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IO320 Help

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Elwell81

Member
I made my first flight today and had an interesting event occur. I climbed up to 6500 ft to just do some quick stalls and then come right back down for landing. However, when I started to level off and pull the throttle back, I got to about 1400 rpm and the engine died. I tried everything thing to get it back but it would just crank and not start. I was about to shut everything down and prepare for a dead stick landing (I was directly over the airport) when I decided to try to restart like I would on the ground, with the mixture in idle cutoff. It came to life and ran better with the mixture pulled out quite a bit from full rich. I left it like this all the way to the ground and had no more problems.

Any opinions on what might have happened?

Its a Superior XP IO-320 with dual P-mags and Silver Hawk EX. I've got the data-log from the G3X touch through entire sequence of events so if any additional info is needed let me know. Thanks
 
Awful Quiet

Initially sounds like fuel system is dumping way too much fuel thru engine and over rich mixture is putting the fire out. The Bendix RSA servo's have exhibited this failure mode. More info is better, did this happen on first flight with just 20 minutes on new plane and engine? Do you have EGT and fuel flow readings up to power interruption? And after relight? Look at Fuel Vents yet? Did you switch tanks on this flight?

Don Broussard. A&P, IA

RV 9 Rebuild in Progress
 
cajunwings said:
Initially sounds like fuel system is dumping way too much fuel thru engine and over rich mixture is putting the fire out. The Bendix RSA servo's have exhibited this failure mode. More info is better, did this happen on first flight with just 20 minutes on new plane and engine? Do you have EGT and fuel flow readings up to power interruption? And after relight? Look at Fuel Vents yet? Did you switch tanks on this flight?

Don Broussard. A&P, IA

RV 9 Rebuild in Progress
Click to expand...

To answer your questions, yes, happened on first 20 minutes on new plane and new engine. I had 30-45 minutes of ground run before first flight. Fuel flow at take off peaked at 13.6 gph @ 2400 rpm, with EGT's from 1205-1285.

After restart, the fuel flow was 4.5 gph @ 2000 rpm, with EGT's from 1300-1390. This was leaned quite a bit.

I switched tanks when trying to restart, from left to right, and it finally restarted. Although I believe it had more to do the mixture setting than anything. The boost pump was on through the whole event and the fuel pressure never dropped below 28 psi. Would it still maintain fuel pressure if there was a venting problem? The vents are per plans. Thanks for your help.
 
Fuel Syst

By the way, congrats on your first flight and successful return to Earth.

Logic says this has to be either ignition or fuel trouble. Sounds like wing tank fuel venting is probably OK but take off the fuel caps and by mouth pressure up the tanks verify vents are clear. Mahlon has a good suggestion as well Do you have EGT & FF data @ 6500' right before power reduction and engine quitting? Where was the mixture set during the climb? When the engine quit did it run rough and die or stop instantly like you turned off the mags? Will it now make full power on the ground and give you the same EGT & FF as before?
 
Flow Divider Vent?

mahlon_r said:
Make sure the vent in the flow divider isn't blocked!
Good Luck,
Mahlon
Click to expand...

Now that's something I hadn't thought of, mainly because I didn't know there was one. Is it fairly obvious on the flow divider? I remember seeing a blocked off port that says "pressure" I think, but nothing else. I will pull the top cowl and take a look.
 
cajunwings said:
By the way, congrats on your first flight and successful return to Earth.

Logic says this has to be either ignition or fuel trouble. Sounds like wing tank fuel venting is probably OK but take off the fuel caps and by mouth pressure up the tanks verify vents are clear. Mahlon has a good suggestion as well Do you have EGT & FF data @ 6500' right before power reduction and engine quitting? Where was the mixture set during the climb? When the engine quit did it run rough and die or stop instantly like you turned off the mags? Will it now make full power on the ground and give you the same EGT & FF as before?
Click to expand...

It didn't die like a killing the mags, it seems like it was fuel related, either to little or too much. Mixture was full rich except for one brief moment in the climb when I leaned it a bit to see if I had any rpm gain. Here are a couple snapshots of the logs. It runs fine on the ground, haven't seen any changes in FF or EGT. Going to check the fuel vents and flow divider vent today when I get to the hangar.

fuel%20flow%20and%20EGTs_zpsbdyzu7ra.jpg


egt%20and%20rpm_zpsebk2qka3.jpg
 
Fuel Flow

Elwell81 said:
It didn't die like a killing the mags, it seems like it was fuel related, either to little or too much. Mixture was full rich except for one brief moment in the climb when I leaned it a bit to see if I had any rpm gain. Here are a couple snapshots of the logs. It runs fine on the ground, haven't seen any changes in FF or EGT. Going to check the fuel vents and flow divider vent today when I get to the hangar.

fuel%20flow%20and%20EGTs_zpsbdyzu7ra.jpg


egt%20and%20rpm_zpsebk2qka3.jpg
Click to expand...

It appears that something disrupted fuel flow. One thing you don't show in your data is manifold pressure. If you can't find any fuel system related issues, I would look carefully at your induction system and make sure you don't have something loose in your air box partially or intermittently obstructing your FI servo inlet.

Skylor
 
Congratulations on first flight!! Sounds like more than expected, but you were ready - too much excitement to be sure. Good job on getting it back on the ground safely. Keep us posted on your findings.

Edit: if you wouldn't mind - can you post a link to the Savvy analysis file for greater detail?
 
Last edited:
Andy, Maybe you have found something this weekend. The data stream does not seem to reveal the root cause. The FF seems to drop off with RPM, a bit delayed, though. The MAP does not jump or fall like something blocking the airflow, and the fuel pressure seems pretty steady. If it was too rich, it did not happen suddenly. Maybe the plugs fouled, but unlikely they all went at once. The EGT's did act like either and enrichment or leaning event took place just as the RPM dropped. I think the FF is delayed, but don't know why - the EFIS guys should be able to tell us.

Maybe DanH will take a look at your data and posit a theory.
 
BillL said:
I think the FF is delayed, but don't know why - the EFIS guys should be able to tell us.

Maybe DanH will take a look at your data and posit a theory.
Click to expand...

When I first saw the fuel flow, I thought it was delayed as well, but the more I look at it, I'm wondering if the info is correct.

As I was pulling the throttle back, the fuel flow drops with a corresponding drop in rpm. That is until it hit about 1600 rpm where the fuel flow stayed fairly steady. Now, I don't recall how far I pulled back on the throttle (I had lot going on at the moment) but if I had continued pulling back on throttle and fuel flow stayed the same, it would go extremely rich and do exactly what it did. Possibly the servo is way to rich a the lower end? If that's even possible? I did some ground runs yesterday to get some info for Precision, hopefully they'll have an idea.

I'm still open to anybody else's theory as well.
 
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