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Starter cranking / wiring question

TimO

Well Known Member
So I keep forgetting to ask this question as it's mostly a nuisance, but it would be nice to some day not have to have it happen anymore...

I wired my starter solenoid and starter per plans. That extra wire (WH-K910) that is on the "I" terminal of the solenoid on the firewall connects to the starter, and I removed that factory installed jumper jumper on the starter.

I'm thinking that the way it works is, if you left the jumper in place and excluded WH-K910, then when you hit the key, the big starter wire WH-P16 just energizes both the starter solenoid and the starter motor at the same time.

But, if you remove the jumper, then the "I" terminal which also gets +14V when cranking, will activate the starter solenoid on the starter, and the firewall contactor closing will feed the primary power to the starter to crank the engine too.

Somewhere on the forum I once read something to the effect that the WH-K910 is there for preventing some noise that bothered pilots that happened after the engine started. It maybe helps the starter retract quicker or something like that. I can't remember anymore. But I just wired per plans and figured I'd be good to go.

Anyway, what happens to me often enough is that when I hit the key, I hear the firewall mounted contactor close, but the starter does nothing. It just sits there. If I hit the key a few more times, it may or may not start...but eventually by letting the key off and hitting it again, the starter engages and the prop spins just fine. It may not happen at all, or it may take me 2, 3 or probably the worst I've had is 5 or 6 clicks before the engine cranks.

I haven't done any testing with meters or anything while cranking, because it's really just a nuisance, and I'm not wanting to remove the cowl and hook up all sorts of wires and crank the engine to just check for voltage. It seems that whatever the issue is, should be easy enough to figure out. But I'm still at a loss.

Either the firewall contactor isn't closing enough and feeding the fat wire, which I doubt is the problem because the contactor makes a heathy clunk when you hit the key, or the "I" terminal wire isn't sending the +14V to the starter to tell it that it's time to engage, or, the 2 wires ARE supplying the +14V to the starter and something is just being sticky in the starter and it isn't engaging. I'm just not sure which. Whatever it is, it's been happening since the first engine start, but not all the time...probably ever 2nd or 3rd flight I have to hit the key more than 1 or 2 times.

I know it all works fine when it works, so if anything, the biggest reason I want to get it working better is to get rid of the embarrassment that happens when you give someone a ride. When they see the starter not crank 4 or 5 times in a row, they may start to wonder if they should be riding in this contraption.

Anyone have any good advice on where the most typical issue is with this setup? Stock IO-390 from Van's, per-plans wiring, Van's provided solenoids...

Otherwise, everything has been humming right along. I may have a slight prop hub seal leak, as I've seen very small amounts of prop grease on my cowl and on the windshield. Hoping that doesn't turn into an $800+ re-seal job like what happened on my RV-10. Right now it's pretty minor. I'm going to see if the only reason I'm seeing it is all the unusual attitudes the plane has seen lately. Maybe on an x/c flight I wouldn't get anything.
 
Hi Tim, the thread you're looking for is probably mine , titles "starter disengage wire". I wired mine as per Van's instructions and I have had maybe twice that I turned the key that nothing happened ( did not think I heard the solenoid kick in , just nothing. Turned the key back and try again and away we go. My SuperCub does the same thing from time to time.
I'm also still noticing a very small amount of oil/grease coming from the hub area. It use to make it to the windscreen but lately it appears to only make a small streak part way up the cowling. At 40 hrs. I would have thought it would have stopped by now, and certainly no aerobatics on my part.
Ron
 
Put a Meter on It

Tim--

To paraphrase Beyoncé you need to put a meter on it. Your problem could be due to a lot of things but you won't know the cause until you do. There's some information at Sky-Tek. They have several wiring diagrams but say,

"*** NOTE: THIS IS A VAN'S AIRCRAFT WIRING DIAGRAM

SCANNED DIRECTLY FROM VAN'S AIRCRAFT PLANS.
WE CAN NOT EXPLAIN WHY YOU WOULD WIRE YOUR
STARTER IN THIS MANNER. BUT IT WORKS FOR VANS.***

Good luck, and be sure to note the comment on the diode to protect your starter switch. There was an AD on the Aircraft Spruce Switches getting burned contacts to the lack of snubbing diode.
 
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Thanks for the info on the 4 bolts loosen/tighten on the prop spinner bulkhead connection to fix the grease leak. I'll have to give that a shot.

Regarding the SkyTek diagrams, yeah, I've seen that before. Thanks for pointing me there to re-read it. Indeed it is confusing why they (Van's) chose to wire it that way. I do think I remember a Van's person posting on VAF on some old thread (not RV-14 related) about why they do it that way...something to do with a noise that people complain about. If certified planes use the jumper installed, and they seem to have a reasonable service history, I don't see why that wouldn't just be simpler for us too. I'd like to hear exactly why Van's thinks their way is superior.

What I think is that Van's is using the "I" terminal and the firewall starter contactor as the "Start Switch" that's shown on the SkyTek diagrams. With all of the notes about needing the 20-30A start switch capacity, and the diode to give good service life on the start switch, they probably are just doing something that's a mix between the experimental diagram that SkyTek has, and the Certified Diagram. i.e. The experimental diagram needs a heavy duty switch and all that stuff, so by offloading the higher current stuff to the firewall solenoid you can effectively use a lighter duty keyswitch and not burn out the contacts. But, unless there is some bigger reason they went with the use of the "I" terminal, they could have taken it that next step and just used the normal jumper and eliminated a whole wire from their diagram.

I'll just have to think on what I want to do. I'm tempted to just wire it the skytec way and see if I continue to have problems. If not, I'll be satisfied with that. It's easier than taking a meter to it. The problem with wasting the time to do that meter jazz is that I already know what's going to happen...I'll get out all the meter stuff and hook it all up, and have someone hit the key, and the starter will crank...every time. Then I'll button it all up and go to fly and it'll just do it again...maybe that day, maybe the next day.
Intermittent issues suck to troubleshoot when they don't happen when you want them to.

Thanks for the feedback guys.
 
Ron,

Your giving the exact search words found that thread that I had read previously, thanks! "starter disengage wire"

I just re-read it all. It sounds like it all makes sense. Scott gave the reason why (i.e. the starter takes longer to disengage) if you use the SkyTec method of wiring. The I terminal should indeed work fine to do it the way they do it.

So, wiring per-plans is likely the "best" way if you want a timely disengaging starter and long service life. Doing it the "certified" way should also work fine, but just may give you that added noise of the late starter disengage.

In the end that just sucks for me because that means I probably do want mine wired how it currently is, but how it currently is, is not 100% reliable to start on the first twist of the key on every flight. So I'll have to troubleshoot that out. Or, at least, I'll have to develop a "here's why it's doing this" story that my un-nerved passengers will understand, so that they don't think negatively of seeing it happen. :D Maybe just saying "It's just doing that because the starter is wired with the best method to make the starter last long, but it isn't necessarily the best method to make the solenoid engage every single time."

So I guess I don't have much more to ponder on this issue other than to check everything over and just hope it goes away.

On the upside, reading all the skytec stuff is getting me in the mindset to finally get rid of my PM/LS starter on my RV-10 and maybe buy the NL. My RV-10 IO-540 doesn't crank as strongly with the PM/LS type starter.
 
More info from the Super Cub guys

I found this at SuperCub.org. Apparently these solenoids were designed in the thirties for Ford vehicles. "S" = Start; "I" = Ignition
It appears to be a Ford type automotive solenoid. The " S" is for start. When Power is applied to this terminal the coil is energized which closed the contacts to send power to the starter. The coil is grounded thru the case and what you are seeing is that the coil is good. The "I" terminal is for ignition. When you turn the key there is no voltage to the ignition system momentarily while the starter is engaged. The voltage to the ignition system while the starter is engaged is thru this terminal.


Here's a brief rundown on how it works...

You should have the following voltages coming from these terminals with the key in the "on" position. Zero volts at "S" and about 8 volts at "I". The starter solenoid "S" terminal is nothing more than the positive side of a wire wound electro magnet. The negative side of the winding is internally attached to the mounting bracket of the starter solenoid and becomes a ground when the bracket makes contact with chassis ground by the bracket's contact with the inner fender when it's bolted down, completing the circuit.

When terminal "S" gets energized, (12 volts, key in "start" position), it creates a magnetic field that draws the contacts of the large terminals together and the "I" terminal also gets energized and delivers a full 12 volts at the same time. You will only have the 12 volts there when the solenoid is energized and voltage to the starter side, (large terminal), is present.

Again, the only time there should be voltage at the "S" terminal is when the key is in the "start" position. The "I" terminal wire will have 12 volts at the same time. This wire is connected to the ignition coil circuit and provides a full 12 volts to the coil to make it easier to start the engine. It by-passes the coil's ballast resistor wire, which when in the "on" position, delivers a lower 8 volts to the coil (the voltage is now routed through the ballast resistor) to prevent the coil from overheating and to help the ignition points to live longer...

There is a copper disc inside these solenoids which, when energized, bridges the gap between the Battery terminal and the Starter terminal. If I recall correctly, the "I" terminal is connected to the copper disc via a flexible wire. I really don't know why one would want to even use the "I" terminal in an airplane, but Van must have a reason. I also note that the Sky-Tek site shows single-terminal relays for most of the diagrams.

I have a double terminal relay in my plane and I connected a large MOV between each of the large BAT and START terminals to the "I" terminal in the hopes of keeping the main contacts from burning. I haven't had any problems so far in 140 hrs. but there is probably a better way. "It's experimental"
 
I found this at SuperCub.org. Apparently these solenoids were designed in the thirties for Ford vehicles. "S" = Start; "I" = Ignition


There is a copper disc inside these solenoids which, when energized, bridges the gap between the Battery terminal and the Starter terminal. If I recall correctly, the "I" terminal is connected to the copper disc via a flexible wire. I really don't know why one would want to even use the "I" terminal in an airplane, but Van must have a reason. I also note that the Sky-Tek site shows single-terminal relays for most of the diagrams.

I have a double terminal relay in my plane and I connected a large MOV between each of the large BAT and START terminals to the "I" terminal in the hopes of keeping the main contacts from burning. I haven't had any problems so far in 140 hrs. but there is probably a better way. "It's experimental"

The "I" was for more than ford. Most ignition coils can not tolerate full 12 volts continuiously, but need the hotter spark for starting. This provides 12v shunting the coil resistor for these systems.

The RVAtor specifically outlines why the wire is needed. Apparently, the back EMF from the permanent magnet starter is enough to keep the solenoid engaged for some time after the power is shut off from the main solenoid. At the time one would hear the zipppppppp (flywheel spinning the starter) after the key was released. Not trying to explain it fully, just search back in the PDF version of the RVAtor to get the original explanation.
 
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The "I" was for more than ford. Most ignition coils can not tolerate full 12 volts, but need the hotter spark for starting. This provides 12v shunting the coil resistor for these systems...

Semantics, I know, but it is not that "hotter" spark is needed to start, but it does need "sufficient" voltage.

GM used a nichrome resistor wire to drive the coil voltage down to about 9 volts during the normal "run" operation, while Ford and Mopar generally used a stand alone resistor to accomplish the same thing. Problem is, with the starter engaged the massive load drags the entire system voltage way down, taking the coil on it's resistor even lower. The "I" terminal bypasses the resistor during the start sequence and provides "full" system voltage to the coil. Even though this terminal blasts the coil with full voltage, thanks to the starter cranking it still sees far less than the 13+ volts normally seen on the buss.
 
FWIW, I followed Bob Nuckols' wiring diagrams from the Aeroelectric Connection on my 8A and did not wire anything to the "I" terminal. Never noticed any noise that sounded like the starter wasn't disengaging in a timely manner.

The Skytec starters have a history of issues with their built-in solenoid not being the most reliable part. If you can hear a relay clicking when you turn the key I'd suspect that the firewall mounted solenoid is working fine and the problem is the Skytec. Let us know what you discover.
 
Defective starter

Tim:

FYI with 15 hours TTSN on my IO-390 the Skytech starter exhibited the exact symptoms you have. Worked perfectly up to then and since I had a spare identical starter I installed it. Since all functioned well with the spare, I sent the removed one that came on the new Lycoming back to Skytech with a description of the symptoms. They confirmed a "tooth on tooth" problem and replaced the defective component under warranty and returned it two days later. It now sits on the shelf as the backup.

It appears you may have the same problem.

Bill Marvel
Grand Junction, CO
RV-8A 1650 hours
RV-14A SN 140134 43 hours
 
Good to know, Bill, thanks!

I went flying the last 2 nights and it happened both nights. I think one night it took 3 tries and the next it took 4 before the starter took off.

I'll just contact them and tell them I have the issue, and hopefully they'll work something out for me where I won't have too much time on the ground.
I've got a lot of flying stuff going on coming up.
 
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