[DieselStu]

Greetings! I hope I don't get banned for asking Q's about a 116 here. I've tog
I have a 1980 300SD. It has lacked power for the past 5 months. And the amount and duration of the lack changes from one trip to the next. There have been a couple of occasions when it drove just as it ought to. Nothing happens at the RPM when normally the turbo creates the kick we're used to (2100rpm).
On some trips, the car will BARELY move. Gradually it builds speed--very, very slowly. But it will no go faster than 60 km, and a that speed the rpm's are at about 3600--way too high.

I have investigated, cleaned and snooped the following places:
-clean the ALDA and line
-checked the leak down on the ALDA itself.
-changed primary and secondary filters
-changed air filter.
-turbo is fine.
-yesterday, I removed the fuel tank and looked at the screen in the bottom. That was less work--although dirty and stinky--than I expected. I will try to attach a pic.

A neighbour of mine told me of a story about similar fuel starvation type symptoms he had with an old snowmobile. The fuel broke down the fuel line in one section, and the hose collapsed, like an artery, when the pump created a vacuum in it. Thus, at high demands by the carb, in that case, the machine would starve and stall.

My car died on the highway after about 15 minutes of 60mph driving. I'm beginning to think the fuel line collapse story might be relevant. If I bleed the fuel system at the main filter, the car will start. After about 20 seconds it slowly starves and turns off.

Does anybody have a suggestion? Could it be a vent problem? Maybe the tank vent is blocked? Should I replace sections of rubber hose?
I'm attaching pics of my fuel tank screen (123 part number even though my car is a 116). The tank appears to have been free of fungus/algae/small rodents. Or is my line of thinking just wishful thinking--is it a problem with the IP, namely?

Stu
1980 300SD

 

[jdc1244]

Yes, replace the fuel tank screen, even if it’s not the problem.

I think you answered your own question – I can only think there my be a problem with the IP as well, may be time for a rebuild. I don’t know how much. (Knock on wood…).

All OM617 owners are welcome here, btw…

[]

 

[N0RT75O]

as another 1980 116 owner, (2 of em), i vist here more than any other forum,,,,kompression ck? will be watching , my $.02[]
n0rt

 

[blkchambers]

Hey, JDC1244A, I live in TPA area too.
New to this forum.
I have W123 coupe undergoing transplant with 5.0L V8.
(don't worry, guys, The OM617 will be put to good use in a custom truck!)

email me [email protected]
Bob

 

[afroney123]

Interesting problem indeed. There are two situations where I had a problem similar to yours. The first was in my 82 300D. The car wouldnt stall, but it would lose power, and run very rough. If the fuel system was bled, it would run well for another half hour or so. Turns out that air was getting into the fuel line through that last cigar hose on the injector pump (The one that dangles) Check all your fuel lines for cracks/leaks, and replace as necessary. The second was in an 86 caravan where I had the exact problem you are describing. This one turned out to be an EGR valve that had crapped out. Not sure if the early 80s modles had EGR valves or not...

 

[DieselStu]

Thanks for the feedback,
About the compression question, I have to believe it's OK. During the last Ontario winter, the car behaved better than in past years. Even at -20C, it would start up. I had the valves adjusted about 5000 miles ago. And Low compression wouldn't explain why it starts and then gradually dies.

I suppose I could pressurize the fuel lines with air, or vacuum, and see whether they leak down. I have a mity vac, so that might be the easiest thing to do. My old style IP primer pump doesn't leak, so I don't think the air is getting in there, as people sometimes warn that it may.

As for the EGR, well, I blocked that off 5 years ago. I don't understand the vacuum lines that continue to run into the top of it. What do they do? Is there any manifold vacuum, even just a little, that supplements the rest of the system? I know that Diesels produce none, or very little, but I can't figure out what else those two lines are doing there.

Questions:
1) Short of removing it and sending it to a Bo$ch shop for evaluation, is there anything I can do to rule out a fault with my IP?

2) Is the fuel tank cap supposed to seal the tank, or let it breath?
3) Is it, as I suspect, very unlikely that the steel fuel lines between the tank and the engine bay are letting air in? Sometimes the metal gets thin where the clamps attach. I should replace rubber pieces before steel, right?
4) Where do the vent lines open to? Could silt or other FOD get in there and cause a blockage that restricts the flow of fuel?

Sorry for the string of questions. I learned a lot from the old * site, and I intend to write up my findings properly, with pix, once I make some progress.
Thanks,
Stu

 

[MetaPhysicalPajamas]

There was a thread over at mercedeshop about a problem maybe similar to yours. It was a 116 also. Search for a long thread started by BoneheadDoctor. He went through everything and it ended up being a clogged crankcase breather. The crankcase pressure in the injection pump was pushing out on the shutoff diaphragm and killing the fuel flow. Bizarre eh?

 

[DieselStu]

Boneheaddoctor's saga took me an hour to read. I was breathless through the whole epic. I took a piece of hose from an Audi at a wrecking yard in order to fix the original, weeping crankcase vent. The hose has been a big help, cosmetically. But I began to have problems at about the time I made the change. Tonight I will remove the hose to see if that fixes anything. Could it be that simple?!

Thanks for the tip. I didn't even know about that forum. You wonder if the sharing of automotive information is having the effect on the normal disseminators of that info that the sharing of music is alleged to have on record labels. I ask, How did people fix their kooky, idiosyncratic cars before the internet? Kids ask, where did people download their music from before the internet?

Stu

 

[DieselStu]

Hahaha. Nope, it's not something simple like removing the crankcase breather. My 1980 300SD still shuts itself off after 5-10 seconds of running. It bleed it and it starts again.

I am armed with new fuel line today. I will replace everything rubber from the tank forward. I should say, just for the value of future searches of the archive, that pulling the trunk mounted tank from a 116 is not a hard job. With the rear raised, there is enough vertical space to slip in a 5 gal gas can. Close your eyes and drain the fuel into the can. Then climb into the trunk and pull out the false wall at the back. A mere 4 nuts hold the tank in place. It's made of Aluminum, and comes out very readily. My fuel tank screen looked as good as new.
I think my problem is fuel lines drawing air. The car will start after it's been primed. Then it just slows down and eventually dies.

I don't think it's IP timing, because I haven't done anything to change that. What would be another cause of raised crankcase pressure? If there was a blockage somewhere, then the oil pressure would build and shut off fuel at the backside of the IP shutoff solenoid, right?
Thanks,
Stu

 

[jdc1244]

I don’t think it’s IP timing either since that would be just a lot of smoke and shaking, worse case a no start – you are also correct about the IP high oil pressure shut off as that could damage the pump. Since the vacuum system is integrated perhaps the new (non leaking) fuel lines will return the system to normal pressure, just a thought…

 

[MetaPhysicalPajamas]

DieselStu - 5/2/2005 2:23 PM
On some trips, the car will BARELY move. Gradually it builds speed--very, very slowly. But it will no go faster than 60 km, and a that speed the rpm's are at about 3600--way too high.

Stu
1980 300SD

Are you saying here that it will not shift into high gear? This statement makes me wonder if you have a transmission problem. It sounds like you are on the right path with making the car run. After you get it to run make sure your tranny is ok before you kill it.

If you have the original primer pump and it leaks when you prime the system it needs to be replaced. It will let air into the system. You mentioned this earlier but it is worth repeating. It is a cheap part and maybe worth replacing now just to avoid future problems and eliminate it as a possibility.

 

[DieselStu]

Well, I replaced the cigar hose and the little fuel filter hose yesterday. I went through maybe six or seven episodes of the bleed-it, crank it, watch it die, even after I changed fuel lines. I was delighted to find big, deep cracks in the cigar hose, but replacing it with new line didn't get me anywhere.

I wanted to try boneheaddoctor's method (suggested a few times by others during his saga) of setting up an in-term, temporary fuel tank under the hood so that I could rule out a leak in the line somewhere closer to the tank. I couldn't really figure out which line to feed from. Is this right?:

Fuel is drawn out of the tank, into the small plastic in-line filter, through the handpump mechanism, up into the large, metal filter and from there into the IP? If this is the correct path, and I haven't mistaken the return line for the draw line, then I should be able to set up a temporary fuel tank under the hood with a hose leading to that first, small plastic filter. Does that sound OK?

Now I have this question:

Whenever I get the engine to stutter to life, and it dies (5-10 seconds later) I crack the fitting on top of the metal filter ("main filter"?). The fuel that I bleed out is full of tiny, little micro bubbles. I mean, like the bubbles you'd get in saliva if you swished it around in your mouth for a while (sorry--only analogy I could think of). I pump until the fuel is clear again, but I find if I wait, and resume pumping (with the white, old-style bleeder pump), I get more micro bubbles. And I am sure that the symptoms I have are related to air in the fuel. My car has been increasingly low on power, and now in the warm weather, won't stay running for more than 10 seconds.

Are the tiny bubbles a clue? I bled it lots in the good ole' days (when it ran fine and I was just changing filters), and I don't remember these troubling little bubbles.

Just look at this handsome, original Sunshine Yellow Merc as it drives onto the Wolfe Island ferry in happier days. It's dirty, but surely worth saving,
Stu

 

[RoyH]

You create a vaccuum with the primer. It sounds like the bubbles are the result of an air leak into the feed line whether the vacuum is from the IP or the primer pump.

 

[N0RT75O]

http://www.benzworld.org/forums/forums/thread-view.asp?tid=716409&posts=7&hl=fuel+primer+replacement

interesting reading,,,,,,
n0rt[]

 

[jdc1244]

Micro bubbles – hmm… can’t say I’ve seen micro bubbles come out when I open the main filter. I know what you mean by micro bubbles, they come out when I bleed the fuel line after a new filter change. It sounds like you’re repeating the air purge procedure over and over again with no result. I think the under the hood test is the say to go now.

That is the correct path for the fuel except the fuel line from the tank to the engine bay is longer. That may be where the air leak is.

Yes, your 116 is worth saving.

 

[DieselStu]

Hmmm,
Will a primer pump be faulty even if it appears to be fuel-tight? Mine has never leaked, and even though it's the old style, I have a hard time believing that it's the problem.

What's a good source to buy the new style pump?
thanks,
Stu

 

[jdc1244]

I know mercedessource sells the new pump – more than likely the other onlines like GermanStar, Fastlane, and Rusty’s – just do the IP purge procedure but with diesel fuel in a larger container and see if the engine will run longer than a few seconds. If it does you know there’s a problem between the engine bay and fuel tank.

 

[drebdy]

i had that same problem in my w126 300SD before but my car doesnt die, it just looses power up until it will not run anymore when uphill, it turned out to be a broken vacuum line from the IP, replaced it and also saw that the main filter was leaking on the top bolt so i replaced that filter also, and everythings back to normal now, check also for cloggs in ur fuel lines, a friend of mine had his 300sd pressur flushed all the fuel lies with air pressure and we were surprised to fine so many dirt and algae in his lines, it madehis car run smoother

 

[drebdy]

i had that same problem in my w126 300SD before but my car doesnt die, it just looses power up until it will not run anymore when uphill, it turned out to be a broken vacuum line from the IP, replaced it and also saw that the main filter was leaking on the top bolt so i replaced that filter also, and everythings back to normal now, check also for cloggs in ur fuel lines, a friend of mine had his 300sd pressur flushed all the fuel lies with air pressure and we were surprised to fine so many dirt and algae in his lines, it made his car run smoother.

 

[N0RT75O]

keep us posted???
n0rt