Problems starting both electrical and engine related??? - PeachParts Mercedes-Benz Forum

1977busman · #1 11-09-2010, 04:08 PM

Ok I have two problems, both related to starting... Its my 1983 300sd

Issue one
This problem started before it got cold out, It used to take me 4 or 5 turns of the key to get the starter to spin. All lights would come on, and the interior light would dim down slightly, but no spin. Eventually i started taking 15-20 turns to start so i parked it because I didnt have time to work on it. Well its back on the road, taking 4-5 key turns. Suggestions on what this could be? I was thinking bad ground, bad starter solinoid, or bad starter. Since it does spin pretty fast once you get it to turn over I am doubting its the starter.

Issue two
Once I do get the car to turn over, the first start of the day in my mind is really bad. Over the summer my car would start fairly well with no glow, just an extra revolution or two. Now I wait for the glowplug light to go out, then wait 5-10 more sec and attempt to start. It will fire and die unless I rev it up slightly, and I have to keep it reved for 10-15sec or it dies after I let off. It then will die if I throw it right and gear and try to go immediately, so I let it idle for a few minutes. It does this the worst when its in the low 30's. The Glowplugs when tested from the relay ports all tested fine. And the interior lights dim down when I glow. What else should I be looking for?

Diesel911 · #2 11-10-2010, 02:33 AM

Concerning the first paragraph there is at least 3 items involved. The Ignition Switch, The Neutral Safety Switch and the Starter Solenoid. Of course all of the wire/cable connections have to be good also.

For trouble shooting I would hook up a remote Starter Button to the Starter Solenoid. If the Starter functions normal like that you may have an issue with the Ignition Switch or the Neutral Safety Switch (on an Automatic Transmission Car).
If the Starters Function is not normal when you use the Remote Starter Button (and all the wire/cable connections are good and clean; including the ground) you have narrowed it down to a possible issue with the Starter Solenoid or Starter Motor.

Look up the Neutral Safety Switch trouble shooting in the DIY Rpair section; if you think that is what it might be.

With the exception of eliminating the other causes of the starter not spinning there is no way that I can tink of to test the Ignition Switch.

Diesel911 · #3 11-10-2010, 02:45 AM

The 2nd issue sounds like a Fuel Supply issue.
If this is a problem that happens after the car has sat for a long time; like overnight it could be that due to an Air leak or leaking Valves in your Fuel Supply/Lift Pump allowing the Fuel to drain back to your Tank. Often referred to as a pump losing its prime.

A way that might work to test for this is after the Car has sat overnight is before you try to start the Engine spend a lot of time pumping on the Hand Primer before you try to start.
If after the above your Engine starts and runs OK after Pumping on the Hand Primer but runs badly when you do not Pump on the Hand Primer; that would be an that you are losing your prime.

t walgamuth · #4 11-10-2010, 06:06 AM

I agree. First thing I would clean all cables including grounds where they bolt to the chassis.

1977busman · #5 11-10-2010, 06:42 AM

ok im going to clean up all the grounds and see how that goes this weekend, and tommorow morning i will try pumping the primer and see what happens.
Thanks for the help,
zach

kerry · #6 11-10-2010, 09:17 AM

On 126's there is a wire junction box on the inner right fender low and towards the front. I believe this junction box is the same as the box in front of the battery in a 123. You should be able to open the plastic cover and jump 2 terminals in that box to activate the starter. In a 123 it is terminal 1 and 3. Not sure if that is the case on a 126 but you can experiment. If the starter functions ok when jumped at that box, then the problem is either the neutral safety switch or poor connections in the ignition switch circuit causing a voltage drop to the solenoid. This is a very common problem in 123's and I assume it could be similar in a 126. I looked at a 126 a few weeks ago and the owner described this problem, although it occurred mainly when the engine was hot.

1977busman · #7 11-10-2010, 10:44 AM

Mine does get worse when the engine is warmed up. Saturday, i ran errands for several hours and never shut it off just in case. Now if it has time to cool off i trust it...

kerry · #8 11-10-2010, 10:47 AM

Quote:

Originally Posted by 1977busman

Mine does get worse when the engine is warmed up. Saturday, i ran errands for several hours and never shut it off just in case. Now if it has time to cool off i trust it...

Then the junction box trick should solve it. My TD does this periodically. I just carry a short piece of romex with the insulation stripped back so I can jump the terminals.

1977busman · #9 11-10-2010, 10:51 AM

so am I just attempting to jump terminal 1 to 3 or am i jumping from the battery?

kerry · #10 11-10-2010, 10:57 AM

Quote:

Originally Posted by 1977busman

so am I just attempting to jump terminal 1 to 3 or am i jumping from the battery?

Jump the terminals, not from the battery. The 126 terminals look different to me than 123 terminals (4 instead of 3?) so I'm not sure which ones to jump but I'm pretty sure jumping two of them should activate the starter. The connection will be from one of the heavier wires to one of the lighter wires.

1977busman · #11 11-10-2010, 11:04 AM

Quote:

Jump the terminals, not from the battery. The 126 terminals look different to me than 123 terminals (4 instead of 3?) so I'm not sure which ones to jump but I'm pretty sure jumping two of them should activate the starter. The connection will be from one of the heavier wires to one of the lighter wires.

Thanks! Will try later

1977busman · #12 11-10-2010, 07:44 PM

Ok this is probly a dumb question, but where is the primer on this car?

kerry · #13 11-10-2010, 08:10 PM

On the side of the IP.

1977busman · #14 11-10-2010, 08:23 PM

Is it the white plastic cap? If so do I unscrew it as much as it will go, and pump it? If so is it normal for this to dump fuel all over the place while im pumping it?

kerry · #15 11-10-2010, 08:34 PM

Quote:

Originally Posted by 1977busman

Is it the white plastic cap? If so do I unscrew it as much as it will go, and pump it? If so is it normal for this to dump fuel all over the place while im pumping it?

You found your problem.(most likely) That is how you use it. They are notorious for leaking. There is an updated replacement with a spring loaded plunger.