Rough Idle, Smoke at start-up, miss on #2

[mikesdl]

Hello All

On my 87 300 SDL, Very rough idle at start up shaked really bad and has a miss on the #2. Did a compression test (360+ - 3), cracked fuel lines notice dif in all but the #2 moved injectors around same problem. # 2 will not fire lots of carbon build up o injector test run. Can the pre chamber be cloged? if so how to pull it I can not find a manaul.

Thanks for your help

[psfred]

Mike:

Do you also have hard injector knock on that cylinder? Runs rough until the turbo kicks in, then runs fine, no smoke?

I bought my 300D for cheap because of a similar problem (affected more than one cylinder). Turned out to be the pressure valve holder seals on the IP -- one holder was only finger tight!

Check the postings for what I did, you should be able to even dig up the part numbers. Cheap and easy fix.

One clue is that you get normal fuel delivery with the injector line cracked but no injection -- fuel bleed is the same as the others, with the line loose, but obviously no fuel is being injected.

The alternitive is that the IP has problems in the plunger and sleeve set.

[mikesdl]

Thanks for the info, checkedpressure valves all tight. But I could not find the post you are refering to. whats my next step. Do I need to remove the IP for the other repairs, I will need instruction if so

Thanks again Mike

[psfred]

Did you try a new glow plug on #2? A bad plug will make for rocky starts and lots of smoke, until the engine warms up a bit. The 603 is bad for missing cold, especially if it hasn't had and "italian tuneup" recently.

Peter

[MikeTangas]

Hi Mike,

No help here, just noticed you are from Temecula, which part of town?. That makes three of us, you, Placo1 and myself, our own Temecula Chapter of MBShop.

Follow Peter's advice and if you need assistance, or pertinent sections of the manual, I have a CD and can print out the necessary section.

[mikesdl]

Psfred
thank for all of your help, but zero luck with the pressure valve. The hard part was finding the 32 spline 12MM socket to remove it, was able to get one loaned to me from a great little repair heree in town, can you tell me where I might pick one of those sockets up.

any way back to the miss on #2, today I pulled the injector again to check things and found a puddle of fuel in the perchamber it slowly drained out. Also when i first checked it there wan't a heat shield in that hole. picked up a set and placed one in. Used the injector hold to perform the compression test so I wouldn't think the holes in the perechamber were clogged.I just don't know i also did a fuel flow test using the #1 and #3 all pumping the same amount of fuel in the given time. Replaced injector and torque to 80nm. Have any ideas

Thanks for your help

Mike

P.S. blocking off the egr worked great thanks

[BJ300SDL]

Peter, what is an "italian tune -up"? And while I am at it what is "lol"? Sorry for my ignorance!!

[BJ300SDL]

Peter,sounds like my sdl is doing the same thing as mikes 603. Could the pressure valve holder seals be faulty on our 603 as well? Do I need special tooling to check this? Finally, that pressure valve, is it located at the top of the IP where the lines screw in?

Thanks fellow HOOsier!!

[psfred]

No seal will give you very low compression, probably hard to see since the compression fitting may fit better than the injector.

Raw fuel in the prechamber means it isn't igniting, of course, so you need to find out why. Get the injector tested to make sure it works properly, they can get carbon in the little holes in the pintle -- you can't see this unless the are actually firing. Also, make sure you have the correct prechamber (there are two different ones for the 602, but only one for the 603) and that the ball pin is in good shape.

Pressure valves are in the holders on the IP -- they act as one-way valves to hold pressure in the injection lines so that the tiny amount of fuel sent up to be injected actually opens the injectors. The seal on the 603 pump is right on top.

The pressure valve itself can fail, too, especially if someone seriously overtightened it in the past.

An "Italian tuneup" is to drive the car hard. My 300D runs much nicer now that I did that 640 mile trip in two days last week!

I would check the injectors and compression first if I had rough running problems, since these are the most likely trouble spots. Once you have determined that the injectors and compression are OK, eliminate glow plugs as a trouble spot, then timing and the IP.

Peter

[BJ300SDL]

Peter, is it possible that the delivery valve assy. could have internal leakage causing a rough idle.

And is this usually due to it being loose or just age.

Finally, when I get the removal tool do you remove the lock, unscrew the delivery valve holder and then reseal and retorque?

I have the w126 service dvd, I was looking at the parts breakdown.

[psfred]

BJ:

Mine was a bad previous repair, the pressure valve holders weren't torqued down properly. One was so loose I didn't have to use the wrench to take it off!

The drill is to remove injector lines, then lock rings, then use the splined wrench to remove the holders. Seal sits on top of the holders. Make sure you put the spring back, it usually stays in the holder and drops on the floor. Spring is vital, without it, the line won't hold pressure and will operate the injector only and high speed and load.

Replace the o-rings on the pressure valve holders while you are in there, they are cheap. I suspect this is why mine were screwed up -- evidence of a fuel leak.

Make sure to use antiseize on the screws holding the lock rings down, else you may not be able to remove them again later!

Copper seals don't usually leak from age, but anything is possible. Certainly, not replacing with new when changing the o-rings will cause trouble!

Peter

[BJ300SDL]

Peter, thanks for the info, hope I can return the favor some day.