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Car Forum / Mercedes-Benz Cars / November 2008300D Hard Starting
What started out as a minor annoyance, i.e. slow starting, has now become a problem of very difficult starting. Part of the problem with this 300D is that the manual throttle has been disconnected and I have not had the opportunity to restore it. However, suddenly, I need a fully-charged battery and have to go to half-throttle to start, and even then, sometimes the start fails before the starter engagement limit occurs. Upon these cold starts, there is a profusion of smoke, which clears as the engine smooths out after start. In the worst of the cases when the start fails, there is white smoke in profusion during the latter time of the start attempt. This phenomenon never occurs on a warm engine, as the engine starts rapidly, on the first turn at any temp but dead cold. Am suspecting injectors (glow plug light is normal) but don't want to troubleshoot by replacing parts. Thanks in advance for the ensuing advice. Good observations on your part. You should specify year. GLOWPLUGS!, GLOWPLUGS!, GLOWPLUGS! If the glowplugs do not function, you will get hard starts when the engine is cold. If it starts at all. There is a great detail of how to check individual glowplugs in this discussion group, you will have to go back through old discussions to find the thread. The year of make also determines which type of glowplug will most likely be on your engine. You will need a electrical meter (can get a usable one for about 20 US - and you can use it in the home also). When was last replacement of fuel pre-filter?? I replace mine about every six months (4 bucks and change at advance auto parts). When was last main fuel filter change?? I do mine in the fall once a year. If you replace fuel filters, remember to use the primer pump to purge air from the system. Best of luck!! Bob > Good observations on your part. You should specify year. > [quoted text clipped - 17 lines] > Best of luck!! > Bob Bob: Thanks very much. Fuel filters are all fresh. I have always been given to understand that in this model (W123 300D), if the glow plug light comes on, then the plugs are functioning. That is to say, if one goes out, the light does not light. There is always the chance that I may be wrong about that. On Nov 25, 1:29 pm, "randallbr...@mac.com" <randallbr...@gmail.com> wrote: > > Good observations on your part. You should specify year. > [quoted text clipped - 27 lines] > does not light. There is always the chance that I may be wrong about > that. Sorry: 1979 W123 300D On Nov 25, 1:29 pm, "randallbr...@mac.com" <randallbr...@gmail.com> wrote: > > Good observations on your part. You should specify year. > [quoted text clipped - 27 lines] > does not light. There is always the chance that I may be wrong about > that. One more aspect to the inquiry: Given the particular circumstances, would it be better to change glowplugs or fuel injectors (or both). There seems to me no reason to suspect injectors, as there is no problem with running, power or other symptoms. Just like Bob said. Glow plugs! However, you need to do diagnostic first. For 1979, you have those huge resistor between the glow plugs... if not, it has been updated to the later version. As for glow plug light on if all glow plug is okay or not depends on if it is updated or not.It doesn't matter which one, you need to use a multimeter to determine which one is burned out. They all should be around 0.5 ohm. Another matter for your car is valve adjustment... when is the last time you had teh valve adjusted? It needs to be done once a year. If not, hard starting. Injector is the last thing that would cause problem on your car. Newer injector will give you more power and less smoke but if your valve is not adjusted, then make no difference. > Just like Bob said. Glow plugs! However, you need to do diagnostic first. > For 1979, you have those huge resistor between the glow plugs... if not, it [quoted text clipped - 11 lines] > injector will give you more power and less smoke but if your valve is not > adjusted, then make no difference. Tiger, very succinct and helpful as usual. My glowplugs are the type with the small end-nut, which I believe are the "later" version for that year. The car was manufactured late in the year, so it seems to follow. I understand that the "earlier" version plugs for that year have much larger nuts on the wire ends. At any rate, I will install new glow plugs and see if that does the trick. I agree that the injectors are probably not at fault, as there is no other symptomatic indication of a problem with them. I am mystified by the whole issue of when, if ever, the glowplug light quits glowing if one or more glowplugs fail. Thanks again! > Just like Bob said. Glow plugs! However, you need to do diagnostic first. > For 1979, you have those huge resistor between the glow plugs... if not, it [quoted text clipped - 11 lines] > injector will give you more power and less smoke but if your valve is not > adjusted, then make no difference. And in answer to your question about the valve adjustment, that was done professionally this year, less than 2,000 miles ago. randallbrink@mac.com ha scritto: > What started out as a minor annoyance, i.e. slow starting, has now > become a problem of very difficult starting. Part of the problem with [quoted text clipped - 17 lines] > Thanks in advance for the ensuing advice. > Mmm... no, not injectors. Glow plug system. Which is made of several different devices, to be carefully checked. I.e.: glow plug time-delay relay, fuse (an 80 A fuse!!! be extremely careful with it!) and the glow plugs. I don't know the engine model details but it was quite common to parallel the glow plugs. So, a single glow plug running makes the glow plug light work correctly, but with a single cylinder it's hard to start an engine! As already mentioned by other ng-ers you need an electric resistance and voltage tester to check all these devices. And someone to help you, switching glow plugs on, while you measure voltages and resistance. On Nov 26, 12:14 am, Cordy <stefano.corderaNONMIpiaceloS...@tiscali.it.invalid> wrote: > randallbr...@mac.com ha scritto: > [quoted text clipped - 29 lines] > voltage tester to check all these devices. And someone to help you, > switching glow plugs on, while you measure voltages and resistance. Thanks very much. I have taken the initiative to remove and replace all of the glowplugs, as I do not have a great deal of time for diagnostics and dissecting the individual components of the system. I hope that the new plugs will solve the problem. |
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