Thanx fellas ! .

I'm still not happy but at least I'm not alone in this .

__________________
-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

I got 30 mpg flat on a highway drive when I drove my '76 W115 240d 4 speed manual home after purchasing it, with a partially seized caliper, worn injector nozzles, worn front wheel bearings with long expired grease and cheap, wrong sized tires etc.

I'll report back now that most of these issues have been addressed.

__________________
Why I will never do business with "DieselKraut" again

http://www.peachparts.com/shopforum/mercedes-benz-used-parts-sale-wanted/378935-why-i-will-never-do-business-dieselkraut-again.html

I eventually had to give up in attempting to find a specific issue on the millage issue between 240ds. I did not see the same issue on the five cylinder models.

Back then there was a gap where almost nobody was present in it. You either got 25mpg or less or you got 30 or more. This far more recent post shows some examples in the gap area now. These examples may be improved perhaps just with maintenance. As time moves along and we learn more about these engines. It could be worn delivery valves. Other than that one poster that said his 240d never could get more than 25mpg no matter what he did. From brand new. I always found concerning.

What I believe more than I doubt still. Is low fuel pressure to the injection pump creates heavier loading on the 616 engines number one rod bearing. It takes time for this to wear it excessively. Probably measured in years. How much do I believe this?

If I found the fuel pressure low on a 616 I purchased or owned. It is not that hard to plastigauge the first rod bearing. There were a lot of 616 engines that went to the junkyard with that issue.

Catch it early and the crank is probably not scored. They will run seeming okay with low fuel pressure. Yet will run enough stronger to feel it with good fuel pressure. The idle is also quieter and some members said they thought the engine was quieter on the highway as well.

How is this diagnosed and fixed? I suspect I may have low fuel pressure from my IP but have no way to be certain other than testing the IP timing (drip).

I've just had my injector nozzles and life pump rebuilt, so if this is an issue, the new injectors will likely make the cold starting issues I've faced (no start without slight throttle, smoke on startup) worse.

__________________
Why I will never do business with "DieselKraut" again

http://www.peachparts.com/shopforum/mercedes-benz-used-parts-sale-wanted/378935-why-i-will-never-do-business-dieselkraut-again.html

As Mercedes factory tuneup specifies. Check the fuel pressure in the base of the injection pump with a pressure gauge periodically.

Since you rebuilt the lift pump you might remove the spring in the overflow or relief valve on the injection pump and stretch it back to 27millimeters. If it has sagged with age. This overflow valve is actually the fuel pressure regulator in the system.

If you had not rebuilt the lift pump I would have suggested closing off the return line from the injection pump. If no difference was observed you have issues in the system.

The 240d cars are a favorite of mine. I know it is safe to have 19 pounds of fuel pressure. The only way you can really do this is with a cheap 0-30 pound liquid dampened pressure gauge from harbor freight and the fittings to use it for the test. Should still be under twenty dollars for it all.

Checking that pressure say every two years will catch things that are or will cause fuel supply issues down the road as well. It is fairly easy to tune it to 19 pounds pressure. All 240d owners will appreciate the slight power gain. Plus usually the quieter idle. The most important issue is you learn about the fuel supply system in the process.

Your start up issues are usually the knob on the dash that controls the initial idle of the engine may be in the wrong position. It can be other things as well but it would be wrong not to mention that.

Thanx Barry ;

I've purchased the relief valve spring from greazzer (SP) and installed into my OM617 and likely this '82 OM616 too but I had the I.P. rebuilt and assume they didn't keep that relief valve....

I'll have to did out my test gauge and see what's what .

I addition to a damped pressure gauge you'll need to add a restriction to the line or maybe a simple damper as I managed to kill several good quality American made liquid filled pressure gauges by driving with the test gauge connected ~ in every case the pulses were so strong they snapped the needle off after while .

Military surplus stores tend to have good quality gauges uber cheap, like $5 .

__________________
-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

I've seen you mention this a few times over the years.

I don't understand the point of checking the pressure every few years if the only variables are a.) lift pump health, b.) OFV spring length.

If someone -me for example- has rebuilt their lift pump and installed a new OFV spring, is there any other factor at all that would affect fuel pressure?

If so, what is it?

__________________
1981 240D 4sp manual. Ivory White.

So much armchair speculation in such a short amount of time! Rod bearing failures from low fuel rack pressures? Wow! Someone better get a hold of the Cummins and Caterpillar guys since their pumps use the exact same spring valve design and see if they're having rod bearing failures too! Flame me if you want, but with claims that low fuel pressure causes rod bearing failures, I want to see some damn data to back up that bold claim.

Seriously though, if it took 30+ years for the spring to fatigue, it's going to take that long to fatigue again. If you really think your car is going to make it to 70 years old as a daily driver and never ever want to worry about it again, swap out to the 60x "new" style banjo bolt. They rely on a drilled orifice, not a spring acting on a ball.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

It is probably too long of an explanation. Unless you want it. To describe why I felt the path of the first rod bearing failure led to the fuel pressure issue.

Historicaly years ago a poster asked my why the first rod bearing was the one that always failed on the 616. The problem had been ignored as the generally accepted reason was it was the last rod bearing. On the crank to see lubrication. The suspected reason did not come easy. I was satisfied enough to recommend not to run the 616 on substandard fuel pressure.

Ultimatly I thought of a test to prove it. Yet since there are other issues with running with sub standard fuel pressure. It was just common sense to rectify it anyways. So why do the test?

A gauge is only useful for testing. As the rapid high level spikes will fatigue the tube in the pressure gauge. I am not even certain if an accumulator would save the gauge. These spikes are violent and have some effect in the low fuel pressure situation. Simply because with low fuel pressure the relief valve is not open. So there is no attenuation of the spikes at all with the cigar hose. On a properly functioning system if the engine is running the relief valve is open.

I do not recommend running without the cigar hose either long term.

I always stated that I was never absolutely positive. So over the years I have always looked for anything that might be in conflict with what I thought. I have only found the occasional thing that further supports the ideal. Nothing that does not. To keep it ultra simple.

The first cylinder sees either more fuel or fuel a little earlier or both. When the fuel feed pressure to the elements is substandard. When these pumps are calibrated. It must be done at a certain constant fuel pressure. If you lower that pressure in service the calibration in practice will not be the same.

Remember the damage I suggest happens does not occur fast. It takes running for a long time with sub standard fuel pressure. I stayed away with recommending more than 19 pounds pressure without doing some serious testing. As many injection pump places where calibrating at this pressure in the later years. I also hoped it would slightly reduce the power balance of the first cylinder a small amount in comparison to the others. To equalize any existing wear a little over time. There is no easy way to measure some factor as small as that. So that remained just a hope. Almost a totally worthless one though at best.

I almost ordered one of those variable pressure relief valves once to run the test. A member was selling. It would have involved setting up a cluster of milli volt gauges.

I did buy five meters and a few other bits and pieces. To build the tester in the last year. I am almost certain that as you change the fuel pressure the milli volts will change in relation to each other. From all the cylinders. What I do not know is if it is safe to take the fuel pressure really high. It would depend on what the millli volts where indicating.

Again I have not bothered to prove it. I firmly suspect that on low fuel pressure the milli volts would indicate the number one cylinder is running hotter than any of the others. This higher percentage of loading over time wears the rod bearing faster than the others.

If you take a 240d with say three pounds operational fuel pressure. Up to say 19 pounds pressure. You will hear a real difference in the idle. That is because the power balance is better. In a way this is almost proof in itself but unproven by testing. You will also have slightly more power as well. Reports seem to indicate it also makes the engine a little quieter on the highways.

I am not quite sure how you would detect that on a 240d as your hearing is already somewhat impaired at high speed.

As for what can be messed up in the fuel system. Filters including the one in the fuel tank. The lift pump may be tired. The relief valve may be off calibration. Also remember in gauge testing. To close off the line from the relief valve. As another test. This gives you the terminal pressure the lift pump is capable of producing.

Mercedes recommends a fuel pressure check every thirty thousand miles in their service literature. In far too many cases it has never been checked. I would not want a dollar for all those 240ds that have had the fuel pressure checked in the last 100K miles. I do not think it would buy a tank of fuel. Although I believe without knowing. A working mechanic that is no longer on site is probably doing it. As he probably is still working on some 123s.

As for the future. There remains a possibility that with testing. Really elevated feed pressures may safely be engaged. The testing is required to make certain it is not at the cost of distorting the power balance. As this could reduce the expected lifespan of engines. This is one tough little engine if it is fed properly. As for the five cylinder 617 owners if a rod bearing fails it will usually be on the number one or two cylinders. It happens a lot less frequently than on the 616. There are reasons for this in my mind. Yet the cause may be the same basically.

You do understand that low fuel rack pressure leads to low fill rate of the pumping elements and thus a *LATE* injection timing as opposed to early right? There just aren't a lot of reports complaining of failed rod bearings on these engines. If your claims had any merit whatsoever, the same would apply to any other IDI diesel with a mechanical lift pump setup. A bearing failure is far more likely to be due to tolerance issues or lubrication starvation than injection timing. You're talking a couple of degrees here in timing issues, not several to tens of degrees as some of the tuners run without problems on the stock bottom ends.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

The heavy failures where occurring some years back. They were fairly frequent. It would take pages to describe just what may be going on with low fuel pressure.


A not too large variation over time is what is important. I got past the lubrication issue fairly easy. The n/a five cylinder is almost identical other than having an additional cylinder and another rod bearing. The front rod bearing is fed from the back of the crank. If it was lubrication we should have seen more failures on the five cylinder than the four. Where there where almost none in comparison.


I also assumed more five cylinders where sold than four. Also that basic four cylinder engine was in production long enough that Mercedes probably would have dealt with a poor lubrication issue. This also was not ever a real issue with any of their engine designs.


I have to be careful that I do not touch on things that some member. Might go off on a tangent that is damaging. So I just left it at the car is more reliable as well as runs at least a little better with some semblance of reasonable fuel pressure.


It is in general cheap and easy to keep the fuel supply system in good condition. Plus much easier to troubleshoot if you understand it. Because of the use of milli volts I can document the changes with fuel pressure. At least enough to tell if they are damaging or not.


. For my age I am buried in far too many non car projects. I would like some time to do testing of what are only possible suspicions.


I have two 240ds for testing. A 1979 with a recient Mercedes dealer later installed rebuilt engine at the time of acquisition. Plus a 1983 with about 200k on the original engine I suspect. Neither have accumulated many miles since purchase.


Things that interest me. We had an older member some years back running his 240d on thirty pounds fuel pressure. It was gauged. I really wanted to get into this area of how the power balance is doing with testing. He dropped off the site too early after his first impressions where posted. There may or may not be any issue with heavily increased fuel supply pressures. Testing though is the only way to be pretty certain. I purchased the five digital meters to make a tester. In the last year. To have a look if the time can be found.


.

Discrepency is best explained by some people are honest, others arent.

__________________
This post brought to you by Carl's Jr.

We may have got cheated anyways. I think these engines might have gotten better fuel milage on European fuel Quality. Over the years to the best of my knowledge we have never gotten millage reports from European users. Is all diesel fuel sold in north America about the same quality in all regions?

For example we had a gulf station a brand that is gone now up here. We got really poor fuel millage on the product they sold. Usually in this region all diesel fuel no mater the brand was coming out of the same refinery. All us guys that were driving diesels at the time experienced this. The best millage was on the fuel that the refiner sold at their own Irving stations. This was also the refinery that supplied the other brands in our region.

I thought of driving habits etc for the claimed difference. I also went looking for any identifiable difference. I never really found anything.

We had a lot of response at the time for samples. What really seemed odd at the time was this pronounced spread of about five miles per gallon. There was nobody in that area. Now I see there are a few.

Another thing was I forgot then to get all the various model years that people where reporting on. They did change the cam at one point and claimed a six? horsepower gain.

Fuel usage wise it appears overall the turbo 5 cylinders are decent. More power with almost no penalty fuel consumption wise versus the better examples of the 4 cylinder owners.

Plus it takes some effort to get really accurate fuel millage results.

Mercedes developed the father of the last 616s way back in the late 1930s. There were changes but overall the last 616 to me was much the same.

We never saw much interest with the American car companies building any car diesels. Fuel was really cheap back then in north America. It was five American gallons for a dollar in much of my early driving experience. Or fill the tank for 4-5.00. I remember driving back and forth to work all week for a couple of dollars.

Hindsight is great as well. The old IDI volkswagon diesels did get better fuel milage on really hot days. I noticed this consistently. I wonder if the 616 does the same? It was pathetically hot the time we came out of Cleveland one summer. It seemed to us the old 240D was doing well on fuel consumption. After we got home I took it back into America after a time. In much cooler weather .

Not really cold though. I felt it was not doing as well for fuel milage. Just a seat of the pants kind of thing though. Logically you should get a little better overall fuel millage on synthetic engine oil. Enough to justify the additional cost is the question though.

Thanks Barry - I've purchased a replacement spring from Greazer as well. So new Monark nozzles, filters, lift pump and spring all going into the car this week. Not sure what else is left to change from a wear n tear fuel standpoint?

Startup issue doesn't improve when the dash knob is turned to increased idle revs but it does prevent stalling. The car wouldn't start without a slight dab on the throttle (before the renewal of the above components) - hopefully, it will resolve itself now.

As an FYI, I'm based in the UK. So it is very likely I will exceed 30mpg US (last measured fuel economy despite worn bearings with hardened grease, seized caliper, peeing injectors etc.)

__________________
Why I will never do business with "DieselKraut" again

http://www.peachparts.com/shopforum/mercedes-benz-used-parts-sale-wanted/378935-why-i-will-never-do-business-dieselkraut-again.html

I've noticed that the average 240D driver over revs the engine on every shift, be it a stick shift or slushbox tranny .

My '82 had seriously low shift points when new, I hated how quickly it shifted out of first gear since I had the tranny rebuilt it up shafts far too late unless I feather the throttle to force it to up shift sooner .

I imagine my perceived low mileage is due some what to this .

__________________
-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