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sky tec starter XLT

Mauleguy

Mauleguy

MEMBER
I have a new Sky Tec XLT starter on my Lycoming O-360 with 10.5 to 1 compression, I am using the Odyssey PC-680 battery under the pilots seat in a experimental PA-18. Here is my question: I can start the airplane when it is cold but I sometimes have to bump the starter through a few times. When the airplane is hot i.e. after just fueling up I am having a problem even getting it to go threw the compression stroke and yesterday for the first time in 35 hours I had to hand prop it because it just would not create enough power to push through the compression stroke. I have checked the voltage at the starter and it was 12.2 volts the day I did that. I use to run a B&C starter with this same engine in another airplane with the PC-680 and never had a problem. Is anyone else using the XLT light weight starter having problems or is it just me.

Greg
 
I should add I have the master solenoid under the seat with the battery and the starting solenoid on the engine side of the firewall.
 
master or starter solenoid lug tilted/rotated? (they are a square head bolt inside solenoid)

try jumper wire at solenoid from hot to the start button small lug, you'd be surprised how many starter switches are burnt....

ground wire from engine to airframe screw coming through firewall(don't use that phony ground strap to engine mount piper did)
 
mike mcs repair said:
master or starter solenoid lug tilted/rotated? (they are a square head bolt inside solenoid)

try jumper wire at solenoid from hot to the start button small lug, you'd be surprised how many starter switches are burnt....

ground wire from engine to airframe screw coming through firewall(don't use that phony ground strap to engine mount piper did)
Click to expand...

Mike, The solenoids were new so I don't think that is it. Could be but not high on my list yet, I did switch the starter solenoid out already and it did not make a difference.

I am using a switch not a push button and it was the switch from the aircraft that I had no problems with starting using a B&C starter.

The grounding comment I find interesting because I am using the ground strap from engine to engine mount. What size wire should I use to complete the ground through the firewall, I will try that first.

Thank you,

Greg
 
What's the starter p/n? A long shot, but could it be they sent you a -24XLT? That would explain the half-power output.
 
Grounding is always an issue with these engine/engine mounts. If you replace it, it needs to be the same gauge as your starter cable. The usual is a 4 gauge cable to the starter so use a braid that is the equivalent of that. A piece of 4 gauge cable will work temporarily for testing. Run the ground from the crank case to STRUCTURE. I like using one of the screws that are welded to the fuselage frame and stick through the firewall. The other part of this to check is the ground connection at the battery. Here, again, the connection needs to be directly to the structure. NOT through a bolted or riveted joint. I prefer a bolt welded to the torque tube boss under the pilots seat.

Otherwise, re read what Mike said above. Don't 'think' with troubleshooting. Verify. It's not a matter of going directly to the problem, it's a matter of positively eliminating each possibility.

Web
 
Thanks guys, I will look at each item. I have felt it could be the ground all along so I will rule that one out first.
 
Mauleguy said:
I have a new Sky Tec XLT starter on my Lycoming O-360 with 10.5 to 1 compression, I am using the Odyssey PC-680 battery under the pilots seat in a experimental PA-18. Here is my question: I can start the airplane when it is cold but I sometimes have to bump the starter through a few times. When the airplane is hot i.e. after just fueling up I am having a problem even getting it to go threw the compression stroke and yesterday for the first time in 35 hours I had to hand prop it because it just would not create enough power to push through the compression stroke. I have checked the voltage at the starter and it was 12.2 volts the day I did that. I use to run a B&C starter with this same engine in another airplane with the PC-680 and never had a problem. Is anyone else using the XLT light weight starter having problems or is it just me.

Greg
Click to expand...

Your description of your starter sounds just like my 9:1 O-340. Better cranking when cold than hot and never will go a complete rotation when hot. And I have the same starter and battery.

Please let let us know what you find. I've been suspicious of my ground too but haven't chased it down yet.
 
I have a PM12-122 and have found it to be of marginal torque. It turns it over OK but not great. This is a stock 150. My first Sky-Tek (also PM12) was much more energetic, but this one is kind of lazy. I have new cables - grounded to the airframe - new batt. and good alternator. A hangar neighbor recently had Ly-Con build him a high-perf O-360 and a PM-12 wouldn't turn it over. I realize you're talking about the XLT here, but I guess my point is I don't think these starters are as gutsy as the mfg. would like to think.
 
You can sometimes find the connection with high resistance by touching them just after trying to crank, or while someone else does it for you. Often it gets surprisingly hot....
 
After insuring good continuity on the ground and start circuit. With the starter engaged...check the cranking voltage, should not be less than 10.8 volts. Also check the starter load with an amp shut/ meter... You'll see a spike when the starter overcomes the inertial mass. Then should drop to near 150 amps. Below 10.8 volts under load...poor charge on the battery or its toast. North of 200 amps on the starter...it be toast.


Sent from my iPad using Tapatalk
 
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Load test the battery, even if it is new! Make sure the post on the battery aren't bad...Check your cables & terminal ends.
 
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I was just getting ready to purchase one of these lightweight starters now I'm not all that sure I'll have to wait for the outcome
 
Greg,
I've got a new B&C and flywheel on the shelf (where all starters should be). If you want to try it, I'll run it down to you.
 
Greg

Talk to DW. He had the same problem. He fixed it. I can't remember what the fix was but he is a happy camper now.

Bill
 
I know I said it in the early post but I did check voltage right at the starter when I was having the problem a couple weeks earlier with an IA friend of mine. It was showing 12.2 volts at the starter. He said the voltage should be good enough, the reason we were checking the voltage is the solenoid that is on the starter itself sometimes just clicks when I hit the key and we want to rule out the firewall mounted start solenoid as the problem. The starter is going to get returned to Sky-Tec for service because of that issue but I was waiting for the Holidays to be over.

Can it be a ground issue and still be getting a solid 12.2 volts to the starter?

I have a B&C starter but I can't use it with the exhaust system I chose.
 
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Static voltage at the starter doesn't mean much. Where does that number go when the starter is engaged ? That's the number that really matters.
 
that is what it was when it was engaged, actually that is what it measured when the key was turned to start and the solenoid had power but was not cranking (just a click). so maybe you are correct when you say static?

Not sure about that so I guess I have another check to do.
 
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Maybe Carey is right, just get rid of the crap. If it was not so difficult to start when it was hot sometimes I would ditch the starter. It is a real pain in the ass to reach it on 35" hand prop and I am shorter every year.
 
Sounds like another starter is in your future. I haven't been into the XLT starter...so guess work.... Using permanent magnets.. Pretty sure it uses the wound rotor and commutator...no commutator would make it an induction motor..... will not make a good starter. The problem potentially exists in two places. One at the solenoid. It doesn't sound old enough for the contacts within the solenoid to be toast...test the post opposite of the stater cable post. Same voltage on both posts?.... Problem is likely internal at the commutator/brushes.....I'm a fan of the NL inline starter. 6.5-1 ratio...


Sent from my iPad using Tapatalk
 
Mauleguy said:
Mike, The solenoids were new so I don't think that is it.
Greg
Click to expand...

sure it can be, the big bolt heads are square, and they are held in a piece of plastic, and they can rotate in that plastic, then they plunger plate will only contact one corner of the bolt so its like having a tiny wire in the system, current wise, not voltage wise...
 
OK.
FIRST! The voltage measured at the starter is, in fact, NOT 'static' voltage. There is voltage there only when the start solenoid at the firewall is engaged. If the voltage measured is 12 volts and the starter is not engaged, it means that the problem is with the starter assembly or engine ground. Go to the back of the starter. There is a solenoid mounted piggyback on the starter motor. There are two large terminal studs on the back of the solenoid, one connected to the starer solenoid and on to a strap that goes directly into the motor. That second terminal stud is where you need to measure voltage.
When you engage the aircraft start solenoid, it sends 12 volts to the first large terminal on the piggyback solenoid. This solenoid, in turn, energizes and sends 12 volts from the first large terminal stud to the second, energizing the motor. If you do not measure voltage at that second terminal stud, while trying to start the engine, the piggyback solenoid on the starter motor is bad. If you do measure close to battery voltage there and the motor will not engage, there is a bad ground from the engine to the air frame.
I'm curious where the 10.8 volts figure comes from. With most 12 volt equipment, roughly 9.5 volts has been a rule of thumb for minimum voltage for proper operation. And when measuring voltage on a high current circuit like a starter motor, anything with a decimal point is splitting hairs.
I've heard lots of stories of slow turning SkyTec starters over the years but have never had one that turned out to be the starter itself. Usually urns out to be grounding issues.

Web
 
Mauleguy said:
that is what it was when it was engaged, actually that is what it measured when the key was turned to start and the solenoid had power but was not cranking (just a click). so maybe you are correct when you say static?

Not sure about that so I guess I have another check to do.
Click to expand...

right, you ONLY care about the voltage as it IS CRANKING, not when its not cranking..

this gives you a good clue of the current flow... just like a water hose, might have a big hose, but if it full of holes you only are getting a small amount of water out of the bussiness end, not what it "could" carry in theory...
 
Even ground straps go bad. Whenever my radios start getting noisy I go in and clean all the grounds. We had a noisy Cub last month, and discovered that there was no ground strap at all! I wonder what path those two hundred amps were taking - throttle cable?
 
spinner2 said:
Your description of your starter sounds just like my 9:1 O-340. Better cranking when cold than hot and never will go a complete rotation when hot. And I have the same starter and battery.

Please let let us know what you find. I've been suspicious of my ground too but haven't chased it down yet.
Click to expand...

Since Im experiencing the exact same problem and had the cowl off today I did some checks on my system. I cleaned the ground strap connections from the engine to the motor mount. I didn't see any problems but cleaned everything well.

Turning the the engine over I see 12.2 volts or so until I get to a compression stoke. Then it struggles and slows down and I see about 9 volts momentarily and then back to 12+ until the next compression stroke. It'll do this for about 4 compression strokes and then it will barely turn over at all. If I let it rest a minute or so it will do better but it is a quick downward trend.

The battery is a PC680 that is about 3 years old.

Thoughts?
 
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