P-Leads getting hot

[Justin H]

I tried starting my engine today after a top overhaul, the right P-Lead got
really hot and smoke came off it when I hit the starter button. where should
I start looking for a short? could it be shorting back thru the starter
motor?

[Kyle Boatright]

Check your ground connections. You should have a ground strap between the
engine and a ground point on the airframe (or maybe back to the battery).
If someone forgot to hook that up, you might get the symptons you describe.

KB


"Justin H" > wrote in message
...
>I tried starting my engine today after a top overhaul, the right P-Lead got
>really hot and smoke came off it when I hit the starter button. where
>should I start looking for a short? could it be shorting back thru the
>starter motor?
>

[Dave Hyde]

Justin H wrote...
> I tried starting my engine today after a top overhaul,
> the right P-Lead got really hot and smoke came off it
> when I hit the starter button.

Is your engine grounded to the airframe? If you saw smoke
the damage is probably already done, but while you're
replacing the wires you smoke-checked check your engine
ground - probably a braided strap somewhere between the
engine case and the airframe.

Dave 'Kapton video' Hyde

[[email protected]]

Dave Hyde > wrote:
: Justin H wrote...
: > I tried starting my engine today after a top overhaul,
: > the right P-Lead got really hot and smoke came off it
: > when I hit the starter button.

: Is your engine grounded to the airframe? If you saw smoke
: the damage is probably already done, but while you're
: replacing the wires you smoke-checked check your engine
: ground - probably a braided strap somewhere between the
: engine case and the airframe.

Many engines only have an impulse coupling on the left mag, so the right mag
is supposed to be grounded when starting to prevent kickback/backfire. If you don't
have a good engine ground (i.e. top overhaul guy forgot to reconnect it), it'll try to
suck starter ground current through the right p-lead just as you described. It
probably fried your ignition switch, p-lead wire, points, and possibly the whole mag
(case, coil, etc).

-Cory


--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[Justin H]

Thanks! All of you were correct. It appears to have never had a grounding
strap. It does now! and the starter works alot better too!

thanks again

[[email protected]]

The bigger question is how much damage ($$$) did it do and who's responsible
for it? I'm sure that a $20 ignition switch used in an airplane costs $500, no?

-Cory

Justin H > wrote:
: Thanks! All of you were correct. It appears to have never had a grounding
: strap. It does now! and the starter works alot better too!

: thanks again




--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[Dan Thomas]

wrote in message >...
> The bigger question is how much damage ($$$) did it do and who's responsible
> for it? I'm sure that a $20 ignition switch used in an airplane costs $500, no?
>
> -Cory
>
> Justin H > wrote:
> : Thanks! All of you were correct. It appears to have never had a grounding
> : strap. It does now! and the starter works alot better too!
>
> : thanks again


That ground current may have traveled through control cables,
too, heating them and ruining the temper of the wire and melting any
plastic liners. Might be a good idea to make sure they're OK.

Dan

[Richard Lamb]

Dan Thomas wrote:
>
> wrote in message >...
> > The bigger question is how much damage ($$$) did it do and who's responsible
> > for it? I'm sure that a $20 ignition switch used in an airplane costs $500, no?
> >
> > -Cory
> >
> > Justin H > wrote:
> > : Thanks! All of you were correct. It appears to have never had a grounding
> > : strap. It does now! and the starter works alot better too!
> >
> > : thanks again
>
> That ground current may have traveled through control cables,
> too, heating them and ruining the temper of the wire and melting any
> plastic liners. Might be a good idea to make sure they're OK.
>
> Dan

OR?
How about the braided steel cover on a fuel line!
Could be interesting.

I even had a real live braided ground cable between the engine case
adn the airframe.

But

My starter (mounted on the accessory case, instead of the engine case)
also found a lower resistance path thru the P lead.

So, my engine is now grounded at the _starter_, rather thatn the other
side if the engine block...

The stuff ya learn!

Richard

[Barnyard BOb -]

Richard Lamb spoketh:

>I even had a real live braided ground cable between the engine case
>adn the airframe.
>
>But
>
>My starter (mounted on the accessory case, instead of the engine case)
>also found a lower resistance path thru the P lead.
>
>So, my engine is now grounded at the _starter_, rather thatn the other
>side if the engine block...
>
>The stuff ya learn!
>
>Richard
++++++++++++++++++++++++++++++++++++++++++++++++

In the department of "my penis is bigger than yours"....

My engine has TWO ground cables.
Never know when one might not be enuff.

Yeah, it adds weight, but the only time it's
a factor is when the runway is shorter
than the aircraft's take-off distance. <g>

It'll still cruise 200 mph no matter what.

<smirk>


Barnyard BOb --