Problems troubleshooting low voltage at starter solenoid
 

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?
http://www.peachparts.com/shopforum/...pictureid=2389
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.
http://www.peachparts.com/shopforum/...pictureid=2390
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.

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.

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

I would not remove the purple wire.
 

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.

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.

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.

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.

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

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.

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.

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!

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.

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

I hope I am not confusing the issue.
 

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.

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

You are correct there is 1000 milliamps in 1A but you are way off on what the starter solenoiud draws. I just measured it on my 300DT and it drew 7 amps.

WOW. 7A. That is 84W for a solenoid. I do not expect that. That is still very small wattage compare to the total energy a battery can hold.

Additional info:

It was my mistake, I worked with switching relay before and normally the current is small. The solenoid needs to push the pinion gear in position, may be that is why it needs more energy. When I read the Wikipedia, it says

"A small electric current flowed through the starter relay coil, closing the contacts and sending a large current to the starter motor assembly." May be it is not that small after all.

Thanks for the info.

To accurately measure wire resistance, you need specialized test equipment. i.e a micro-ohmmeter. Fluke does not make one. They usually start at $400 and go up from there.

Here's one

http://www.ietlabs.com/IET/LOM-510.html

Note the range: 1 micro-ohm to 200 ohms

1 micro ohm is 1/1,000.000 of 1 ohm.

I totally do understand what you mean. I am curious about what the specific connection points you would use to do it, for my car. again, the solenoid for example, would use the solenoid lead, and the starter housing, and get the voltage while someone is cranking.

I dont know where they would be, if there are any, for the nss and the ignition switch.


Maybe this is where the confusion is...its the lead that activates the solenoid that I have been refering to. the smaller (I guess 7A load carrying) terminal. In your terms, its the primary circuit I have issues with. I am getting good starting, with the seconday.

If you were going to do a voltage drop test for the nss and ignition switch, what connection point would you use?

You were kinda doing it when you figured out that you dropped 0.7 volts across the solenoid wire. You can measure all your voltages from a reference point like the negative battery post, or you can measure from one end of a wire to the other end. Whenever you have current flowing through a resistance you'll see a voltage drop which can be measured.

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.

Regardless of the Ohmmeter used, it will not give you the same information as a voltage drop test. There is a miniscule amount of current passing through the element under test with an Ohmmeter. With a voltage drop test, you are passing plenty of current through the element, thus testing it's ability to pass lots of current.

To get the voltage drop across the NSS, you connect your meter leads on the terminals of the NSS. You don't isolate anything, you simply measure voltage drop across any individual element in the circuit.

Okay, the solenoid activation circuit can be tested in the same manner as the high current portion of the circuit. Just put your voltmeter leads across the item under test and see if it is dropping voltage. If it is open, then virtually all of the battery voltage will be dropped across that point.

It's DIFFICULT to describe things electronic without a schematic or black board, but let's say that you have B+ going to an ignition switch, then a neutral safety switch and then to the coil of a solenoid. If everything is correct, when the ignition switch is turned to start you will have virtually all (99+%) of B+ ACROSS the solenoid. That is with one lead on ground and the other on the solenoid power wire you will have B+, say 12 Volts.

NOW, let's say the resistance across the coil (yes I know it is an inductive load, but I'm trying to keep it simple) is 2 Ohms, then 12 Volts across 2 Ohms gives you 6 Amps although exactly how much current is in the circuit doesn't matter in what I'm trying to explain.

So NOW, let's say the NSS is open. Put your voltmeter leads across the NSS and turn on the ignition switch to start and you will see 12Volts across the switch. WHY? Because the resistance across the switch is infinite, while the resistance at the solenoid remains 2 Ohms. So you have BEAUCOUP resistance across the switch and relatively nothing across the solenoid. Forget the exact calculations, just remember that 99% or more of the circuit resistance is at the NSS, SO.. the Voltage is dropped across the NSS in your test.

Now take that same thinking to a situation where there is a dirty connection in the circuit causing say 2 Ohms resistance when carrying full current. That would mean that this dirty connection is dropping the same amount of voltage as the solenoid. So, the dirty connection would be dropping 6 Volts leaving only 6 Volts across the solenoid, which probably wouldn't pick it.

Does this help?

I appreciate the time and detail that you are providing. It is apparent you are trying to teach me over a very difficult medium (a forum) with the tools available. I really am thankful.

I just want to make it clear: I understand the theory (V=IR, In a series circuit the summation of Voltage drop at individual elements is equal to voltage applied to the entire circuit)
I understand the general methodology (apply dmm leads in parralel i.e. across element you want to determine Voltage drop on, looking for voltage draw at element while cranking, this is done sequentially on each element ).

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.

Okay, great. You're more than half way there. Understanding what you're testing and how to test it is the hard part.

NOW, what you're looking for is the location of the switches. I wish I could be more help with that. It seems like someone earlier in this thread or another thread recently described where to find the NSS. My 123 cars have been manual transmissions except one that my wife had and I never had to deal with this particular problem.

I would expect that if you get underneath and look at the transmission shift linkage you can find the switch. Maybe someone on here has an FSM for your car.

I am assuming that you have already checked for a voltage drop at the starter solenoid. That one is relatively easy to get at.

Probing the test points can be a PITA if they are hard to access.

You said jumping the termimal block (small screw to big screw) nothing haopens. Did you try jumping small screw to battery + terminal? put a 20 A ammeter between the small screw and battery + terminal. The should pull in the startier solenoid and draw 7A..

One comment - high current DC ammeter is very expensive as ammeter is inherently intrusive to the circuit. It needs a very small value and precise resister to do the measurement. Most DIYers do not have one. Need plan B.

Most DVMs have a 20A scale that will do the job. I have a HF and a Craftsman at $15 and $25 respectively both have 20A scale. I wouldn't call that expensive..

So where did using an ammeter come into the discussion?

Since I measured my starter solenoid drawing 7 amps, I suggested Hinu do the same (if he has an ammeter). Real easy to do. Jump the terminal block with the ammeter. He should see around 7 amps and it should crank unless........

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.

LOW VOLTAGE AT STARTER
 

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

From my post #35 in this thread...

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.

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

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.

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.