Intermittent no start, 2007 NCV3

Froggy

Member
Vertigo: You wrote, "Even a 5000CCA battery will not change the load on the solenoid."

What you say is true. But I'm not discussing the load. A 2KW starter is a 2KW starter. That's the load no matter the CCA of the battery may be. I am pondering the badly burned starter post inside the solenoid. It is burned so bad that it will not pass electrons.

OK, I have opened one failed solenoid. In terms of arcing across the solenoid posts (and burning one up), a 5000CCA battery will create a lot more flash/burn on the starter motor post than a 750CCA. I am pondering what role a burned starter post within the solenoid might play.

I am going to cut open solenoid #4 to see what (if anything) is burned up in it.
Will post back when I can get to it.

Thanks!
 

showkey

Well-known member
^^^^^^^^^^^^^^

No the load through the the solenoid is the load of the starter. So let's say the 2kw is 2000 watts which is likel close given the info we have.

2000 watts / 12 volts = 166 amps

Now if on the bench test no load it might draw 60-80 amps. ( just a guess)
At zero degrees cranking a cold engine the same starter might draw 400 amps. ( just guess)
In both cases above the same battery can be used and the size of the battery does no change the amp draw.


The key is determining if your starter system is drawing more amps to start the truck. If it does draw more than normal you would have a good reason why your solenoid contacts are arc damaged.
 

Froggy

Member
Showkey: Yes, what you say is correct, I fully agree. Evidently, I am not communicating well for you and Vertigo have overlooked the issue that I am pondering. I am pondering the role and consequences of the burnt starter post inside the solenoid.

If you examine the pictures of solenoid #2 I posted earlier, you will see that the contactor and the internal solenoid post that goes to the starter are badly burned. Burned so bad that no conductivity through that part of the circuit is possible unless I manually punched the push rod several times. This means the hold in coil would not activate because that coil activation is dependent on the contactor and the internal solenoid post properly connecting.

Let's suppose the van has a "start until run" circuit. In other words, you insert the key, turn to start and the solenoid remains engaged until crankshaft sensor says "engine is running" at which time the computer shuts off the solenoid circuit.

If this supposition is true (and I have noticed this behavior on my van -- that I do not have to hold the key in start position to start the van, I merely have to touch the start position and let go and the starter will continue to engage until "engine is running").

If there is a "start until run" circuit operating, and the contactor and the starter motor post cannot pass the necessary amps, the pull in coil is not activated. In other words, the computer does not get "engine running" signal and hold in coil is not activated and this ultimately burns up the pull in coil. It shorts out. Less than two ohms resistance for the pull in coil means it heats up fast.

I am looking for a cause whereby the pull in coil becomes weak. The ONLY thing showing thus far is the burnt contacts inside the solenoid. And the number of amps available will determine the size of the electrical flash when the contacts approach each other. This is why you can't put a 50 amp circuit across contacts rated for 10 amps. The size of the contacts matters.

Vertigo seems convinced the problem is in the van. Five new starters in 60,000 miles might be indicative that my "start until run" circuit (if such a thing exists) is faulty, however, why would all five new starters work properly for a thousand starts (+/-) ever since 2007?

I am anxious to see inside solenoid #4 to see what is burnt. Something is because starter #4 failed just like the others.

Thanks!
 

showkey

Well-known member
I get what your saying. Weak pull could be a cause for arcing on the contacts and along with excessive amp draw. I am still not with the big battery causing a big arc or flash.

Yes many cars including the Sprinter have the "auto start" or "crank until run future". It does have a time out at about 5 seconds if it does not start.

Not sure about the auto start causing the solenoid failure. The whole starter system is intermittent duty so any over time run could take its toll. If the solenoid is remaining energized to long a starter whine or over run might be heard.
 
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Froggy

Member
Showkey:

Bear with me for a moment. The inrush current to a coil can be many times greater than the nominal load for the coil. Coils (such as starter windings and solenoid windings) have almost no resistance until their magnetic field stabilizes and the coil's inductance begins to function. This physical phenomenon enables a huge discharge across the starter posts inside the solenoid. This discharge can be anywhere from 10 -50 times more than the nominal amperage rating for the coil (which, let's say, is approx 150 amps). In our vans, this discharge is only limited by the CCA of the battery.

A 950CCA battery will produce more inrush current and a larger flash during the inrush moment than say, a 750CCA battery. And given the small physical size of the internal contacts within these solenoids, 200 more amps surging during inrush may explain why I have had four solenoid failures.

If you care to look into the properties of inrush current, here's a good article: https://en.wikipedia.org/wiki/Inrush_current

My hunch, after four starter failures and dissecting one solenoid, is that these Bosch solenoids are simply inadequate.

I will post some pictures of solenoids #3 and #4 when I dissect them.

Thanks!
 

bcislander

'07 Mercedes-badged Dodge
Bear with me for a moment. The inrush current to a coil can be many times greater than the nominal load for the coil. Coils (such as starter windings and solenoid windings) have almost no resistance until their magnetic field stabilizes and the coil's inductance begins to function. This physical phenomenon enables a huge discharge across the starter posts inside the solenoid. This discharge can be anywhere from 10 -50 times more than the nominal amperage rating for the coil (which, let's say, is approx 150 amps). In our vans, this discharge is only limited by the CCA of the battery.
This is completely incorrect. Solenoids in DC circuits have NO inrush current. They are inductors whose current builds from 0A to a maximum value determined by the DC resistance of the inductor. See: http://www.electronics-tutorials.ws/inductor/lr-circuits.html

You are confusing the starting characteristics of a motor with those of a solenoid/coil/inductor. A motor consists of windings which are inductive, but their resistance is low so the current builds very quickly to a large value (the inrush current) which is determined by the total resistance in the circuit = winding resistance + resistance of the cabling (Battery to starter + grounding cables) + internal resistance of the battery.

Once the motor starts to rotate it produces what is called a back EMF which opposes the flow of current, eventually reducing the current to the 'normal' running value when the motor is operating at its designed speed & load. It is then the amount of LOAD (the power required to rotate the diesel engine) that is the main determinant of the amount of 'normal' running current.

A 950CCA battery will produce more inrush current and a larger flash during the inrush moment than say, a 750CCA battery. And given the small physical size of the internal contacts within these solenoids, 200 more amps surging during inrush may explain why I have had four solenoid failures.
The CCA capacity of the batteries is, in your example, irrelevant. The current delivered by the battery depends on the LOAD, not its capacity to provide current, with the proviso that the load does not require a current larger than the battery is able to provide. I would expect the current draw of the starter motor to be less than 500A max (no data, willing to be corrected).

In short, while the 950CCA battery can provide 200A more current, it is highly unlikely to do that in the case of a starter motor, unless the motor is jammed, or otherwise malfunctioning.

Finally, in the case of inductive DC loads, such as a starter motor & a solenoid, the worst arcing will occur when the contacts open, not when they close. The inductor (e.g. motor winding) stores energy in its magnetic field & there is mechanical energy in the rotating mass. This energy tends to keep the current flowing until the energy is dissipated, which causes an arc at the switch contact that is trying to stop the current flow.

If you care to look into the properties of inrush current, here's a good article: https://en.wikipedia.org/wiki/Inrush_current

My hunch, after four starter failures and dissecting one solenoid, is that these Bosch solenoids are simply inadequate.

I will post some pictures of solenoids #3 and #4 when I dissect them.

Thanks!
Having typed all of the above, I'm sorry to say that I have no idea as to what is causing the premature failure of the starters/solenoids in your van. If this were a common problem, such as the Y-Cable & ground strap, I'm sure that others would have chimed in with a 'me too'. So, my conclusion is that there is something peculiar to your van, such as the 'tolerance stacking' mentioned in previous posts, that is causing the problem.

I hope that I have at least been able to correct some of your misconceptions regarding the electrical characteristics of the starter system.
 

Froggy

Member
BCIslander:

Thank you for your comments and maybe I need to be corrected.

My comments above were not directed at either the pull in coil or the hold in coil. My comments were directed at the starter motor circuit which, I believe, does have a serious inrush amperage. Yes No?

Please notice the burned contactor and starter motor contact pictures posted earlier. Badly burned because of arcing. I am pondering whether or not my many starter failures are due to a battery that provides too much inrush amperage given the physical size of the contacts within the solenoid.

Here's a study on dc motors that may be helpful:

http://www.electrical4u.com/starting-methods-to-limit-starting-current-torque-of-dc-motor/
 
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bcislander

'07 Mercedes-badged Dodge
BCIslander:

Thank you for your comments and maybe I need to be corrected.

My comments above were not directed at either the pull in coil or the hold in coil. My comments were directed at the starter motor circuit which, I believe, does have a serious inrush amperage. Yes No?

Please notice the burned contactor and starter motor contact pictures posted earlier. Badly burned because of arcing. I am pondering whether or not my many starter failures are due to a battery that provides too much inrush amperage given the physical size of the contacts within the solenoid.

Here's a study on dc motors that may be helpful:

http://www.electrical4u.com/starting-methods-to-limit-starting-current-torque-of-dc-motor/
Yes, the starter motor does have a large inrush current & I tried to describe why. Your link just goes into more detail. I was trying to KISS.

If you reread the post to which I replied you stated:

"Coils (such as starter windings and solenoid windings) have almost no resistance until their magnetic field stabilizes and the coil's inductance begins to function.
"
This is not correct on many levels, not the least of which is equating starter (motor) windings to solenoid windings. Solenoid windings have relatively large resistances to limit the steady-state current, while motor winding resistances are relatively small for the reasons outlined in your reference link.

As I also stated, it is highly unlikely that the high CCA of the starter battery is the cause of your problem. The small difference in the internal resistance of a 750CCA battery vs a 950CCA battery would not increase the inrush current by 200A.
 

Froggy

Member
Yes, I misspoke. My error. My thoughts were going in one direction and my words were going in another. Not the first time.

The original sentence should have read: "Coils in starter windings have almost no resistance until their magnetic field stabilizes and the coil's inductance begins to function."

My present concern has narrowed to the badly burned contacts within solenoid #2. Maybe I am going in a wrong direction. I've gone in many directions.

I will soon dissect solenoids #3 and #4 to see what I can see. Something has killed four solenoids thus far.
 
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ponderosaTX

2010 Airstream Interstate
Hi Froggy,

It has been well over a year since you posted the following:

Meanwhile, it would be great if I could find replacement solenoids to see what that would produce. The only design flaw that I see in the dissected Bosch solenoid is that the copper insert in the contact bolts is too shallow. Copper mass and exposure to the contactor should be greater.
I presume that you have seen the thread

https://sprinter-source.com/forum/showthread.php?p=466045

providing a source for an NCV3 solenoid (at least 2007-2008 vintage). A slightly cheaper source is:

http://www.ebay.com/itm/BOSCH-2339305066-/302224829477

I just replaced the starter in my 2010 Airstream (2008 Freightliner chassis) after 20K miles on the replaced starter so I am purchasing a replacement solenoid to create a spare nearly new starter in my parts bin. If you find a less expensive source for early NCV3 solenoids please post your information to this forum.
 

Our idea

New member
Had similar intermittent starting problem. Mercedes diagnosed it as a starter going bad. Replaced and now works fine.
 

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