault. I guess you are probably using the texa system.

[1Mozzy]

Yes it is a texa system, fantastic bit of kit,

The replacement Hp pump I fitted was second hand and tested by our diesel specialist prior to fitting..

So with the new pumps pressure regulator it starts normally but cut out often until I removed that little mesh filter, did 120 miles perfectly until this morning when it decided to act up again, but now it's getting hard to start as in it turns over extremely quickly like no fuel is entering the injectors, then it slows down and fires up after about 10'seconds of cranking, it will run on idle all day and I just limped it to my workshop not taking it over 30 and it was fine, as soon as you give it a little throttle it just cuts out.

If I fit the regulator from the old Hp pump it's hard to start but runs fine for 5-6 miles then the cutting out begins.


What I did notice today is occasionally the low pressure pump makes a clunk but does not pump, flick the key a few times and it will then work, so I have fitted the old twin relay back in but avail

If it's not saved today it shall be crushed as I can not put up with unreliability

Ps the lp pump is a brand new genuine Bosch unit and if a permanent live is put to it, it works as it should but it t almost seems as though something it telling it to stop when on the cars power

[1Mozzy]

[1Mozzy]

[1Mozzy]

And a live reading

[1Mozzy]

Ok so after this mornings nightmare I dug out my 5 year old snap on ethos, did a live read and went for a drive , every time it cut out the fuel rail pressure dropped to 76bar so way below the 150bar minimum, I went to a scrap yard ( and upsettingly lost a snap on t30 torx bit and extension bar from my brand new set) Bought a replacement FPR (bought one and borrowed 1 lol) both with different part numbers, neither matching the original, put the cleaner looking of the two, then drove 27 miles faultlessly, touch wood that the problem solved, also cleaned the filter housing which had some brass swarf in the bottom. Thanks for th help, Tom

[BX]

The problem is more than likely all due to contamination due to the low pressure pump failing. You need to be ultra careful changing fuel filters. The easiest to get right is the round filter. The other type is also round but has a seal on top of the filter which takes D shaped detours round the top of the filter. It also has a locating tab on the bottom. I have seen a few of them incorrectly fitted. If not correctly fitted the fuel can bypass the filter. This link shows the one I am referring to
http://www.google.ie/imgres?imgurl=http ... MwhJKCMwIw

Common rail is almost everywhere now including hgv, marine and tractors. You will have to get used to it.