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Car Forum / Mercedes-Benz Cars / May 2005Hard Starting 300D diesel
My newly purchased '77 300D seems to be harder to start when it's warm than when it's cold. The glow plug light will go off after about two seconds but I have to crank at least 8 seconds before it catches when it's warm. It starts much faster when it cold. Sometimes there is a puff of smoke when it first starts but it doesn't smoke after that. Valves are adjusted, fuel filters replaced. It was suggested to me that I run a can of injector cleaner through it and consider replacing the injectors. Any other ideas? Sounds like something is wtong with your glow plug system. > Sounds like something is wtong with your glow plug system. Why would glow plugs be a problem in warm starting? Do they even turn on when the engine is warm? cp >> Sounds like something is wtong with your glow plug system. > > Why would glow plugs be a problem in warm starting? Do they even turn on when the engine is warm? > > cp First of all, yeah, the glow plugs do need to heat up to (oddly enough) a glowing temperature even if it's just a few seconds after the engine has been cut off. They are the ignition source. At idle, let's say 1000 rpm (because the math is easier), each glowplug is heated about 500 times per minute by combustion. As soon as you shut the engine down, they go from glowing hot to engine block temperature very quickly. What I don't know, is when in the starting sequence the glow plugs are no longer powered. Anyone? I _think_ the glowplug light turns off when the system thinks the plugs are hot enough, but they get power longer - till the starter is kicked? Try this simple experiment - turn on the ignition to run position - then as soon as the glow plug light turns off, quickly turn off the ignition, then back on again and try to start the engine when the light goes off the second time. If that helps, the glowplug temperature circuitry may be gimpy. Or the temp sensor. The fact that your car starts well when cold bodes well for you. Sounds like the engine, pump and injectors are working, and you just have a sensor or control issue. Good luck, Conrad try the easy way turn on the dome light in the car. turn the key to the glow position and see if the dome light dims a bit. if it does WAIT till the GLOW LIGHT turns off. STILL WAIT. it SHOULD brighten up after aprox 30 secs. then try to start. it may start better it may not. you may need GLOW PLUGS or a relay box. do the plugs first. 4 out of 5 of them are not to bad o get out. if it is a 5 banger. some one here knows the size bit to stick in the plug hole to knock the carbon out. one thing i forgot to do my self. the case, minus a few cans! Since the engine fires quickly when it's cold speaks well for its compression and glow plugs. Given the description I'd suggest the shutdown device (bellows) isn't quickly releasing the fuel rack from its OFF position as the key is turned from OFF to ON and then to START. The shut down device is a small bellows that eventually wears out usually allowing the engine to trail off rather than a quick stop and then a slower start as the bellows is oil logged. I believe the key clue is whether the engine stops quickly or if it trails off to a stop. The device is in the aft end of the injection pump; it has a vacuum line attached to it. As a test, when the engine is hot, shut it down and remove the vacuum line, then start the engine to determine if it starts as quickly as it should. (You will then have to shut down the engine using the STOP lever.) The delay in starting and stopping will increase if the shut down device is bad. Eventually the engine won't stop when the key is turned to OFF - then you'll know it's time to fix it. > My newly purchased '77 300D seems to be harder to start when it's warm > than when it's cold. The glow plug light will go off after about two [quoted text clipped - 4 lines] > that I run a can of injector cleaner through it and consider replacing > the injectors. Any other ideas? what do you mean by warm? Do you mean it's a warm day? or the engine was just running? >> My newly purchased '77 300D seems to be harder to start when it's warm >> than when it's cold. The glow plug light will go off after about two [quoted text clipped - 7 lines] >what do you mean by warm? Do you mean it's a warm day? or the engine >was just running? Sorry. Warm as in- "the engine is up to normal operating temperature." Cold as in- "the engine is at ambient temperature, which these days is anywhere from about 30 degrees F to 50 degrees F" >My newly purchased '77 300D seems to be harder to start when it's warm >than when it's cold. The glow plug light will go off after about two [quoted text clipped - 5 lines] >that I run a can of injector cleaner through it and consider replacing >the injectors. Any other ideas? I upgraded the glo plugs to the new pencil type, along with a new relay, which was apparently intermittent. Starts wonderfully now. >>My newly purchased '77 300D seems to be harder to start when it's warm >>than when it's cold. The glow plug light will go off after about two [quoted text clipped - 8 lines] > I upgraded the glo plugs to the new pencil type, along with a new > relay, which was apparently intermittent. Starts wonderfully now. same here, the new pencil type works great. Fairly easy to install too. J. > >>My newly purchased '77 300D seems to be harder to start when it's warm > >>than when it's cold. The glow plug light will go off after about two [quoted text clipped - 14 lines] > > J. Is that the style with the wire loop on the end? |
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