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Car Forum / Mercedes-Benz Cars / May 2005300SD needs a little gas to start
Hi, My 1984 300SD with 127k always needs a little gas to start it. I turn the key, wait for glowplugs in 40 degree weather (May in Michigan, lemme tell ya), press gas lightly, and it starts right up (with mandatory little cloud of grey smoke). It wants to idle at about 350-450 and almost chokes, but it sounds most healthy at 650-750 with a little gas. Valve adjustment time? Thanks a lot! Mia You might have an open glow plug or 2. Check the resistance of each one, they should all be below an ohm.  Signature73 Hank WD5JFR > Hi, > [quoted text clipped - 10 lines] > > Mia How can glow plugs be an issue with stalling when idling? Mia > How can glow plugs be an issue with stalling when idling? The glow plugs make thing go smoother until the engine warms up. So a rough idle when COLD can be caused by glow plugs. Marty T.G. , I'm wondering what, in your mind, is the perfect combination of microchip-controlled components and plain mechanical ones? Once when my Chevy just died, the reason wasn't the starter, or the battery, or the ignition. It was the $250 circuit board that regulated fuel distribution. Obviously, I wished for no chips in my car AT ALL. Now I don't have chips, and as you mentioned, the tranny on my Benz is not as smooth as tranny on my old 1991 Cavalier. There has to be a happy medium or computer chips that are more reliable and mechanical parts that fit snugger. Respectfully. Mia J. The mechanical, if well maintained, will outlast the electronic, IMHO. But, that said, the mechanical is frozen in time whereas the new, being electronic, progresses and is cheaper to make, but not to repair. So cars, like TVs and appliances will become obsolete more quickly and more absolutely and so go to the bone yard sooner than the old mechanical cars. Their complexity is software driven and software ties one to its author's plans so the manufacturers and dealers will determine their products useful lives more so than the buyers. In 1980 I paid about $28K for my then new 300SD. Since 1980 the consumer price index has risen 2.3X so that 300SD car should cost $65.7K today. But it lacks ABS, dual front, side or curtain airbags, ESP, Brake assist, Pre-Safe, dual climate control or a pretty good gas V-8 with an electronic 7 speed - all of which are in a new S430 that costs about $76K today. All those new features were added for about $10K! I paid about $3.5K for my first Mac 512K system and $1.5K for a vastly superior iMac. These old cars are just a breather from the relentlessness of progress and its costs. I enjoy my 300SD on that basis but buy new, disposable, cars too. Excellent statement!! I think price (to make) and flexibility/functionality are the major factors driving the manufacturers towards electronic control. How many experts/genius are there who can design/enhance a diesel injection pump? How many programmers can write code? There are many more programmers and they probably have much cheaper salary. I have seen a literature describing the optimized timing parameter in relation to engine temperature and rpm. I don't recall the car maker or the engine type. Based on the graph, I can't imagine any mechanical solution, at least not with any reasonable cost. Even an electronic solution will probably be based on a large parameter table instead of a few formula. Also, for manufacturers, it is much cheaper to correct mistakes by reloading programs than redesigning/replacing parts. I believe one day owners may not even need to go back to dealers to reload the programs, and may not even know it happens. However, as a owner (and a DIYer), I prefer mechanical cars. > The mechanical, if well maintained, will outlast the electronic, IMHO. > But, that said, the mechanical is frozen in time whereas the new, being [quoted text clipped - 4 lines] > author's plans so the manufacturers and dealers will determine their > products useful lives more so than the buyers. > The mechanical, if well maintained, will outlast the electronic, IMHO. This actually shouldn't be true, although it often is. Autos are a very hostile climate for electronics, and any electronics designers/vendors have done a poor job of building/ruggedizing this. As we go forward and these system become better, this should move in the direction of electronics being more durable and reliable then mechanical systems. My 2c (US) Marty PS I repair electronics/computers for a living and like to have cars that don't have any... > The glow plugs make thing go smoother until the engine warms up. So a rough idle when COLD can be caused by glow plugs. To get my 300D jalopy up and running smoothly (it getting valve adjustment and chain changed next week) I glow the plugs 4-5 times before actually starting the engine, at which it starts very smoothly and "quietly" with no "gas"; am I causing severe premature damage to the glow plugs by doing this? TIA cp >> The glow plugs make thing go smoother until the engine warms up. So >> a rough idle when COLD can be caused by glow plugs. [quoted text clipped - 7 lines] > TIA > cp Don't hesitate to put in a new vacuum pump when you replace your timing chain. A vac pump failure will negatively interfere with your new chain and ruin your day! > Don't hesitate to put in a new vacuum pump when you replace your timing > chain. > > A vac pump failure will negatively interfere with your new chain and ruin > your day! Glad it's already been replaced, shoulda replaced the chain too... I gots me a good (and cheap) Benz mechanic in Chiliwack BC who works out of a farm that looks as if its cashcrop is a field of old benzes:-) , if anyone in the BC lower mainland area needs a good mechanic email me. cp In my 25 year experience with this engine it doesn't start smoothly when cold, like a gas engine. There may be a marginal glow plug - they last about 100K miles - but remember, its a compression engine and until it runs for about 30 seconds it may have a few misfires. I don't touch the throttle until the engine fires, then I shift into gear and give it a bit of throttle to drive off. In very cold weather the engine should be glowed a couple of times. ON, glow, wait 10 seconds, OFF, ON, glow again wait ten seconds and START. M-B suggests flooring the accelerator, others say NO that, the additional fuel quenches the then hot glow plugs. I've never floored it. The shifts are sometimes a bit snappy, especially when the transmission is cold. Clean transmission fluid and a clean filter may help but "they all (occasionally) do that." Remember, we're all getting used to cars that have electronically controlled engines and transmissions that shift almost imperceptively (the gas engine's timing is briefly retarded to cut its power prior to an up shift); this c.1980 machinery simply can't achieve 2005 levels of smoothness and lack of noise and vibration. Likewise, the old steering boxes can't match the terseness of rack and pinion systems. That's why new cars are bought - they really are better - and cost a lot more! My brother has a car that does the same thing... It almost always starts better if the accelerator is pressed one time before starting. It has about 240k miles. My 1983, on the other hand will always start without pressing the accelerator first. It is a 1983 300D with 166k miles. I would check the glow plugs to see what condition they are in. Also do the valve adjustment if you haven't already. I had a 1982 300D as well with unknown mileage, and it started better if the accelerator was pumped before cranking unless the engine was close to operating temperature. When very cold (+13°F here) the 1983 started outside in the cold without being started for over two weeks, and without being plugged in. It had Delvac 1 oil in it at the time. I glowed it two times and when I started cranking, I held the accelerator to the floor and held the starter. It took about 20 seconds for it to start firing. The owner's manual suggest you can crank for about one minute (maybe even two, I don't remember). The key is to crank it until it starts firing and not interrupt the process. When you hear the engine start firing start easing off the accelerator slowly so the engine doesn't over-rev. > Hi, > [quoted text clipped - 10 lines] > > Mia |
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