W210 EGR Sticking vs. K40

[BigBen]

I am experiencing a somewhat strange situation with our w210 when starting it from cold.

Before I go with the symptoms, here is a summary of the vehicle conditions:

- 1998, 172 000km or so.
- glow plug tested and good in september, but none changed, not retested yet, but no behavior to lead me to think that there's one bad.
- Fuel lines and o-rings all replaced including the return lines and the whole cut-off solenoid w/ o-rings.
- Fuel filter changed in september.
- Car has done 13 000 km since May, split in half between 2-day 600km trips and around town stop and go...

So, with dropping temperatures (-10 to -15°C), the car has started to show this symptom:

i. Turning key, pre-heat glow, gp light turns off, start car
ii. Engine will fire as normally, will run fine for 2-3 seconds, and occasionnally, there will be a strong hesitation that, in the worst case, will cause the car to stahl (happened 3 times).
iii. If engine stahls, restarting is impossible. Only cure was, in one case, to wait for one hour and re-try with foot on fuel pedal half-way so to cause overfueling at start-up, and in 2 other occasions, to push car into heated garage, luckily very close(!), and let sit 24h. By the way, plugging in the block heater did not help on the last two events.

About the above mentionned engine hesitation, I could also describe it as with an older type diesel engine that had a manual (pull-type) fuel cut-off, and that you pull the cut off half way only, creating a sudden drop in engine RPM. It doesn't run well under this condition...

I have therefore read the forum about this but no clue.

Before I leave this to my indy, I'm trying here with two questions:

1. Could what I am describing be consistent with K40 relay failure?
2. Have these 606 engines been prone to having sticking EGR valves? The reason I'm asking is because if engine is getting an excess amount of recirculated exhaust gases, it could create the symptoms I described...

Any thoughts will be much appreciated,

Thanks

[mbdoc]

K40 is a strong possibility.

When were the fuel lines/o-rings changed?

[Parrot of Doom]

Position of the accelerator pedal shouldn't make a difference when starting, its an electronic throttle.

I'd check the continuity of the connections on the fuel shutoff valve. Its a 4-pin plug that pulls straight off, and it can get wet in there.

EGR can stick but I doubt it would cause the problem you describe. More likely it would just produce a lumpy idle.

[TMAllison]

When in a no start mode, open hood and listen for click of shutoff valve opening when key is turned to pos 2; no click, no start. K40 relay provides power to the SOV.

Check for fuel leaks/air bubbles in fuel lines; you prob have more than one issue at play.

[nhdoc]

Originally Posted by TMAllison

Check for fuel leaks/air bubbles in fuel lines; you prob have more than one issue at play.

Yes, as Terry said, look for signs of air in the lines. If it is more prone to failure when the tank is less than 1/2 full or parked nose-up then it is definitely related to air in the fuel lines and caused by a faulty seal.

[BigBen]

Originally Posted by M.B.DOC

When were the fuel lines/o-rings changed?

I changed the o-rings and shut off valve in early June 2007.

Having said that, I realize not ALL o-rings were changed because I did not replace the fuel delivery valve o-rings.

I have done the delivery valves on the W124, hence the mistake!

[BigBen]

Originally Posted by nhdoc

Yes, as Terry said, look for signs of air in the lines.

Fuel tank is currently 7/8 Full. No air bubles anywhere, nor any fuel leaks.

Originally Posted by nhdoc

If it is more prone to failure when the tank is less than 1/2 full or parked nose-up then it is definitely related to air in the fuel lines and caused by a faulty seal.

Indeed, my problem first occured on a fuel tank quite empty (1/4 full).

I will let the current tank lower again and see what happens.


By the way, where is the K40 located? Is it underneath the main fuse box, near the driver's side fender?

Thanks,

[TMAllison]

Then check the top of the IP closely for wetness and a quick look at the rest and then consider the K40 relay.

The relay is failry cheap (~$80USD) and a 10 min job to replace. Is the front most item in the computer box on the right (pass) side.

[nhdoc]

Originally Posted by BigBen

Fuel tank is currently 7/8 Full. No air bubles anywhere, nor any fuel leaks.



Indeed, my problem first occured on a fuel tank quite empty (1/4 full).

I will let the current tank lower again and see what happens.


Thanks,

You won't see the bubbles nor have the trouble on a full or nearly full tank. If it runs OK with the tank full and starts acting up when it is low, then look for the bubbles and you'll know for sure. Often times techs will fail to replace the o-ring on the prefilter simply because they don't order one and don't realize it is a separate part so they re-use the old one not thinking that it is a critical part of the fuel system...well it is critical and that $0.10 part causes more trouble than you would ever imagine.

Why hasn't M-B just included it with the filter I will never understand, except the conspiracy theorist in me has one idea of why they would want a bunch of cars being worked on by non-MB techs and DIYers breaking down and desperately being towed to the dealers for costly diagnosis.

[BigBen]

Originally Posted by nhdoc

Often times techs will fail to replace the o-ring on the prefilter simply because they don't order one and don't realize it is a separate part so they re-use the old one not thinking that it is a critical part of the fuel system...well it is critical and that $0.10 part causes more trouble than you would ever imagine.

When you say the fuel prefilter, do you refer to the spin-on fuel filter element located in the upper-front part of the engine?

Just want to make sure I'm not missing another filter!

Thanks,

[aklim]

Originally Posted by BigBen

When you say the fuel prefilter, do you refer to the spin-on fuel filter element located in the upper-front part of the engine?

Just want to make sure I'm not missing another filter!

Thanks,

http://www.peachparts.com/shopforum/attachments/diesel-discussion/21471d1097441908-99-e300td-injector-pump-leak-iplines.jpg

Item number 26 and 29. 26 is the prefilter and 29 is the gasket or O-ring. You MUST, MUST, MUST change the O-ring when you change the filter or you will have hell to pay

[TMAllison]

Originally Posted by aklim

http://www.peachparts.com/shopforum/attachment.php?attachmentid=21471&d=1097441908

Item number 26 and 29. 26 is the prefilter and 29 is the gasket or O-ring. You MUST, MUST, MUST change the O-ring when you change the filter or you will have hell to pay

Also don't forget to renew the o-ring on the main filter bolt. See #20 on the diagram. Some applications use one o-ring, others two.

[BigBen]

Originally Posted by aklim

http://www.peachparts.com/shopforum/attachment.php?attachmentid=21471&d=1097441908

Item number 26 and 29. 26 is the prefilter and 29 is the gasket or O-ring. You MUST, MUST, MUST change the O-ring when you change the filter or you will have hell to pay

Wow, this is new to me! I did NOT changed these on my prior maintenance, I did not know about this pre-filter.

I have seen quite a few times on this forum that there were 20 o-rings in total. I will count them all and replace them with Viton in the near future. Will keep you posted!

Thanks

[aklim]

Originally Posted by BigBen

Wow, this is new to me! I did NOT changed these on my prior maintenance, I did not know about this pre-filter.

I have seen quite a few times on this forum that there were 20 o-rings in total. I will count them all and replace them with Viton in the near future. Will keep you posted!

Thanks

Maybe the pre filter is clogged and/or the O-ring is leaking air. I'd change them.

Don't know about 20 but I would change all the hoses at that mileage. That might be small cracks in them too for all you know.

[BigBen]

Well, that was the problem for sure.

I replaced both pre-filter and o-ring and the car did absolutely no stupid things this morning, even in -20°C temperature. Just a normal cold morning start!

So pre-filter was 5,83$ (Can) and the o-ring 1,40$ taken at the dealership. I have no idea if the dealer supplied me with a viton o-ring, but I've used it anyways.

Many thanks to all who helped me on this one!

Bye