Anybody have experience with really old Diesels?

-
MopaR&D

MopaR&D

Nerd Member
Joined
Jan 4, 2008
Messages
5,534
Reaction score
2,837
Location
Augusta, GA
My friend's parents want me to get their old early-'50's Mercedes-Benz running and I want to know where to start. It has the 1.7L 4-cyl. Diesel (rated at a whopping 40 HP!) that I believe hasn't ran for at least a year. I was thinking of cleaning the injectors and changing the vital fluids, as I would assume it has mechanical injection and the electrical system is operational (owner cranked it the other day but it didn't fire). Is there anything else I should take into consideration? BTW my friend's dad has a repro factory service manual (in English of course) for me to use.
 
I would look at preheating the intake tract, to help speed up the process. A heat gun, on metal intake, would help raise the temperature. I would also look at a new battery, or good battery with charger or jumper system, so it cranks over as fast as possible, to help it kick. A LITTLE ether can also help.
 
ethers not good for a deisel. I,d try wd40 as it has lubrication qualities as well. It works great for priming deisels without breaking the injectors.Just spray it in the intake tract while cranking. A deisel can run off it.
 
I've owned several diesel land rovers and those direct injection pump engines are simple. Prime the system and make sure you have fuel and no air or water in the lines. Check your glow plugs are heating up and you should be good to go. 99% of the time with those old diesels the fuel filter if full of crud and water. Remember, diesel fuel floats on water so if its been sitting you may not be pulling the best fuel out of the tank. In tug boats they force water into the fuel tanks and the pick up is on the top of the tank. That way they always have a full tank to keep the ballast centered. I'd look at your fuel first.

Dave

Dave
 
You said he cranked it but it wouldn't start, did he leave the ignition on to warm up the plugs before cranking it? I would assume he did, but had to ask.
 
I think he did, as it is a pretty user-intensive car (compared to, say, the Chrysler cars of the time) and he has driven it a couple times. I'm going over there in about a half-hour, so I'll try all those things. Should be fun!
 
Well, we got it running! It just needs a thorough tune-up (oil+filter, coolant flush, air filter conversion, injection timing) and cleaning (injectors, etc.). I'm now wondering if there are any ways to increase the power of this engine, as it seems like it might be able to handle more. It is unbelievable slow; so slow that I think it would be dangerous to drive on modern streets (a factory-rated output of 40 bhp and a curb weight of 2800 lbs!). I was at first thinking about a turbo, but that might get too involved and I don't want to compromise the engine's durablility (the engine isn't supposed to go over 3200 RPM!!!). I tried reading in the service manual about how to crank up the injection pump but I think I need to take apart the pump to get a good understanding of it.

Something I don't understand is that the injection pump has some sort of weird vacuum regulator thing (along with a throttle(?) valve at the opening of the intake manifold). Can this be modified somehow to increase performance?
 
I'd leave it alone as the car will run forever as long as the filters are clean. Most likely the pump cannot be turned up much, if at all. You'll have to find a old mercedes guy to give you any clues to any other benefits you could get out of playin with it. That thing is a tank and can take a lifetime of driving and abuse, as long as you keep up with the filters. My dad drove one thru some of the jungles of Vietnam to get back to camp before curfew.
 
Old Merc diesels are great engines,they were also used as an industrial engine,very durable,built to last forever but not for h.p. I think the same as dartwagon just leave it alone,probably couldn't get much more out of it anyhow.I had the experiance of working on 4 and 2 cylinder mercedes motors in some old TK reefer units. If diesels sit for a long time and compression is low due to dry rings daredevils idea of wd-40 works great, provides sealing and lube for rings and is combustable to help starting, ether can ignite from glow plugs and break rings from the explosion.
 
Jeez, I guess he used that 4:1 granny gear a lot because my friend's can hardly get up a slight grade in 2nd gear. Who knows though, maybe it won't be too bad after a tune-up.

I figured I'd probably have to consult someone experienced with these cars. I'll have to read up on diesel engines too, because I just know the bare basics about how they work.

edit: So I probably couldn't get it to go at least 70 mph? I think it might be possible if I figure out exactly how the governor works. It's supposed to cut off fuel delivery above ~3200 RPM.
 
You must log in or register to reply here.
-

Back
Top