Problems troubleshooting low voltage at starter solenoid - Page 4 - PeachParts Mercedes-Benz Forum

ah-kay · #46 07-01-2010, 04:45 PM

Most DVM with high current are not full duty cycle ones. Just make sure one knows the limitation of the meter and do not bust it. If one thinks it can resolve the problem then go for it.

RAYMOND485 · #47 07-01-2010, 09:18 PM

1984 300D TURBO 152K
INSTALL A RED TOP 34 REV. OPTIMA BATTERY, WILL FIT, MOUNTS AT BOTTOM
COST 2X,NO LEAK, SHIP TO HOUSE, FREE SHIPPING , USE LONG GROUND CABLE AND GOOD POWER

micalk · #48 07-02-2010, 11:48 PM

Quote:

Originally Posted by HinuWahie

I don't know the specifics of application for an '83 300sd, primary ignition circuit (e.g. nss, and ignition switch). I don't know where connect my leads to execute the test. Thats all I dont know about this test. Thats what would be helpful.

From my post #35 in this thread...

Quote:

Originally Posted by micalk

If you want to measure across the NSS and the start switch look in the schematic you should be able to do that at that junction box on the fender. You may have a few connection points thrown in the path, but you'll get a good idea of what's going on. With the solenoid connected, put one lead from your meter on the right hand pair of connections and put the other lead on the left hand connection where the solenoid connects. When you crank the engine, the voltage drop will tell you if you need to look at those switches.

Measuring at this point will measure both the NSS and the ignition switch and the wiring to them. If you see very low voltage drop, then you've eliminated both switches as potential problems. If you see a relatively high voltage drop, then you'll know you need to look into this part of the circuit further. If this test eliminates the two switches, then you can kick the "need to know" about their locations and how to test individually down the road a bit.

Also, the schematic I uploaded has pictures of component locations. See page 215 as noted at the top of the Start/Stop schematic (page 107) According to the manual, the NSS (aka Starter Lockout/Backup Light Switch) is on the left hand side of the tranny (see page 210). The connector for it is in the driver's footwell, and you probably have to remove the carpeting or at least the center console to access it. These are in much more prohibitive locations than the fender, so you're best off testing at the fender well first.

HinuWahie · #49 07-03-2010, 07:00 PM

Quote:

Originally Posted by micalk

Also, the schematic I uploaded has pictures of component locations. See page 215 as noted at the top of the Start/Stop schematic (page 107) According to the manual, the NSS (aka Starter Lockout/Backup Light Switch) is on the left hand side of the tranny (see page 210).

What schematic; uploaded where? I'd love to see this...

Quote:

Originally Posted by micalk

put one lead from your meter on the right hand pair of connections and put the other lead on the left hand connection where the solenoid connects. When you crank the engine, the voltage drop will tell you if you need to look at those switches.

isnt this the equivalent of testing between left hand connector and ground, only the result would be the lost voltage (12.3-11.2)??

I was able to spend some time last nite, testing the influence of the glow plug relay.

With everything connected as it's supposed to be, measuring voltage between rearmost connector on fender terminal strip and ground, wit key in start position, I still get 11.2V.

1. I disconnected the gp relay large connector ( 5 pin, supplies plugs). With key in start position, I get 12.3 V (to ground).

2. I tried disconnecting the small connector (4 pin, relay signals), same result.

3. I also tried removing the purple lead (start on signal. I'm unclear if this continues, or halts glow during start). This had no observed effect on voltage supplied to solenoid. I had hoped that disconnecting this lead would "fix" this...

What I did notice with 1. above, was that if I held key in start position long enough (~15 seconds), there was a relay 'click' some where, and the voltage to solenoid jumps to 12.3V. I figure this the glow plug relay clicking. This, with 2. above, makes it seem like its actually the glow being on, thats stealing the 1.1 V to solenoid. This does not make sense to me. These systems (glow and starting) are connected in parralel, so voltage suppied should not be altered by glow turnning off...

I gave up at 1:30am thinking I should just stick a relay in the primary starting circuit to ensure that the solenoid always sees 12V.

vstech · #50 07-03-2010, 08:19 PM

1.1 volts is nothing during start.
unless you are below 12.6v to begin with.
if you are below 12.6 with everything off, your battery is low or bad.

micalk · #51 07-03-2010, 09:52 PM

Quote:

Originally Posted by HinuWahie

What schematic; uploaded where? I'd love to see this...

Sorry, different post. Here's a link.

126td83-85.pdf - 29.13MB

Quote:

Originally Posted by HinuWahie

isnt this the equivalent of testing between left hand connector and ground, only the result would be the lost voltage (12.3-11.2)??

Essentially, yes. However, you would also need to check the voltage at the solenoid and note the difference to find the voltage drop across the switches. The point is you can find the voltage drop directly by measuring across the two terminals. This form of voltage test will be used below so don't discount the distinction. It's important that you check voltage drop vice voltage differences. Voltage difference is a subjective test depending on the reference, i.e., where you place your ground. Voltage drop is an objective test, and has no reference issues.

Quote:

Originally Posted by HinuWahie

With everything connected as it's supposed to be, measuring voltage between rearmost connector on fender terminal strip and ground, wit key in start position, I still get 11.2V.

1. I disconnected the gp relay large connector ( 5 pin, supplies plugs). With key in start position, I get 12.3 V (to ground).

2. I tried disconnecting the small connector (4 pin, relay signals), same result.

Check the schematic for circuit flow. The reason it works for both is that the relay doesn't have the 12V to pass (#1) or the relay doesn't energize (#2).

Quote:

Originally Posted by HinuWahie

What I did notice with 1. above, was that if I held key in start position long enough (~15 seconds), there was a relay 'click' some where, and the voltage to solenoid jumps to 12.3V. I figure this the glow plug relay clicking.

The fact that your glow plugs are causing the drop in the solenoid tells me that you should also be seeing a similar drop either at the the large double connector on the fender (C105) and/or in the fusebox.

Check these voltage drops with the system all connected up and the engine cranking:

1. Voltage drop between the positive battery post and the large (double) terminal on the fender (C105).
2. Voltage drop between the large (double) terminal on the fender and the large terminal on the glow plug relay.
3. Voltage drop between the negative battery post and a solid ground point on the fender well.
4. Voltage drop between the large (double) terminal on the fender and the solenoid wire on the same terminal strip.

You should see your 1.1 volt drop in one of the first three locations. In the first case, the voltage drop is between either the battery and the starter or between the starter and the large terminal on the fender (or spread across both). Do voltage drop tests to figure out which.

In the second case you are dropping voltage between the large terminal on the fender and the fuse box. If this is the case you'll need to access the bottom of the fuse box to troubleshoot further.

If the third test shows a voltage drop you need to check the connection from the negative battery post to the ground point next to the windshield washer bottle.

I'd expect the fourth test to come up with a very low voltage drop based on your previous description of symptoms.

Quote:

Originally Posted by HinuWahie

This, with 2. above, makes it seem like its actually the glow being on, thats stealing the 1.1 V to solenoid. This does not make sense to me. These systems (glow and starting) are connected in parralel, so voltage suppied should not be altered by glow turnning off...

You're looking at it wrong. The high current from the glow plugs energized is highlighting your problem, which is a poor connection up to that point. If you turn on your lights and honk your horn while trying to start you will probably drop even more voltage to the solenoid. It's the current through a resistance that's dropping voltage, not something further up the line. If all your connections and wires were perfect, you wouldn't be seeing any voltage drop. This is why I told you to clean all your connections. This includes the battery connections and the starter connections.

Quote:

Originally Posted by HinuWahie

I gave up at 1:30am thinking I should just stick a relay in the primary starting circuit to ensure that the solenoid always sees 12V.

You likely have a poor connection between the battery and the fuse box. If so, you'll fix your solenoid issue, but you may have other electrical issues where low voltage occurs under high current situations (lights on, stereo going, wipers, heater, etc.) The relay won't solve that problem. Find the source of the problem, don't put a band-aid on it.

HinuWahie · #52 07-08-2010, 01:16 AM

Quote:

Originally Posted by micalk

Sorry, different post. Here's a link.

Thanks, the diagrams were very, very helpful in "seeing" the system...

Quote:

Originally Posted by micalk

Check these voltage drops with the system all connected up and the engine cranking:

1. Voltage drop between the positive battery post and the large (double) terminal on the fender (C105). .36V
2. Voltage drop between the large (double) terminal on the fender and the large terminal on the glow plug relay. .84V
3. Voltage drop between the negative battery post and a solid ground point on the fender well. .05V
4. Voltage drop between the large (double) terminal on the fender and the solenoid wire on the same terminal strip. 0V

Quote:

Originally Posted by micalk

You likely have a poor connection between the battery and the fuse box.

You called it dead on...

I tried to narrow this down by using the ohmmeter and got 3.4, 7.7, and 0.1 ohms respectively for the above points. I did these a few times, to make sure I got good clean readings.

Attempting to narrow down the biggest drop/resistance, I opened the fuse box to get to the 10RD wire at the bottom of the fusebox well and got the resistance to the big glow plug terminal...This was 0.3 ohms. Moving the lead from the glow plug to terminal to the double terminal on C105, I expected to see the difference of 7.4 ohms, but got 0.1. This left me scratching my head; so I went back to the glow plug terminl but got 0.1 ohms this time.

I didn't have time to see if something was loose, or if voltage drops have also changed. I gotta go back and try again in the next couple days, just thought I'd let you know the progress and to thank you for the diretion. I'll report back when I have somethin in the next few days.

funola · #53 07-08-2010, 06:33 AM

Quote:

Originally Posted by micalk

Sorry, different post. Here's a link.

126td83-85.pdf - 29.13MB

/.

I tried downloading (did a save as) and after it downloaded i clicked open file and nothing opened. I then clicked on the link and went to the zshare site and downloaded from there and same thing, nothing opens. Then I got a warning that the zshare site is unsafe. What's up with that? I hope I didn't download a virus.

More info
The file that was downloaded was 7794160320080dc3.html not 126td83-85.pdf

HinuWahie · #54 07-08-2010, 09:27 AM

It worked for me. Same process, had to wait for adds to before download started, but got the 126td...file.

nealpellecchia · #55 05-05-2013, 07:24 PM

Quote:

Originally Posted by HinuWahie

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.

The solenoid should pull in and work at like 9.5 volts or so because often you get low voltage through a cars life span. my first gm starter never failed despite low old batteries etc. It lasted 15 years.

I have the same problem as you! It's a 1993 chevy turbo diesel. My chinese rebuild was suppose to be new. It has been a problem with noise from the beginning. I have my "giggle wire" attached to the solenoid switch terminal because I knew the problem would act up again and I don't feel like taking it out again like you. After 3mos. he gave me a new solenoid. that stopped working after another 4mos. I used a screwdriver for many mos. cause I didn't want him to have to take it out again. Finally I got another guy to open up the solenoid and look at the contacts. He immediately saw a very thin contact washer and replaced it with a much thicker new one I hope. It was good for 4 days. Out again and back to the original guy and he replaced the cap with it's new contacts. I thought great we got to the heart of the problem; good for 4-5 days. Hence my giggle wire.

This is how it works. It's a pretty thick wire well attached to the solenoid S terminal and it hangs loose near the battery. When the key won't start it and it will "click" but not start, I pull out the wire and at first it will start by just touching the wire to the + post.More amps I presume. But often this won't work and I have to scratch, scrape, or giggle the wire on to the post so it will giggle the solenoid contacts enough to make a connection. This never failed until yesterday. And it was hot ...no glow plug voltage used. I had to leave the hood up and perhaps cool the engine and lower the resistance in the wires and then it started. I need to put a gauge right on the starter motor wire and see how much current I am getting across the solenoid contacts to the starter motor when it fails. If it's normal then I'll have to see where it's grounding-shorting out or where the current stops at a bad ground. I think.

nealpellecchia · #56 05-05-2013, 10:40 PM

Quote:

Originally Posted by LarryBible

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

very good sir

HinuWahie · #57 02-01-2016, 07:10 AM

Quote:

Originally Posted by HinuWahie

I didn't have time to see if something was loose, or if voltage drops have also changed. I gotta go back and try again in the next couple days, just thought I'd let you know the progress and to thank you for the diretion. I'll report back when I have somethin in the next few days.

Needless to say, I never found the time to go back and recheck the resistances...

Knowing the glow cycle draw would cause a voltage drop to the starter solenoid, I started waiting for the glow plug relay cycle to end before I cranked the engine over. I have doing this ever since for the the last 5+ years and never mustered enough desire to dive back in to find root cause.

The starter just died a week ago.

I had a bout of multiple back to back start attempts trying to force the car to start with what turned out to be two bad glow plugs. Not a bad run, but root cause still tickles my curiosity.

My hunch is that the voltage drop from the fender terminal to the glow plug relay power in is also causing my glow plugs to die early, seems like I go thru them every year or so.

Ive got a starter relay kit on the way an will install with a reman starter.

funola · #58 02-01-2016, 10:23 AM

Starters should last a long time if everything is right. No, it is not possible to have so many bad starters in a row. It is quite possible you have problems with the high current wiring harness to the starter. Are you in a wet damp environment? Since you were not able to diagnose where the problem is by voltage drop test, just replace the starter harness assembly with a good used one from a dry desert climate area. The crimped wire lugs are heat shrinked but not soldered and I bet some of them are corroded. Take a razor and cut the heat shrink open and see what they look like. Good chance they are badly corroded.