Another 135 TDCI problem - limp home

[markcbz]

So, a long story short, my MK6 Delphi TDCI has issues lol

In the last year it has had several problems, namely 2 injectors with high leak back, one with electrical corrosion in the body causing short to gnd.

Injectors replaced, fuel filter inspected (changed anyway for a new tdci spec) not particles in it. As a precaution a new IMV (gen delphi) but at 75-80mph I get the van going into limp home.
Light throttle, not big load, (van weighs 3 tons all the time), if I drive it at 70mph or below the van never faults. So much so I can put a 2 ton trailer on it and it still never faults if I stay below 70/75mph indicated on the dash.

Now, within around 3-6 seconds of me hitting 80mph on the dash, glow plug light on, straight to limp home. Van on the hard should, cycle ignition and its away again.
No excessive leak off, no corrosion in the injector plugs, (little water guide made to prevent water sitting on top of the injectors).

On the logs what appears to happen is fuel rail pressure increases to 24,200psi when demand is at 20,600psi, and this is the point it cuts, logs show demand drops to 0psi and fuel rail pressure drops to 275psi and subsequently cuts out. Restarts no problem.
ECU is totally standard (been compared on the maps to make sure no one has messed with it).

So, high rail pressure? anyone had this?
I have not replaced the rail pressure sensor as it actually reads fine, we are seeing high pressure.

[wojciech]

If the difference between the set and actual pressure exceeds 50 bar - 725 PSI (here as much as 250 bar), the ECU turns off the engine, assuming the injection dose is zero.
The pump pressure regulating valve IMV may be suspected. Don't be influenced by the fact that he is changed. If you have an old one, test it and see if there are any pressure surges. This exchange is a moment. If the pressure spikes happen again, look for the cause elsewhere.
Second - the fact that the rail pressure sensor reads high pressure does not mean that it reads correctly ...

[markcbz]

So 50 bar is the trigger for limp home then. This fault was the same with both IMVs hence not suspecting a control issue. The fact that high pressures can be obtained does not indicate a pump issue but agree could be a fuel rail sensor issue.
Interestingly, I can do 80mph fully loaded in this van in 5th and the fault does not happen (circa 3800rpm though), as soon as I do it in 6th at 2800rpm the fault occurs and shuts down.

Odd for sure. Not typically a common TDCI fault.

[wojciech]

Interestingly, I can do 80mph fully loaded in this van in 5th and the fault does not happen (circa 3800rpm though), as soon as I do it in 6th at 2800rpm the fault occurs and shuts down.
Odd for sure. Not typically a common TDCI fault.

In tdci, all faults are ... atypical. You don't know the day or the hour.
At speeds below 3,000 rpm, the injection doses are highest and torque is very high. But the high pressure pump is not at top speed, so it works close to the capacity limit and dose regulation. Thus, it may be that the IMV exceeds the range of possible capacity adjustments and uncontrolled pressure surges occur. I have encountered a case where the engine was in limp mode (errors P0251 and P1211), and the IDS showed a pressure jump. Completely illogical.
If so, the pump needs to be removed and checked - possibly for regeneration.
Regardless of the fact of replacing the injectors, I would do a leak back test.
So your atypical case is ... typical.

[markcbz]

Love the Atypical
Simple thing, no matter what, same codes. Leak back checks are good. For the sake of a rail pressure sensor it can have one. After that it needs a pump I guess.

Thanks for the help.

[Jim Archer]

The pump is just a pump. Your issue is with the pressure regulation on the HP side, pop the IMV out and check it for swarf or marks. Problem is, if the pump is going, it's taking the rest of the HP side with it by filling them with swarf.

Jim

[markcbz]

The pump is just a pump. Your issue is with the pressure regulation on the HP side, pop the IMV out and check it for swarf or marks. Problem is, if the pump is going, it's taking the rest of the HP side with it by filling them with swarf.

Jim

Had the IMV out, no bits, replaced it with a new genuine Delphi one just as a matter of potential issue. Fault remained exactly the same as the previous IMV (now my spare one lol).

Even chopped open the filter and seived it, zero particles so don't think its a pump mechanical failure as in case hardening.

[Jim Archer]

If no swarf, you might be looking at a electrical issue, multi-meter and loom wiggling time I fear.

Jim

[markcbz]

If no swarf, you might be looking at a electrical issue, multi-meter and loom wiggling time I fear.

Jim

Yes I think perhaps this too. Had the usual corrosion in the injectors with the scuttle panel leaking onto the camcover, deflector plate made and fitted now. Can you not buy engine looms for these?

[fumbduck]

If no swarf, you might be looking at a electrical issue, multi-meter and loom wiggling time I fear.

Jim

Yes I think perhaps this too. Had the usual corrosion in the injectors with the scuttle panel leaking onto the camcover, deflector plate made and fitted now. Can you not buy engine looms for these?

Did you ever get to the bottom of this Mark ?
My bro has the exact same problem with his MK6

[knobby1]

Did you ever get to the bottom of this Mark ? My bro has the exact same problem with his MK6

He hasn't been back on the forum since Nov 2022...so we may never know.

Lord Knobrot

[markcbz]

If no swarf, you might be looking at a electrical issue, multi-meter and loom wiggling time I fear.

Jim

Yes I think perhaps this too. Had the usual corrosion in the injectors with the scuttle panel leaking onto the camcover, deflector plate made and fitted now. Can you not buy engine looms for these?

Did you ever get to the bottom of this Mark ?
My bro has the exact same problem with his MK6

Hi yes I did, new pump. Drove like new after.