[aero165]

Hello I was driving my i39 diesel tonight and after turning at the end of a dead end the car engine shut down without warning.
I managed to restart it after cranking it for 5 seconds or so and drove no more than 100 metres before it shut down again after turning into a side street no more than 100 metres down the road. I cranked it again but it didn't want to start so I got out an pumped the filter primer for 10 or more times and tried to start it again. After a few seconds of cranking it fired and I managed to drive home, probably 5 kilometres. No engine warning light has appeared and I am wondering if there are any opinions on why this would happen. About 10,000 k's ago a new RYCO fuel filter was fitted......could  this be the start of a clogged fuel filter?

[Dazzler]

Welcome aero,

How long since you got fuel? Could be a bad batch or maybe you have diesel bug (Google that). Basically an algae I think that can grow in diesel and block the fuel
 system.

[aero165]

Hi Dazzler the fuel has been in the tank for over 400 kilometres.  pumped some out this morning and it looks clear

[aero165]

Well its gets deeper in confusion. This morning I fitted a brand new RYCO Z707 fuel filter. Before fitting I could rev past 3000. After fitting filter and driving it I had the ability to rev cleanly past 3000...drove for 20 minutes all good stopped car for an hour or so started and all good drove well could rev past 3000. Stopped car let sit for 2 1/2 hours get back in car needed a little more cranking to start that normal and now cant rev past 3000...damn.   No engine warning lights brand new fuel filter and from looking at fuel that came out of the replaced filter , clean fuel. The filter replaced was  a RYCO Z707 .  any ideas again?

[eye30]

Have you checked fuel pump is ok.

[aero165]

Have you checked fuel pump is ok.

Im not sure how to do that can you shed any light on that....?

[aero165]

Damn car its now been sitting again for a couple of hours and now its reving past 3000?????

[The Gonz]

Have you considered calling it Christine?

Funny you mention 3000 rpm. The way I drive, I've never been over 2500.

[aero165]

lol  I guess it could be possessed.   Just weird that is doing what it is doing I guess I will see how long before it goes back into limp home

[Dazzler]

Not revving past 3000 rpm is part of what is called limp home mode. Which has previously related to various fuel and fuel filter issues in the diesel including a very hard to detect crack in the fuel filter housing.

If you search "limp home mode" in diesel problems this topic would probably be the first one to come up.

Maybe worth a read (209 replies!)

Limp Home Mode

[aero165]

Yeah thanks I have looked into it but I am just a bit confused as to why its going from good to bad then back to good....damn car should pick a side and stick with it.

[Dazzler]

Yeah thanks I have looked into it but I am just a bit confused as to why its going from good to bad then back to good....damn car should pick a side and stick with it.

Yep, I hate intermittent faults. Could something need tightening. I think the problem can occur if any air is getting in. But, I'm no mechanic.

[The Gonz]

I admit I haven't had cause to look at the LHM thread but I doubt it's a feature that locks in until cleared in software, so something gradual like a small air leak isn't unreasonable for creating this seemingly intermittent condition.

* Still wondering how many years I might have spent in LHM. 

[aero165]

Will make sure all is tight and see if its going to suck air overnight

[sundiz]

I had similar issue. I put 3rd party fuel filter, engine went to limp home mode (revs max 3000rpm). No MIL light. But when engine was running and limp home Mode active I was able to read OBD codes which told low fuel pressure. Shutting the engine made the code disappear. Went and got OEM fuel filter. It fixed the issue.

[aero165]

I had similar issue. I put 3rd party fuel filter, engine went to limp home mode (revs max 3000rpm). No MIL light. But when engine was running and limp home Mode active I was able to read OBD codes which told low fuel pressure. Shutting the engine made the code disappear. Went and got OEM fuel filter. It fixed the issue.

Yeah I am aware of the filter issue but I have run Ryco filters for ages without issues.

[sundiz]

Try to read the codes when limp home mode is on. I assume it is caused by low fuel pressure...

One known issue with Korean diesels is cracked fuel heater. There are some cases where the heating element has cracked and lets air in the fuel pipes, which causes fuel pressure to drop. Heater is located In the filter assembly. But I would not change that before better information. Fuel filter housing costs something around 100-300€ depending where you get it.