B&C Starter Balking

[kyleb]

Riddle me this.

I have a B&C starter on the RV-10's IO-540. It performed well for the first year the airplane has been flying. But...

The last two times I landed for fuel (of course at somewhere other than the home field), it has refused to cooperate. Turn the key and I can hear the relay click, but the starter doesn't make any noise, it doesn't engage, and it doesn't turn the prop.

The first time this happened, I assumed it was a bad starter solenoid, so I replaced it. It took about two hours to find a new relay at the auto parts store and replace it on the ramp. The engine started right up, so I assumed I'd fixed the problem. The second time it happened (a day later), I just waited two hours for things to cool and the engine spun right up. All of the wiring and connections appear to be in good shape.

My next move (the airplane is currently uncowled for its condition inspection) will be to run the engine to get things warm, then shut down and try the (warm) starter again while monitoring voltage on the input side of the starter.

Any other suggestions?

 

[Isosceles]

i'd take it to an auto starter shop and asked them to iran it. afaik, b&c starters are repurposed hitachi automotive starters,

 

[kyleb]

i'd take it to an auto starter shop and asked them to iran it. afaik, b&c starters are repurposed hitachi automotive starters,

Given that it has been in service for a year, B&C is the first option if it comes off the airplane. But I'd like to rule out any issues on "my" side before I take that action.

 

[Dan Thomas]

That starter has an onboard solenoid that engages the gear but also has a set of contacts in it that don't close and run the starter until the gear is engaged with the flywheel. Those contacts might be bad.

Or the master contactor, near the battery, might also be bad.

You need to take voltage readings in several places while cranking to zero in on the problem. And voltage drop readings across the master and starter contactors and that onboard solenoid. The voltage across those big contacts should drop to zero when cranking, indicating no resistance in the contactor.

 

[kyleb]

That starter has an onboard solenoid that engages the gear but also has a set of contacts in it that don't close and run the starter until the gear is engaged with the flywheel. Those contacts might be bad.

Or the master contactor, near the battery, might also be bad.

You need to take voltage readings in several places while cranking to zero in on the problem. And voltage drop readings across the master and starter contactors and that onboard solenoid. The voltage across those big contacts should drop to zero when cranking, indicating no resistance in the contactor.

Any sense of why this would (seemingly) be related to heat?

 

[Stewartb]

Start here. Then call B&C for tech support. They’re good. My guess is it isn’t the starter.

https://bandc.com/wp-content/uploads/2018/05/starter_troubleshooting_revA.pdf

 

[Lndwarrior]

Starter switch itself is a frequent culprit.

 

[Dan Thomas]

Starter switch itself is a frequent culprit.

He can hear the starter contactor clicking up on the firewall. If the starter switch was bad, there would be no click.

From a 172N POH, the typical start system is shown:



The flow is from the battery, through the mater contactor, to the starter contactor which is fired by the start position of the ignition switch, through the starter contactor to the starter. On the B&C starter (and Skytecs and other PM starters) there is another solenoid that engages the gear and then closes a set of contacts to run the starter. There are a lot of places that might not be closing properly.

The old starters on Lycomings used an inertial device to engage the gear when the starter first spun. It works fine until it gets dirt in it, or until some well-meaning mechanic sprays oil into it. The oil attracts dust and forms a sticky sludge that inhibits the engagement, sometimes preventing starting altogether. Starter runs, does not engage. The service manuals specifically prohibit that sort of lubrication, but people hate reading or something.

 

[flyingbrit]

That starter has an onboard solenoid that engages the gear but also has a set of contacts in it that don't close and run the starter until the gear is engaged with the flywheel. Those contacts might be bad.

And voltage drop readings across the master and starter contactors and that onboard solenoid. The voltage across those big contacts should drop to zero when cranking, indicating no resistance in the contactor.

Why even have a starter contactor when the starter has an on board solenoid? Seems redundant and an additional failure point.

 

[Stewartb]

Kyleb, did you read the two paragraphs under “Starter” on page 4 of the B&C link?

I had issues with my old Cub’s B&C. It took my mechanic about a minute to fix it. He cleaned a couple of terminal connections. That airplane was near new when it happened.

Good luck finding the culprit!

 

[Dan Thomas]

Why even have a starter contactor when the starter has an on board solenoid? Seems redundant and an additional failure point.

To dump the airframe's starter contactor would require more STC expense, and B&C would have to prove that the starter's solenoid wouldn't hang up easily. Since it's operating a gear running on splines, it's much more likely to stick and keep the starter running than the typical contactor that only works a set of contacts, though that too has happened.

 

[Bell206]

Any other suggestions?

Perform a complete starter system voltage drop check on both the power and ground sides. The results from this will give you the next direction to follow.

 

[kyleb]

Perform a complete starter system voltage drop check on both the power and ground sides. The results from this will give you the next direction to follow.

That's basically the troubleshooting procedure in the B&C document. I figure that if I check voltage right at the starter (during starting), that'll tell me if low voltage at the starter is the problem. If it is, then I do the full voltage drop check from the battery to the starter, component by component. And of course, starting with verifying that the battery hasn't lost a cell or something...

Anything amiss with that approach?

I will ask - how do you check voltage drop on the ground side? Am I looking for no/little difference between the starter case and the negative battery terminal (and points in-between)?

 

[Dan Thomas]

This is better: https://skytec.aero/aircraft-starter-performance-issues/

And yes, there should be no voltage indicated between the starter case and firewall when the starter is cranking. If there is, you have engine grounding issues. Similarly there should be no voltage between the battery negative post (not the cable terminal) and the airframe. If there is, the cable and/or terminals is suspect.

 

[Stewartb]

The B&C instructions are pretty simple. Jump the two posts on the starter. If the motor spins up? The problem isn’t the starter. Can’t get much easier than that.

 

[Bell206]

Anything amiss with that approach?

No. Dan's link pretty much sums it up. I will add that be sure to check the voltage on the component studs/hardware vs only the wire terminals. Have seen where the terminal had good voltage but the stud did not. It doesn't take much between the faying surfaces of the terminal and the stud to reduce voltage.

Also since your starter does appear to work as you noted, but intermittently, be sure to mind your starter duty-cycle limits. Repetitive starts can generate a lot of heat and possible skew your checks or induce its own problem. Maybe even check to see if the main start system components get hot in between attempts??

 

[Dan Thomas]

The B&C instructions are pretty simple. Jump the two posts on the starter. If the motor spins up? The problem isn’t the starter. Can’t get much easier than that.

That would only work if the master and starter contactors are closed. The current is not available at the starter solenoid until the contactors are actuated.

The jumper referred to in the B&C document is a permanently-installed wire to actuate the starter's solenoid.

It's the white wire. The airplane's starter contactor energizes the big stud on the left. That jumper carries current to the hot side of one of the solenoid's coils, to extend the gear into the flywheel, and once that solenoid is fully pulled in, a contact on the solenoid plunger closes the circuit between the two big studs, and the stud on the right feeds the starter motor and also energizes a second coil in the solenoid to keep the gear engaged. The circuit is shown in that document.