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Author Topic:   Electrical Starter Problem
Firewood posted 04-09-2013 10:39 PM ET (US)   Profile for Firewood   Send Email to Firewood  
About three years ago I bought a 1992 Outrage 19 with a 1991 Johnson 120-HP outboard. One problem I am having is that when I start the engine the starter motor initially struggles to turn the engine over for about one second. After that initial one-second the starter turns the engine at what I would call full speed and the engine starts. I have cleaned and polished the battery cable connections at the batteries, battery switch, starter and solenoid but that didn't help at all.

Over the winter I replaced the batteries which are in the console with Optima Blue tops which helped some. Today I checked the starting battery terminal voltage and found 12.78-Volts and at the engine it was 12.62-Volts. Also, when I put the two batteries in parallel and start the engine there is no hesitation in the starter when starting the engine.

I'm looking for advise on what the problem might be: battery cables, starter motor? Thanks,
Mike

jimh posted 04-10-2013 08:42 AM ET (US)     Profile for jimh  Send Email to jimh     
You probably have too much voltage drop in the battery cables between the batteries in the console and the engine. When you parallel the batteries, there is more voltage at the battery end, and the engine cranks over normally.

What is the length of the battery cable between the battery and engine?

What is the gauge of the cable?

Are there any connections in the cable?

Firewood posted 04-10-2013 06:19 PM ET (US)     Profile for Firewood  Send Email to Firewood     
Jim,

Thanks for the reply. The length of the battery cables is about 18 feet. I'm not really sure of the gauge of the cables but they are heavy and there is only one connection of the battery cables at the battery switch.

Thanks,

Mike

jimh posted 04-10-2013 09:15 PM ET (US)     Profile for jimh  Send Email to jimh     
For battery cables of 18-feet you will need cables of monster size to provide proper starting. The BRP Pre-installation and rigging manual, available free as a download on line from BRP as part of their fantastic on-line literature resource at

http://www.operatorsguides.brp.com/Index.aspx?lang=e& s1=e208f917-c847-44f7-b176-acb19aa6d427&brands=ej&type=og

shows the minimum size for that length will 1-AWG cable. Unless you have replaced the original cables that were provided with the outboard engine with new cables (about four times larger) and provided a one-piece run from engine to battery, you are probably not meeting the required cable size. There is no way to overcome the voltage drop in smaller cables.

If you have to replace the cables, I'd just go all the way to 0-AWG wire, to give your battery circuit some added margin.

You wil have to investigate the present wire gauge, but, based on your narrative, it sounds like the wire length and inadequate wire size have combined to create this problem.

jimh posted 04-10-2013 09:16 PM ET (US)     Profile for jimh  Send Email to jimh     
Try this link for the rigging guide:

http://www.operatorsguides.brp.com/OperatorsGuidesAttachments/ OwnersManuals_EJ/attach/Accessories/5008815%20EN.pdf

AZdave posted 04-11-2013 01:52 AM ET (US)     Profile for AZdave  Send Email to AZdave     
Mike, could you add a bit to the information in your original post? You said that when you connected the two new batteries in parallel the problem went away. Do you mean that you turned the battery switch to the "both" or "all" setting, or did you actually use jumpers to rewire the battery circuit? When you measured different voltages at the battery terminals vs at the engine, was the engine turned off, running, or was the starter being engaged? Two identical batteries in parallel should provide exactly the same voltage as either one by itself. This would not be true if the batteries were connected to a circuit with very low resistance (like a starter). If the starter works normally with two batteries in parallel, I would still be suspicious of the starter or the batteries, rather than the cables. Dave
jimh posted 04-11-2013 09:43 AM ET (US)     Profile for jimh  Send Email to jimh     
quote:
....when you connected the two new batteries in parallel the problem went away....

This is precisely the information I used to conclude the conductors were too small. When the two batteries are in parallel, the drop in their terminal voltage (during engine cranking under extreme load) is much less than when either battery alone is used. The higher terminal voltage at the battery then produces a higher voltage at the starter.

The starter motor draws the most current when it is first beginning to move from its stalled position. This is the moment of highest current, and also the moment of maximum voltage drop in the connecting circuit. It appears from the narrative that with just one battery the voltage delivered is marginal, and the starter motor just barely gets into motion.

Once the starter motor overcomes the initial stalled condition, the current being drawn is much less. This makes the voltage drop much less. That is why the starter motor spins faster once it gets the engine turning over.

jimh posted 04-11-2013 09:48 AM ET (US)     Profile for jimh  Send Email to jimh     
In any case, if you don't already have battery cables of 1-AWG size--and those are huge cables--you are not compliant with the recommended size for your installation. It would be nice to know what gauge is being used now. If you already have 1-AWG cables, then we can look for another cause, but, until the cables are ruled out as the cause, they are the most likely source of the problem.
Firewood posted 04-11-2013 12:53 PM ET (US)     Profile for Firewood  Send Email to Firewood     
Dave, When I mentioned putting the batteries in parallel I did mean putting the battery switch to "both or all", combining the start and house batteries. When I measured the voltage I was showing the difference between the start battery voltage and the voltage at the solenoid with the engine off.

Jim, Your narrative above about the starter motor describes the problem exactly. I did confirm today that my battery cables are 2-AWG at 18 feet in length. I also noticed that the positive wire from the solenoid to the starter is 8-AWG at about 6 inches long. I'm not sure if that difference in size makes any difference.

I'm pretty sure that the way my boat is set up with the batteries in the console and the cables is original. I'm wondering what size battery cables other Outrage 18/19's with batteries in the console are using?

Thanks for all the help,

Mike

DVollrath posted 04-11-2013 01:49 PM ET (US)     Profile for DVollrath  Send Email to DVollrath     
When diagnosing system failures generically, it is very helpful to determine if and when things were working at one point, and noting what changes to the system occurred subsequently. If you believe that this cabling is original and that the boat did not have this problem straight from the factory or dealer, then you can assume that the cables are sized appropriately. You are not the original owner, so you likely do not know whether these symptoms were present from the get-go, but:

When you bought the boat 3 years ago, did it exhibit this same behavior? If not, then I'd suspect starter deterioration, or corrosion at some terminal on the battery switch or other connections. Since you've polished the connections already, I think that makes the starter the most likely culprit. I'm not familiar with failure modes of starters, but excess current draw at start-up seems like one reasonable mode. Staying longer in the "stalled" position weakened magnetic fields or failing bearings might explain it.

If this behavior was present when you bought the boat, you have one less clue, but the answer still might be the same.

Dennis

jimh posted 04-11-2013 02:31 PM ET (US)     Profile for jimh  Send Email to jimh     
If the cables are 2-AWG they would be undersized for the present-day recommendation.

There can be voltage drop in any part of the circuit. For example, the solenoid contacts could have a build up of carbon from arcing. Connect your voltmeter across the solenoid contacts and measure the voltage drop during engine cranking. A new solenoid is about $30 and can be installed in five minutes.

You seem to have already done a careful check and refurbishment of all the electrical contacts in the system. The only other component where there may be a voltage drop is the primary power switch. Measure the voltage drop across the switch when cranking over the engine, too.

Firewood posted 04-11-2013 05:07 PM ET (US)     Profile for Firewood  Send Email to Firewood     
Dennis,

When I bought the boat I did notice the problem but I didn't really use the boat much the first year. As I became more familiar with the boat I just assumed that the batteries were the problem. After replacing the batteries, the problem only slightly improved so I started to look at the cables or starter as the problem.

Jim,

Over the winter I replaced the battery switch with a BEP switch so I doubt thats the problem.
I'm not really sure how to check voltage drop across the solenoid contacts. Can you explain this a little better for me? Can I do that with a basic voltmeter? It might take a few days for me to get that done.

Thanks again,

Mike

kwik_wurk posted 04-11-2013 05:45 PM ET (US)     Profile for kwik_wurk  Send Email to kwik_wurk     
While this may be a hassle in your situation, I temporarily re-wired a battery closer to the motor, to see if the suspected cable was the issue. --- Even jumper cables will work.

But from your description, I would not 100% state that battery cable is root cause. You could still have a starter (or starter circuit) issue, but typically clicking or partial turnover or stalling would be present.

From a troubleshooting perspective, cut the problem (or potential problems) at the half way point. -- So that would be about the solenoids, given the upstream improvements you have made.

You may need some alligator clips to attach to solenoid wire lugs/nuts, plus you have to start the engine and read the voltmeter at the same time. If you have a trip switch or the shift lock out mechanism that allows the engine to turn over but not start, you can use that to allow for longer cranking. Otherwise, you can physically remove the solenoid and bench test it (safest method by all means).

jimh posted 04-11-2013 10:33 PM ET (US)     Profile for jimh  Send Email to jimh     
To measure voltage, connect one probe to one circuit point, and the other probe to the other circuit point. To measure the voltage drop across the solenoid, connect one probe to one high-current contact and the other to the other high-current contact. Crank engine. Read voltage drop across the solenoid.
Firewood posted 04-15-2013 01:50 PM ET (US)     Profile for Firewood  Send Email to Firewood     
I checked the voltage drop across the solenoid and here is what I found.

At the battery: 12.76V
At the solenoid: 12.57V
Across the solenoid while cranking the engine: 9.87V
At the starter while cranking the engine: 9.80V

I hope I did it right.

Thanks,

Mike

kwik_wurk posted 04-15-2013 03:43 PM ET (US)     Profile for kwik_wurk  Send Email to kwik_wurk     
Can you please explicit as to what was used for the readings, as in:

Battery Negative terminal - Battery Positive terminal: 12.76V

This will reduce and refine some of the questions that will come up in the very short future.

But if I read this correct, you had a 9.87V drop across the solenoid, and then 9.8V from X (somewhere on solenoid) to the starter lead?

Firewood posted 04-15-2013 04:26 PM ET (US)     Profile for Firewood  Send Email to Firewood     
Okay, I'll try to explain a little better. The 12.76V at the battery is the terminal voltage of the starting battery before cranking the engine. The 12.57V at the solenoid shows the voltage difference between the battery and the solenoid through the battery cables before cranking the engine. I measured this at the point where the positive cable attaches to the solenoid and at the negative ground at the engine. I then moved the positive probe of my volt meter to the other side of the solenoid and kept the negative probe attached to the negative ground. Then I cranked the engine and got the 9.87V reading on the volt meter while the engine was cranking. I then moved the positive probe to the starter where the positive cable that leaves the solenoid attaches to the starter. I then cranked the engine again and got a reading of 9.80V.

I'm not really sure that's what I was suppose to do to measure the voltage drop. Hopefully this makes a little more sense.

Thanks,

Mike

jimh posted 04-15-2013 08:17 PM ET (US)     Profile for jimh  Send Email to jimh     
Mike--Your sorta measured the voltage drop across the solenoid. It looks like only 9.87 - 9.80 = 0.07-Volts. That tends to indicate there is no problem in the Solenoid contact.
dbrown posted 04-15-2013 11:16 PM ET (US)     Profile for dbrown    
If I read it right, he had a 2.7 Voltage drop across the Solenoid when cranking the engine. He had 0.07 voltage drop in the cable from the Solenoid to the starter positive terminal. Is that correct?

12.57V (Battery side of Solenoid)
9.87V (Starter side of Solenoid)
-------
2.7 Volts

jimh posted 04-16-2013 12:39 AM ET (US)     Profile for jimh  Send Email to jimh     
It would be a lot simpler if we could just get the voltage drop across the solenoid measured directly. The reason for measuring the voltage drop across the solenoid is to eliminate the solenoid as a possible cause of the voltage drop.

A voltmeter has two leads. It measures the voltage between them. Connect the two leads of the voltmeter to the solenoid. Connect the (+) lead to the side of the solenoid that has the battery connected. Connect the (-) lead to the side of solenoid that has the starter motor connected. Crank over the engine. Read the voltage on the meter. That is the voltage drop across the solenoid.

kwik_wurk posted 04-16-2013 12:51 AM ET (US)     Profile for kwik_wurk  Send Email to kwik_wurk     
Well how's this, I don't think you measured the solenoid at all. -- You have indirectly measured the voltage drop of the cable that runs from the solenoid to the starter, 0.07 volts, which is fine.

As jimh mentioned across the solenoid would be good, make direct measurement, as described. Or indirectly by doing comparing these two readings: ground vs solenoid input (battery), and ground vs solenoid output (starter). -- Be safe.

It would also be beneficial to know what the voltage at the starter battery is during cranking. (Measure negative and positive terminals.) -- This can then be compared against your prior readings, unless you put the unit on a charger or something.

Off hand, 9.8 volts at the battery during cranking isn't bad, but there is more to the equation than just the voltage.

DVollrath posted 04-16-2013 01:03 AM ET (US)     Profile for DVollrath  Send Email to DVollrath     
quote:

12.57V (Battery side of Solenoid)
9.87V (Starter side of Solenoid)

Two different conditions. 12.57V was measured with starter not engaged, 9.87V was measured cranking. This does not seem unreasonable.

Something that confuses me is the measurement of the non-cranking potential at the solenoid. While it appears that there is a 190mV drop, it is not clear why this should be. There should not be any current flowing through that cable (if I understand how it is wired), and no current means no voltage drop. The meter should be mega ohm range impedance, so that would not account for it. Assuming the cables are 18' of 6ga, 190mV would require 26A or so to be flowing. 4ga would be even worse, requiring over 42A to produce 190mv.

I suspect this is measurement error, probably from using 2 different grounds.

Do you have a diagram of the wiring?

Can you retake the measurements using the negative lug of the battery as the ground for each reading? Make the ground connection to the meter solid, scratching through any oxide present.

Firewood posted 04-19-2013 12:29 PM ET (US)     Profile for Firewood  Send Email to Firewood     
I was able to get to the boat today and measure the voltage drop across the solenoid the way Jim explained and had a reading that fluctuated between .02 and .04 volts while cranking the engine.

Just to make sure its clear where I connected the leads of my volt meter, reference the diagram "Starter Circuit" in the article Jim wrote on "Electrical Starting Circuits" in the reference section
. I placed the + lead of my meter at point #6 and the - lead at point #7 then read the meter while cranking the engine.

I also checked the battery terminal voltage while cranking the engine. Terminal voltage was 12.75 at rest and 12.75 while cranking so no change.

I hope I did this right. Thanks again for all the help.

Mike

jimh posted 04-19-2013 02:04 PM ET (US)     Profile for jimh  Send Email to jimh     
I think Mike is making reference to the components and callouts in this drawing:

http://continuouswave.com/whaler/reference/graphics/electricStart/ electricStart734x510.png

A voltage drop of 0.02 volts across the high-current circuit of the solenoid during engine cranking is a very good indicator that there is no problem in the solenoid. This more or less eliminates the solenoid from being considered a possible cause of the excessive voltage drop in the starter circuit.

Firewood posted 04-19-2013 02:09 PM ET (US)     Profile for Firewood  Send Email to Firewood     
Jim,

Is there anything else I can test? Or should I just assume that the cables are the problem and consider changing to larger diameter cables.

Mike

jimh posted 04-19-2013 02:15 PM ET (US)     Profile for jimh  Send Email to jimh     
Based on the latest voltage measurements, it looks as if most of the voltage drop is occurring the power distribution cables. This means there is too much resistance in the cables. The cause of the resistance can be in two general areas:

--the cables themselves are too small and have too much resistance, or

--one or more or all of the terminal connectors attached to the cables have too much resistance in their connection to the cable or to the associated terminal post.

Inspect the cable very carefully at the terminal connectors to see if there is any indication of a bad connection. Look for oxidation and corrosion. It may be hard to measure resistance because the values are very low, but, if a good meter is used, you may be able to measure the resistance of the cable-to-terminal connection. Measure first from one terminal at one end of the cable to the other terminal at the other end. Then try to measure just the cable resistance by putting the probes directly on the wire of the cable, not on the terminal. If there is any sort of difference in the readings it would indicate the terminal-to-cable connection was not very good.

If there is no sign of a problem with the terminal connectors, the cables themselves may be the problem. The remedy is to use larger cables. Using extremely large cables is one of the drawbacks of moving the batteries so far away from their biggest and most critical load, the electrical starter motor.

DVollrath posted 04-19-2013 02:23 PM ET (US)     Profile for DVollrath  Send Email to DVollrath     
Mike,
I think that your measurement of 0.040V (40mV) under load means your solenoid does not have excess resistance.

I am a little surprised by the single battery voltage not drooping at all when cranking. This would mean it is an ideal voltage source. Was this measurement done with both batteries in parallel perhaps? Still should see some reduction, but not as much I would think.

Were you able to measure the voltage drop across the positive cable under both loaded and non-loaded conditions? The most reliable way would be a direct measurement, like you did with the solenoid. This takes out any uncertainty regarding grounds. Alternatively, you could take 2 sets of measurements, one at the battery (+) and one at the solenoid (battery side), using the same ground each time.
You can extend your meter leads as necessary for voltage measurements if you are using a reasonably good meter with input impedance in the mega ohm range.

If we assume your measurements to this point are correct and consistent, it seems that there is a 2.66V drop across the positive starter cable:
12.75V - 9.87V - 0.04V = 2.66V

Bear in mind that there will be at least this amount of drop across the negative cable as well, assuming it is the same length and gauge as the positive. So instead of seeing 9.87 across the starter, you may be looking at:
9.87v-2.66V = 7.21V. This may be a bit low.

Using resistance tables for various gauge wires, and assuming the 2.66V drop is accurate, you get steady-state cranking currents of:
8ga: 235A
6ga: 374A
4ga: 595A

I don't think that 595A is reasonable for steady state cranking current (load beyond the initial stall requirement), so I'd guess that you are looking at 8ga or 6ga cable.

Any way you can measure the diameter of the cable conductor (without the insulating jacket)? Perhaps at the battery terminal?

Dennis

Jerry Townsend posted 04-19-2013 04:34 PM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
Mike - your solenoid is fine. In actuality, solenoid contacts are normally trouble-free.

Your cleaning the contacts and connectors was a good move and probably ensured that is not your problem.

The starter lead from your solenoid to the starter, being long and having to carry a lot of current should be large - as Jimh points out. I would guess that 1 gauge would work fine.

Connecting your batteries in parallel and the result shows the problem could be a battery that is too small. I am not familiar with the Optimus batteries that you installed.

Another possibility - and in my mind perhaps a probability, might be the starter starting to drag a bit. This would cause an initial resistance.

Remember, an electrical problem will not correct itself - and the solenoid and contacts look good. A voltage drop across the starter cable of 2 - 3 volts when starting is reasonable.

So - with a properly sized battery and with at least a #1 cable - look at the starter. ---- Jerry/Idaho

DVollrath posted 04-19-2013 06:06 PM ET (US)     Profile for DVollrath  Send Email to DVollrath     
I agree with Jerry that it may be the start of starter problems. I also agree with the rest that the battery cables may be undersized for your motor. I'm not as clear you need to go to 0ga, or even 1ga.

I looked at the BRP document Jim referenced. Those are some big cable recommendations, even for the smaller motors. I also have a copy of the Yamaha rigging guide, whose cable length recommendations seem much more lenient. For example, an F150 comes with a cable length of 8.6' from the factory (unspecified gauge). The extension guide table states that it is permissible to add up to 10' to each conductor (20' total) using 4ga. 2ga can be used to extend an additional 33' total, while 1ga get 52' more than factory.

You can also infer from the granularity of the table that not all motors and starters are created equal, and that some require more current than others. Perhaps E-TECs are more like the larger Yamahas with respect to starting power requirements.

If you do buy the analysis I did above that the starter is using 375A or less, using 4ga for 18'+18' will have a total drop across the cables (both + & -) of 3.33V, which should be fine.

Dennis

kwik_wurk posted 04-20-2013 12:28 AM ET (US)     Profile for kwik_wurk  Send Email to kwik_wurk     
Firewood, voltage drop across the solenoid sounds good, I assume that while you did some of these tests the 'clicking' of the solenoid was not delay or making a double clicking sound. -- So we have eliminated this more or less.

So now onto the next step of troubleshooting.

Measure voltage drop of the cables themselves (pos. and neg.).

You can do this directly if the leads are long enough, going from one end of the wire to the other, or indirectly by measuring the voltage at the starter battery, and solenoid.

You need to re-measure the battery during cranking. There is no way on earth that your starter battery did not drop in voltage during cranking. Unless you are plugged into a large (very very large) battery charger, there has to be some drop. --- So this needs to be redone, make sure you are not capturing the peak (max) voltage or something.

Firewood posted 04-23-2013 02:33 PM ET (US)     Profile for Firewood  Send Email to Firewood     
I went down to the boat today to check the terminal connections and check the resistance of the battery cables and found a big problem. I have been mistakenly measuring the house battery voltage in stead of the start battery voltage. I'm really sorry for the mistake and confusion, so I started all over.

Here is what I found:

Start battery terminal voltage @ the battery: 12.70V
Start battery terminal voltage @ the engine: 12.70V

Battery cable voltage drop while cranking engine measured from the battery to the engine: "+ cable" = .90V, "- cable" = .40V.

Battery cable resistance: .2 for both + and - cable (I think I did this right). Measured from the start battery to the engine.

I then checked the battery voltage while cranking the engine:

Battery terminal voltage: 12.65V at rest, 11.45 while cranking engine.
Battery terminal voltage at the engine: 12.65V at rest, 10.20V while cranking.

I also checked the battery cable to lug connections and they all seemed to be secure and not corroded.

Again, sorry for the mistake. Hopefully these numbers make a little more sense.

Thanks,

Mike

DVollrath posted 04-23-2013 03:26 PM ET (US)     Profile for DVollrath  Send Email to DVollrath     
Mike,
OK, these are more consistent and believable.

Some points I'm still not clear about:

quote:

Battery cable voltage drop while cranking engine measured from the battery to the engine: "+ cable" = .90V, "- cable" = .40V.


I'm not clear what was being measured here.
Was this a direct measurement of the positive battery cable drop? One lead of VOM on battery lug, and the other on the end connected to solenoid? A positive cable drop while cranking of only .4V, .5V, or even .9V for an older 120HP motor does not seem reasonable to me. Jim, Kwik, Jerry?


quote:

Battery terminal voltage: 12.65V at rest, 11.45 while cranking engine.
Battery terminal voltage at the engine: 12.65V at rest, 10.20V while cranking.

Were these measurements taken using the same common ground connection? If so, then this says that your cable voltage drop is 11.45V-10.2V = 1.25V, a more reasonable value. If not, then???


I really want to emphasize this point: grounds are really important! If you take 2 measurements with 2 different grounds, you really cannot know what the true difference is until you also measure the voltage potential between the 2 grounding points.In the case of a boat, this could be as large as the drop on the positive cable.

The whole point of trying to determine voltage drop across cables, connections, and solenoid contacts is to figure out how much is actually left for the starter (and required starting electronics or circuits). I think you can measure this without ambiguity just by connecting your meter across the starter(+) and the motor ground terminal. I'm not clear if your starter has a distinct ground lug, or if it uses chassis ground, but get a good connection as close as possible.

If you truly do only have 1.25V drop across the (+) cable when cranking, I'm still betting your starter is a good chunk of the problem.

Dennis

Firewood posted 04-23-2013 07:01 PM ET (US)     Profile for Firewood  Send Email to Firewood     
Dennis,

I measured the voltage drop of the + battery cable as you describe with one lead at the battery + terminal and the other lead where the + cable attaches to the solenoid. The - battery cable was measured from the battery - terminal to where the - cable attaches to the engine block.

When I measured the battery terminal voltage at the battery (at rest & cranking) I used the battery - terminal as the ground. When I measured the voltage at the engine (at rest & cranking) I used the stud that the - battery cable connects to the engine block as the ground. So, I guess I didn't use the same ground point.

Mike

DVollrath posted 04-23-2013 07:23 PM ET (US)     Profile for DVollrath  Send Email to DVollrath     
Mike,
Thanks for the clarification. Things are now quite consistent. The loop under load while cranking is:

11.45V is (more or less) equal to .9V + 10.2V + .4V

This says to me that your ground cable is of a heavier gauge than your positive cable, and that you have 10.2V across the starter.

I'm not sure what the failure mechanism is, but I think the problem is internal to the starter.

Just out of curiosity, to get the voltage when "cranking" have you disconnected & grounded the plug leads, or how do you accomplish it?

Thanks.

Dennis

jimh posted 04-23-2013 11:03 PM ET (US)     Profile for jimh  Send Email to jimh     
With an electrical motor of the type used to crank an engine for starting, the current drawn by the electrical motor will be highest when the motor is stalled. This is the condition when the electrical motor is first energized. A large current flows but the motor has not yet begun to rotate. As the motor rotates and comes up to speed, the current should decrease.

The voltage supplied to the motor is inversely proportional to the current because the current causes a voltage drop in the battery and in the conductors between the battery and the motor. If the stalled current of the motor is too large and creates too much voltage drop, the resulting voltage will be too low to get the motor to turn under the load.

If the voltage drop due to the initial current inrush is right at the margin of getting the motor to turn, the motor will begin to turn very slowly. As it turns the current drops off, causing the voltage drop to be less, causing more voltage to be delivered to the motor, causing it to turn faster, causing it to draw less current. This seems to be the situation we have in the present discussion: the system has just barely enough power to get the starter motor to begin to spin, but once it does then it cranks up to speed and starts the engine.

The problem with the system as it stands now is there is no margin for loss of voltage in the battery. If the battery is not at a high voltage, that is, near full charge, it probably won't be able to over come the stalling current and the initial voltage drop.

It is also possible that there is some sort of defect in the starter motor or its gears or the flywheel gears that causes the initial engagement of the motor and gears to have a binding or jamming. This stalls the motor, creating the big current inrush, lowering the voltage, and so on.

I do not know of a method to test the starter motor and its gears for binding.

If the starter motor is not malfunctioning, the remedy must be applied to the cables to reduce the voltage drop.

If the starter motor is malfunctioning, the remedy is to get a new starter motor. However, it might still be wise to reduce the voltage drop in the cables as that will create more margin in the system. You will be able to start the engine with the battery charge at a lower charge than you could if there is voltage drop in the cables.

Firewood posted 04-26-2013 12:33 PM ET (US)     Profile for Firewood  Send Email to Firewood     
Guys,

Thanks for all the help on this. I'll let you know if I get the problem solved.

Mike

jimh posted 04-28-2013 12:17 PM ET (US)     Profile for jimh  Send Email to jimh     
In another discussion, I have put some real-world numbers on battery cable resistance and voltage drop. See

http://continuouswave.com/ubb/Forum6/HTML/003374.html

Firewood posted 06-07-2013 09:17 AM ET (US)     Profile for Firewood  Send Email to Firewood     
I just wanted to give everybody an update. The starter was the problem. I replaced it and now there is no hesitation in the starter motor when starting the engine.

Thanks for all the help.

Mike

jimh posted 06-07-2013 04:02 PM ET (US)     Profile for jimh  Send Email to jimh     
Thank you for the follow-up to let us know the resolution and remedy for the problem.

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