IO-360-A1A Power Surge in Cruise

[Cody Stallings]

Really pulling my hair out on this one.

Noticed last week while in cruise at 8500ft I would get a very noticeable reduction in power.

While in level flight @ 24/2475. Would loose 30-50 Rpm an the Egt's would cool down 40-60 degrees, after 5-20 seconds the temps an RPM's would slowly come back up to the original settings.

Something else I noted, the mixture control is not acting normal. #3 was always first to peak an always remained the hottest both Egt/Cht. That's not the case now, it's a crapshoot as to which will peak first.

I have been told it could be bad gas, servo, injectors,ect.

For the most part the engine runs like a top, has plenty of power an never has missed a beat, but with this power surge comes a shutter at times that shakes the whole plane for a second. It can really get your attention when your bored watching the mileage count down trying not to go to sleep.

Any help/ideas would be greatly appreciated.

Thanks Cody

 

[mooniac15u]

Did you do a mag check while this was happening?

[N601RX]

Does your engine monitor include fuel flow and fuel pressure?

[Cody Stallings]

Yes, Magcheck on Grd an in flight. Inflight just adds to the power reduction, but Egt's really climb.

No FF or FP on the EDM 700.

Factory FP gauge stays locked at 16 psi, never changes.

[jetdriven]

Could be the baffle in the muffler has burned up, and a piece of it is randomly covering the exhaust outlet.  

Does the fuel flow change when it lays down?  Are you cruising LOP or ROP?

Edited May 15, 2016 by jetdriven

[Cody Stallings]

On this particular flight I was ROP 20-30 degrees. Have no Fuel flow Transducer 

Will look into the Muffler theory.

[Marauder]

Cody -- 16 PSI is pretty low for the A1A. 14 PSI is the minimum. Mine stays in the 23 - 24 PSI. Was your pressure always this low?

If you were losing a mag in flight, I would expect to see all EGTs climb as the flame front is further down the exhaust. How many hours on the engine and has anything work/maintenance been done on the fuel injection system? With a uniform drop in EGTs, I would suspect something is going on with the fuel getting to the engine.

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[MB65E]

What's the fuel pressure change with the pump on. 

The ever so famous champion spark plugs?

could be something partially blocking the spider.

[Cody Stallings]

Sorry guys. More like 21-22 PSI now that I pay closer attention

[Cody Stallings]

The Servo an Spider was O/H by Mikes fuel metering in Tulsa 2 yrs ago.

Have had no problems after it was reinstalled.

The FP does not fluctuate at all when it surges

[mooniac15u]

5 minutes ago, Cody Stallings said:

Sorry guys. More like 21-22 PSI now that I pay closer attention

Maybe it's because you're out of fuel. 

[takair]

What does the manifold pressure do?  It would be odd that you get a drop in RPM without corresponding change in MP.  Picture the amount of throttle movement or mixture movement required to come off the governor and get an RPM drop....  Did your speed drop significantly?  Also, was the EGT reduction equal across cylinders?

[Marauder]

Sorry guys. More like 21-22 PSI now that I pay closer attention

That fuel pressure sounds better. This is a strange problem. Wish I could say I have seen it before. What keeps coming back to me is the uniform drop in EGTs when this is happening. I would suspect the cylinder temps would begin dropping as well if it is due to reduced fuel flow.

Too bad you don't have a recording engine analyzer. It would help show what everything is doing at the time of the problem.

As for your "peak" cylinder. I find that my "peak" cylinder changes as well. Keep us posted.

[Cody Stallings]

MP stays around 24 inches. Yes it affects all cyl, but it is more noticeable on the hotter Egt's. They really fall fast an get your attention. It's not coming off the gov, it looses the power the rpm drops an the gov flattens the prop RPM's start coming up. Sometimes it will jump from 2450 up over 2500 trying to compensate. I have noticed the P-1000 is to informative, matter of fact it drives me crazy in most cases.

[N201MKTurbo]

The muffler idea seems possible. Also check your induction system, I have had intake risers loosen. Check the ram air door and bellows, it could be falling apart and blocking the airflow. 

Could be a snffel valve issue, but I don't think it would have that big of an effect.

[takair]

I'm sure you've checked, but a slug of water can be a real attention getter and can be similar to what you describe.  Has the plane been outside in the rain?  If so, give the wings a slight shake and then sump.  The finger screen and sump point is not exactly colocated. You fuel pressure would likely not show a difference and MAP may not have enough time to move.  EGT and power would drop with a fast recovery if it was just a slug.

We've seen a few reports of air being sucked at the gascolator.  This may have similar behavior, but usually comes with fluctuating fuel flow as well, so I'm leaning more toward the water at this point....till you tell me it never saw rain.

Have you tried throwing on the electric pump?  Probably a good thing to keep in mind if this happens again.

 

[MB65E]

I would be peeing myself if those photos were in flight!!! Do the gauges work, I hope you were on the ground!

1450 seems hot, but your cylinders are still in check. 

Hope you find the deal soon.

Cheers,

-Matt

[Guest]

My second E model did this as well on a less than 100 hour old engine.  It would suddenly slow down while flying formation with a buddy.  

After going through evererything I could think of, I removed the mags and found the internal timing was off.  I re did the mags and the problem seemed to disappear.  I ultimately sold the airplane and got an IO720.

Clarence

[Yetti]

Sounds mag related.   The P lead(s) could be shorting to ground

[Cody Stallings]

1 hour ago, MB65E said:

I would be peeing myself if those photos were in flight!!! Do the gauges work, I hope you were on the ground!

1450 seems hot, but your cylinders are still in check. 

Hope you find the deal soon.

Cheers,

-Matt

Haha, yeah that's in flight. The fuel gauges pick an choose when they wanna work. I use my watch as a fuel gauge.

As far as the EGT, that's normal for a good cruise tune. 20 ROP works really well

[Cody Stallings]

2 hours ago, takair said:

I'm sure you've checked, but a slug of water can be a real attention getter and can be similar to what you describe.  Has the plane been outside in the rain?  If so, give the wings a slight shake and then sump.  The finger screen and sump point is not exactly colocated. You fuel pressure would likely not show a difference and MAP may not have enough time to move.  EGT and power would drop with a fast recovery if it was just a slug.

We've seen a few reports of air being sucked at the gascolator.  This may have similar behavior, but usually comes with fluctuating fuel flow as well, so I'm leaning more toward the water at this point....till you tell me it never saw rain.

Have you tried throwing on the electric pump?  Probably a good thing to keep in mind if this happens again.

 

It hasn't lived outside in over 15 yrs, previous owner kept it inside an so do I.

I think it may be water too, I took about 40gal at a local airport 15 min into the climb this problem started. However, I have cycled about 55gal through it an the prob is still there.

When I sump the tanks, there is no water. BUT you can see some darker blue an light blue swirling around.

But you can let it sit for hours an nothing ever settles in the bottom...... Strange

[M20F]

My caps leak when the O-Rings are more than a year or so old.  I have drained out at least a quart of water at times.  If you have water it will run exceptionally rough to where you think the engine is going to fly apart.  I don't think it is a contimination issue sounds like mags.  

[takair]

8 minutes ago, Cody Stallings said:

It hasn't lived outside in over 15 yrs, previous owner kept it inside an so do I.

I think it may be water too, I took about 40gal at a local airport 15 min into the climb this problem started. However, I have cycled about 55gal through it an the prob is still there.

When I sump the tanks, there is no water. BUT you can see some darker blue an light blue swirling around.

But you can let it sit for hours an nothing ever settles in the bottom...... Strange

When I first bought my plane it was outside and I had a couple of bad fuel caps.  Would get drops of water that I would drain off....but I found out the hard way that the fuel servo would retain a little in the screen area.  In my case the problem manifested itself in cold weather with strange operation on ground, the servo actually had some internal corrosion due to the injection of water.  I don't suspect that is the case for you, but I recall removing the screen and having a waterline on it.  It may be possible that the water is catching there, getting to a certain volume and then injesting.  Kind of a long shot, but in this case it may be worth checking that fuel screen anyway.  There is an print their that you may need to replace too.  In a previous airplane I had partial loss of power due to water accumulating in a similar fashion at a junction.  Took some time to diagnose.  It is nice to be hangared now, but airport fuel tanks are not immune from adding water to our aircraft.

[Cody Stallings]

Just now, M20F said:

My caps leak when the O-Rings are more than a year or so old.  I have drained out at least a quart of water at times.  If you have water it will run exceptionally rough to where you think the engine is going to fly apart.  I don't think it is a contimination issue sounds like mags.  

Mike, if the mags were grounding out or loosing power, wouldn't the Egt's shoot up like when your doing a mag check?

[carusoam]

Trying to summarize this one....

1) Issue: RPM drop in cruise flight @8500' in an M20F.  Self fixing over time, slowly...

2) 24"mp, 2475rpm. Would loose 30-50 Rpm and the Egt's would cool down 40-60 degrees.

3) fuel and fuel system are high suspected...

4) No recent work done.  Some fuel system work a couple of years ago...

5) Fuel pressure seems steady, indicating the fuel pump is working properly.

6) EGTs are noted as dropping quickly during the event. Quickly AND evenly.

7) MP is steady. Kind of ruling out things related to air blockage (filter, ram-air, or throttle)

8) The Even drop of EGT on all cylinders rules out a single blockage of a single fuel injector. 

9) air entering the fuel system can allow air bubbles inplace of fuel.

10) Sniffle valve, leaky fuel selector or other sources of leakage were listed...

11) exhaust blockage was mentioned. 

12) adding possible mag issues including timing. How old is that plastic gear in there?

13) fuel spider and the filter upstream

14) No FF data is available

15) FL instruments seem to have a grounding issue in flight.

16) Some responses include peeing one's self and solutions like replacing the IO360 with a larger engine like an IO720

17) there have been four additional replies while I was type up to here....

18) worn or failing gov. How old is it?  An OH or replacement isn't very costly.  See if the flyweights aren't misbehaving.

19) ever present water entering the fuel system from somewhere and not draining out.

20) Check for Champion spark plug resistance issues.

From a safety point of view, I would be interested in seeing if something has been deposited on the fuel screens leading up to the fuel injector equipment (spider).

As usual, I'm only a PP, not a mechanic.

Best regards,

-a-