Starter question

[JOhnH]

Is there any measurable way to determine if a starter is spinning the engine fast enough? My lightweight starter doesn't seem to be spinning the engine fast enough and it is becoming harder and harder to start, even cold but especially hot. I'm considering swapping it out for a heavy duty starter and if that doesn't fix it, I might have the adapter replaced, but I'd like to have some sort of benchmark to let me know if that might actually help. The current starter is about 2 or 3 years old and we have really tried to follow the advice regarding starter engagement times and cooling off periods, but it seem half of our startups are hot-starts and make higher demands on the battery and the starter. (It is a relatively new Concorde battery).

 

[Capt. Geoffrey Thorpe]

Just go ahead and replace the starter since it's the most expensive component and don't waste any time looking at connections, master / starter solenoids, etc which seem more likely to me to be the problem. [/smartass]

To start (no pun intended), compare voltage at battery (+ to ground terminals) while cranking, then compare the voltage at the starter (+ terminal to starter case) while cranking - more than a couple volts difference means you need to track down the offending connection / solenoid/ ground.

Warning: I ain't no A&P, just an old hillbilly who has been fixing **** for more years than I will admit to.

 

[JOhnH]

Just go ahead and replace the starter since it's the most expensive component and don't waste any time looking at connections, master / starter solenoids, etc which seem more likely to me to be the problem. [/smartass]

Why would you assume we haven't considered those other steps?
At least you acknowledged that you were being a smartass. As I fully expected many of the responses to be. Did it ever occur to you that I have already discussed this with my A&P and he has already looked at the electrical system and replaced the massive plugs with fine wire plugs and put in a new (Concorde) battery? He suggested the next step to hanging a new heavy duty starter because that is less expensive than a new adapter. I was actually just asking for a second opinion about changing out the starter.

 

[Dan Thomas]

Why would you assume we haven't considered those other steps?
At least you acknowledged that you were being a smartass. As I fully expected many of the responses to be. Did it ever occur to you that I have already discussed this with my A&P and he has already looked at the electrical system and replaced the massive plugs with fine wire plugs and put in a new (Concorde) battery? He suggested the next step to hanging a new heavy duty starter because that is less expensive than a new adapter. I was actually just asking for a second opinion about changing out the starter.

Replacing sparkplugs won't fix a slow-cranking problem. A new Concorde battery won't fix it either if the contactors are shot. I have seen way too many expensive starters and batteries replaced simply because one or two $30 contactors were just tired out. You mechanic should know how to take voltage drop measurements across contactors (solenoids) and major cable connections. Even a one-volt drop is enough to cause trouble. Ohm's Law applies everywhere, and when we're dealing with hundreds of amps it only takes a tiny vraction of an ohm to drop the voltage enough to inhibit cranking. A heavy-duty starter will draw even more amps and cause an even bigger voltage drop, and you'll have a big bill and great disappointment.

 

[Matthew Rogers]

There are a lot of factors, and I am not an AP, but my old 1966 C150 was having a starter that seemed to be getting slower. Turns out that nobody had replaced the starter brushes since about.....1966. One brush was completely gone and so it was a relatively painless removal and trip down to a wonderful local motor repair shop for new brushes and an overhaul kit with new bushings and seals (this is the old pull-style Delco starter that is a purposed tractor part). We turned down the worn commutator on a lathe, pressed in new bushings, new brushes, cleaned it up, and with $50 of parts had it working like new. Did this all at annual time and the AP re-installed it for us when buttoning it all back up. Still wondering about the starter adapter as it (maybe?) had a small rough spot when turning. Didn't want to replace that $500 part with a new one from Niagara, but I have also heard that hey can fail and dump metal into the case, so it is on the mind.

 

[Bell206]

I was actually just asking for a second opinion about changing out the starter.

If the voltage drop check mentioned in Post 4 doesn't indicate any issues, take the starter to a local shop and have them bench check the amp load and winding resistance. Similarly, I've seen more electrical starting issues due to voltage drops than the actual starter especially if the starter is 2 or 3 years old. Was this starter installed for the same reason back then?

 

[Capt. Geoffrey Thorpe]

Did it ever occur to you that I have already discussed this with my A&P and he has already looked at the electrical system

One can only work with the information that has been provided, which was: "cranks too slow, want to replace the starter" without even a hint that any kind of previous diagnostic work had been done.

 

[Pilot Steve]

Is there any measurable way to determine if a starter is spinning the engine fast enough? My lightweight starter doesn't seem to be spinning the engine fast enough and it is becoming harder and harder to start, even cold but especially hot. I'm considering swapping it out for a heavy duty starter and if that doesn't fix it, I might have the adapter replaced, but I'd like to have some sort of benchmark to let me know if that might actually help. The current starter is about 2 or 3 years old and we have really tried to follow the advice regarding starter engagement times and cooling off periods, but it seem half of our startups are hot-starts and make higher demands on the battery and the starter. (It is a relatively new Concorde battery).

I went through a few lightweight starters and had a similar issue as you describe. I put in an Energizer starter and now it starts like a champ. While my intentions were sound to go with the lightweight starter, in the end putting the beast back in was the best thing I did.

 

[NordicDave]

There are a lot of factors, and I am not an AP, but my old 1966 C150 was having a starter that seemed to be getting slower. Turns out that nobody had replaced the starter brushes since about.....1966. One brush was completely gone and so it was a relatively painless removal and trip down to a wonderful local motor repair shop for new brushes and an overhaul kit with new bushings and seals (this is the old pull-style Delco starter that is a purposed tractor part).

My lightweight starter doesn't seem to be spinning the engine fast enough and it is becoming harder and harder to start, even cold but especially hot. I'm considering swapping it out for a heavy duty starter ...

Many aviation forums are full of threads with light weight starter issues and their not standing up like the heavy duty factory starters. No doubt there are people who install them and love them for years. It seems we hardly never get threads about the old heavy duty starters dying young like the lightweight versions.

Is there any measurable way to determine if a starter is spinning the engine fast enough? My lightweight starter doesn't seem to be spinning the engine fast enough and it is becoming harder and harder to start, even cold but especially hot. I'm considering swapping it out for a heavy duty starter ...

To start (no pun intended), compare voltage at battery (+ to ground terminals) while cranking, then compare the voltage at the starter (+ terminal to starter case) while cranking - more than a couple volts difference means you need to track down the offending connection / solenoid/ ground.

The captain is right, check your voltage and current from battery to starter. Battery strength, battery to starter heavy gauge wire resistance (as they get old/corroded/etc. and sometimes need replacement.), contractor, and wire ends/lugs for corrosion or anything that might be a insulating barrier to current flow.


Commentary:
Those old heavy starters were made to turn 400-500 cubic inch motors, and designed to stay together when a customer started the car with the clutch engaged. Couple of examples; Modern cars have electronic interlocks protecting drivers from starting a car with the drive train engaged. Also modern automotive fuel injection kicks the engine over with nearly any rotation. Both of these improve longevity of lightweight starters.

When I think of the power needed to rotate my O-470 with the mass of a big 3 blade Hartzel prop, and cranking needed to sometimes start; I'm sticking with the heavy duty starter.

 

[JOhnH]

One can only work with the information that has been provided, which was: "cranks too slow, want to replace the starter" without even a hint that any kind of previous diagnostic work had been done.

I admit I didn't go into the history, but my question was merely if there is a measurable way to determine if the starter is spinning the engine fast enough.

But to go into a little more detail, the problem I am trying to solve is hard starting, not a slowly turning starter. (And I really don't want this to turn into another "here's how I start my engine" thread. I've tried them all. For a while It was doing fine, but it is getting harder and harder to start while it "seems" or "feels like" the starter is turning too slowly.

True that new plugs won't make the starter spin faster, but they can cure a hard starting problem if the old plugs are worn (and they were).
Similarly, a new battery won't fix a starter problem, but if the battery is weak, it won't spin the engine fast enough to start quickly.

As for @Bell206 s question, the other starter was replace because it was bad. I was at a remote airport and it wouldn't engage, even with a booster on it. An old pilot hanging around suggested I spin the prop by hand a few times. Id did and then the starter engaged and the engine started, so we flew it home and my A&P said the starter was bad so he replaced it (with another lightweight starter) and I have had no failures since then. But it is getting harder to start and it was my A&P that mentioned that the engine turns over slowly during the last oil change so he charged the battery. I asked him if that could be causing my hard starting issue and he said it could. If the problem continues he recommended swapping the starter. That was why I asked the question as to whether there was a measurable test to tell if it is spinning fast enough.

 

[JOhnH]

When I think of the power needed to rotate my O-470 with the mass of a big 3 blade Hartzel prop, and cranking needed to sometimes start; I'm sticking with the heavy duty starter.

And that's why I'm interested in replacing my lightweight starter in my IO520 (with 3 blade prop). But I would prefer to be able to measure the starter speed before I swap it. I don't mind writing the check if I don't have to calculate the engine and OAT before I decide to refuel, especially if I don't have my Redline Sidewinder with me to move the plane away from the pumps.

 

[chemgeek]

Having owned a completely trouble-free SkyTec starter for over a decade, I'd be surprised if it can't spin much, much faster than the old Prestolite starter. (For what it is worth--turning speed is not the be-all and end-all for a successful start.) For context, I'm only turning a Lycoming O-320-E2G with high compression pistons. Quite frankly, anything is better than the old Bendix gear starter mechanism. I was happy to get rid of the constantly failing Bendix gear.

Maybe it's different for a larger engine or a Continental, but I'd check for proper voltage delivery first. If starting is becoming harder, the first place I'd look is the impulse couplings. More turning speed won't fix failing impulse couplings.

 

[JOhnH]

I appreciate all the comments from everyone that is trying to be helpful, but so far, nobody has addressed my question. I'm not sure if it is because I gave too much information, or not enough information in my original post. I wish I never mentioned the starting issue.

If this were just a hard starting question then the comments would have all been appropriate.

At any rate, my A&P is going to hang a loaner starter on the plane next week to see if that changes anything.

 

[NordicDave]

Start with the easiest and obvious first. Are you getting enough voltage and current to the starter? Power cable condition (measure resistance), were the connectors to power and ground cleaned? Is the starter adapter slipping? Etc.

 

[Arnold]

I appreciate . . . At any rate, my A&P is going to hang a loaner starter on the plane next week to see if that changes anything.

I am happy to hear the mechanic is going to loan you a different starter. Troubleshooting before replacing seems like the way to go, though the latter will likely eventually work.

 

[Ravioli]

Not a mechanic.

If you use the rotation of the prop as a proxy for "spinning the engine fast enough" you should be able to use the infra red rotation device that they use for tach calibration checks to know what speed the starter is giving. Also, I'm sure the starter overhaul type people know how fast the motor and gears are spinning.

Is that your root question?

 

[flyingbrit]

To determine the cranking speed you could crank for say 10 seconds (at idle cutoff) and count the number of blades. Then calculate the speed using the formula: (6)*(# of blades counted)/(2 or 3 depending on prop). For example if you counted 20 blades and have a 2-blade prop it would be 60 rpm. A typical gasoline engine needs about 50 rpm for good starting.

 

[idahoflier]

Not a direct answer to your question, but maybe in the ballpark...

 

[Tom-D]

Start with the easiest and obvious first. Are you getting enough voltage and current to the starter? Power cable condition (measure resistance), were the connectors to power and ground cleaned? Is the starter adapter slipping? Etc.

that is Called a voltage drop test.

 

[Bell206]

I'm not sure if it is because I gave too much information, or not enough information in my original post.

The info in your 1st post stated your starter was not turning fast which normally indicates an electrical problem. Your follow up posts seem to imply you have an overall engine starting problem that you are unsure of the cause...?

 

[mondtster]

But to go into a little more detail, the problem I am trying to solve is hard starting, not a slowly turning starter. (And I really don't want this to turn into another "here's how I start my engine" thread. I've tried them all. For a while It was doing fine, but it is getting harder and harder to start while it "seems" or "feels like" the starter is turning too slowly.

So it sounds like the starter is actually fine then, and the real problem is hard starting?

Remember, these engines can be hand propped so they don’t have to spin fast to start.

Based on what you’re describing, I’d be investigating your ignition system before spending money on a starter. Does this have impulse couplers or shower of sparks? Do you know that whichever one you have is actually working right?

 

[Dan Thomas]

Based on what you’re describing, I’d be investigating your ignition system before spending money on a starter. Does this have impulse couplers or shower of sparks? Do you know that whichever one you have is actually working right?

That there. If it's not firing even at a low cranking speed, it will be weak ignition 90% of the time. How long since those mags were off for internal inpection and internal timing?

 

[Doug Reid]

What Dan said !

FYI, internal timing can only be checked with mags on the bench. If points are pitted, the e-gap changes.

The coming in speed would also be affected.

 

[donjohnston]

These kinds of posts can be... challenging.

First it's "Is there any measurable way to determine if a starter is spinning the engine fast enough? My lightweight starter doesn't seem to be spinning the engine fast enough".

No information on the type of plane or what's been tried so far.

People try to offer some advice and then on the 10th post the problem becomes "the problem I am trying to solve is hard starting, not a slowly turning starter".

Kind of hard to keep up sometimes.

 

[Let'sgoflying!]

John, here are some cranking speeds for certain situations quoted by Aviation Consumer.
Maybe it will help you in the right direction.
https://www.aviationconsumer.com/maintenance/so-long-bendix/

 

[JOhnH]

John, here are some cranking speeds for certain situations quoted by Aviation Consumer.
Maybe it will help you in the right direction.
https://www.aviationconsumer.com/maintenance/so-long-bendix/

Thanks. Good article.

These kinds of posts can be... challenging.

First it's "Is there any measurable way to determine if a starter is spinning the engine fast enough? My lightweight starter doesn't seem to be spinning the engine fast enough".

No information on the type of plane or what's been tried so far.

People try to offer some advice and then on the 10th post the problem becomes "the problem I am trying to solve is hard starting, not a slowly turning starter".

Kind of hard to keep up sometimes.

You are right, and I apologize for that. But the thing is, I have been working with my A&P on this. He has diagnosed and repaired several problems.
A few years ago, the old starter died and needed a new replacement.
Two years ago, the old massive plugs had about 600 hours on them and were worn, so I opted to replace them.
Last year the old Gill battery wasn't holding a charge. If I went 3 weeks without flying, the Gill would be low, so I had him replace it with a Concorde.

Last month during the oil change, he told me he thought it *the starter) was turning over slowly. I had actually noticed that but the gradual degradation took a while. The plane was in annual in May and the slicks came out and were inspected at that point, but there was no noticeable difference in anything. I asked him if that could be contributing to it being harder to start than it used to be. He said yes, since he had already gone over the charging system. If the engine is not spinning fast enough, it will be harder to start.

So that led me to asking about starter cranking speeds here. I'm sorry I didn't give the full history, but I wasn't looking for SGOTI to fix my starting issues. I just wanted to get a better feel for whether a slow starter could cause the hard starting and how to measure it. I was only asking for a second opinion on the validity of a slow starter causing the hard starts. I'm sorry if I asked the question wrong. I didn't think a full history was important to answer that question.

 

[3393RP]

It doesn't take much effort or billable time to break down the battery and solenoid cable connections, inspect, and clean them.

 

[JOhnH]

It doesn't take much effort or billable time to break down the battery and solenoid cable connections, inspect, and clean them.

I wouldn't swear to it, but I'm pretty sure he has done that.

He is a very good A&P I/A. I haven't turned wrenches since around 1979, so I'm not going to micro-manage him. I have been at his shop when he gets calls from other A&Ps for advice. I sometimes question him, but that is usually to gain an understanding.

 

[Dan Thomas]

It doesn't take much effort or billable time to break down the battery and solenoid cable connections, inspect, and clean them.

The heavy contacts inside the solenoids themselves get oxidized (with age) and burnt (with use) and make resistance. That's only detectable with a voltmeter during cranking by measuring the voltage drop directly across those two big terminals. The resistance will be too small to measure accurately with an ohmmeter, and a tiny resistance makes a big voltage drop when the amperage is large.

If a healthy battery's voltage, in a healthy system, normally drops to, say, ten volts during cranking, that's bad enough. It's a function of the battery's limited capacity. If the solenoids (the current passes through both the master and starter solenoids) drop the voltage another two volts, this is much worse. If we assume a normal 250-amp draw at ten volts, that's 2500 watts--3.35 HP--and the starter is offering 0.04 ohms of resistance. If we see a two-volt drop through the solenoids, the current falls to 200 amps, which is only 1600 watts--2.14 hp--at that eight volts. And that doesn't even account for the reduced starter resistance at its lower cranking RPM (reduced inductive reactance) that demands more amperage, which can cause an even bigger voltage drop. Ohm's Law is really inconvenient at times. Making things worse yet is that those contactors, offering resistance like that, are getting their contacts heated up, accelerating the oxidation and burning.

The extra two-volt drop implies a 0.04 ohm resistance in the contactors. Good luck with measuring that with an ohmmeter. And note that such a tiny resistance is a seriously big deal.

 

[Bell206]

I sometimes question him, but that is usually to gain an understanding.

FYI: A pertinent question to clarify with your AP would be if he performed a voltage drop check, as mentioned above by Dan, between the battery and starter.

 

[flyingbrit]

The extra two-volt drop implies a 0.04 ohm resistance in the contactors. Good luck with measuring that with an ohmmeter. And note that such a tiny resistance is a seriously big deal.

No sweat with a "4 wire" ohmmeter. Not cheap though, about $500 and up. Here's an example:

https://www.newark.com/b-k-precision/310/digital-milli-ohmmeter-4-wire/dp/54M5383

 

[NordicDave]

Or take an assumptive approach and remove the contacts from their mounts and clean them. Should be done every once in a while anyway.

 

[Dan Thomas]

Or take an assumptive approach and remove the contacts from their mounts and clean them. Should be done every once in a while anyway.

The solenoids are sealed. Only the really old ones were designed to be openable. By the time a mechanic has fooled with opening those old ones he could have sold and installed brand-new ones.

The contacts get deeply pitted and burned and cleaning them isn't going to help much. Sometimes the big round contact disc in the starter solenoid wears so deeply into the contacts that it will expand with the heat of resistance and lock itself in there and the starter will continue to run. That cooks the starter.

New solenoids are one of the better ways to spend money on an airplane.

We had a discussion of contactor problems a few months ago: https://www.pilotsofamerica.com/community/threads/a-different-kind-of-hot-start-issue-help.125285/

 

[NordicDave]

The solenoids are sealed. Only the really old ones were designed to be openable. By the time a mechanic has fooled with opening those old ones he could have sold and installed brand-new ones.

The contacts get deeply pitted and burned and cleaning them isn't going to help much. Sometimes the big round contact disc in the starter solenoid wears so deeply into the contacts that it will expand with the heat of resistance and lock itself in there and the starter will continue to run. That cooks the starter.

New solenoids are one of the better ways to spend money on an airplane.

We had a discussion of contactor problems a few months ago: https://www.pilotsofamerica.com/community/threads/a-different-kind-of-hot-start-issue-help.125285/

Maybe I misunderstood the situation. I was referring to cleaning external contacts external such as connector to the battery lugs or the power cable to solenoid/contactor, etc. to ensure full current delivery. I agree if there’s an issue internally to the solenoid or contactor, it should be replaced.

 

[Dan Thomas]

Maybe I misunderstood the situation. I was referring to cleaning external contacts external such as connector to the battery lugs or the power cable to solenoid/contactor, etc. to ensure full current delivery. I agree if there’s an issue internally to the solenoid or contactor, it should be replaced.

Cleaning the various terminals is a good idea. But many cables have crimped-on terminals that, over time, develop corrosion right inside the terminal and among the fine wires that are crimped in there. You can sometimes take an ohmmeter and measure the resistance between the ends of the wires (clean the ends off) and the terminal itself, and find measurable resistance there. (No wonder it doesn't crank.) Those terminals at the battery itself are bad for that. I once fixed a cable like that by running soldering flux into it with heat, then soldering it. But it's usually better to cut the bad section of cable off, strip a new section, clean everything and crimp a new terminal on it. You need a big set of special crimpers for it. Like these:

 

[Southpaw]

Does hand propping turn engine over faster then a starter does ?
Dads old J-5 Always started well hand propping .

 

[geezer]

First, a comment on light weight starter technology. They have 'super magnet' stators, instead of electro magnet stators. The resulting lower current draw produces lower drop on all components in the circuit. This usually results in higher cranking speed. Lighter weight is not the primary goal of the conversion, faster cranking and longer life are.

Our current plane was converted to light weight many years ago, and performance has always been better than the old starter we replaced.

We have replaced starter solenoids on several of our planes over the years, and they were the usual source of slow cranking. I am a skilled electrical technician, and voltage drop tests have been the first step in finding the faulty item.

I believe our starter is a Skytech, and they are well supported with repair parts if needed. No experience with other brands.

If the loaner starter does not correct the problem, voltage drop tests will find the defect.

Flyingbrit's link to a 4 wire precision ohm meter brought a laugh here, it will measure down to 0.2 Ohms. At work, I have used a meter that measured down to 0.001 Ohms. At 200 amps, a typical starter current, the voltage drop across 0.2 Ohms would be 40 volts. Obviously a voltage drop test will be much more valuable than any Ohmmeter test.

The resistances you are looking for are quite small.

Best wishes for a quick determination of the fault and repair. The Geezer has been there many times.

 

[Salty]

I think the answer to the original question is "anything greater than 0rpm". All it takes is the proper ratio of fuel, air, and a properly timed spark. People have been seriously injured from moving a prop slowly by hand with a hot mag.

 

[flyingbrit]

Flyingbrit's link to a 4 wire precision ohm meter brought a laugh here, it will measure down to 0.2 Ohms. At work, I have used a meter that measured down to 0.001 Ohms. At 200 amps, a typical starter current, the voltage drop across 0.2 Ohms would be 40 volts. Obviously a voltage drop test will be much more valuable than any Ohmmeter test.

Balderdash! If you'd read and understood the data sheet you would realize the 0.2 ohms is full scale on the lowest range. Resolution is 100 micro-ohms, or 10 times as good as your meter at work. 200 amps and 100 micro-ohms is a voltage drop of 0.02 volts so this meter would be quite effective for measuring starter circuits.

 

[flyingbrit]

Flyingbrit's link to a 4 wire precision ohm meter brought a laugh here, it will measure down to 0.2 Ohms. At work, I have used a meter that measured down to 0.001 Ohms. At 200 amps, a typical starter current, the voltage drop across 0.2 Ohms would be 40 volts. Obviously a voltage drop test will be much more valuable than any Ohmmeter test.

Balderdash! If you'd read and understood the data sheet you would realize the 0.2 ohms is full scale on the lowest range. Resolution is 100 micro-ohms, or 10 times as good as your meter at work. 200 amps and 100 micro-ohms is a voltage drop of 0.02 volts so this meter would be quite effective for measuring starter circuits.