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#31
05-06-2020, 07:42 PM
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Quote:
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__________________
1981 240D 4sp manual. Ivory White. 
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#33
05-06-2020, 10:55 PM
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Copy that.
Seems like it would also have to be lift pump valves as well? Or do those spring valves rely on the integrity of the OFV? I’ve replaced the delivery valves and the springs in my IP. Those are some heavy duty springs and apply (and resist) real pressure. The springs governing the valves in the lift pump were flimsy in comparison. The spring in the OFV was more robust but only marginally.
__________________
1981 240D 4sp manual. Ivory White.
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#34
05-07-2020, 12:19 AM
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The lift pump valves are not tight seal valves,do leak off after a number of minutes,and are low pressure.
OFV, low pressure,keeps pressure in lower part of injection pump so delivery valves may be filled while engine is running. Too low of pressure engine performance will be noticed. Some leak back at fuel return will not effect starting or running. Pressure valve,keeps high press fuel,in hard lines,any leakage in this system will cause starting or running problems or both. All problems can be found.
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#35
05-09-2020, 07:37 PM
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Update:
Went to the junkyard and found a serviceable OFV to swap out. Took my greazzer spring from the old body and swapped it into the new. I also went through and replaced all copper crush washers with the original aluminum. No change. I think the rough, nailing start was actually the result of a loose glow plug fuse. So as of now, no running issues, no real startup issues... in fact, this issue of mine doesn’t seem to affect anything. It’s just that it’s not normal —unless anyone reading can confirm it is. Either most people don’t notice these sorts of things, their clear lines are old and opaque, and this is normal or I’m missing something really obvious or truly exotic. I’m not sure what else to try.
__________________
1981 240D 4sp manual. Ivory White.
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#36
05-09-2020, 09:57 PM
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Those Damn Air Bubbles
I'll try to remember to look under the hood, it may be a day or three before I'm near my Mercedes though .
If it starts easily and runs fine I'd think this is a non issue .
__________________
-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
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#37
05-10-2020, 01:13 AM
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Quote:
The fuel feed line from the lift pump to the fuel filter head is semi-opaque, so you may not notice air in that line. You may have an air incursion from the primer pump or the lines leading to the lift pump. I replace the rubber fuel lines fore and aft of the primary clear filter when it is changed. The short fuel line from the primary fuel filter to the lift pump tends to leak if re-used. It is subject quicker deterioration at it is exposed to higher heat levels than the fuel hose connecting the primary fuel filter to the feed line from the tank. It looks like you have the "02" fuel filter head. Maybe the 2 o-rings (2.5mm X 14mm top, 2mm X 10mm bottom) on the large central hollow bolt are not sealing well? I can send some brown FKM o-rings your way, just send me a PM.
__________________
78 W116 300SD 'Desert Rose' new as of 01/26/2014 79 W116 300SD 'Stormcloud' RIP 04/11/2022
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#38
05-10-2020, 02:13 PM
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This appears to be some sort of suction based leak back and terminates at a fixed quantity. My guess is when pressure forces have reached some kind of equilibrium. If I had a graduated cylinder to use as a temporary tank, I'm betting that's where I'd find the missing ml of fuel (20ml if I had to guess).
__________________
1981 240D 4sp manual. Ivory White.
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#39
05-12-2020, 06:36 PM
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Fuel Pipe Bubbles
O.K. Shern ;
I drove the car ('82 240D) to get my mail yesterday and popped the hood when I got home, the engine idling and fully warmed up . The clear plastic pipe from the back of the IP to the filter head had two pea sized round air bubbles in it that jumped back and forth . I revved the engine and they both marched forward and disappeared into the filter head, when I allowed the engine to return to idle, one slowly bobbled back out where I could see it . No bubbles anywhere else in these pipes, I replaced them all a year or so ago . I think you're chasing rainbows here , I hope this is helpful .
__________________
-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
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#40
05-13-2020, 03:14 AM
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Nate – I appreciate it but that wasn’t the scenario at all. If you’re going to check, please do so after your car has been *turned off* for several hours, not when it’s idling. I don’t have any issues when the car is running. Again, only after it’s been switched off for several hours Will you determine whether you were getting any air in the return line.
__________________
1981 240D 4sp manual. Ivory White.
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#41
05-13-2020, 11:50 AM
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Okay, will do .
__________________
-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
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#42
05-13-2020, 03:13 PM
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Just for some added complication and another datapoint, I found my 617 style OFV with the Greazzer spring today while digging through a box of stuff looking for something else. For giggles, I sucked on the IP side of the bolt and was able to suck air through it. Perhaps they don't seal as well as we're thinking.
With that being said, perhaps the cigar hose is the important key here. Maybe what's going on is that there is an air bubble that forms in the cigar hose due to decreased velocity of return flow, then when the engine shuts off, it seeks an equilibrium in the fuel system. If the fuel can very slowly leak back through the OFV bolt, that is definitely possible. If that's the case, and if someone else with clear lines can comment on their own car, it could potentially prove that it's completely a non-issue. That said, I'd expect the air to be bled out after a period of time just from absorption of the fuel flowing past it. Even the bubble in the prefilter eventually reduces to almost nothing after enough runtime.
__________________
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!)
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#43
05-14-2020, 11:08 AM
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I did that too with the two OFVs I had on hand.
Re: equilibrium, I think you're right. Just odd that no one else has noticed this (if it's common place). I put a series of markers on the hose and it always ends up around the same mark. And here's another fun data point I haven't fully explained: the lowest point in the drop can be observed first thing in the morning. However, by noon, on particularly warm days, the level may have moved up an inch. This points to expansion during the heat of the day, or running temp, and contraction during parking/night -but where exactly? The tank? The lines? I imagine in some place that doesn't or can't vent.
__________________
1981 240D 4sp manual. Ivory White.
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#44
05-23-2020, 05:52 PM
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A Tiny Bubble Picture
O.K. Shern ;
You've been *very* patient, here's a picture of my 1982 240D's tiny fuel bubble at rest : It's barely visible, right where the clear plastic tube connects to the brass fitting . There's some glare there, the bubble in smaller than a chickpea . I hope this helps allay your concerns .
__________________
-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
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