The importance of a good ground wire for starting an airplane

[Greg Ellis]

I am just putting this in the general section so maybe it can help anyone that is experiencing the issue that I was.  I have a 63 C model with an O-360-A1D.  After a long hiatus of flying, waiting on a cylinder (since August), I was able to get the airplane back in the air.  However, when I tried to start it for the first time since August, it was tough to start.  The prop would barely make it over the first compression stroke and I would have to release the key and try again.  While trying to start, the voltage on the EDM 900 would drop to 8 volts.  If it made it over the compression stroke then it fired right up but getting over that was tough.  My first thought was a weak battery.  It had been kept on a battery minder the whole time but maybe the battery was bad.  I also thought it could be the starter as well.

So, I followed a recent thread about someone else having starter issues (the one that was smoking) and downloaded the Sky-Tec troubleshooting guide and followed it through.  I did every step in the guide and everything checked out fine.  The battery was solid.  After 48 hours resting (not on the charger) the voltage of the battery was still 12.9 which according to battery minder is a good battery.  All voltages across the battery, the solenoids and the starter itself were all within what Sky-Tec would call normal.

The starter to ground resistance was .1 ohms which according to Sky-tec is fine.  The battery to ground however was almost 1 ohm which according to Sky-Tec, anything greater than .2 ohms needs to be looked at.  So, I removed the negative battery cable which is grounded to a stud on the engine.  I cleaned all the washers, cleaned the battery cable ends themselves and cleaned the area on the engine where the ground connects.  I reconnected everything.  Rechecked the resistance and it was .2 ohms.  

The engine fired right up with no resistance on the compression stroke and no drain on the battery upon starting.  I was amazed that a single ground issue could cause this kind of a problem.  Mind you, I know very little about electrical stuff.

The trouble shooting guide saved me a lot of money on a new starter, new battery, and just throwing things at the problem etc...  It did take a while to do all of this.  To access the ground from the negative battery terminal, in order to get a wrench on the nut, I had to remove the intake tube on the #4 cylinder.  But it saved me a lot of money, so I am happy, and it is nice to be flying again after 4 months.

[DXB]

20 minutes ago, Greg Ellis said:

I am just putting this in the general section so maybe it can help anyone that is experiencing the issue that I was.  I have a 63 C model with an O-360-A1D.  After a long hiatus of flying, waiting on a cylinder (since August), I was able to get the airplane back in the air.  However, when I tried to start it for the first time since August, it was tough to start.  The prop would barely make it over the first compression stroke and I would have to release the key and try again.  While trying to start, the voltage on the JPI would drop to 8 volts.  If it made it over the compression stroke then it fired right up but getting over that was tough.  My first thought was a weak battery.  It had been kept on a battery minder the whole time but maybe the battery was bad.  I also thought it could be the starter as well.

So, I followed a recent thread about someone else having starter issues (the one that was smoking) and downloaded the Sky-Tec troubleshooting guide and followed it through.  I did every step in the guide and everything checked out fine.  The battery was solid.  After 48 hours resting (not on the charger) the voltage of the battery was still 12.9 which according to battery minder is a good battery.  All voltages across the battery, the solenoids and the starter itself were all within what Sky-Tec would call normal.

The starter to ground resistance was .1 ohms which according to Sky-tec is fine.  The battery to ground however was almost 1 ohm which according to Sky-Tec, anything greater than .2 ohms needs to be looked at.  So, I removed the negative battery cable which is grounded to a stud on the engine.  I cleaned all the washers, cleaned the battery cable ends themselves and cleaned the area on the engine where the ground connects.  I reconnected everything.  Rechecked the resistance and it was .2 ohms.  

The engine fired right up with no resistance on the compression stroke and no drain on the battery upon starting.  I was amazed that a single ground issue could cause this kind of a problem.  Mind you, I know very little about electrical stuff.

The trouble shooting guide saved me a lot of money on a new starter, new battery, and just throwing things at the problem etc...  It did take a while to do all of this.  To access the ground from the negative battery terminal, in order to get a wrench on the nut, I had to remove the intake tube on the #2 cylinder.  But it saved me a lot of money, so I am happy, and it is nice to be flying again after 4 months.

Great tip, and glad you’re back in the air!

[Fly Boomer]

26 minutes ago, Greg Ellis said:

The trouble shooting guide saved me a lot of money on a new starter, new battery, and just throwing things at the problem etc...  It did take a while to do all of this.  To access the ground from the negative battery terminal, in order to get a wrench on the nut, I had to remove the intake tube on the #2 cylinder.  But it saved me a lot of money, so I am happy, and it is nice to be flying again after 4 months.

Great report.  Thanks for sharing your experience.

[A64Pilot]

In my many years of troubleshooting electrical stuff, it’s most often the ground, I don’t know why but it is, and very few people look at the grounds, they check voltage and assume wiring is good. Your lucky your voltage meter wasn’t checking battery voltage because battery voltage wasn’t dropping, system voltage of course was.

But a bad or loose ground can cause other pain as the system may find another electrical path.

Many years ago the Chrysler K cars were eating up CV joints, Replaced under warranty and later failed again, Chrysler was stumped, driveshaft alignment was perfect nothing could be found, then research found that it was only on cars built in one plant and on one shift.

Further digging found out that one person doing the engine install wasn’t tightening the frame side of the engine ground wire, thought it was done in a different place on the line, since the ground wire was loose the engine was grounding through the driveshafts and starting current was burning spots on the bearings and of course they eventually failed.

[47U]

6 hours ago, Greg Ellis said:

I was amazed that a single ground issue could cause this kind of a problem. 

I replaced my engine Lord mounts a few years ago.  The battery ground to the engine and ships ground from the engine to the copilot’s footwell were termintated using the Lord mount bolts.  I guess it works, but seems hinky to me.  I moved both grounds to holes cast in the engine case.  I replaced the braided ground from the engine to the footwell.  It got tore up removing the bolt.  I hope none or yours look like this.  

 

[Greg Ellis]

10 minutes ago, 47U said:

I replaced my engine Lord mounts a few years ago.  The battery ground to the engine and ships ground from the engine to the copilot’s footwell were termintated using the Lord mount bolts.  I guess it works, but seems hinky to me.  I moved both grounds to holes cast in the engine case.  I replaced the braided ground from the engine to the footwell.  It got tore up removing the bolt.  I hope none or yours look like this.  

 

That could have just been cleaned up with some simple green and put back into service, no?....

[bcg]

I can't tell you how many electrical problems I've solved on boats, cars and heavy equipment by fixing the ground. So many that it's usually the first thing I check.

Sent from my Pixel 6a using Tapatalk

[Red Leader]

That makes perfect sense. Several years ago I was looking at an Arrow II for sale and was serious about buying but never could get to start. The symptoms were the same - the starter was just too weak to spin the prop around. Changing the battery to a new one did not help. Thinking it might be an expensive fix, I didn't purchase the plane (now with some regret as it was a great deal), but had I known it might be something as simple as a poor ground, I might've gone through with it and been flying a nice Arrow all these years. Of course, had I done so, I likely wouldn't have purchased my Mooney and been in this forum to allow all others to enjoy my sad stories.

[Flash]

20 hours ago, Greg Ellis said:

So, I followed a recent thread about someone else having starter issues (the one that was smoking)

Glad my thread was helpful. I have a new starter, which solved my problem. No more smoking.

I'm happy for you that you saved the substantial cost of a new starter.

[Will.iam]

On 12/18/2023 at 10:18 PM, Red Leader said:

That makes perfect sense. Several years ago I was looking at an Arrow II for sale and was serious about buying but never could get to start. The symptoms were the same - the starter was just too weak to spin the prop around. Changing the battery to a new one did not help. Thinking it might be an expensive fix, I didn't purchase the plane (now with some regret as it was a great deal), but had I known it might be something as simple as a poor ground, I might've gone through with it and been flying a nice Arrow all these years. Of course, had I done so, I likely wouldn't have purchased my Mooney and been in this forum to allow all others to enjoy my sad stories.

Sad sorry?!?! That helped you dodge a bullet.