rough running cold diesel - PeachParts Mercedes-Benz Forum

McDiesel · #1 07-12-2003, 04:15 PM

have a 1992 2.5 turbo diesel.
when starting cold from sitting overnight she runs rough blows white smoke until warms up. then she is fine

i have done the following checks.

swapped air mass flow sendors
swapped vacuum modulators
replaced all 5 glow plugs
adjusted rack dampening screw
cleaned crossover pipe and wastegate area

McDiesel · #2 07-12-2003, 04:19 PM

sorry ht the wrong key

i have swapped preglow relay
ran 2 cans diesel purge after changing spin on and inline filters

could it be the i.p. pump timing...?
also i hear there is a special tool to hold the crankshaft and
a tool to check the ig pump timing
anyone have any ideas i would appreiate it

also did a search on rack dampening screw.. local dealer has an updated screw and spring but wants 72.00 for it.

when she is warm she has no nailing or hiccupos etc.. only when starting cold...

engatwork · #3 07-12-2003, 04:20 PM

uh oh - I hate to say it but it sure does sound like coolant where it is not supposed to be (white smoke out the exhaust). This is normally caused by a head/head gasket issue. It will make the car run a little rough when cold.

McDiesel · #4 07-12-2003, 04:46 PM

if it is the headgasket .. i hope not.. but what i smell out f the exhaust is unburned diesel. I have kept my eye on oil and coolant levels and all appear to be the same..

but if it were the headgasket wouldnt the car run like cwap
all the time?,,

the new glow plugs made a diff she isnt as rough but after 30-45 secs all seems fine... she runs like a top...

first i thought timing chain stretch.. ip timing or possibly the injectors..
car has 140k

engatwork · #5 07-12-2003, 05:44 PM

Surprisingly enough they will still run pretty good hot with head gasket issues. Tomorrow morning before you start the car for the first time remove your coolant over flow cap and see if it seems to be "pressurized". This is an indication there there are head gasket issues too.

ohcaptainron · #6 07-13-2003, 12:11 AM

I have a 93 300D, had the same problem, car would start well then after the glow plug relay clicked off the car sounded and felt like it was running on two or three cyl. for a minute or so then ran perfectly, White smoke, definitly unburned diesel, no coolant leaks or head gasket problems. My mechanic said this was quite common on higher millage 2.5 turbos, problem is you have one or more slow leaking injectors, overnight the faulty injector bleeds down fuel into the cyl., during pre glow there is enough heat to burn most of the fuel, heat off overfueled cyl. no burn rough idle until the fuel is cleared, I would drive 100 ft and the car would then run perfect. I removed all injectors and had them rebuilt by a Bosch certified shop, had them all opening within 5 bar, 10 bar is min. spec, no more leaking car idles when cold as before like a sewing machine very smooth. Good luck hope this helps
Ron
2003 E55 AMG
1999 E320 WAGON AWD
1998 E 300 D SOLD
1993 E300D 2.5 Turbo
1985 300 TDT
2004 E320 CDI on order

McDiesel · #7 07-13-2003, 09:27 AM

Ron that is exactly what is going on...

i will experiment swapping 1 injector at a time from my other 1992 to nail it down no pun intended!

thanks

jeff

engatwork · #8 07-13-2003, 12:05 PM

Thanks for setting me straight. My friends 300SD does the same thing and I have changed out the injectors at least once trying to clear it up. Next time I have his injectors out I will get them set at my local Bosch shop.

DieselAddict · #9 07-14-2003, 12:46 PM

Nobody mentioned valve adjustment so I'll mention it. Also check your idle speed. Raising it slightly might cure the problem, but don't raise it above the proper range. If the white smoke has blue tint to it, then most likely it's unburned fuel, not coolant. Also, letting the plugs glow longer before starting should help.

McDiesel · #10 07-14-2003, 08:42 PM

we adjusted the rack screw on friday and raised the idle up to about 850 prm... started her this am after putting 5 new glows in her on friday and she ran smooth for about 20 seconds then back to rough idle.. big improvement with new glows in..

Today we decided to pull the delivery valves out and del valve o-rings and pressure valve seals.. clean the crap out of everything before we dissassembled everything... replaced seals and orings torqued and retorqued to 30 Mn then back off then to final 35 nm torque, 4 of the 5 valves bled.. # three was stubborn.. we took it apart again to l@@k at the f@$in thing again.. there is a sring seated ontop of a -nozzle- type fitting we removed all of them and cleaned them up again.,. we noticed that -base- part the -milkstool- if you will that the fitting sits on would not lift out with a magnet and was stuck.. after some fiddling we finnally got it out cleaned it up and refitted #3...
we took out #2 just to comapre and all seems fine..

hooked everything up again and now all 5 delivery valves are bleeding fine.. crow footed all fittings again and tried to blled out as much air as poss.. now she seems like or two cyls are not firing correctly #4 and #5 .. 1,2,3 seem ok...

tomorrow we are going to take apart again and see if everything is seated correctly...

thanks all for your replies...

i have heard there is an updated rack screw thru the search option but i cant seem to find it on fastlane .. someone posted a per part # but it came back as not app to my car...
egads whats next!!

McDiesel · #11 07-15-2003, 08:45 PM

man its getting ugly.... now engine is missing.. re-did delivery valve o-rings several times... still no help...

local dealer is booked up until july28th...

what a nightmare..

car used to idle rough... until warm,,, now engine stutters, and is missing badly and blowing light white smoke..

also she now seems to take longer to throttle down.. almost like the fuel delivery diaphram isnt working right..

called a bosh repair local guy and he told me to swap the pressure delivery valves from # 3 to # 4 and this is the result

oh my god.. what have i done!

Denrac · #12 07-16-2003, 10:37 PM

My car has a similar problem : with a cold engine, as long as the glowplugs are on, it runs smoothly (on 92 W124, the glowplugs stay on up to 60 seconds after the engine starts, depending on the temperature). When the glowplugs turn off, it starts to misfire with unburned fuel smoke. The misfire is worse when the outside temperature falls. When warmed, it idles without any problem.

I've got my injectors rebuilded and although there was a notable improvement at high rpm, it didn't cured the cold idling problem.

I didn't change the glowplugs : current readings (AMP) are all within specs.

I was up to do the "delivery valve" job, but your story scares me a little.

From what I have read in this forum and in other sources, cold idling problem seems to be common on the 602 engine : I think the afterglowing time was extended on later models to get rid of that.

Keep us informed on your work.

McDiesel · #13 07-17-2003, 05:44 AM

after fiddlin around since thurs july 10th with those delivery valve
0-rings and pressure valve seals we finnally got it back together with no miss now... we must have undid and untorqued those lines 10 times.. final torque we tried 30Nm on each 3 times in a row and now she is back to square 1.. ie rough running when cold ok when she warms up.. turned out that 1 of the brass delivery valve seals wasnt up to par.. replaced it with an old one
and put me back to square 1.. running a it rougher than before
we did the seals but it is acceptable...

going to local dealer on july28th to see wtf is going on

in the meantime i am going to replace the motor mounts for they
were replaced about 80,000 miles ago and are getting soft in the humid hot heat we are having..

my suggestion is to let the dealer do any o-rings from here on in..
although my other 92 had no problems with this procedure at all
we did torque those to 30nm again to 30nm and finnaly to 35nm..
got the air out of the lines and she is now leak free and runs the same as before.. thats why when we approaced the other 92 i figured it was so simple what could happen? ALOT OF AGRIVATION!

THANK GOD SHE IS ALMOST THERE NOW... thanks to all for your replies

McDiesel · #14 07-19-2003, 01:41 AM

what should one expect to pay for a new timing chain and rails in a 92 124 2.5 turbo diesel??

how many hours labor.. any idea?

thinking about getting it done at a local mb independant dealer i have been doing buiss with since 1996

thanks in advance!

McDiesel · #15 07-30-2003, 03:09 PM

Took car into local trusted MB mechanic today...

he said he doesnt have the meter that costs 500 bux plus the cost of cables to diagnose.. he said the rack seems to be searching for idle...

now i must bite the bullet and go to the local cherry hill mercedes dealer,,,

he did suggest i try to swap the idle control sensor from my one 92 to the other to see if it is the sensor.]

if that isnt it than i am forced to go to dealer ..

ugghh...
this guy who worked on her today for over two hours refused o take any money from me for i ring all 3 of turbos to him when im schtuck!

i returned with coffee and 2 dozen dunkun doughnuts for
his shop.. they sure appreciated it..

he gave me the name of his friend in cherry hill motors who can diagnose this problem.. he used to be the shop forman there
and knows this guy nicknamed fottie can get it right for me.. he even offerd to tell them they could call him and he would tell fottie what he did as not to waste time on it..

just goes to show you that there are good ppl still out there

justeverybody on this forumeveryone tries to help a felow dieselhead pull through again and again