I just bought a 1979 300cd for $500. The body is rust free and the interior is in very good shape, new battery and starter.

It starts right up but it idles very poorly; however, it drives well once moving.
It does have significant blowby (1 quart+) per tank of fuel.

The fuel filter is dirty.

So, I may have to replace the engine, but I want to try other things first.

I will replace the fuel filters, adjust the valves, and clean everything I can clean.

What else can I try before I resort to another motor?

Thanks, as always!

Don

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84-300D 256K
81-300SD 217K (Wife's)
79-300CD 212K - Project
89-Volvo 245 305K

If it's using 1qt of oil per tank, make sure it's not just leaking it out. Burning that much oil will usually produce noticeable blue smoke.

Try injection timing and a compression test too.

How do you know that oil is being lost through blow-by and not in some other way?

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

Always finding new things to learn on the Mercedes Forum. Today it is measuring "blow by" by the quart Really though, blow by and the amount of oil consumed don't go together. Blow by is a smokey vapor that should be routed back to the crankcase via the drain in the aircleaner. And we know that a low level of blow by is good, just as a low level of engine oil used is good.

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Junqueyardjim
Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis



1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!

A lot of oil is coming out of the crossover hose on the top of the manifold cover...it is a lot. It smokes a little at start up, but not that much.

Why would it leak that much there?

I really love the car, the paint job could be fresher, but it looks sharp.

Don

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84-300D 256K
81-300SD 217K (Wife's)
79-300CD 212K - Project
89-Volvo 245 305K

I bought my 240D about 4 1/2 years ago and it had a lot of blow-by. I've put about 50,000 miles on it and it still runs well, so if you're happy with the way it's driving now, then don't worry about rebuilding the engine anytime soon.
Your engine might have blow-by for different reasons than mine, but I dought that it's anything to panic about.

Otto

Otto,

I appreciate the information. What steps should I take to improve the poor idle?

Don

__________________
84-300D 256K
81-300SD 217K (Wife's)
79-300CD 212K - Project
89-Volvo 245 305K

Diesel purge (probably won't do anything, but it’s worth a shot), injection timing, rebuild injectors, or maybe just raise it using the idle screw. How many RPMs does it idle at now?

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

My car idles much better on biodiesel than it does on petro diesel. You can try the adjustments BGKAST mentioned and if those don't work, you should get a compression test done to see if you've got low compression in one of your cylinders.

If this engine was recently rebuilt then the rings might not be broken in yet.

__________________
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
George Carlin (Wonder where he is now..)

1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.

dazsa,

Run Castrol Syntech synthetic oil in it. It decreased oil usage in my 300SD from 3 quarts to 1 quart in 10,000 miles. Don't expect it to change overnight, it took 30,000 miles for the improvement above .

P E H

I am planning to change the oil anyway, so I will go to the synthetic. I haven't ever messed with injection timing or the injector rebuild, so I will have a learning curve there. I will search the forum for the procedures.

Oh, this is a non-turbo so I don't have a idle pin. Where is the idle adjust screw?

Thanks and I will post some pictures in the next few days.

Don

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84-300D 256K
81-300SD 217K (Wife's)
79-300CD 212K - Project
89-Volvo 245 305K

On my turbo engines it is between the injection pump and the block. It simply adjusts where the linkage stops when no pressure is on the pedal. Don't forget to loosen and tighten the lock nut.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

I replaced the oil filler cap and cleaned the crossover pipe. Most of the oil that is being lost is coming from the oil filler cap. I started it and stemmed the flow for about 8 minutes and then a small amount of oil started coming from one side of the oil cap.

After I stopped the car and took off the oil cap it smoked out of the motor...is that normal? It is about one quart low of oil.

Also, there is a thick electrical wire about 3 inches long with a loop electrical connector on that is loose and the other end is attached to engine block. It is located below the front glow plug. It looks like the loose end should be attached to that close glow plug. Could it be a ground strap? It is not on my 81 300SD or the 84 300D.

I will attack the injection timing pin tomorrow.

Any further info will be appreciated.

__________________
84-300D 256K
81-300SD 217K (Wife's)
79-300CD 212K - Project
89-Volvo 245 305K

dazda,

BTW Use 5-50 o 15-50 Syntech weight oil. THat will decrease some of the oil consumption. ALso, U won't have to change th oil for at least 10,000 miles since U will be adding quite a bit initially.

P E H