Compression, Missing, and Injectors - PeachParts Mercedes-Benz Forum

ctsoth · #1 12-10-2005, 11:22 PM

I have a few questions that I need help with.
My engine misses and runs pretty rough in sub freezing temperatures. It has started up on the SECOND TURN down to -12F so far. Still runs like **** once it has been running for a few seconds though. Engine runs fine when warm.

Car has 176,000 miles. 1984 300D turbo.

I know that I have an algae problem, I just ordered stuff to make that go away. I am thinking that it is possible that my fuel lines running between the pump and the injectors could be gummed up with algae. Is it plausible that the algae has gummed up the fuel system enough that it affects the engine at low temps?

Could the missing and real rough idle be compression, timing, bad injector spray? I am going to get my injectors checked as soon as I get my other car back. [Had to borrow it to one of my brothers...] I just adjusted my valves, so unless I majorly screwed something up valves are not the issue. I checked over my work multiple times, and I am extremely attentive to detail, so I am certain I didn't mess the valves up...

Any ideas on what could be causing my problems?
When I pull my injectors I plan on checking my compression, speaking of which, what should my compression be?

Peace

Chris

EDIT: What additives should I be using in the coolant to prevent cavitation?

t walgamuth · #2 12-10-2005, 11:40 PM

will stop al the algae before it gums up injcetion lines. the filters will plug with the stuff and cause running problems.

it sounds like you have a bad glow plug or two. runs rough at startup but smoothes out in a minute or so? classic glow plug problem.

use the fungicide at least three times. the fungi should pull thru the filter just fine, after the treatment.

good luck

tom w

ctsoth · #3 12-10-2005, 11:53 PM

It runs fine when the glow plugs are still hot after it starts, and starts to get rough as the glow plugs cool. It always starts on the 2nd turn, which makes me think its not compression.

My idle is at 600 or so, is that what it is supposed to be?

t walgamuth · #4 12-10-2005, 11:58 PM

what the idel spec is maybe 700. a lot are 700. yes your description of the hotness of all the gp seems to indicate other problems.

the compression checked cold is about 320 at sea level with a minimum of 220. tested hot it is higher i dont remember what exactly but over 400.

this problem doesnt sound compression related but never hurts to take it.

solve the algae first before doing any mechanical things, i think.

tom w

#5 12-10-2005, 11:58 PM

Quote:

Originally Posted by ctsoth

It runs fine when the glow plugs are still hot after it starts, and starts to get rough as the glow plugs cool. It always starts on the 2nd turn, which makes me think its not compression.

My idle is at 600 or so, is that what it is supposed to be?

I believe 600 is the low end of the idle range. I turned mine up to about 700-750 when the weather got cold because it was tending to stall when cold. Does it only run rough at idle, or when you driving?

Palangi · #6 12-11-2005, 12:00 AM

700~750

If you have algae/fungus, you may have water also. Dump out the main filter into a container and check for water. The prefilter will also separate a bit of water. I duuno how, but it does. Depending on what you find, you may want to run some addatives for a couple of tanks to get rid of the water.

ctsoth · #7 12-11-2005, 12:10 AM

I run additives with every tank, I replaced both filters 2 months or so ago. I doubt it is water in the system. My dad is CONVINCED it is the compression, and it is really starting to grate on me. He doesn't understand that it could be lots of different things....

ctsoth · #8 12-11-2005, 12:11 AM

Runs fine while driving, idles fine when the engine is warm. Only misses when engine and ambient temperature are cold at low RPMs.

#9 12-11-2005, 12:22 AM

Quote:

Originally Posted by ctsoth

EDIT: What additives should I be using in the coolant to prevent cavitation?

I'm not sure I understand, what are you trying to do to "prevent cavitation"?

Regarding you rough idle, there may be some variation in the compression between the cylinders, but that's to be expected. I would increase the idle to about 700-750 and see what happens. That fact that it starts easily and run well when warm seems to indicate the engines in good shape. I suppose it could be one injector acting up, do you hear any injector "nailing" when its up to temperature?

ctsoth · #10 12-11-2005, 01:29 AM

My dad says he can hear some nailing when the engine is warm.

With my Ford I had to add FW-15 to the coolant to prevent the engine from "cavitation." The coolant foams and bores holes in the cylinder walls in diesel engines. The additive takes the damage instead of the cylinder wall. I do not know if that is a reality for mercedes engines though, for my Ford it was standard maintenance...

Like I stated earlier, I AM going to get the injectors tested, I just can't until I get my other car back.

What is the best injector brand to go with? Would I assume its Bosch?

#11 12-11-2005, 05:02 AM

Maybe you need to be more specific about what you are considering "rough idle" and how you are characterizing "missing"

Remember this is an old benz...they do not sound glassy smooth when cold. Give us a better idea of how it sounds if you can before we all go looking for problems.

ctsoth · #12 12-11-2005, 10:28 AM

When it misses it blows additional smoke out of the tailpipe [unburnt fuel.]

The car also shakes pretty bad when it misses.
I understand the rough idle, my ford diesel chugged bad in the winter. It is the miss that I am concerned about.

Mitch H · #13 12-11-2005, 10:42 AM

First, check the valve lash when it's totally cold on a cold day. The valves tighten when cold.

t walgamuth · #14 12-11-2005, 10:55 AM

whitish blue smoke sounds like injector issues.

again, first deal with the algae issue.

tom w

Hatterasguy · #15 12-11-2005, 11:21 AM

At -12 a diesel isn't going to fire up like a gas car. Heck a gas car isn't going to be happy!

Replace the glow plugs, and send the injectors off to be tested if you think you have a problem.

Or just plug it in.