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W123 no start/ start puzzle- beyond archives
Hello, I searched the archives for a hint of an answer but I still am inquiring.
This morning was quite cold for San Francisco. 47 degree F. 1979 300D. After only cycling the glow plugs once, I turned the ignition on and the starter engaged normally and the engine turned for about 3 seconds, then it seemed like the starter disengaged without mechanical noises with what seemed like a disconnection of electricity as if due to a 'breaker' doing its job. The 'breaker' is an analogy, I know there is no fuse or breaker on the starter itself.(aside from the strip fuse for the glow plugs) tried again and same. No weird noises other than the sensation of a quick disconnect of electrical power. So later I moved the trans selector to neutral and allowed the glow plugs to cycle three times before starting. Started normally. Went for a short ride, parked. Restarted in Park with no problem. Temp outside was about 49 F. I am curious to know what caused the symptoms. Does the glow plug timer intervene when the glow plugs are not hot enough? Although I did not hear the glow plug timer 'click' as the starter 'lost the power source'. (normal sequence is to wait until glow plug light goes out and then turn ignition all the way) I don't suspect the neutral safety switch or solenoid because the symptoms don't add up. I have not tried cold starting it normally yet nor just in neutral. In the meantime this query. Here is a bullet list: 1) Did the engine turn over? -- yes for 3 seconds 2) Any clicking sound from the starter solenoid?-- NO, no starter grinding either. 3) Did you cycle thru the gear shift in all gears and end in park again? --later 4) Did you try to start in Neutral.-- later, coincidentally worked. 5) Did you check the battery terminals ?-- yes, new battery. Thanks for your insights.:) |
Suggestion: One or more of your shifter bushings is disintegrating, causing the shift lever to not always line up when in park... neutral has more play for how the shifter sits.
I had a 300sd where I had to always nudge the lever forward, in park, in order for it to start. When people asked, I told them it was a rare Mercedes anti-theft feature. |
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I am not entirly sure on your year of Car. But, on mine the Temp sensor controls how long the Glow Plug Light remains lit when the Key is in the Pre-glow Position but that light does not control how long the Glow Plugs stay on. If you keep the Key in the Pre-glow positon even after the GP Light goes out your Glow Plugs remain on until the Timer in the Relay shuts them off. On mine the Total length of them till the Timer shuts off is about 30 seconds. If you want you can cycle the Key again and start over for another 30 seconds. When My Starter Motor is cranking the Glow Plugs are also turned. The reason for that is the Glow Plugs heat the Air in the Precombustion Chamber hotter than the compression of the Engine heats the Air; especially in the cold. |
Thanks for your insights.
Its a 1979 300D auto trans. I had the shift lever bushings replaced about 6 months ago, so they are all sound. Also sound below on the shift linkages. I will see how it behaves tomorrow during a cold start. And report back in case further insight is needed. Its just that the symptom experienced did not match the bad neutral safety switch syndromes posted in the archived threads. |
Is the NSS adjustable? Maybe it needs to be reset to the middle of the range. On a 722.3 I enlist a spotter, put the transmission in reverse then set the NSS so it's in the middle or arc of the reverse lights coming on and going off.
Sixto 87 300D |
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I agree. Unless the shaking engine caused enough vibration along the shift rod to make a statement at the NSS. And the NSS itself is beginning to fail and interrupted the starter signal. The only other thing I could think of is that the ignition module is worn out and unless you keep a good torque on the key, you may lose contact. |
Can worn engine and tranny mounts shift the tranny relative to the shift lever?
Sixto 87 300D |
How new is the battery?
I had this same issue this morning, cranked for a few seconds....then everything went dead, including the lights.....took the battery in...they attempted to charge it....started boiling over.....got a new battery not an issue....battery was only a year old.... But then I got power but no starter noise.....the ignition wire in the screw, at the solenoid wiggled its way out.... Yes been one of those days... List.... Battery Battery cables Starter.....FYI California models of this year came with a low power starter due to warmer climate...since discontinued... Grounds...battery to chassis....chassis to transmission.... |
Whilst I agree with the comments about the NSS and bushings and ground connections (which should be removed cleaned and then lightly coated in grease) you might also want to consider feeling how warm the starter is getting.
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Update
Hello and thanks for the great insights.
I cold started this morning with ambient temp at 47 F. I cycled glow plugs four times and it started in park, with only a very quick metallic report like the starter gear snapping back off the flywheel. I let it idle for a while. Shut off and restarted in Park. No problems and no noise associated with starter. Established the fact that the back up lights work in Reverse selection. Came back hours later after driving my other car for tasks. Cycled four times, and in Park, again it stopped short of going through the starter cycle but this time the slight quick grind sound-report was apparent. So it did not start. Turned off ignition, Put it in neutral immediately and it started fine without noise or fuss. Turned off, immediately placed in park and it started without issues or noise. Noticed excessive black carbon splatter on ground under rear exhaust pipe. (fairly recently had the valves adjusted) I need to get under this car next week and inspect the neutral safety switch connections and general starter visuals. Its trying to tell me something, I just need to narrow it down. battery is fine. New Interstate battery. When it starts, it starts smoothly and fairly fast. Could be the cold causing a sticky starter or something, but I have not experienced this before in cold ambient temps. (not often encountered). So, next week I hope to get under and inspect.:) |
35° degrees here....one glow cycle and she popped right off...
You should not have to glow four times to get it to start at 47, at 47 I don't even let my glows, glow the completely cycle and trust me my engine isn't in the best of heath....about a half quarter oil burnt per 300miles.... What the car is telling you, it needs a new starter....now.....its possible the worm gear on the starter is worn not engaging with the fly wheel or you may have a bad fly wheel let's hope not... The only thing visually you will tell by looking at the starter, is it is a filthy grease mess.... A bad started will kill a good battery....mine killed three! List of things to do.....again.... Replace starter.... Upgrade battery cables..... Have battery tested....its free.... Upgrade glows.... Nss should be fine....but when mine went, it keep my back up light on....regardless of shifter location.....I was curious why people were staying so far behind me.....it is very very cheap and easy to replace.... |
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When were the valves last adjusted? Is the starter turning over fast? |
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However, it could be lined up correctly and inside the Switch could be worn or the contact area buggered up from use. I have never seen a Thread or Post where someone had taken apart a bad Neutral Safety Switch to see why it failed. Maybe someone will do that ans post some pictures. |
I don't know if the erarlier models have the Neutral Safety Swich Connector inside of the Car in the same Place. But, if you use the Connector to bypass the Neutral Safety Switch and is starts all the time with the Switch bypassed you have found your problem.
Some pics in the thread: http://www.peachparts.com/shopforum/diesel-discussion/333784-neutral-safety-switch-troubleshooting-84-300d.html |
Tentatively normal
Hello and thanks for the additional insights!
Update, Yesterday I began a methodical observation routine. Checked the oil. Needed one quart (10-40 Delvo). I started the car up in the morning (approx 42F) in Neutral after cycling the glow plugs three times. The start up was crisp and fast (2-3 seconds). Propped one side of the car on a curb and checked the underside. All was clean, starter clean, wire connections looked clean and sound, NSS looked clean and nothing seemed loose or movable by hand probes. Wire harness was clean and snug and sound. Battery cables tight and clean as were the wires. I took a 30 minute drive and up some highway grades. Lots of carbon soot flushed out the exhaust pipe ! Two hours later after car sat in garage, the hood was still warm, I started it while in Park. I did not cycle the plugs. After 5-7 seconds of normal starter activity, the engine started normally.(ambient around 48F) This morning (about 49-50F) I cold started engine in Park after cycling the glow plugs three times. It started normally with a crisp 2-3 second start time. (same 2-3 seconds as previous successful start ups after cycling the glow plugs). Went out. Parked. Car started in park normally again. Did another task. Car started normally in Park. Not sluggish start ups etc. I was beginning to doubt the NSS since it appeared that the starter was OK, but so far so good. So, tentatively the car is normal. I did not check the braided ground strap. Where is this located in the W123? I read that sometimes that can cause false starts if not tight, clean etc. At this point it seems that the cold and perhaps the carbon build up may have been factors. Aside: cycling the glow plugs in the cold ambient temp. allowed a very fast and crisp start up. Not cycling, the start up was a few seconds longer. |
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