Hard Starting
 

I have an IO 360 in my plane and it turns over slowly and barely starts. Put a load on the battery and it checked good. Would like ideas on what to check next. Thanks for the help.

What make/model of starter do you have? Some starters are better than others.

Is there a dedicated ground strap (a fat wire or a braided ground strap) between your engine and the firewall? You'll have problems without one of these.

What engine/prop do you have? A high compression engine combined with a wood or composite fixed pitch prop can be more of a challenge.

Have you checked the connections from the starter through the starter relay, and all the way to the master relay? Bad connections = poor starting performance.

Put a volt meter across the battery while you crank. It should hang in there north of 9-9.5 volts or so. If not battery isn?t up to snuff.
If it does hold >9 volts check it again at the starter to test the positive side of the circuit including the master and start relays and wiring.
If you still have >9 volts there you?ll want to check the ground connections.
Putting the volt meter in parallel with the ground circuit, engine case to battery ground, look for less than 1 volt while you crank.
You can use the same method over on the positive side also, and pin down the actual point of high resistance by going connection to connection.
Tim Andres

Welcome to VAF
 

Larry------first post time, welcome aboard.

Are all the connections on the supply side clean and tight? if so, start with the ground circuit, would be my advice.

Is this a new plane, or a new problem on an older plane?

Check start circuit for high resistance
 

This trouble shooting guide shows how to identify if any high resistance points are in the start circuit. http://skytec.aero/starter-performance-issues/

If your 6 is getting on in age it may be time to replace one or more of the contactors. My 6 is 19yo and start performance had deteriorated over time to the point that the starter would almost stall after turning half a blade. After replacing the starter solenoid, master contactor and starter contactor, starter performance is like new again.

When doing those tests to check voltage under starting load, be sure to get your test leads on the battery terminals; not the cable clamp, screws/bolts, etc. Every transition is suspect. Between post & terminal, between terminal and wire, etc etc.

My -6 did the same thing when i bought it. I replaced the pc680 battery with no help. I ran a dedicated ground cable from the battery directly to the skytec starter and still no help. Engine would barely crank over the compression stroke. I replaced the starter solenoid and voila, she starts like a turbine. I cracked opened the solenoid and found the copper disk had severe pitting. Everytime you release the starter button, the solenoid disengages and creates an arc that pits the disk. It gets to the point that it is only making partial contact. They are cheap and easy to replace.

Hard Starting
 

I would like to thank everyone for the suggestions. Heading to the airport tomorrow morning to run through the suggestions. The engine is a 180 hp Io 360 with a light weight Whirlwind prop. The airplane is 11 years old with 860 hours. The problem only happens on the initial start of the day, starts normally on the return trip for a $100 hamburger.

Whether you have one of their starters or not, the Skytec starter performance troubleshooting guide (available HERE) might be helpful.

The Skytec troubleshooting guide is great. I was sure the problem was NOT the ground between the starter and the engine case so skipped that step. After much aggravation and some $s I removed the starter (B&C) so I could hook up a battery right to it and verify it was operating properly. The starter ran great.When I looked at the mating surfaces I found some oil and some dirt and dull metal. I cleaned it really good and used a scotch brite on the surfaces and the engine turns over beautifully. I'll add a ground strap from starter to engine at the next oil change just to be sure.

I don't know if that is your problem but I wish I had followed the troubleshooting tips completely. I would have figured it out much sooner.