e300td fuel economy - PeachParts Mercedes-Benz Forum

mojo7676 · #1 03-22-2007, 04:19 PM

hi

Just thought i'd post some info re poor fuel economy and my attempts to improve it. i am new to this forum but have been pointed to a few v useful posts/articles on this site.

my car is a 1998 e300td elegance, estate. the car was bought a few weeks ago, has some service history with mercedes and seems in fairly decent condition. i'll cut to the chase...

v poor fuel economy- between 20-25 mpg (uk), very steady driving. changed oil, air filter, oil filter and fuel filter and hoped for improvements. shoved in a load of redex (diesel treatment stuff that's supposed to clean injectors etc) and still no real difference. anyway, i was asked to check under the nylon fuel pipes in case of leaks - sure enough, there was slight wetness under one of nylon fuel pipes. After several/many communications from a guy called parrot of doom on the forums.mercedesclub.org.uk site, i changed the nylon fuel pipes on top of fuel pump (about 6 in all, i think). no improvement and, to my surprise, there was still a leak/drip. After advice, i then changed the small o ring that seals the shut off valve into body of fuel pump. still no improvement and still a drip which is pretty much where i am at present. am considering doing the o ring thing again in case it's been botched/misaligned or whatever and will also check out the maf in case it's dirty - but had the engine management thing read and no codes are present. not sure if there's anything else to add - the car drives very well, has plenty of go and responds well enough. there don't appear to be any leaks along the fuel lines under the car and i don't have any damp patches under the car when i check in the morning. no clouds of black smoke coming out the back end, either. any ideas, please let me have them...

tia

mojo

Matt L · #2 03-22-2007, 04:29 PM

The diesel could be sitting on the panel under the car until you move, preventing a spill on the driveway.

Take the panel off, clean everything up, run the engine and watch for leaks.

TMAllison · #3 03-22-2007, 04:35 PM

My commute mileage is usually around 31 mpg.

Spray the fuel filter housing and IP clean with spray cleaner of your choice then see where the leak is comming from. Brake cleaner in moderation works well.

From what you describe it sounds like the Delivery Valves are the only thing that hasnt been replaced.

scott19_68 · #4 03-22-2007, 05:10 PM

I second the delivery valve seals. My mileage dropped to less than 25mpg and had a bad case of the drips when mine were bad.

mojo7676 · #5 03-22-2007, 06:04 PM

will check the tray/cover over the weekend and clean around the area. re delivery valve seals - are those the metal/copper pipes coming out of the top of the fuel pump? do they need to be timed/torqued or anything or is it a fairly straightfoward job to replace the seals - which, i presume, are available from mbenz.
mojo

Alastair · #6 03-22-2007, 06:21 PM

Quote:

Originally Posted by mojo7676

will check the tray/cover over the weekend and clean around the area. re delivery valve seals - are those the metal/copper pipes coming out of the top of the fuel pump? do they need to be timed/torqued or anything or is it a fairly straightfoward job to replace the seals - which, i presume, are available from mbenz.
mojo

The 'delivery-valves', are the portion the high-pressure fuel lines attach to at the IP (Injection-pump)

It is Highly Unlikely the seals are available from M.B.UK, Best get a service-kit from Merlin-Diesel but you'll need to quote your IP number, (On the side near the back of the pump, something like PES 6xx.xxx

You would need to remove the steel High-Pressure lines, (DO NOT BEND THESE--Unscrew at the injector end and all clamps holding them to the engine and remove completely--When done, re-fit all clamps exactly as they were to prevent fuel-line fracture!)

Then with the splined tool for removing the delivery-valves, unscrew the delivery valve holders. These have 'O' ring seals on their outside which seal them to the case. You should also replace the copper washer under the holder for a new one when these are disturbed too. Inside the holders, you'll find a spring and a tiny shim. Left in the pump, you'll see the delivery valve plunger. These can be left alone, but will appear loose. Thats fine they are located by the holder

TAKE GREAT CARE that NO dirt or anything else enters the 'holes' when the holders are out or you could cause a plunger/barrel to be destroyed....

The Holders should be cleaned carefully and new seals fitted. There IS a torque setting, but not sure what it is on your later series ECU controlled Bosch PE type IP

I would well de-grease the outside of the IP first and run the engine to confirm that it IS leaking there first before going to the above trouble.

It is just possible the lift-pump is leaking internally, Ive not had this fault but have heard about it....

Keep a close eye on the lube-oil level to see if it is increasing....

TMAllison · #7 03-22-2007, 06:32 PM

DV torque value is 35nm one time only, per most current instructions.

Orings and copper washers are same part for all OM60x series.

F18 · #8 03-22-2007, 08:21 PM

Mojo,
I just did the mileage conversion to US gallons on your fuel/mileage figures
Your Imperial Gallons (UK) are 24% larger than US Gallons.
That converts your figures to 15.2 - 19mpg (US)
You must have some serious leaks and or combination of other issues.....
I have delivery valve leaks and experienced a slight drop in economy but I am still getting low 30 mpg (US) on the highway and mid 20s city driving.
Could there be that much difference in economy between your Estate wagon and my 98 E300 TD saloon (sedan) ??? They have the same engine.

mojo7676 · #9 03-23-2007, 06:17 PM

Thanks for the comments, Fred. not sure how much the diff is between estate and sedan/saloon but imagine the estate would be a little less economical but not huge.

will tinker etc and update if any changes are noticed

mojo

jnc19610 · #10 03-23-2007, 06:37 PM

I drive mostly highway, and usually pretty brisk. (80) This time of year (cold), I seem to get about 27-29. In the spring and fall, I top out at about 31-32.

My 'in town' mileage is about 20 when my wife drives it. Her car has an on board computer. Her average speed is about 25. I suspose her drive pattern should be about the same, when she drives my car. In her Jag, she gets about 16.

Parrot of Doom · #11 03-28-2007, 03:05 PM

I've been trying to help this member with this problem, and hes found that one of the vacuum lines to the EGR valve has been disconnected, and capped. He says that his mechanic did this, and the vacuum line is now flopping around the engine bay.

Its an OM606 turbo engine (3.0 TD as fitted to the W210)

I don't think this is helping matters. From his description, it sounds like the pipe in the picture on the left (the portrait orientated one) - which connects to what looks like a sensor, bolted to the firewall.

Please note that these are pictures from my engine bay, not his. Also note that this EGR system is not the same as what you'd find on a non-turboed engine - the intake manifold does not have a crossover pipe. It cannot simply be disconnected with the methods described elsewhere in this forum.

Now I'm guessing that its a sensor that tells the ECU when the EGR valve is open/closed, or the relative position? You can see the vacuum line heading up into the base of the device to a point just below one of the bolts that holds it in place.

I have no idea what the other device is.

Could somebody enlighten us as to the purpose of these two components, and how their failure/removal might adversely affect the running of the engine? I have a feeling that the ECU is getting all confused, and this could be why hes getting such poor fuel consumption - although thats a guess on my part.

TMAllison · #12 03-28-2007, 03:20 PM

I've been hesitant to disconnect my EGR because so many sensors and componets are interrelated. Personally I'd look for what else the mechanic or PO did to it and reconnect it.

Reviewing the first post it seems there remains a fuel leak.....our OM606.9xx mantra "always fix the fuel leaks first".

F18 · #13 03-28-2007, 03:38 PM

Parrot of Doom,
The second picture is the Vacuum Solenoid for the EGR Valve......it is identical to the solenoid hooked up to your turbo wastegate. If either solenoid goes bad it would throw a defective code up on your instrument panel. I have never had the one attached to the EGR go bad but had to replace the wastegate solenoid about a year ago. There is a considerable lack of acceleration and slight drop in economy when turbo wastegate one goes bad.
I would assume that if any part of that EGR system fails it would throw a code.
When I had to replace the wastegate solenoid I moved the bad solenoid to the EGR and good one to the turbo wastegate as a test and the code changed/moved with it.

Parrot of Doom · #14 03-28-2007, 04:56 PM

I think the sensor is likely working ok, hence no codes (I presume, the car isn't here with me). Its just that its receiving a permanently open or closed signal, because its not connected.

I think the best option is to reconnect it - if its faulty, its not as if anything would change, and if its working then either the car's performance should improve, or another fault will make itself obvious?

F18 · #15 03-28-2007, 05:16 PM

Quote:

Originally Posted by Parrot of Doom

I think the sensor is likely working ok, hence no codes (I presume, the car isn't here with me). Its just that its receiving a permanently open or closed signal, because its not connected.

I think the best option is to reconnect it - if its faulty, its not as if anything would change, and if its working then either the car's performance should improve, or another fault will make itself obvious?

Do you think that someone just plugged the EGR vacuum line when the EGR failed due to sludge build up?........instead of doing it right and pulling the manifold and cleaning everything including testing and cleaning the EGR?? That is a possibility. It certainly won't hurt to hook it back up.