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  #1  
Old 07-29-2000, 11:54 AM
LarryBible
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Okay here's the rundown:

Daughter's '81 300D sometimes felt like it was misfiring on one cylinder. She was doing a good job watching oil, coolant and everything. You know part of her learning to maintain a car.

She called from town, twenty miles away, and it had overheated. She had shut it down on the spot, "good girl".

When I arrived with gallons of water and tool box in hand, I could find no leaks or anything. Refilled the radiator, left water with her and followed her home.

It would overheat on the twenty mile run thereafter, same fire drill, and I believe that it was at this time that the misfiring cylinder became permanent. I told her not to drive it while I was on vacation. At this point, I could not find oil in coolant, or coolant in oil.

After coming back from vacation, I loaded up water and ramps, and drove twenty miles to the car wash to wash engine compartment thoroughly before tearing everything apart. It ran cool with no problems, even with 100 degree outside and running a/c. both ways. It did still have the dead miss. Still no coolant in oil or vice versa.

At this point, I loosened each injection line, one at a time, while idling, the engine seemed to falter equally on every one.

Was 90% convinced that I would find a dead cylinder when doing compression test. Tested compression this morning to find four cylinders between 280 and 300 psi while number 3 was 340 psi.

Now I'm totally perplexed. If the overheating problem was not involved, I'd think that the thing to do would be to dive right into the injectors or injection pump. When I moved the car out of the shop this morning to sweep underneath before tearing it apart, it still had a dead miss when cold.

Should I warm the engine and retest compression, even though it has the dead miss even when cold.

Any thoughts or previous similar experiences will be appreciated.

Wish me luck,



------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles
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  #2  
Old 07-29-2000, 12:28 PM
Harvey Sutlive
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Hi Larry
This is guessing. Could something be off in the accelerator linkage?
I was wondering if faulty timing in diesels can make them overheat as is possible with gas powered cars. But your overheating is intermittant. If the accelerator linkage is catching or slipping maybe the pump and the throttle aren't working together the way they're supposed to.
Also - what was the last work done on the car? Sometimes the root of a current problem is in the last work.
Good luck and hope whatever it is is minor,
Harvey


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  #3  
Old 07-29-2000, 03:08 PM
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Join Date: Feb 2000
Location: Santa Clarita, CA, USA
Posts: 133
Larry,

could it be possible that you got a batch of bad fuel and clogged up one of your injectors? This happened to our '82 240D. It ran like it was missing, but on acceleration you can almost hear a sort of nailing. I later found that the bad injector had the pintle, or needle, seized inside the injector body. Good luck finding the problem.

Nolan
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  #4  
Old 07-29-2000, 04:45 PM
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Join Date: Jan 2000
Location: New Bedford, MA USA
Posts: 1,583
Larry, I'd lay my money on an injector going bad. When you pulled the lines was the miss still present and if it was, there should of been one cylinder that stood out like a sore thumb. Another thing that comes to mind is a bad cam lobe (hope not!!)

------------------
Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE

[This message has been edited by jeffsr (edited 07-29-2000).]
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  #5  
Old 07-29-2000, 05:31 PM
LarryBible
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That's one of the puzzling things, when loosening the supply lines at the injectors, they all reacted the same, no faltering.

If a cam lobe were flat, it would seem that it should have shown up in the compression test.

Is there anyway to test the injectors without taking them to the Bosch center and having them tested. I know that they calibrate them and all that, but if it's an injector, it's absolutely dead.

I still go back to the overheating. I sure was expecting a blown headgasket.

Thanks for the responses, please keep them coming everyone.

Wish me luck,

------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles
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  #6  
Old 07-29-2000, 05:38 PM
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Join Date: Jan 2000
Location: New Bedford, MA USA
Posts: 1,583
Larry, if a cam lobe was worn, but the valve was still opening, the choke on either induction or exhaust wouldn't necessarily show at the low rpm's that the starter will produce. Once the engine gets going, the choke will be evident as the partially opening and closing valve will now make it's presence known. Just a thought. Maybe remove valve cover, get a dial gauge and measure the lift on each valve..

------------------
Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE
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  #7  
Old 07-29-2000, 05:52 PM
LarryBible
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jeffsr,

I think if a camlobe is bad enough to cause the problem, I will probably be able to see it without a scientific test.

I adjusted the valves for her not long after she got the car, but I wasn't paying any attention to camlobes particularly. The valve cover will probably have to come off anyway, I'll probably go take a look. If I don't find anything else, then I'll use a dial indicator.

Thanks for mentioning this. I need some things to make me think "outside the box".

Wish me luck,


------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles
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  #8  
Old 07-29-2000, 06:50 PM
Moderator
 
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
Did you solve the overheating problem?

If you had a single cylinder misfire, due to any reason, it should show up in your cylinder balance test.

Is it a single cylinder misfire?? Cylinder head cracks let water into the chamber and cause misfires at idle. If they were large enough to misfire beyond idle they would eventually fill a cylinder (while shut off) and prevent starting due to hydrostatic lock.

Timing issues can cause overheating; did the overheating go away? If so thats not an issue.

Hard to make recommendation against the data supplied. If you have a single cylinder misfire it should act like a single cyclinder misfire.

------------------
Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician
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  #9  
Old 07-29-2000, 09:36 PM
LarryBible
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Steve,

The overheating went away at least for two twenty mile trips on hot day with a/c on. Temp was at about 85 degrees C all the way, both ways.

The misfire is at idle at low speed, at high speed, any time.

You say that the miss would show up in cylinder test, could it not be an injector, or something injection related? Is it your experience that injection system problems just don't cause a dead miss. I've never experienced a dead miss in a diesel, so I'm on unfamiliar ground in that regard.

I am still very concerned about the overheating, but it did temporarily go away.

Also the miss is so bad that it makes a resonant soft vibration at highway speed.

Thanks very much for your reply,


------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles
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  #10  
Old 07-30-2000, 12:51 AM
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Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
>The misfire is at idle at low speed, at high speed, any time<

Does this statement mean that it misfires at all speeds?

Almost anything can cause a single cylinder misfire. You should be able to identify the single cylinder by cracking each line loose and noticing the difference. The cylinder that doesn't work won't make any difference when the fuel flow is diverted.

If this doesn't work then you most likely don't have a single cylinder misfire.

You don't have a couple of gallons of gas in that diesel do you???
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  #11  
Old 07-30-2000, 06:59 AM
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Join Date: Apr 2000
Posts: 166
Larry,
Wish I hadn't read your post just before going to bed. Been lying awake for hours! You asked for any thoughts, so here are a couple.

Overheating: The only thing that comes to mind that would cause intermittant overheating is an intermittantly functioning thermostat. If it were mine, I would install a new one and await further developments.

Missing: I would be very suspicious of injector problems. Two possible courses of action (if it were mine). (1) Dismantle, clean and check each injector in accordance with MB manual or (2) obtain a rebuilt injector, install it in number 1 cylinder, check operation. If no improvement, install injector removed from number 1 cylinder in number 2 cylinder, check operation, etc. This wouldn't take a lot of time and when you got through you would know for sure if it is an injector problem.

As is so often said on this site, "Just my $.02 worth." Best of luck!

------------------
Ted
1979 240D
160,000 miles

[This message has been edited by Ted2222 (edited 07-30-2000).]
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  #12  
Old 07-30-2000, 11:35 AM
LarryBible
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I tried breaking loose all the injector lines at idle and found no difference. However, that was earlier when the misfire was not as pronounced as it is now. I'm gonna try it again.

Although my daughter is pretty sharp and aware, at least for a sixteen year old, the gasoline is a possibility. My son who is twenty and a college student who knows more than anyone else on the planet (at least in his mind) has driven the car some. He would be much more likely to have added a little gasoline.

I've never had a thermostat intermittent, but if someone else has seen it, it must be possible. I have a good thermostat and it's easy to change.

Thanks for the responses, I will check a few more things. But keep the thoughts coming, I appreciate everyones help very much.

Wish me luck,

------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles
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  #13  
Old 07-30-2000, 04:00 PM
LarryBible
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I just put the injectors back in, started it and cracked each line individually at idle. It faltered on every cylinder. There did not seem to be one that acted any different than any other.

The vibration is bad and feels like a dead cylinder. I'm completely perplexed about the miss.

In looking back at the log book and speaking to my daughter I found a time where my son put 2.50 worth of diesel in. My daughter said he did that a country store out here. The pumps are not marked well and I'll bet he put gasoline in it. Maybe that explains the previous overheating.

I really don't know what to do at this point. Do I put injectors in to see what happens?

Thanks for any ideas anyone may have,


------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles
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  #14  
Old 07-30-2000, 04:17 PM
Registered User
 
Join Date: Feb 2000
Location: Santa Clarita, CA, USA
Posts: 133
Try a can of Lubro Moly Diesel Purge. Run the engine directly off the can. You'll get a good cleaning and at the same time you can isolate the fuel. By doing that you can see if indeed you got a batch of bad fuel, or gas, mixed in.

Does the car smoke a lot? When I had a bad injector in my 300SD, it shook like it was missing and smoked more than usual at idle. I too cracked the lines one by one and almost didn't notice any difference except in the #5. I pulled that injector and opened it up,the needle was really tight, almost seized. A rebuilt injector cured that.

I'd try the diesel purge first before messing too much with the injectors. Your son could have gotten some really bad fuel at that country gas station. This way you can isolate any bad fuel from the tank and the same time get a really good cleaning of the injectors. Good luck.

Nolan
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  #15  
Old 07-31-2000, 10:27 PM
LarryBible
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Came home this evening and tried cracking the injector lines again, and could not find a cylinder which acted worse than any other.

In the course of all this I have come up with two findings;

One is the engine no longer overheats.

The second is that I don't believe it is a dead cylinder. There is a vibration that you can feel sitting in the drivers seat holding onto the wheel. It is very pronounced. When standing at the engine reving it up, you can hardly tell that there is anything wrong. The reason I have thought that it was a dead cylinder is that the vibration is at engine speed. It's like the torque converter or harmonic balancer are heavily out of balance.

I'm still stumped. Driving down the road is brutal, the vibration is so pronounced that it warbles. If you've ever sat between two airplane engines both at slightly different speeds, that's what I mean by warbling. The vibration goes in and out, in and out.

It is so bad I won't drive the car, or let my daughter drive it. It feels like something is going to tear up.

I've thought motor mount, but even if the engine were welded to the body structure, it shouldn't vibrate this bad.

The harmonic balancer runs smooth visually, is tight and seems to run out perfectly.

I'm totally stumped,

Thanks to everyone
Larry
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