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  #1  
Old 11-28-2001, 04:54 AM
baporter
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Starting problem

I have a 1980 300cd and it has been hard starting for a while now. It sounded as if the starter was going out so I waited until this morning and low and behold it would not even try to crank. I have power and I have just replaced the starter. Everything seems to work fine except for it will not crank. I have even cycled through the gears to no prevail. Any ideas?

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  #2  
Old 11-28-2001, 06:55 AM
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When was the last time the valves were adjusted? What about the glow plug system - are you getting a light on the dash that eventually goes out? Time to do some troubleshooting.
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  #3  
Old 11-28-2001, 09:25 AM
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Please clarify

My understancing is that you replaced the starter, and you have power to the starter, and the problem is that the car won't crank. Clarify If I am wrong.

If the above is correct, you have one of the following problems:

1) bad battery
2) bad wiring from battery to starter, or
3) bad starter.

It sounds like you are not getting enough power to the starter .....so try jumping it from another vehicle....you may have a bad battery that will not hold a charge. If that starts the car, you should probably get a new battery....if the battery is three years old or more, and especially if it has been drained a few times (this kills car batteries) buy a new one...get an "Interstate".

If jumping doesnt work, check to make sure electrical connections at battery, ground to body, starter connections, etc. are good.

If the above still doesnt work, try running jumpers from a good battery directly to the starter...If the starter runs, you have a wiring problem; if the starter does not run, you have a bad starter...this would not be the first time a "new" rebuilt starter was junk. When replacing a starter, you should get a Bosch factory rebuilt....dont get an AutoZone or Pep Boys special...these rebuilds are of questionable quality, and I always see people at the counter in these stores returning parts

good luck

mark
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  #4  
Old 11-28-2001, 12:41 PM
baporter
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My power is fine so the battery is Ok (I have had no previous problems with the battery as it cranked well before and it is new) and the starter runs. I have disassembled the ignition switch and cleaned it as much as I could as there were trace amounts of oil in the switch housing from a previous shut off valve problem.

Could oil have leaked into the 7 or 8 pin ignition assembly (Brown male connecter) and shorted out a connection or am I on the wrong track here?

Is there a transmission switch (start safety as in park only) that is killing some juice in the lines that possibly could be worn out? And if so where could I find the switch and how would I test it?

I am thinking that it is a grounding or wiring problem somewhere, however, I am not ruling out worn parts. Any more ideas?
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  #5  
Old 11-29-2001, 11:53 AM
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MarkM:

Do you mean discharging the battery by saying drained ( I wish people would use correct technical language). Discharging does not "kill" a battery. I read in one of the MB manuals (I can't remember which one) that a car battery should be discharged periodically and recharged. Its the same reason rechargeable Cadmium batteries should be discharged and recharged periodically. It works the electrolyte deeper into the solid part of the battery in the discharge and recharge cycle.

You also missed the possibility of the starter solenoid not working. Also, you don't get power to the starter, you get electrical current (flow of electrons).


P E H
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  #6  
Old 11-29-2001, 12:43 PM
PaulC
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When you try to start the car, is there evidence that the starter is drawing power (current) from the battery? Turn on the headlights, turn the key to the "start" position, and see (or have an assistant see) if the lights dim during the period the key is turned to "start" and return to full intensity when the key is released back to the "on" position. Do not keep the key in the "start" position for more than a very brief period of time if the lights dim, or things may become a bit smoky underhood.

Obviously, if the lights dim, the starter motor is receiving current, but not turning.

When the key is in the "start" position, do you hear the starter solenoid attempting to engage (at least one fairly loud click, but might be light rapid-cycle clicking if battery is low or solenoid is bad)?
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  #7  
Old 11-29-2001, 07:51 PM
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Neutral saftey switch is on the transmission surrounding the shift linkage. There are four wires in a round plug, held on by a rotating clip. Two are for the backup lights, two are for the starter. If the switch is bad, it won't connect and won't allow the starter to run.

You can short the wires to check it -- wires labeled "50" are for the starter.

You can also check for voltage at the purple wire on the starter -- if there isn't any voltage with the key in "start" there is something wrong with the neutral switch or the relay system.

Peter
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  #8  
Old 11-30-2001, 10:04 AM
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Give me a break!!

To P.E.H. ..please be a little more tolerant and don't be so picky...."power" means energy available to do work...I did not intend to distinguish between voltage and current, nor was it necessary to do so given the context of my discussion. There may be electrical potential (voltage) at the starter, but not electron flow (current). You get current when you engage the starter...but depending on failure mode of the starter, you may or may not get current ("draw") when you engage the starter, but you may still have energy available at the starter to do work ("Power"). And if there is a problem with the starter, further investigation is appropriate to determine whether the problem is with the solenoid or the motor...saying that there is a problem with the starter does not imply that I overlooked the solenoid.

And what do you mean by "works the electrolyte deeper into the solid part of the battery in the discharge and recharge cycle" .... you mean the lead plates soak up aqueous electrolyte like a sponge??? C'mon....proper technical language??

Regarding your comments on discharging batteries....Car batteries (lead-acid) are not the same as rechargeable cadmium batteries (nickel cadmium)...period!! Car batteries are NOT designed for periodic deep discharging and re-charging...a regular car battery is designed to provide a lot of current in a very short time, to withstand regular numerous slight discharges, and to then be brought back up to full charge ("topped off") by the automobile's meager charging system. Periodic DEEP discharging of a car battery (like when you leave your headlights on overnight) WILL shorten its life...car batteries are not like "deep cycle" marine batteries, which are designed for this.

Batteries designed for diesels are generally very big (as in mercedes diesels) due to the heavy demands of heating glow plugs and excessive cranking as often needed in cold weather. Nevertheless, the reality with diesels is that batteries are stressed more (discharged more deeply and more often) than in gas cars, and as a result will generally not last as long (all other factors being equal). With a mercedes diesel in cold climates, batteries need replacing about every three years for optimum performance...any longer and you will find that you will need a few jumps each cold season.

Have a nice day,


MarkM
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Last edited by MarkM; 11-30-2001 at 10:17 AM.
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  #9  
Old 12-01-2001, 09:41 PM
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MarkM

"Power means energy available to do work" WRONG. Power is how much work is generated or user per unit time as in 1 Horsepower equals 33,000 foot pounds (work) per minute (time). Potential energy is energy available to do work.

Y
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Old 12-01-2001, 10:01 PM
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MarkM

"Power means energy available to do work" WRONG. Power is how much work is generated or user per unit time as in 1 Horsepower equals 33,000 foot pounds (work) per minute (time). Potential energy is energy available to do work.

You only get current if there is a continuous circuit from a charged battery thru the starter circuit ( wires, solonoid, starter motor and return ground) back to the battery. So if one of the former is not continuous you do not get electron flow (current) even though there may be a potential energy (voltage) available.

You only get energy (watts )when there is a current flow across a voltage drop. (watts equals amps times volts).

As far as the battery, why did the MB manual say to discharge the battery and recharge it periodically?

P E H
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  #11  
Old 12-01-2001, 11:13 PM
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OK, OK

You are correct on specific meaning of "power", and I was incorrect. All the rest of what you say is also correct (except about the battery...I don't buy it).

Anyway...did "baporter" ever get his car started....apparently he had problems with the wiring, neutral safety switch, or something, and he wasn't getting power to the starter....sorry P.E.H.
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  #12  
Old 12-11-2001, 03:57 PM
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To psfred and all, thank you for your help. I was able to isolate the problem to the neutral safety switch on the transmission as I was able to find it with your description. All it needed was some cleaning as corrosion and dirt got into the plastic housing corroding the connection . Now I can get to work.

This problem was very frustrating as I pondered it for days tearing everything apart replacing parts, so forth and so forth. At least I know my car better now(identified more things to fix) and to know to ask questions before diving into a problem.

However, I did a drastic mistake by taking apart the 8 pin ignition wiring coupling. I did not correctly transcribe the color coded wires before disassembly. I have the order and I know that the purple wire starts out on 50. However, there are 8 slots with only seven wires. Can anyone tell me which slot to skip? The car starts and runs fine except that the radio does not turn off with the ignition switch. Sounds like I put a direct power supply wire to it somehow. What do the numbers correspond to? As 50 relates to the starter.

Secondly, I noticed that I have a lot of oil in the intake system (it was very oily and dirty) and some oil in my air cleaner housing. It also looks as if there is an oil leak underneath the air cleaner housing somewhere, possible EGR valve? I have never owned a diesel before let alone a non turbo, so is this normal? I would think not or do I have a blown seal? Engine power seems fine to me as I drive from San Diego, CA to Los Angeles often with no problem. Any ideas?

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