Sorry for the saga... I have an ongoing problem with my starter that has me confused and unsure of my next move.

I have had my '83 300sd (with 265k) for 4 years now, and it was trouble free for the first 3 1/2. Right after I bought it, I transfered SVO from my previous sd and it has really been the worry free daily driver we all expect from our diesels.

About 6 months ago I started having starter troubles. In retrospect, they were the classic signs of an old starter, eg slower cranking, intermittant no cranking, occational non responsiveness when warm etc. After ignoring the problem one weekend too many, it left me stranded at work on a friday night . Needing to get to work monday, I bought a starter at the only place that had one, Shucks (no rocks please...). The first one had a problem with the contact plate welding itself in on position, the second had stripped threads. The third one lasted for about 5 months, but had had a few intermitant problems with the contact plate, and just seemed weak. I tried bypassing the NSS and ignition by jumping the leads at the terminal block, but got nothing from the starter, just a clicking that came from the glow plug relay. Upon removal the solenoid was unresponsive, though starter motor would spin if I bypassed solenoid.

It was at this point I thought something was going on with the car and not the cheap starters. reading the posts here, I convinced myself its was the ignition switch causing problems, so it was replaced. Starter 4 came from Napa, but only lasted 2 weeks. This one also had an unresponsive solenoid. Again I had tired jumping the terminal leads, just the click at the glow plug relay. From what I gather here, this may be normal, as the relay was set up stop energizing the glow plugs on start...

I'm on starter 5 and tying to get to root cause before I take another one out.

Someone at work was telling me low voltage at the solenoid would cause it to fail prematurely (the low voltage allowing the solenoid to activate, but at a higher current draw, causing heat...).

Sure enough, at the connection on the solenoid I get 10.5 V to ground (at the battery). Thinking it may be the ground straps, I ran a jumper cable from the starter housing to the neg battery post; same result.

Working my way back, I disconected the white solenoid lead (shown with with green arrow) at the termimal strip, left it unconnected and checked starting voltage up to its signal lead (connector with two purple leads, one about 10-12 ga, and one 14-16 ga, shown with red arrow). 11.2 V on start. So I'm losing ~.7V in the wire to the solenoid, but where is the rest going?

The ignition switch is new, so maybe NSS? Tried locating the connector, above the acc pedal, under carpet to right of acc pedal, no luck... So I pulled the NSS connector on the tranny. It was a little oily, but not corroded. I cleaned the leads, reconnected and tested. Still 11.2V. I also noticed the igntion signal lead (still measured at purple leads at terminal strip) was giving low voltage signals during glow (1.3V), prior to start (2.6V right after a click from somewhere, 5-6 sec after glow light turned off), after "start" .2V, and even when key goes back to "0" position of -.2 V! (going back to verify this -.2V, it seems to drop off over a few minute period; like a capacitor discharging)

Unsure about what to do next, and thinking about the glow plug clicking from before, I pulled the likely connector that contains the link from terminal strip to glow plug relay, and retested voltage during start. 12.3 V.

The low voltage signals seemed to be reduced with connector removed, to .2 V prior to start (of course there s no "glow" light with the connector removed).

At this point I'm thinking the glow plug relay/timer is bad, but thats just cause it seems like it acting funny, actually drawing power from starter signal (but they're in parrallel,right??), not because i understand the problem. Before I drop 100+ (plus install time I dont really have)on a new relay kit, I was hoping someone here may have an insight as to what the cause of the voltage drop might be.

Or should I even worry about it. I was considering installing a low voltage starter relay (like the Bosch WR-1 kit), just to make sure the solenoid sees 12V. That may be masking a future problem with the glow plug relay, I just dont know.

Thanks in advance for your help/advice.

[QUOTE=
Sure enough, at the connection on the solenoid I get 10.5 V to ground (at the battery).
QUOTE]

Do you mean that you measured 10.5 volts between the battery negative terminal and the terminal on the starter where the positive battery cable connects?

If this is the case, you have one of three problems:

1. Discharged battery--verify battery voltage is at least 12.6 volts measured at the battery posts, if OK load test battery to determine condition. If battery is indeed discharged, charge battery fully and load test. Further troubleshooting with a bad battery will get you nowhere.

2. Corroded/poor connections at battery and/or starter. Clean and tighten connections at both, recheck voltage.

3. Defective positive battery cable--replace if battery is ok and cleaning and tightening connectins does not get rid of your voltage drop.

I hope this helps.

I read it as 10.5 v read on the lead to the solenoid on the starter. I don't think he's measuring the voltage at the positive lead on the battery.

What is your battery reading ? It would appear that is the core issue.

__________________
1985 300D 198K sold
1982 300D 202K
1989 300E 125K
1992 940T

"If you dont have time to do it safely, you dont have time to do it"

"The democracy will cease to exist when you take away from those who are willing to work and give to those who would not."

Thanks for the replies.

Yep, on testing voltages to ground with the black lead of the multimeter connected to negative post on the battery.

During the testing I did yeterday, I was getting as high as 12.3 V at the starter (with the aforementioned glow plug relay connector, disconnected).

I just drove in (so freshly charged) and retested battery at posts. 12.9 V. Just to be thorough, I checked voltage between hot lead at terminal strip and a random bolt on body. 12.9V. I had battery tested when these issues started up. I forget the stats, but it passed for taking a charge and providing sufficient CCA. This, with the 12.3 at the solenoid yesterday(albeit with the glow plug connector disconnected) , lead me to think the battery, battery cable, and battery connections are good. These would not explain the increase of voltage (from 11.2 to 12.3) when the glow plug relay connector is disconnected.

Well the voltage test while the starter is not cranking is kind of meaningless. Voltage under solinoid load is the important thing. As soon as the load or current tries to flow the voltage probably drops off. The resistance in the original circuit is too high.

To end the trouble or suspected trouble. Wire a ford starter relay in the circuit to stop all the voltage drop across the thinner wires. Twelve volts to the relay and one wire to the solinoid. Common cure for your description of problems.

Everything has to be in really good shape for the original system to function properly. Your wiring and connections are old.

This starter relay is the one that for years ford bolted to the fender apron. It will see that good current and voltage arrive at the solinoid. The relay used to be about ten dollars.

barry123400,

Thats what I was refering to with the Bosch WP-1 relay kit. I was about to get such a relay, when I thought about the glow relay click, and wondered if the relay was going out, and giving me clues.

If I get no takers on advising about the apparent glow plug relay influence, the extra relay between the ignition lead and the solenoid will be my next step.

Anyone ave any ideas? Thanks.

The purple wire to the glow plug relay can be left disconnected and basically it will never tell the GP relay that you tried to start the car so your plugs will glow after starting. The purple wire is the cranking input that tells the relay to de-energize (pin 2 on relay), not the run/start signal that energizes the relay (pin 1). However, it really shouldn't be drawing alot of current, which is what it appears to be doing. If both purple wires share the same terminal connection (two wires on one lug, looks that way in the picture) try disassembling the connector at the GP relay, pull out pin 2 and wrap it with electrical tape.

Clean the connections on all the wires in the junction box there on the fender well to make sure that everything is clean and tight. That's the weak link here. With high current, a little resistance will drop alot of voltage.

Now when the engine is cranking, check the voltage drop between the white solenoid lead and its other end at the starter. Don't check from screw head to screw head, check from wire terminal to wire terminal if possible - you want to minimize the number of connections you are measuring. If you still have a 0.7V voltage drop, try building a new wire and using that to connect to the solenoid as a test. (If you can, solder the wire to the terminals to ensure a great connection rather than just crimping for a good connection.) 0.7V is alot of voltage to drop through a wire and you may have a break internal to the wire or a bad connection at one of the terminals.

__________________
mjk

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)

micalk,

Disconnecting the purple lead sounds like a good idea. I was just looking up the replacement gp relay/timer. It looks like the replacement does the same thing, leaving the glow plugs on for up to three minutes (seems like a long time...).

I'll give that a try, install a new solenoid lead, clean up the remaining connections in the junction box, and retest.

Thanks,
Hinu

If you leave the glow plugs on then it will draw more current. I do not know the exact rating of the plugs but each plug should draw about 100W, that is a lot of power from the battery. Do not mess with the glow plugs wires.

I suspect you have a weak battery. Low voltage would not stop the starter from cranking, it may crank a bit slower but it WILL crank. Also low voltage would still pull in the solenoid, it probably would work at 10V, it only draws milliampere. You must be quite handy if you know how to by-pass the NSS.

This is what you can try

1) Make sure you have a good battery
2) Remove the BIG connector at the glow plug relay, i.e. disconnect the glow plugs - to leave it out of the equation for now.
3) Connect the red probe of the DVM to the small terminal of the starter.
4) Connect the black probe of the DVM to chassis (ground). It should read 0V.
5) Turn the key and see whether you have 12V on the meter. If you have then the solenoid should kick in and pull the massive relay to connect the battery DIRECTLY to the starter. The engine should crank.
6) If you do not have 12v then the problem is elsewhere, between the ignition switch and the starter, NSS etc.
6) If solenoid clicks in but no crank then it the solenoid itself. The massive relay is not conducting.
7) Also check you ground strap at the engine to the -ve terminal of battery.

Good luck.

__________________
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.

ah-kay-

If you note, the replacement relay does the same thing as this mod - it's referred to as 'after-glow'. It helps smooth running a cold engine, especially at lower temps. And it doesn't have to be permanent, just until all the other problems are found and corrected. The idea is to isolate down to a minimal circuit where the problem is still exhibited and can then be found. This part of the glow plug circuit shouldn't be drawing much current and it seems to be doing just that. So removing the connection has a two-fold purpose. Once he's happy with his circuit, he can reinstall the GP relay connection and decide if he needs go further. Besides, he seems to have found a large voltage drop in the solenoid wire already, so he's on the right track.

__________________
mjk

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)

I understand the 'after-glow' as it is in all of my SDLs. My suggestion is to leave the glow circuit out of the equation, try to find out why the starter will not crank. The glow circuit takes 500W to 600W combined. Low voltage can mean only 2 things - weak battery or high current drain from somewhere. Unless there is a massive short, the only thing that can draw current is the glow circuit. This is only my suggestion and I do not mean to side track you guys.

__________________
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.

Does it only start slow when hot? My 76 300D does that, the battery and starter are both new, and both have been tested and passed. All grounds have been cleaned, but it still turns over slower hot than when cold. I have kinda givin up on it, it hasn't left me stranded yet so lets hope it never does. When you find the issue please let us know.

__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

did you do some ohm tests on the wires? If you havent done that do so, may have some bad sections of wires.

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