C250D (OM605) Wont Start - Not Air in the Fuel Lines

[tsharkey]

The perennial problem of the non starting OM605 returns again.

This time it is NOT air leaking into the fuel lines. The system is sealed. O Rings replaced. No air in the plastic pipes. An electric pump pushing fuel into the system to make sure. Fuel vapours coming out the exhaust when cranking (so fuel is getting through the system) !!!

4 out of 5 glow plus are reading between 50 to 180 ohms. The fifth is shot and is hard up against the firewall, so my drill and tap the seized glow plug out wont fit there. Always started OK on 4 out of 5. Relay sends 12.5v out across all 5 and you can year it clunk after 10 secs.

Lots of cranking - sometimes starts after 10 to 15 seconds. Sometimes takes a long, long time (with vapour coming out up rear). Once started, runs fine (not rough). No EPC or other error lights on dash. Once started for the day, will start within 5 secs there after. Next day, back to square 1.

Didn't progressively get worse. Used to start within 3 secs, then all of a sudden, became a reluctant starter as described above.

I know there are only a few tortured OM605 owners out there on this board but any suggestions would be helpful before I send off to have a diesel mechanic run through their check list for correct startup conditions.

Maybe an intermittent fault with crank angle sensor miscuing the IP at startup ? (But the why does it run A-OK once up and running and can be restarted easily for the rest of the day)

Maybe not enough glow in the 4 working glow plugs (but why is it sometime much quicker to start than other times ?)

After a lot of searching, I found 1 post on the net with similar symptoms from 2009 - as is often the case, the problem is posed, suggestions offered (in this case, all suggesting to check for air in the system) but no solution is provided.

Thanks in advance

[Tony From West Oz]

Here is a list of possible causes:
.Without all GP working, you are going to have hard starts.
.Air is a perennial issue due to the O rings in the fuel system.
.Shut down valve has been known to fail.
.Fuel quality issues?
.Injector(s) may not be spraying properly. Even one injector spraying will give smell of fuel at exhaust if cranked long enough.
.
.
.
.

With one GP out of action, even one injector with poor atomisation will make a big difference.

You did not state in your post whether the engine fires at all when cranking. If no firing, check SOV and then IP.
If firing on one or more cyl, then check all injectors for atomisation. Replace GP#5.

Others may have more suggestions.
I hope you get to the bottom of this problem and get the vehicle back onto the road soon.

[tsharkey]

Thanks Tony,

There is absolutely no firing going on whilst cranking (not struggling to start at all) and once it "fires", it runs immediately and is fairly smooth. It's like a switch going off. Endless cranking then runs.

There is a lot of smoke coming out back. So fuel is getting through into the chambers, so I suspect SOV failure and air in Lines is probably not on the list.

Will do a rebuild of injectors and balance them.
Will try to replace the failed GP.

Just to add insult to injury, when it started yesterday, the BAS + ABS lights remained on. So yet another thing to look into.

[gazman]

#1 fuel shut off valve

[SantoC]

when it started yesterday, the BAS + ABS lights remained on. So yet another thing to look into.

Most likely requires a new brake light switch.

[Tony From West Oz]

Thanks Tony,

There is absolutely no firing going on whilst cranking (not struggling to start at all) and once it "fires", it runs immediately and is fairly smooth. It's like a switch going off. Endless cranking then runs.

There is a lot of smoke coming out back. So fuel is getting through into the chambers, so I suspect SOV failure and air in Lines is probably not on the list.

Will do a rebuild of injectors and balance them.
Will try to replace the failed GP.

Just to add insult to injury, when it started yesterday, the BAS + ABS lights remained on. So yet another thing to look into.

What colour smoke is coming out the exhaust pipe - Black or White? Black is partly burnt fuel (Engine is running, white is unburnt fuel (also present when air is in fuel lines).

[tsharkey]

Thanks Tony,

White smoke and the tank is full of dino diesel. Smells very strongly of diesel too. When I get an adaptor madeup for my leakdown tester, I'll rebuild the injectors as it nails loudly at idle so I suspect it is poor spray.


Usually the bad brake switch only triggers the BAS (and i have replaced to remedy that fault), this is both the ABS + BAS and the lights remaining on is intermittent. I'll give the system a pressure bleed and see if that remedies.

[svengali0]

I would be inclined to use an elimination approach.
If ether in the intake brings the engine to fire up, then this narrows the culprit cause a bit.
Other items are the wiring harness but I'm guessing you have handle on that issue given previous posts and comments.

Fuel shutoff assembly as another commented- this seems more likely than not.
There is tutorial on how to repair this item. One of the English forums I believe.

If you have installed an additional pusher or pulling type electric pump at some point in the supply circuit, then the original lift pump may need examination- perhaps it is blocking at some point. Non return valves on the IP outlets can also bring hard starting issues. I think Dieselmeken has posted a tutorial on this somewhere. But If I recall, you had to have the IP overhauled at some point a few years ago?

Another- (more unlikely perhaps) issue may be pre-chamber loosening. I have now established why that OM605.960 engine on my workstand destructed - two of the pre-chambers let their heads go. This was after 515k km of regular use and servicing. I understand that this issue can come about from glow plugs deteriorating and destructing themselves into the pre-chamber.

I have a glow plug fitting machined up onto which a test line (air) can be attached to perform leakdown testing. I doubt that this is the issue though. I can loan the item if you promise to return it.

Do keep us updated!!
Cheers mate.

[Harvey]

Re air in fuel lines on om605 can anyone assist in what sizes the orings are? And where to obtain them?
Thanks in anticipation of the advice.
Harvey

[tsharkey]

Hi Harvey - Give the sponsor a call, quote the VIN and he can get the O Rings in. There are a few sizes if you want to do the lot, from those on the push on hoses, the one behind the shut off valve, the one in the prefilter. Some of the UK forums may be able to supply actual sizes but I have found that the substitutes end up needing to be replaced by an OEM one eventually.

[Tony From West Oz]

Did you eventually find out the cause of the poor cold starting?

[tsharkey]

Did you eventually find out the cause of the poor cold starting?

Thanks for the prompt Tony - Too many threads out there end with no conclusion - Frustrating when it is the very problem you are dealing with !

It was the injectors. Caked and Coked. I bought a set of Monark Nozzle from Julian many months ago and the pop tester I bought many years ago for the W123 injectors works on these as well.

The hardest part of the job is the gunk that accumulates in those injector valleys on top of the engine because the return lines popped off over the years. Whilst at the time I cleaned the valleys out as best I could, the remaining BioD in there gelled up. I had to pull the rocker cover off and buy a few gaskets from John G. I also had to put a helicoil in the head for one of the inlet manifold bolts (It has been off quite a few times).

The real lesson for me is while my BioD production for the OM617 was satisfactory, on the OM605, higher quality control is required. That means washing the BioD to get more impurities out.

[Tony From West Oz]

Thanks, I read the post and thought that something was missing, hence the Question.