C250 TD Starting Problem - Help Please -
 

Hello everybody,

Any help with my problem greatly received... I am considering buying a (p) reg 1996 or 1997 C250 TD Estate this weekend at what seems a bargain price.
How ever it seems to have a problem sometimes in starting, sometimes it will fire straight away and other times you can be cranking the engine over for several minutes before it will eventually fire, in this case there is a strong smell of diesel from the exhaust so seems fuel is there.... it has covered 200,000 miles with no service history to see other than what has been done in the last 6 months, full service, including all filters, brakes etc.(just inspected car more fully, has new glow plugs fitted. 1 new metal pipe on the injector sytem, new radiator and waterpump..
I desperately would like the car but at the same time dont want to buy a sick pup that could cost ££££ to fix. if anyone can give me some guideance on diagnosing some possible causes would be fantastic, I am not familiar with working on modern cars, how ever I am a trained mechanic from from my youth but this was 20 + years ago
Owner informs me hes sick of spending money onit and just wants it gone, admits that sometimes takes for ever to start. help about to buy it blind and take a gamble its nothing Really serious

What could it be...it has obviously been looked at, and apparently from a specialist garage, they have fitted new glow plugs a pipe and a FULL service and still has the same problem

Thank you in advance

Best Regards Mike

There's not too many of us here with much expirience with the CDI's as they have just arrived here 2 years ago and are still under warranty, but.....it sounds as if it has a fuel leak somewhere that is allowing air to enter the fuel system causing hard starts. The CDI's still rely upon oring seals at plastic fuel lines feeding the fuel filters and IP that cause problems on the 606 engines. The 606 IP relied on oring seals at the delivery vlaves too. Your pump is considerably different so that may not apply on your engine. The above assumes the car runs good once started.

Is also possible is an electrical glitch controlling the shutoff valve or a sticking SOV.

Thank you for that, the car is a C250 TD 1997 i think, once the car starts it runs sweet as a nut, and also restarts fairly easily when warm. where shall I start bearing in mind somebody else has already had a go at fixing it, whats the next reccomended step. Thanks again for any help, going to buy it in the morning but i think its to cheap not to have a gamble on, its the esprit version as well which is quite nice

Is it a CDI? It's right on the cut off point I think.

Assuming its not CDI, every I said about fuel leaks is VERY applicable. In addition you should look for fuel leaks at the IP delivery valves too as they also have oring seals.

Keeping the tank more than 1/2 full and parking nose down hill will help with the first start of the day.

Just checked it was registered Feb 1998, so not sure what that means ?
Under the bonnet everything seems bone dry and no obvious leaks, thanks for the tip, healf full down hill, im 99% sure that will help, assuming I cant see any leaks do you reccomend getting a servce / overhaulk kit for the injection system, if there is such a thing, whats my next step? Thanks again. Regards Mike

I'm pretty sure its not a CDI engine. It also is not an engine we ever got in the USA.

You can purchase all new plastic fuel lines fairly cheaply. On the 606 engine it runs about USD$60 for all of them. Or, you could purchase the orings only and replace them yourself. Is an easy DIY job. This link pertains to the 606 again, but the sizes and counts should be very similar. http://www.peachparts.com/shopforum/showthread.php?t=177588

The fuel lines are clear when new, yellowed if aged. Is kind of nice to have new ones as you can see if any bubbles are present which helps one track down where they come from.

Fuel/Air leaks are fairly common, any MB "diesel" mech ought to have been able to figure that out???

If leaking at DV seals you might want to let a mech do that job as it is a lil bit technical if inexperienced and can cause irreparable damage if done incorrectly.

Thanks again, What are DV seals ? I will look into replacing all the pipes, i just cant believe the mechanic didnt do that 1st, When the engine is running there is clearly visible bubbles in the fuel line, is this normal ? and do you know of a good supplier of parts for the UK? im guessing genuine ones are expensive>

Thanks Mike

DV is delivery valves. On top of the IP (injection pump) where the metal fuel lines attach. The valve in the IP has an oring.

If you see ANY bubbles, therein lies the problem.

Just worked out what DV is, delivery valve, ok, what damage could I do, what is the danger ?

Thanks again

Mike

Bubbles hey, ok well at least I have some where to start, i guess now i have to find how they are getting in and where, would this make the car take 2 or 3 minutes of cranking in the morning to start ??? and then run lumpy for a few seconds

DV - beneath valve holder where the metal line attaches is a fuel element (ie: a tiny valve). If it is distrubed, knocked over, twisted, turned, etc the best case is the pump will come off and go to Boach to get recalibrated and if torqued down with element in worng orientation it will get replaced with a new pump.

Yep!

Right ok, thanks for that.... it does have 1 new metal pipe, im assuming its safe to replace all hoses pipes etc, just dont go any further than take the pipes off from the DV yes?

The metal lines should be fine unless someone ahs bent them such that they wont seal. They are simple compression fittings.

Just replace the plastic fuel lines, pre-filter and it oring and possibly the oring behind the shut off valve onthe side of the IP (black plastic valve).

do you know if there is such a thing as a service kit which would comtain all the hoses pipes o rings etc ?

You have been so helpfull, thank you, off in the morning to buy the car, assuming it starts i will get it home and no doubt be asking for some more help, hopefully i will fix it and be able to close the post with a happy ending.

Excellent thats my Monday sorted assuming I can get the parts easily enough, i will let you know how i get on if thats ok

Thanks again for your time and help

Much appreciated

Hi there,

Just met with the mechanic who has serviced the car, he is 100% syre all glow plugs are workking ok, I mentioned all the air in the pipes in the moring and ha agrees that this must be the problem, although he doesnt know where to look, he has suggested replacing a little valve like thing on the block with a pipe on it going to the filter housing its only small but he thinks its a good start, would you happen to know what this part is and if so could it be letting air in, thanks again in advance for any help or info. Regards Mike

Thats going to be the shut off valve (black plastic solenoid) or the lift/fuel pump. Each has two lines, one of which goes to the filter housing.

Tell us which line(s) you see air in???

http://detali.ru/cat/oem_mb2.asp?TP=1&F=202128&M=605%2E960&GA=722%2E436722%2E612&GM=717%2E460&CT=M&cat=19S&SID=07&SGR=120 &SGN=04

It's not a CDI, The engine is similar to the 2.5 diesel that was in the E300D

c250 TD starting problem
 

Mike
I have a similar problem with my E300D, 1996. I have not gone as far as you yet with repairs. However when I start my car, I push the fuel pedal a little which helps.

One could find and remove the return line on the pump when it does not want to start. If you have fuel at pressure in the system there should be discharge even when cranking I suspect. The bubbles should not be in the fuel supply lines though either. Forget about the injection pump itself right now.
Another check might be to loosen the #1 injector line a little on the
#1 injector when it will not start and look for fuel pulses. Or spray a little wd40 into the intake. If the engine fires right away you have positive proof it's fuel supply related.

The posters IP and fuel lines are identical to that used in the OM606.

Able - You can push your gas peddle as much as you wnat when starting, it wont do anything. It is a fly by wire system. The computer will meter the required fuel until startup occurs. What is helping you is the fact that you are cranking it and therefore repriming the fuel system. Try keeping the tank above 1/2 full and parking nose downhill at night instead. Look for air in your fuel lines when you get a chance.

bubbles in 32 56 74
 

Firstly a big thank you to everyone contributing to my problem, Ok heres the latest, this morning I checked the fuel lines prior to starting and there was a few tiny bubbles in 32 a big one in 56, but there was a lot more fuel than bubbles unlike some mornings, she statred perfectly this morning, god knows why, and after 2 seconds I looked at all the fuel lines and 32 was clear 56 a quite a lot of bubbles but 74 had even more and while the car was running every time a bubble whizzed past in pipe 74 the engine would immediately cut out / miss for half a second, this continued for 2 mins until the fuel ran clear and then she ran smoothly.. so yes air did get in over night but only a little.... now going to check remove and check fuel lines for any signs of a obvious fault and maybe the fuel filter too. and let you know what I find. Thanks againto all, I feel we are really getting some where, if a resolution is found im sure many other people could learn a few things from this thread. Best Regards to all Mike, off out to get oily..again

You have a bad seal where line 32 plugs into the pre-filter, at the big oring beneath the pre-filter itself, where line 56 plugs into the fuel filter housing or all of the above.

Remove those lines and observe the orings. They are supposed to be round. If they appear to be oblong in section, they need to be replaced.

You've now ruled out everything prior to the pre-filter and after line 56.

New fuel lines
 

Superb, have purchased some torque head sockets, fuel lines and o rings on order, watch this space. Thanks Guys

c250 fuel problem
 

hi guys , new to the forum. have a 1997 c250 with the same problem. i was trying to have a look at that diagram that tmallison posted here but cand open it as service is unavalable. has anyone got a copy of it or point me to one.thank you.

Russian EPC service is no longer available
 

'Shame, really.
'Those were some great diagrams in a user friendly format.

The Mates over @ http://www.mbclub.co.uk/forums/

Have much more experience with the 5cyl 20 valve DOHC W124 chassis.

thanks for the reply. i,ve been there and same link for this. thanks again.