#1
IP: 174.61.245.219
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How much voltage drop at Starter while cranking?
Still troubleshooting my low voltages while cranking.
I see like 12.4 at the starter to begin, but upon cranking it drops to 10.4 or less fairly quickly. Batteries are fairly new 2x Group 27 charged up. What's the norm? I'm beginning to suspect the starter or solenoid... Jack |
#2
IP: 71.118.13.238
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Need more input
Jack, that's not really that bad at the starter when starting I assume(?) depending on battery condition and age.
Did you clean ALL of the big wire connections at the battery, switch and starter? What is the voltage at the "starting" battery or batteries not the starter at rest and cranking? Dave Neptune |
#3
IP: 174.61.245.219
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Batteries same voltage at rest. Not sure while cranking, sort of hard to deal with by myself. Connections at battery cleaned. Not seeing any corrosion at starter, but will have another look at it.
Bigger issue is small spark from coil - about 1/4"+. Low voltage there while cranking - 12.4v "resting" - 9.4v cranking. So I'm seeing a 1 volt drop on ignition circuit. Even with the battery charger on and the banks at 13.5, I still am seeing a pretty big drop and weak spark. Ignition switch is just a push button, shows continuity. Gauges at helm are in series with it. the only other things on the circuit are the fuel pump (newish MM electric) and an hour meter. Have older Ignitor magnetic ignition from MM. I'm going to replace the primary wire from it to the coil as it is old, and has one splice in it. I assume 12 gauge is enough. Battery cables are in good shape, will double check ground, but have also tried second isolated battery bank with similar results, same when I change neg leads over to 1st bank. Aargh. Jack |
#4
IP: 161.213.49.150
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Jack
If you want to fool around with it you could do this: Disconnect the primary wire at the switch and coil +. Connect a jumper wire to one end and run the wire near the other end and lay an ohm meter on the other two ends. S\B zero ohms of course. What size wire are you running switch to coil? What's the voltage reading at the switch? TRUE GRIT |
#5
IP: 107.0.6.242
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Anything over 10 volts at the coil+ will start the engine; however, you need every bit of it. If you have other items like an electric fuel pump in parallel that is where you are losing voltage. You may be one of those rare cases where the use of the "R" terminal on the solenoid is warranted. The "R" terminal is energized only by the cranking (push button) switch. Run a #14 direct from "R" to coil+.
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#6
IP: 174.21.254.190
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Yeah, some interesting ideas to try. The wire to the coil is about 14 gauge I'm guessing, but has one butt joint, due to an "issue" ;-). I will check the voltage at the switch.
However, this is a new issue. I've run the fuel pump etc and this configuration for years... Hanley, so I leave the starter wired as is and run an extra lead from the "R" term to coil? What advantage does this give...? Jack Last edited by JackConnick; 10-24-2013 at 04:05 PM. |
#7
IP: 71.118.13.238
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Argh the R
Jack, the "R" wire hookup will do nothing for you unless you are using a resistor on the EI. The "R" terminal just runs full voltage to the coil by bypassing the resistor during cranking which is the only time it is activated. This supplies "full voltage" for starting while cranking only.
Dave Neptune |
#8
IP: 174.21.254.190
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No, I'm using an internal resistor coil, a Flamethrower. Which although it seemed ok (3.5 ohm across the leads), I am having to replace as I broke off one of the terms. yesterday.
But full voltage to the coil while cranking sort of seems like it may help... You leave both R & S connected? |
#9
IP: 71.118.13.238
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No R
If your not using an external resistor it will make no difference, but it may supply a bit more than your switch but only during cranking.
Have you had your batteries "load tested" by any chance. If they're week which 12.4 at rest would indicate for a fully charged battery and it just may be your meter. Did you check the connections at the battery switch and on the starter? Also take a good look at the ground from the engine back to the battery, if it is weak it will show up as a voltage drop too. Dave Neptune |
#10
IP: 174.21.254.190
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I haven't had them tested, they are maybe about 1.5 years old at most. But even with the charger on and everything at 13.5, I'm still only getting 9.4 at the coil. I went out and bought another meter yesterday, as I was getting some spurious readings with the old one.
Jack |
#11
IP: 128.183.140.38
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The problem of the drooping voltage during cranking all stems from the high current that the starter draws while cranking the engine. So even a tiny amount of resistance can produce a significant voltage drop.
<WARNING=MATH CONTENT> Consider: Ohm's law says V = I x R (Voltage equals current times resistance). So, for convenience, let's say your starter draws 25 Amps. Even 1/10th of an Ohm of resistance will produce a significant voltage drop: 25 Amps x 0.1 Ohms = 2.5 Volts !! </WARNING> So all of the (tiny) resistance of the heavy starter wire, and the battery lugs, and ring terminal, are going to be in series with the heavy terminal on the starter, and are going to be responsible for the voltage drop seen there. And yet, for some unfathomable reason, almost every stock boat wiring I've ever seen seems to take the ignition + feed from that terminal!! It's a guarantee that you're going to see a lot of voltage drop on the ignition during cranking! If, instead, that + feed to the ignition is moved to the other end of that big cable, directly on the battery, then you will avoid all of that voltage drop across the cable and its connectors! Any remaining droop will be a function of the condition of your battery.
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@(^.^)@ Ed 1977 Pearson P-323 "Dolce Vita" with rebuilt Atomic-4 |
#12
IP: 107.0.6.242
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Why not do a little test? Check voltage at the "R" terminal during cranking. See if you might like to have that delivered to coil+ (during cranking).
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#13
IP: 174.61.245.219
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OK, more tests on Saturday... ;-)
Quote:
Jack |
#14
IP: 184.0.109.29
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Quote:
The voltage on a fully charged battery should be about 12.7-12.8 volts. If it's higher, the charger is on. Batteries will usually fail to start an engine at 12 volts or less. This is dependent on the age of the battery. A new, but depleted battery may only fail to start at a voltage as low as 11.5 volts. Be wary of electric panel meters; they are often very inaccurate. Use a multi meter to test the batteries and then reset the panel meters if they are adjustable.
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-Jerry 'Lone Ranger' 1978 RANGER 30 |
#15
IP: 174.21.220.230
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Back to it...ignition battery volt problem
Well, I got to traveling and busy with life and haven't had too much time to work on the boat.
But I went down yesterday and finished rewiring a new coil in as the wiring to it was messy. In the process I broke off a terminal to the coil, so I have a new one. Went to try to start it and same issue, crank and crank, no start. Tried a jumper per Don's instructions from the starter to the + of the coil. No difference. Checked the batteries and they showed 13.75 with the charger on. So I filled them with water and decided to put the charger on an equalization high-volt charge. It takes them up over 15v to boil off the sulfates. They are about 3-4 years old at this point. So I was looking at all that high voltage and tried to start the boat. Off she went very easily! No hesitation, very light crank. So I'm thinking bad batteries, or some sort of serious voltage lose with the wiring, except hat none of that has really changed... I'll see how it goes tomorrow, probably pull them out (2x Group 27HD on one circuit) 1 on another, isolated. I am thinking to replace the primary ignition wire it has one splice in it, although it's run for years with it in place. If anybody has a better ideas, let me know. Jack |
#16
IP: 107.0.6.242
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Once again, if you have anything on that ignition circuit (like an electric fuel pump, for example), it is robbing you of voltage to coil+. Run the direct #14 wire from "R" on the starter to coil+ and watch her start easily.
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#17
IP: 24.152.131.153
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The 'R' terminal
I'm so against this it's hard to find the words. Here goes.
Using the 'R' terminal in this instance only masks the problem, does nothing to solve it. Jack, as you've discovered you have a massive voltage drop to the coil input during starting and we haven't really found the root cause yet. As discussed it could be the batteries aren't cuttin' the mustard any more, maybe the ignition wire with splice has developed a high resistance for one reason or another, could be the battery cables or their terminations, any number of things but installing an ignition system bypass and calling it good will only delay the inevitable. Whatever is really wrong ain't gonna get better on its own. The idea that an electric fuel pump is contributing to the problem doesn't fly for me for at least two reasons:
Back to the 'R' terminal I suggest that our engines don't need it period. If your ignition wiring and components impart such a voltage drop that the engine can't start without the 'R' terminal bypass, there's a problem or several that need to be addressed. The bypass is not a solution, it's a band-aid. Before you say it, for those (not Jack) who need to bypass a ballast resistor during starting to get her to fire, your resistor is way too aggressive, simple as that (assumes the rest of the ignition system is in good repair).
__________________
Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others Last edited by ndutton; 03-22-2014 at 10:30 PM. |
#18
IP: 107.0.6.242
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Quote:
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#19
IP: 76.122.168.101
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Quote:
Oh, BTW I also bypassed the ammeter entirely. I am using a voltmeter in it's place. |
#20
IP: 107.0.6.242
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There are many ways voltage can be hijacked in a system before coil+ can be fed; that's the beauty of the "R" terminal - ever so briefly it gives coil+ all the system can deliver.
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#21
IP: 76.122.168.101
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I recommend that you check the resistance of some of the wires/components in you ignition circuits.
The easiest way is to use a decent mulit-meter or ohm-meter. You should see essentially zero resistance. Remember to zero the meter! If you do not have a decent (read high quality) meter be careful measuring resistances. My experience with inexpensive multi-meters is that they often do not do a fantastic job measuring small resistances even if they are pretty good at higher resistances. But many of these meters are better at reading small voltages. YMMV, so the first commandment is "Know thy meter." I am basing this on the 30 meters from 5 different manufacturers in my HS physics lab and the 4 meters I have at home. NOTE: If anyone from the FLUKE company reads this, I have a couple of your meters and I am ready with my testimonial!!. SO if I am using the cheap meter I leave in my tool box and I suspect a wire has too much resistance due to size or age or damage what I do is to measure the voltage drop across the wire. Specifically, measure from one end to the other when current is flowing. In this case, your meter should read zero volts when you have the leads on each end of the wire and current is flowing through the wire. Somewhere you have a series of little voltage losses or one big loss that is robbing your coil of the energy it wants to make spark. Find those and you will solve your problem! Last edited by marthur; 03-23-2014 at 10:31 AM. |
#22
IP: 76.122.168.101
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Quote:
I would consider the R terminal. But I would not rest well until I tested the components the ignition and starting circuits. A corroded terminal or broken wire can fail unexpectedly or get hot due to the increased resistance and cause real trouble. Better safe than sorry. |
#23
IP: 107.0.6.242
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+1 on FLUKE, and digital is best.
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#24
IP: 107.0.6.242
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#25
IP: 23.241.157.69
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Battery bet
Jack, volts and power(amps) are not the same. Seeing 13+ on the charger and seeing 12.something at rest is just volts not power. As you increase the load the voltage will begin to drop and the worse off the batteries the more the voltage drop. You added water and with the charger she'd spin well enough to start that's adding "POWER" or amps to start!
Take the batteries out and get them load tested!!! I'll bet a liquid bread that is your problem. Weak batteries especially a load of them tied together not being able to spin the engine fast enough but with the charger all is bliss. That's batteries in a weak state. I have the need for new house batteries at the present. The house side in my set-up are a pair of 6v235's for the house and an isolated grp27 for the engine. I usually start on the both and when out I use only the house for starting and power at anchor, to save the start battery if needed. The 2 big 235's will run the lights tv and stereo for days and all is well to start on them. At the present the "charged voltage" at rest is down a bit and they will barely start the engine when cold. The voltage drops considerably upon cranking and they will be replaced before the summer cruising starts! The "R" terminal was a necessary part on the original wiring and ignition set-up on the A-4's equipped with the "old style ceramic ballast resistors". The ignition was reduced to 8v for the stock 8v coil and full voltage was tendered for the cranking circuit to boost the available spark! Dave Neptune |
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