300D turbo starter motor cranking slow - PeachParts Mercedes-Benz Forum

funola · #1 10-12-2010, 06:45 PM

My starter sounds slow. I have a photo tach and it was measured at 115 RPM (good battery). I also checked another 300D turbo with a good starter and it measured 156 RPM. I have no trouble starting the car now but I am not sure if that will be the case in the dead of winter.

Is the 240D starter motor the same as a 300D turbo?
Are the Autozone/ Advance starter motor bench test worthwhile to do?
Where can I get a good deal on a quality rebuilt and how much will it cost?

toomany MBZ · #2 10-12-2010, 07:27 PM

If your battery is good, as well as your connections, I'll suggest the starter motor itself too.

Either motor will fit, many install a 300 starter, it's beefier.

Check with the folks here for a reman unit.

vstech · #3 10-12-2010, 09:05 PM

that's a bad sign.
be happy it's giving you this sign, and change it before you are stranded, or it kills a battery, or even worse, catches fire!
I'd not put your 240 parts car starter on it though. the 300 starters are stronger.

Diesel911 · #4 10-13-2010, 12:04 AM

Somewhat a repeat of the above.

Starter runs slow because:

It is not getting enough current due to resistance in the cables/grounds (contact areas not clean or corroded cables).

Starter Brushes are shot, main contacts inside of starter solenoid burned and not allowing enough curent to pass into the Motor.

Some issue with the Engine that is causing it not to rotate easily.

I have read on this form that the Starters for the Turbos crank the Engine Faster.

funola · #5 10-14-2010, 09:22 AM

Well, I wire brushed the battery terminals and the ground connection at the fender and checked with the phototach and the cranking RPM is a little higher now at 130. I also took a voltage drop reading between the starter + terminal and battery + post and it was 0.33 V. Is that an acceptable drop? I will clean the ground strap connections next and repeat the measurememnts.

How do you normally access the upper starter bolt? Mine is missing since I bought the car. Maybe it's part of the problem. I tried putting in a new bolt from the bottom and could barely get it started by hand but could not get the 10 mm hex driver on it. Do I go from the top? Looks like I have to remove the battery, heat shield, air cleaner and the transmission oil fill tube?

Carpenterman · #6 10-14-2010, 09:30 AM

Yea, if you remove the heat shield and air cleaner it will be a lot easier. I can do it without removing the battery. And all you have to do is loosen the dip stick tube where the brace bolts to the manifold.

I found it easiest to cut 1'' off an allen wrench, insert it in the bolt and use a gear wrench or open end on the stub.

funola · #7 10-14-2010, 10:31 AM

Quote:

Originally Posted by Carpenterman

Yea, if you remove the heat shield and air cleaner it will be a lot easier. I can do it without removing the battery. And all you have to do is loosen the dip stick tube where the brace bolts to the manifold.

I found it easiest to cut 1'' off an allen wrench, insert it in the bolt and use a gear wrench or open end on the stub.

Thanks! I have done the 10 mm cut off allen in the past on another car. I may even have the bit already.

zeke · #8 02-28-2011, 03:52 PM

My starter is doing this in the TD.
The symptom is that the starter is very sluggish - pumping the accelerator will lead to a start. As the car warms up it becomes easier and easier to start. This is in concert with the battery charge going down (due to excessive cranking), so electrical seems less likely. Temps here have been in the 80's, so I don't think it is an ambient temp thing either.....

I checked the connections, and they look clean at the starter and battery.
But, there is a pretty fair amount of oil weep around the starter port on the block that is pretty gummy.

Not to eager to pull the starter if I don't need to, considering the annoying placement of it in the 617

How should I proceed? Hotwire the starter to see if it spins cold? Oil change? Pull the starter?

Quote:

Originally Posted by Diesel911

Somewhat a repeat of the above.

Starter runs slow because:

It is not getting enough current due to resistance in the cables/grounds (contact areas not clean or corroded cables).

Starter Brushes are shot, main contacts inside of starter solenoid burned and not allowing enough curent to pass into the Motor.

Some issue with the Engine that is causing it not to rotate easily.

I have read on this form that the Starters for the Turbos crank the Engine Faster.

Diesel911 · #9 02-28-2011, 07:15 PM

Quote:

Originally Posted by zeke

My starter is doing this in the TD.
The symptom is that the starter is very sluggish - pumping the accelerator will lead to a start. As the car warms up it becomes easier and easier to start. This is in concert with the battery charge going down (due to excessive cranking), so electrical seems less likely. Temps here have been in the 80's, so I don't think it is an ambient temp thing either.....

I checked the connections, and they look clean at the starter and battery.
But, there is a pretty fair amount of oil weep around the starter port on the block that is pretty gummy.

Not to eager to pull the starter if I don't need to, considering the annoying placement of it in the 617

How should I proceed? Hotwire the starter to see if it spins cold? Oil change? Pull the starter?

When you checked the Electrical Connections did it include removing the Engine to Chassis Ground Strap and cleaning the contact areas?

Also get something under the insulation of the Battery Cables up near the Battery Terminals. Ofter if you look under the insulation you find the Cables are all green and corroded.

zeke · #10 02-28-2011, 09:55 PM

Yeah, I did that last summer when I had to replace all of the wires that go to the 3-port terminal block on the fender in front of the battery. I will recheck and also check the connection under the insulation. Still weird that it would get better after each start?

funola · #11 03-06-2011, 02:47 PM

I went through this winter with the old starter without getting stranded.

There were a few days where I had to plug in the block heater to get it started. The synthetic oil also helped I'm sure. This starter would crank at its already slow RPM for not more than 30 sec than slow down even more to where it would bog down. I finally pulled it and free spun it with a battery and it would spin fine for a few seconds and then slow down as if something was binding. I took it apart to find the bushing on the brush end of the armature was ovaled with a lot of play in it. That and the armature being dark from heat explains it. The stalling of the motor is very bad while power is being applied to the windings without work being done so all the juice goes into heating up the windings instead of doing work. Oh, the top bolt was missing so it made taking the starter out a bit easier. Also, the grease cap that protects the (worn) bushing was completely dry. The missing upper bolt likely contributed to the premature wear of the bushing.

I have a used starter which I disassembled, cleaned/ lubed, ready to go in. I hope this will end my starter problems.

funola · #12 03-08-2011, 01:25 PM

The new (used) starter is in and WOW what a difference is the sound of the cranking RPM! It starts immediately upon turning the key! I will take a reading with my phototach and post a sound file later. The bad starter's armature also has a short to ground (shaft/core) of 12 ohms (should be infinite).

With the bad starter and a hot engine after shuut down for 1/2 hour, I'd always have to glow the glow plugs or else it won't start on VO or diesel. With the new faster
starter, it now starts on VO or diesel without glowing the glow plugs! My glow plugs are manually controlled, i.e. they do not come on with the key.