Folks-

I just bought a 93 300D 2.5L turbo a couple days ago. It has 74K miles and seems in good shape. I have a couple questions.

1) The plan is to run some biodiesel in this. I have read that earlier than 1994, the fuel lines might be a problem. This is a 93 - seems simple I guess, I am in for it. But - The previous owner said he has run B20 and B100 (both available locally) and I have no reason to not believe him. However, he said he hasn't had any problems with fuel lines. The fuel lines are hard and not spongy or weeping in my assessment. Question - for this car should I worry about these lines with B100?

2) Also I am freaking out over the discussions where B100 and ULSD switching is causing o-ring problems int he IP's due to their different swelling properties. All of the above concerns around the B100 and ULSD are really raining on my parade. What can I do about this seems like a catch-22. I can't rely on biodiesel all the time since it is only available in special locations and do want to run it as much as possible but need to run 100% ULSD at times I am sure.

3) If I need to replace the fuel lines, does anyone have pictures for this year and model that I can view? I think I see the tank outlet line on the right side just in front of the drive axle. If my understanding is correc this is also where my screen is located? Where does the return enter the tank? There is another line on the left side just in front of the axle that I assume is the return but it has something else next to it hanging down about 3-4 inches and feels linke a rubber end on it (like a stub line or something). Again, picts would be awesome if someone has some.

4) When I switch over to B100 which filter needs to be replaced several times typically. The plastic primary or the spin on secondary (or both?).

5) Lastly, I am uncertain about the transmission shifting in this car. It is solid (no slipping) but it seems to be very noticeable when it shifts at the lower gears. No clunking or banging but from 1-2 shifting when I am accelerating at a firm pace it sets me back in my seat. I am not sure if this is typical for this model or if I am in for a problem. The other shifts are smoother but also can be firm when I am standing on it more than normal. I can live with this if it is normal but would like to hear what other experience to determine that. The motor seems to have a slow take off from a stop but alot of power on the freeway for passing. Is this just a turbo or diesel thing?

This is obviously my first diesel car and I am excited but also completely intimidated the more I read. Thanks much for your help

The thing to be aware of when running Biodiesel is that eventually you will have weeping return lines. They are easy to change and I wouldnt worry about it until it happens. I have run Bio in various percentages up to B100 in my 85 300D for 4 years now with only 1 3" piece of line needing replacement. I have only needed to change the fuel filters once. just carry a spare prefilter and spin on in the trunk in case.

The 124 chassis diesels start in second gear which makes them slugish. if you need to stomp on it to beat a ricer manually put the selector into low gear and it will start in first. you will find it to have decent pickup then.

As for the fuel issues, ever single time they change the fuel in this country you hear all kinds of "sky is falling" type scenarios. I dont pay it too much attention.
Remember when they took the lead out?

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1959 Gravely LI, 1963 Gravely L8, 1973 Gravely C12
1982 380SL
1978 450 SEL 6.9 euro restoration at 63% and climbing
1987 300 D
2005 CDI European Delivery
2006 CDI Handed down to daughter
2007 GL CDI. Wifes

Mine doesn't. I haven't seen a 124 Diesel that starts in second. Nor a 126 nor a 140.

The 2.5 does 0-60mph in 12 or 13 seconds and power should build linearly. Put it this way, MB wouldn't have been able to sell it as a $40-45K new car if it had those driving peculiarities.

Clean the hose that runs between between the intake manifold and the device atop the injection pump (ALDA). The hose might go through a switchover valve or branch to a MAP sensor. Clean everything in the circuit.

Boost is controlled by the ECU. You can easily bypass the ECU by providing full vacuum signal to the wastegate (de)actuator and compare performance with full ECU control. Note that the engine is unprotected from too much boost when you bypass the ECU so be judicious. Not much you can do if you determine that the ECU is holding back boost... other than junk the vacuum (de)actuator for a proper boost actuator.

Oh, the turbo might have an ARV circuit. If so, do a search on the system and check that the ARV isn't leaking boost.

Sixto
87 300D

Hi. Any chance of explaining this a little more clearly (any reference to images to ID those parts mentioned (ECU/MAP/ALDA)) Thanks.

My transmission has been progressively lurching especially lower gears. I can rarely get it into 1st on kick down or in "L". Going down grade in L, it'll lurch into 1st after about 1/2 a mile.

Not sure what my engine is/was, but there's a label under hood that says "Retrofitted to R-134a" 3/7/01

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97 RAM2500 Cummins affair. Big longass lifted biodiesel thing. Too big. Too spendy - got rid of it. Sure could pull some weight though.

I've read those 300D with the 2.5 in the early 90's start in first. most Mercs start in 2rd I think. so the 2.5 drives a lot quicker off the line

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1987 300TDT
1981 VW MKI Caddy 1.6 diesel, waiting on engine swap
1983 D-50 Power Ram 4x4 "Mitsubishi" 2.3 turbo diesel
assorted gas powered crap and motorcycles

RIP: 1984 300TDT, 1982 300TDT, 1984 190D 2.2, 1992 300D 2.5, 1987 300TDT, 1982 Maxima LD28, 1983 Maxima LD28, Isuzu C223 P'ups X3, 1983 Holiday Rambler 6.2 Banks turbo diesel, 1984 Winnebago LeSharo 2.1 TD, 1985 Allegro 6.5

ECU = engine control unit, generic term. I think in this case MB calls it EDS for electronic Diesel system.

ALDA = altitude/pressure air-fuel mixture compensation device

MAP = manifold absolute pressure, generic term

ARV = air recirculation valve. Some MB turbos have a valve that leaks pressurized air from the compressor outlet to the compressor inlet. IIRC it's to soften the onset of boost so it doesn't all come into play suddenly.

I'll see if I can find pics to share.

Sixto
87 300D

That means the R12 refrigerant in your AC system was replaced with R134a.

Sixto
87 300D

plutonian, if you're asking about your 82 wagon, it doesn't have EDS, ARV or a MAP sensor.

Sixto
87 300D

Thank you for all the info Sixto.

So I should just take a look at the hose between intake manifold and (device) atop injection pump? I'll take another look, clean it, see if that helps...
thanks

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97 RAM2500 Cummins affair. Big longass lifted biodiesel thing. Too big. Too spendy - got rid of it. Sure could pull some weight though.

In an 82 300TD the line from the intake manifold to the ALDA has no impact on how the transmission downshifts.

For the lurching, check that the cable from the throttle linkage to the transmission is properly adjusted (I don't know the adjustment procedure).

Also check that you have proper modulation of the vacuum signal through the device at the back of the IP. I don't have the chart but the vacuum available at the outlet should decrease as you crank in more throttle. You can test this with the engine not running. If there were a vacuum problem, though, a more obvious symptom would be shifts that are too firm or too soft, soft being an indecisive transition period from one gear to the next.

Sixto
87 300D

1) The plan is to run some biodiesel in this. I have read that earlier than 1994, the fuel lines might be a problem. This is a 93 - seems simple I guess, I am in for it. But - The previous owner said he has run B20 and B100 (both available locally) and I have no reason to not believe him. However, he said he hasn't had any problems with fuel lines. The fuel lines are hard and not spongy or weeping in my assessment. Question - for this car should I worry about these lines with B100?

This may eventually become a problem, but I have run B100 in my '83 for 11K miles and my fuel lines seem perfectly OK as far as I can tell. As for the filters, most of the problems occur early after you begin use of B100. The fuel cleans away all the petro gunk and it gets caught in the filters (primary and secondary). After one change, they should last a good while. Most bio burners (myself included) carry a set of spares with them just in case, but I have never had to do a roadside changeout.

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John Schroader
bio burnin' 83 300D, '83 300 SD, '79 240D
"I've never met a man who was good at making excuses who was good at anything else" Ben Franklin
"You cannot permanently help a man by doing for him what he could and should do for himself" Abraham Lincoln