If you believe the Glow Plug Relay is the issue simply disconnect the Purple wire that goes to it at the Terminal Block.
The Purple Wire is there to keep the Glow Plug Relay on while the Starter is cranking the Engine.
With it removed you sould still be able to use the Preglow with the Key.

Be sure to Tape or otherwise insulate the remove end of the Purple Wire so that it does not ground itself on some thing.

__________________
84 300D, 82 Volvo 244Gl Diesel

Thanks again for the replies. Its SO AWESOME to have others thinking about this with me. Hope I can return to the favor to someone soon.

Just to clear up a point. The starter is currently operating. Started the car four times today. Its acting just like the last one; cranking strong everytime with perhaps a slight delay following turning the key. Its just that the last starter survived for only a couple weeks. The first time I R&R the starter it took 5 hrs. I can do it less than an hour now. Not someting I had planned to get good at...

I did have my battery checked today. It passed with no issues or concerns.

At this point, I am planning on:
1. building/replacing the lead from terminal strip to solenoid. Pretty sure that's not as good as it should be.
2. disconnecting big connector from gp relay, and taking a voltage at the solenoid during start. If its 12v. I will try disconnecting the purple lead from the small connector or at the terminal block. Whichever looks best when I get in there.
3. I'll also take some voltages at solenoid with purple lead disconnected and see where that leads.
4. report back here.

Thanks,
Hinu

The best way to troubleshoot the starter circuit is with a voltage drop test. Most any DMM, even a cheapie gives good enough resolution that you can simply measure the voltage drop across each point in the circuit while someone is trying to crank it. Wherever you have a voltage drop greater than a fraction of a volt is your problem.

The only place where there should be a voltage drop is the starter itself.

For instance if you have measure several volts across the battery post to the battery terminal, you have a high resistance there that must be corrected. The same thing holds true all the way down the line.

Voltage drop test across a wire as LB suggests is the way to go. Ohm tests of wires is meaningless, especially for wires carrying high current. Conventional DVM's are not designed to measure ohms accurately when you are down in the milli-ohm range.

Ah-kay, you sure the starter solenoid draws only milli-amps? Go measure yours and report back. My guess is it is quite a bit more.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

HinuWahie (cool name!), I just re-read your post. It is unlikely you had 5 bad starters in a row. When you measure voltage, use the ground at the device and not at the battery. E.g. when measuring starter solenoid voltage, put the negative lead at the starter solenoid, not at the battery. Have you checked and tightened the ground strap at the bell housing driver's side? When I first got my 300D turbo, I took it for a spirited Italian tuneup. Pulled into the driveway, shut it off and starter motor stopped cranking after that, all I heard was the starter solenoid click. Battery was fine, weird stuff was going on with the instrument cluster warning lights. Turned out the Italian tune-up loosened the ground strap bolt enough to not pass sufficient current. Upon inspection, I found one starter motor bolt was missing, the other was loose, ground strap bolt was loose, 2 or 3 other bell housing bolts missing! I have a receipt from previous owner for a rebuilt transmission. My guess is whoever did that job forgot to tighten the bell housing bolts!

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

If I understand the Voltage drop test right, you:

1. hook up dmm in parralel with element being tested
2. take reading while cranking

I wanted to do that but, couldn't figure out how to isolate the elements in the starter circuit. The lead to the solenoid is easy enough, but where would you hook up to get the voltage drop accross nss, and ignition switch?

[QUOTE=funola;2496781]When you measure voltage, use the ground at the device and not at the battery. QUOTE]

I thought about how do this a bit before I started. Maybe got my logic twisted. I was thinking the test to ground at the battery was really testing the system. If I saw a change in voltage by connecting the jumper cable from starter housing to neg battery post, that would tell me if my ground straps were a resistance point.

I have searched the threads for locations for the ground strap, so I could verify/clean connection points.

My car has a ground strap connected at the 10mm bolt of the starter and the frame. I have not been to locate a ground strap between the engine block and the trans bell housig on the the drives side as other posts mention. They seem to mention location as either/or. I figured my model had just the one at the starter. Is there supposed to be two?!

Thanks,
Hinu

btw HinuWahie is a mash of Hawaiiian words for Oil fuel. Fits well for diesels in general, but in my case my sd is a dual tank SVO set up.

You simply put the leads across whatever might be suspected of offering resistance in the circuit. This is meant for the high current portion of the circuit or what might be called the secondary side, but you could do the same thing for the primary, such as seeing if the NSS is offering resistance in the circuit. Simply put a lead on each terminal of the switch and with the key in start position if you see 12 volts or so across it, then it is not making thus dropping voltage. If the switch were good, you should only see a few milliVolts across it because there would be no relative resistance.

There is 1000 milliamps in 1Amp. The coil is an inductive load and the resistance will increase when you put DC voltage across the terminal. I have never measured it myself and it should be within the ballpark. The bottom line is that the coil wil pull at lower voltage to connect the starter directly to the battery, this is what make the engine to crank.

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

Hinu, I'm not familiar with the SD's ground strap arrangement. The strap at the 10 mm stud on the solenoid sounds like it is ground for the solenoid only, not the starter motor..

If you use the battery ground doing the V drop test, you are correct that you are testing the system. If you want to isolate where the drop is, you need to move the ground point. Don't forget the drop is additive in a series circuit.

ah-kay the solenoid may pull in at a low voltage but it will no hold with enough force with low voltage to deliver full current to the starter windings. The bottom line is you want full voltage and current to all starting components. That includes ign switch, wires and cable terminals, starter solenoid, Having clean solid connections, good battery, starter motor, ign switch is required for a good starting RPM

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

How complicated is the starter? It has 2 terminals, the chassis is ground. One small terminal needs 12V, the wiring is snaked thru the NSS, ignition switch or other security device and end up in the battery +ve. The other large terminal is connected directly to the battery +ve.

As long as you have a good battery, good solenoid, the contacts inside the solenoid is not pitted, then the starter will spin when you put 12V to the small terminal. That is the way I test a starter if I have it on the bench.

If you have low voltage at any segments then you just trace the wiring from the +ve terminal downwards to find the problem. You can ohm it out, you can measure the voltage, this is not rocket science. The OP seems to be very knowledgeable on the circuit as he can by-pass the NSS. I am sure OP will figure it all out, we are just confusing the issue. The glow plug circuit may drop the voltage a bit but should not be by much. A GOOD battery has 700CCA and giving 50A to the glow circuit should be nothing. My suggestion is to leave the glow circuit out if it is suspect. This is just 'divide and conquor', everyone does it.

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

Where is a good place you would reccomend to connect the leads for the NSS and ignition?

I presume the circuit is in series: ign, nss, solenoid.

With everything inplace and connected I can do voltage drop test on:
- the solenoid - by placing dmm pos lead on solenoid power lead, and com lead on starter housing.

- solenoid lead - with dmm pos lead on rear most connector(s) in terminal strip, com lead on solenoid lead connection

- nss - (I assume nss is next upstream) dmm com lead on rearmost connector on terminal strip, pos lead where ??? @ ign switch???

- ign - ??? I just swapped this for new a few weeks ago, and am not certain, but my recollection is that the harness plugs inside the housing. It was not easy to get to (by design, I presume...). Not sure where the other end of the harness end up.

ah-kay/funola,

Thanks to you both for you thoughts. Kinda sound like what goes on inside my head right before my wife says, "you talkin to yourself about that car again!?" . I think I have a good path forward, and will report back when I can get under the car.

funola, I didn't complete the thought about the 10mm bolt where the ground strap is. its the bolt where the 10mm allen is used, the bottom one of the two main bolts attaching starter to the block, pretty hefty.

I don't think you understand what I mean by a Voltage Drop test. The idea is not to check voltage at various points as referenced to ground. The idea is to check the voltage ACROSS individual components and connnections.

Example, if you have a bad battery terminal connection there will be a voltage difference between the terminal and the battery post. If you put one lead on the battery post and one lead on the battery terminal, there should be no voltage measured between them because they are the same electrical point. A bad connection, however, means resistance. Resistance causes a voltage drop that would cause you to read voltage across what SHOULD BE a dead short.

Doing a Voltage Drop test is like testing each link in the chain one by one. Go ahead and put your leads across the battery connection and have someone try to crank it. If there is more than zero volts then there is resistance. Resistance means a bad connection.

Now, let's say you did this and there was zero volts between the battery post and the battery terminal. You know that this is a good connection so leave the lead on the battery terminal and put your other lead at the other end of that cable on the solenoid and check again. There should be only a small fraction of a volt dropped across that cable. If there is more than a few tenths of a volt, then that means the cable has resistance, but that still would not be your problem.

Now, assuming that the solenoid is clicking in, put your leads across the solenoid itself while someone tries to start it. When that solenoid clicks in, there should be a virtual short across the terminals. If there are several volts dropped across the solenoid terminals (the big cable to the solenoid measured against the big connection that goes to the starter) then that means there is too much resistance across the solenoid terminals.

SO.. You are putting your volt meter only across one small link in the chain at a time until you find the bad link. The only component in a properly working secondary starter circuit that should be dropping significant voltage is the starter motor itself. It is the load in the circuit. It has to have voltage across it in order to run. Everything else in the circuit should not be dropping significan voltage.

Remember, the starter motor draws HIGH CURRENT. All secondary connections must be STELLAR! If you have even a little resistance it robs the starter motor of needed energy.

Hope this helps

LOL get a better meter like a fluke

__________________
1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)