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#1 cylinder EGT high on takeoff

Flyyak

Well Known Member
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I have an I0360 with Airflow Performance fuel injectors that have been calibrated. Now have 300 hours and all has run perfectly up until a few hours ago I started to notice in the yellow on #1 on takeoff. I have since inspected and cleaned all injectors. There was no obstruction or debris. After test flight, #1 in the red but would come back in yellow and green when I reduced throttle. I then disconnected all injection line, used 4 baby food jars, initiated boost pump and all fuel collections were identical. Next swapped Alcor 86255 EGT probes between #1 & 3 and test flew again. #3 registered high and I then installed a new probe in #1 and reinstalled #3 back in #3. Test flew and #1 registered in the red on takeoff, would come down to yellow and green on throttle reduction.

Please let me know other suggestions to check. I generally run LOP and the EGTs are within 10* between high and low and CHTs are very close also (#4 highest where oil cooler is located). I have two PMags and they have been flawless to date. Engine has really run very smooth, starts easy cold or hot. Thanks.
 

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Check for induction leaks? Perhaps even replace the intake gasket and pipe clamp if your engine is so equipped.
 
Out of curiosity, how close to the exhaust valve are the probes installed? Are they all the same distance?
 
EGT probes are all the same distance and have worked great for 300 hrs. Thought it was the probe when I changed 1 to 3; photo attached. I will check gaskets. It is odd that when I changed the probes, the #3 probe placed in #1 exhaust seemed to show normal temps. Thanks
 

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If the lean limit spread is good, the EGT is likely a probe issue. EGT's are not really comparable. CHT is a better indication of balance.

Have you checked the thermocouple wires and connections?
 
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Thermocouples are sensitive to poor wiring connections, so maybe start there. If problems move with a probe swap, seems logical that the probe or wiring is to blame.
 
Induction leak is not likely. An induction leak would leak the most at partial throttle (like while at idle, because that is when the differential between manifold pressure and ambient pressure is greatest) and least at full throttle (when the differential is almost nil).

So reducing power, as was indicated, would increase an induction leak (making the mixture worse not better). Things got better with the reduction, so an induction leak is ruled out!
 
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Thermocouples are sensitive to poor wiring connections, so maybe start there. If problems move with a probe swap, seems logical that the probe or wiring is to blame.

The OP said in his first post that he had already performed a probe swap and the high EGT stayed with the offending cylinder #1 (didn't move with the probe). So obviously not a probe. But he then replaced the #1 probe anyway...no difference.

I'm with Vern on this one....one plug not firing properly on Cylinder #1. Could be the plug itself, or it could be the Pmag driving it. As Vern said, easy to check the plug.
 
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I'm with Vern on this one....one plug not firing properly on Cylinder #1. Could be the plug itself, or it could be the Pmag driving it. As Vern said, easy to check the plug.
And check the plug wires. Any crackling or popping in the radio? That could indicate an intermittent connection. You might need to move the plug wire around when checking resistance to get it to short. I had this problem with one plug wire.
 
The OP said in his first post that he had already performed a probe swap and the high EGT stayed with the offending cylinder #1 (didn't move with the probe). So obviously not a probe. But he then replaced the #1 probe anyway...no difference.

I'm with Vern on this one....one plug not firing properly on Cylinder #1. Could be the plug itself, or it could be the Pmag driving it. As Vern said, easy to check the plug.

What I read:

"I started to notice in the yellow on #1"

"Next swapped Alcor 86255 EGT probes between #1 & 3 and test flew again"

"#3 registered high"

What did I miss that makes you think the problem didn't move with the probe? It may have confused you that he then swapped back 1 and 3 and the problem disappeared, but that doesn't change the original troubleshooting data. To me, that points to trouble in the connectors, giving inconsistent results.

I wouldn't rule out a bad plug, but you can't ignore troubleshooting data that points in a different direction.

Larry
 
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Thought it was the probe when I changed 1 to 3; photo attached. I will check gaskets. It is odd that when I changed the probes, the #3 probe placed in #1 exhaust seemed to show normal temps. Thanks

That’s not what I’m seeing. The photo of your EMS shows that when you moved the #3 probe to the #1 cylinder the #3 probe was reading high suggesting that the #1 cylinder is reading high. Conversely when you moved the #1 probe to the #3 cylinder it read normally. This suggests to me that the high EGT is not moving with the probe and your problem is therefore not probe related but cylinder related...cylinder #1.
 
So what was the outcome for the OP after requesting and receiving advice on his problem. Inquisitive minds would like to know and that would also be of benefit to others.
 
I think that posters who request and receive technical advice from VansAirforce members have a responsibility to finally report if any of the suggestions solved their problem (or did not solve their problem as the case may be). That way the thread becomes a more complete and therefore more valuable tool in the archives for others to access later on. It also encourages people who are taking time to provide comments to continue doing so in the future.
 
Ahaaa the good old days when we didn't have any CHT or EGT on every cylinder and lived in ignorant bliss.... Ha ha.

I am kidding but seriously we didn't see this "granularity" of engine parameters like this in GA just 20-30 years ago. Still today most Skyhawks and Archers don't have engine monitoring systems. I remember when I first got my PVT and rented planes. It was like WOW this plane has a single analog CHT or EGT gauge (usually not both).
 
Still high EGT on #1

Sorry for delayed response. This is what I have determined so far-
1. Probe was not the issue. Determined that when I changed #3 probe into #1 exhaust, #3 probe registered high EGT. Just to make sure, I replaced #1 probe with a new one and it also registered high EGT in #1.
2. Checked fuel flow and it was good.
3. Re-checked and cleaned fuel injectors and jets again. Just to be sure, swapped injector jets between 1 and 3 but no change in EGT on 1.
4. Borescope cylinder and all looked great.
5. Compression check was 79/80.
6. Discovered a defective plug wire and replaced it today. Thought that would be the culprit but after test flight, same result, high EGT on #1 at takeoff or at full throttle but it will settle in the green when throttle is reduced.

I have EMAGs so I will check further to make sure that they are operating properly.

Any other suggestions will be appreciated. The combined A&P opinions on our field have not been able to determine what’s next to check.

The engine runs smooth, and mag checks appear normal. Plan to perform additional mag checks inflight to see if that may help determine the issue.
 
Sorry for delayed response. This is what I have determined so far-
1. Probe was not the issue. Determined that when I changed #3 probe into #1 exhaust, #3 probe registered high EGT. Just to make sure, I replaced #1 probe with a new one and it also registered high EGT in #1.
2. Checked fuel flow and it was good.
3. Re-checked and cleaned fuel injectors and jets again. Just to be sure, swapped injector jets between 1 and 3 but no change in EGT on 1.
4. Borescope cylinder and all looked great.
5. Compression check was 79/80.
6. Discovered a defective plug wire and replaced it today. Thought that would be the culprit but after test flight, same result, high EGT on #1 at takeoff or at full throttle but it will settle in the green when throttle is reduced.

I have EMAGs so I will check further to make sure that they are operating properly.

Any other suggestions will be appreciated. The combined A&P opinions on our field have not been able to determine what’s next to check.

The engine runs smooth, and mag checks appear normal. Plan to perform additional mag checks inflight to see if that may help determine the issue.

High EGT is a typical sign of retarded timing and this occurs when only one plug fires. I would replace both plugs in #1 and test. You can even swap plugs from another cyl and see if problem moves. High power mag check should also show this type of problem. Some ignition issues will be present at full power, yet be fine at 1800 RPM.

Larry
 
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Smells like plug, wire or coil/ignition generator.
Mag check during failure to isolate.
Remember high chamber pressure stresses ignition coils, wires and plugs. There is a good reason we check plugs under pressure with a pressure chamber tester. What might spark laying up on the cylinder on the ground might not spark with increased chamber pressures during normal operation.
 
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Smells like plug, wire or coil/ignition generator.
Mag check during failure mode to isolate.
Remember high chamber pressure stresses ignition coils, wires and plugs. There is a good reason we check plugs under pressure with a pressure chamber tester. What might spark laying up on the cylinder on the ground might not spark with increased chamber pressures during normal operation.

In this case couldn't a full power climb doing a mag check conform the hypothesis? It would not take but a few seconds and the data recorder would capture it.

Our airport manager found a plug wire on a new Vans factory IO390 (RV14) that was grounding prior to first flight run up. He found the grounding location, moved the wires and it was gone. I wonder about the forever part as it was a Slick shielded wire.

It is only one of three things, fuel, spark, or instrumentation. My most difficult diagnoses have been where the real issue was erroneously ruled out early in the process.
 
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Finally I think that I have discovered the issue. We thought #1 was running lean but the fuel flow seemed to indicate otherwise. It appears that it has been a fuel injector issue from the beginning. After replacement of the plug wire and determining that the EMAGs were operating correctly, I started to check the fuel issue again. This time I removed all the fuel injectors as a unit and checked the fuel flow using the same 4 baby food jars. I calibrated my fuel injection system during phase 1 and I have .0275 orifices in 1 and 4 and .0280 in 2 and 3.

When checking, I learned that #1 was receiving the least fuel and #2 was receiving the most fuel. The differences in fuel flow were only slight. I swapped #2 orifice with#1 and on a test flight #2 EGT became elevated. I had cleaned the #1 orifice twice using a sonic cleaner and then carburetor cleaner and it appeared unobstructed. It must have become slightly obstructed and caused too lean of a fuel mixture.

When checking the fuel flow from the flow divider before the injectors, the flow was almost identical. The fuel injector units with the orifices showed 1 was receiving slightly less than the rest and apparently that was enough to cause a too lean fuel flow to #1.

I have my original .0280 orifices and plan to reinstall one in #2 and I believe that should get the EGTs all in close proximity.
 
Your goal in swapping injectors is not to get EGT’s in close proximity but to get the fuel flow where peak EGT is reached as close to the same fuel flow as possible for all cylinders. The value of the EGT is not that important. All the GAMI and like testing is based on what FF each cylinder peaks at. Ideally you would like all cylinders to peak at the same point but getting them within .2 GPH is considered very good.
 
If CHTs and EGTs are close when at cruise LOP, I would think that the engine is running happy. Wouldn’t that be an indication of close fuel flow.

When I measured fuel flow with the complete fuel injectors, I used the boost pump, 4 baby jars, then measured the amount of fuel in each jar and they were .825; 1, 8.5 and .9 inches. Not sure if the bottom of the jar was exactly the same or if I was able to see that precisely but it appeared pretty close. When I changed #1 and #2, I was actually baffled at such a small fuel flow difference that created a significant difference in EGT.

It is interesting to see the difference in EGT in my first post photos which was the result of such a small difference in fuel flow.
 
I looked at the pic. As many others have mentioned it looks like a plug not firing. You did a inflight mag check and both plugs were firing?
 
it's da spark, man

I looked at the pic. As many others have mentioned it looks like a plug not firing. You did a inflight mag check and both plugs were firing?
I agree - I had something similar. The wire had to be in just the wrong place to stop firing. I have read several people have had the same issue. If one of your wires was bad, there is a good chance that the same guy made the other wires on the same day with the same components and the same tools and same method.
 
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