Even if a small amount of leakage is present in the relief valve when closed. It really does not matter. If you have no running or starting issues with the cigar hose in place. Keep it in place.

As I do not think this situation precludes a failure of any sort. You can get really anal about it I suppose but even them It may not really change anything.

I kind of sense you have been already .Several cigar hoses purchased. You do not want to land up reaching for preparation H. Chances are that if there is a cause time will indicate what it is.

On the other hand the cigar hose may just be operating better than expected. I am a fringe believer in that the cigar hose is either important. Or the lack of one seems to let another condition become a potential problem.

Ha! You better believe it. Thanks Barry.

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1981 240D 4sp manual. Ivory White.

Update: this was solved by installing a new ball bearing in the OFV. No more leak back.
Checked the return line this morning and it was solid with fuel.

Here's a pic. Left new, right old.



Difficult gleaning from the photo, but the old bearing was like an asteroid.

Smoother idle, more power... seems I'm finally seeing the benefit of the Greazzer spring I installed a year ago.

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1981 240D 4sp manual. Ivory White.

You have obviously learnt a lot from this adventure. You might give some consideration to buying a liquid dampened pressure gauge and keep going.

An overall expenditure of about twenty dollars would do it. For the gauge and parts to hook it up for testing. You want to make sure you have decent fuel pressure at highway speeds.

A couple of issues come to mind that could prevent this. A partially obstructed fuel filter or a tank filter in poor condition. You rebuilt your lift pump so it is probably just fine.

As a maintenance item the secondary filter is going to collect any water from the fuel. So at a minumin should be removed and the contents dumped for examination. Once a year. Also gauging the fuel pressure once a year indicates when there may be too much filter obstruction starting to exist.

An engine can run fine under idle with adequate fuel supply. Place a demand for maximum delivery. If the capability to provide it is not there. You have less power.

This requires a quick test at highway speeds. Or a on the floor acceleration for a short period in top gear. I think for example my 1984 300d really gains speed fast when passing between 50 and 80. Possibly as good as decent gas cars. It is better that most low end four cylinder gas cars by quite a margin I feel.

It really comes to life basically. It takes very little wrong to defeat that type of performance. If a fuel pressure gauge shows a decent pressure under that condition. . You might see the performance that 84 of ours is producing. Nothing has been modified.

If not and the fuel pressure is there. There are other things to look at.

Somewhat interesting that ball was allowing as much leakage as it was.

You may have broken some new ground as a member. That being posting a picture of your balls on this site is probably a first.

Agreed. I replaced my tank screen last year -or rather installed one, as the previous owner had cut the screen out with a pair of shears. It’s pretty wild, I actually have to ease up on a the pedal at times! Never did I think I’d be writing that. Highway speeds are much zippier. I can feel a new band of power kicking in in 4th gear around 40-45mph.

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1981 240D 4sp manual. Ivory White.

Engine starts easily I see no reason to pursue it further at this time. This power band you feel indicates you do have decent fuel pressure. Actually a reflection of fuel volume present at 45mph and up. I was glad you had previously dealt with the tank screen.

It is totally unreasonable to expect it to be free flowing at these years and miles. If it has never been dealt with. I also suspect it may become reasonable to solvent clean and blow out any old fuel lines. There may be buildup over time. Any effort to reduce the amount of vacuum or pull on the tank and fuel line should be worthwhile. It should increase volume flow. By the lift pump.

Now for the nice maybe. We have had a millage issue between 240ds that got my attention years ago. I was never able to find the cause. I also believed it was real. Well we may have found it.

I was not successful in getting people to do various gauge readings. If they had we may have picked up the issue. Some 240ds will run with no relief valve function. This was just one of a multitude of facts I mentally catalogued.

What bothered me with the milage issue is that it was an average 17 percent drop. Then a member reciently mentioned that he had decent milage and lost it. He did the injectors etc with no improvement I think I remember.

My guess is now two possibilities. There is indaquate base fuel pressure at highway speeds. Cheap to repair and a little time consuming but doable by any member. Really just a good maintenance run of the fuel supply system.

The other possibility is bad delivery valves. Personally I would do the maintenance run on the fuel supply system if the engine does not catch when starting very quickly. Even then I still would do it if I had poor fuel millage.

A quick check of the operational fuel pressure in the base of the injection pump under loading on the highway. Should point out the need quite clearly. At this stage I do not think it possible to avoid using a gauge with a hose long enough to visualize. While driving. Plus a valve so you only turn it on for quick checking .

I Suspect on those low fuel millage cars you are going to find almost no fuel supply pressure present under load. They in most cases will have become marginal over time and neglect. I just do not own a diesel engine of a 123 type with any issues. All four are northern engines still in remarkable overall condition.

Although since the last issue posted that made me think. Over time I want to find out if static fuel pressure can be contained in this system between uses. I suspect that one 240d I have does it. Sit it for a long time. As the engine starts to rotate if lights off. That to me indicates the engine is getting a full blast of fuel from the injectors right away. It is not waiting for fuel pressure to develop to fully load the injection pump elements . At an adequate volume. This guess of mine I think may be the millage issue as I suspect I have exhausted all other possibilities in my mind over time.

As for the member long ago that posted he was never able to get more than 25 mllles per gallon on his 240d from new. I have decided there is no reason there could have not been an issue in his fuel system from new.

As for engine compression. Even when we get a slightly reduced amount indicated with a compression check. Under higher piston speeds when running this is perhaps partially corrected. The compression readings major effect will probably occur usually at idle and for starting purposes. Unless the readings are almost in the pits when taken.

Of course I might be wrong. Yet there is a strong possibility this is it. Several pages of details I have gleamed over the years. If I posted them. Tend to indicate what I suspect in this case. Is at least a fairly strong possibility. There is no reason not to apply this to the five cylinder engines as well.

There are several reasons the millage drop on them may not be as pronounced.

People like explanations as well as I do. Logically on slower and uneven filling of elements. The engines timing is retarded. Because the lift pump only reloads every two crank turns. What little pressure or volume available to the sequential elements may taper off. This changes the power balance of the engine. I have never verified it but the first cylinders injection pump element is most likely the first one served after the lift pump recharge. This became the basis of the first rod bearing on the 240ds engines wearing out faster than the others. It sees a little better fuel timing and also gets a little more fuel injected. I never bothered to prove it.

I just mentioned to make certain fuel pressure is at least normal. It also takes a long time for low fuel pressure to take a toll on that first rod bearing in my opinion. If a new acquisition where found to have really substandard fuel pressure. I would plastigauge the first rod bearing. If it was near the allowable new limit or past a small amount the crank should not be damaged. A Replacement set of bearing shells should be a reasonable choice. If you let it go until a knock is detected the crank will probably have some damage. As you are through the babbitt facing on the steel backing. So you are then steel on steel. Nothing that has transpired in all the years since I believed this was a possibility. To change my mind. All the 616 and 617 engines in general. If they have a rod failure it will be the number one on the 616 and the number one on the 617s. Just not as frequently on the 5 cylinder engines. Also there have been the infrequent failures of the number two bearing . On the 617s. There is no way to really prove if a slugged up crank oiling passage might be a contributor as well.

Good replacement engines for these cars are leaving the dime a dozen catagory. So some preventative maintenance is even more reasonable as time moves along.

As I was typing this the phone rang. It was one of our insurance companies. Our yearly house and minimal coverage on the cottage premium has gone from 2500.00 to 3000.00. In rounded off numbers. I imagine it is partial retribution for the break and enter claim we got paid for last year. We all need various insurances. I can just not warn up to the companies that provide them.

Wow ~ that's an obvious problem, glad it worked out well for you .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Thanks for the update. My OFV ball does not seem to have any air incursion issues, but it was pretty crusty. I'll get a replacement, perhaps it will help smooth out my idle a little.

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Milan Brown 1979 240D, rebuilt OM617.952 turbo diesel, rebuilt 722.315 transmission (my only daily driver)

Instagram: @maximed93

Ever find air in your return line, first thing in the morning?

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1981 240D 4sp manual. Ivory White.

I have not checked after I swapped the IP. I'll take a look tomorrow morning.

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Milan Brown 1979 240D, rebuilt OM617.952 turbo diesel, rebuilt 722.315 transmission (my only daily driver)

Instagram: @maximed93