Prop slow to start during hot start

DesertNomad

DesertNomad

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DesertNomad
I typically land and taxi for fuel, then start again to taxi to my hangar.

Sometimes during this hot start, there will be a short (1 second or less) delay after engaging the starter before the prop starts turning. Sometimes it will turn 10-20 degrees, pause for less than a second and then rotate maybe 3 blades and start.

Mine is a O-540 carburated engine.

Is this likely related to the battery or the starter? I have already eplaced the starter wire with copper as this as an SB or AD (can't recall).

The battery and starter were new in May 2013 and have 333 hours.
 
That due to the position of the prop when it stopped. If it stops right before a compression cycle, its hard to get moving. Just move it and try again. Anyway, my Lycoming 0360 sometimes does that too.
 
I assume you mean move the key back to off and try again (which is what I do), not get out and hand-move the prop a bit.
 
Try leaning more aggressively prior to shutting down. You can’t hurt the engine by over leaning at taxi power. Run it dry before you shut it down and see if it helps.
 
I do lean pretty aggressively on the ground. After pulling off the runway: flaps retracted (sometimes while still on the runway), fuel pump off, lean, wing flashers off.
 
Change the battery I think this is the problem.
 
Check the bonding of the starter to the engine, the engine to the mount and the mount to the airframe and battery ground.
 
pilotrick said:
Change the battery I think this is the problem.
Click to expand...

That's one way of throwing lots of money at a problem and not getting any result about 80% of the time.

Hot engines tend to be harder to turn than ones at room temperature. The oil is really thin and the rings have come into contact with the cylinder walls, as have the bearings and journals. At a lower temperature the oil is much thicker and holds the metal bits apart. At really low temperatures the oil gets too thick and stiff and again creates (a sort of) friction.

The impulse magneto may be firing just a hair before TDC. That will cause the prop to hesitate a bit, against the pressure created in the cylinder. Once past TDC the pressure helps get the crank turning.

Look for dirty or corroded engine ground connections as well as all the positive connections between the battery and starter. Especially the battery, master contactor and starter contactor connections. The alternator charges the battery via the connection between the master and starter contactors (the bus connection) and any corrosion or crud in those connections cause a small bit of resistance that ends up causing some heating of the connections, raising resistances further and making hot starting even harder.

A good idea is to take voltage drop measurements across both contactors to see if their internal contacts are shot. They age (years) and oxidize, and arc and burn (start cycles). Both conditions raise resistance, and it only takes a tiny fraction of an ohm to slow everything up.
 
Desertnomad, do you have one of those ignition switches that has to be pushed in in order for it to operate? I do and question for Dan, how often do these type ignition switches cause problems?
 
I can't speak to your airplane, but I can to the 0-470 carbureted engine in the 182. I was having a devil of a time with hot starts until an old-timer around the airport opined this to me. Turn the engine off with the mag switch, and as the engine begins to stop, slowly push the throttle full on.

I haven't analyzed the magic, but I can attest the results. Don't debate me on theory; just try it and see if it works for you.

Jim
 
I hot start mine full lean. Rich when fires. Works pretty good. May have to try above theory also.
 
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