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Old 10-12-2017, 03:09 PM   #1
stran
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Default Hot Start Procedure Carbureted O-320

I find it harder to start the engine when it's hot like after buying gas then starting cold. This tells me that my hot starts are less than optimal, since the engine should be easier to start hot.

POH lists hot start procedure for newer Cherokees with fuel injected engine, but nothing for the older carbureted ones. Any tips? Currently I use the same procedure as cold starts but skip the priming step.

On a related note, do all carbureted engines in the Cherokee have an accelerator pump that squirts fuel into the carburetor when throttle is pushed in?


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Old 10-12-2017, 03:17 PM   #2
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Quote:
Originally Posted by stran View Post
I find it harder to start the engine when it's hot like after buying gas then starting cold. This tells me that my hot starts are less than optimal, since the engine should be easier to start hot.

POH lists hot start procedure for newer Cherokees with fuel injected engine, but nothing for the older carbureted ones. Any tips? Currently I use the same procedure as cold starts but skip the priming step.

On a related note, do all carbureted engines in the Cherokee have an accelerator pump that squirts fuel into the carburetor when throttle is pushed in?

Here's the proper way to start a hot 0-320:

1. do not prime
2. full rich mixture
3. do not pump throttle back and forth....just move it up 1/4 inch.
4. engage starter

I learned the above the hard way by having an engine fire in my Warrior II after 40 years of flying various Piper products. My error was that I pumped the throttle several times and then engaged the starter. A $10k fire was the result as fuel puddled onto the muffler shroud and burst into flames. It was a very hot 95 degree day for a fuel stop.


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Old 10-12-2017, 03:49 PM   #3
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If your carbureted engine is hard to start hot, but not cold, you should inspect and repair the ignition system as needed. Most likely you have Slick magnetos, which are known to have hot start issues. If you have Champion plugs too, you have the worst possible combination.

Normally, a carbureted Lycoming engine is easy to start hot or cold.
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Old 10-12-2017, 07:54 PM   #4
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Quote:
Originally Posted by rick440 View Post
Here's the proper way to start a hot 0-320:

1. do not prime
2. full rich mixture
3. do not pump throttle back and forth....just move it up 1/4 inch.
4. engage starter

I learned the above the hard way by having an engine fire in my Warrior II after 40 years of flying various Piper products. My error was that I pumped the throttle several times and then engaged the starter. A $10k fire was the result as fuel puddled onto the muffler shroud and burst into flames. It was a very hot 95 degree day for a fuel stop.
I will vouch for this. O320E3D. Both with and without the 160HP upgrade. With everything in good tune, I've always just gone full rich, crack the throttle, and hit the key. It starts right up. DON'T pump as some of us have learned the hard way.

I would assume all carbureted engines have an accelerator pump until proven otherwise just to be safe.
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Old 10-13-2017, 02:37 AM   #5
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Here is how I start my hot O-320-D3G. The following works for my engine 99% of the time with very little cranking.

1. Throttle open 1/4"
2. Mixture full rich.
3. One pump of primer.
4. Start cranking engine.
5. Pull throttle back to closed.
6. Engine starts to fire.
7. Throttle back to 1/4".
8. Adjust throttle to 1000 RPM.
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Old 10-13-2017, 12:06 PM   #6
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Yeah I agree, you should have it looked at. Hot start should be a breeze.
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Old 10-13-2017, 12:34 PM   #7
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Quote:
Originally Posted by stran View Post
I find it harder to start the engine when it's hot like after buying gas then starting cold. This tells me that my hot starts are less than optimal, since the engine should be easier to start hot.

POH lists hot start procedure for newer Cherokees with fuel injected engine, but nothing for the older carbureted ones. Any tips? Currently I use the same procedure as cold starts but skip the priming step.

On a related note, do all carbureted engines in the Cherokee have an accelerator pump that squirts fuel into the carburetor when throttle is pushed in?
Yes, hot starts have been a thorn in my side for a long time, too. The problem is really "how hot"?

If you just shut down 10 minutes ago and it's a warm day, then starting without priming makes sense.

If you shut down 2+ hours ago and it's cool out, then it's clearly a cold start (6 pumps of the primer for my engine, but it depends on how many cylinders the primer is connected to; the would be overpriming for just one cylinder).

If it's somewhere in-between, then lick your finger, hold it it to the wind, take your best guess, and hope the airport old guys aren't all laughing at you from their rockers on the porch.


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Old 10-13-2017, 12:44 PM   #8
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Yeah better a little less prime than too much. And you can always add a little with the accelerator pump while the starter is spinning the engine. The key is not to pump the throttle before engaging the starter.
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Old 10-17-2017, 08:42 PM   #9
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Default hot start

I have a 1981 Archer II. When I bought it last year, it had 750 hours on the mags. I had problems with every hot start. Frustrating. I rebuilt the mags, changed the ignition harness, new plugs and hot starts problems went away. However, I only throttle once; mixture rich; no priming; for hot starts. on cold starts, I throttle three times, full rich, no priming and it fires on 2-3 blades. I change plugs every 50 hours with the oil changes too. I never prime cause it itsn't very cold here at klgb. Hope this helps. Brad.
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Old 10-17-2017, 09:46 PM   #10
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I'm curious about what opening and closing the throttle actually does before starting a carbureted engine.

In theory, the throttle just restricts how much air the engine can suck in once it's actually turning; does the electric fuel pump have some awareness of the throttle position? Or is there a hidden fuel switch that the throttle activates when it's open?


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