What's wrong with my #4 EGT?

[jdubner]

One EGT has started acting up on my Lycoming IO-360 after 80 hours total time (SkyView with EMS and Dynon probe package).

Here's what Savvy Analysis reports on my EGTs as I taxied out.  Note the #4 EGT (magenta) decreases to 0 (below ambient!) a few seconds after engine shutdown (for refueling).

Then I turned off the Master Bus but quickly restarted SkyView as I pumped fuel 2 gallons at a time to calibrate a fuel gauge.  Note the #4 EGT weirdness for the first couple of minutes as the engine cooled and then a zero reading again.

After fueling and calibration was complete, I flew a 0.3.  Note the #4 EGT was normal except from about 5 minutes through 11 minutes.  I overlaid fuel flow and RPM so you can see nothing else was out of the ordinary.

Is this simply an EGT probe failure or a failure of a channel of the EMS?  Or something else?

Thanks,
Joe

 

[preid]

Check your connection (female to male) for the #4EGT. I pulled mine off, cleaned, and squeezed the connectors when together again. Has worked well since.

 

[jdubner]

Check your connection (female to male) for the #4EGT. I pulled mine off, cleaned, and squeezed the connectors when together again. Has worked well since.

Thanks.  Sounds reasonable.  I did that upon initial installation when one or two were intermittent.  I didn't even get a year out of that procedure so I need to find a better method of joining the probes to the harness. :-(

Guess I'll save that chore for the next time I pull the cowl since it's only a "gauge problem".

Thanks again,
Joe

 

[mmarien]

I bought a more expensive set a couple years ago and they came with an insulated sleeve and set screw type connectors rather than push together.

 

[preid]

Joe;
the one I needed to replace with a new connector that I mentioned previously was due to the exact same reason you mentioned, the simple did not work well. Like Marien, I bought new more expensive probes and it has worked flawlessly. The intermittent one finally went out and needed replacement, 143 hours after installing.

 

[jdubner]

Thank you, mmarien and reidvaitor. 

Any recommendations on a replacement for the Dynon-supplied EGT probes?  Seems a shame to replace the paid-for probes with something "new and expensive" though.  :-(

Perhaps silver-soldering or another technique is the answer assuming the probes are OK but the connection method is not.  How does Dynon connect the thermocouple wires to the EMS D-subminiature connectors that plug into the EMS?

And a rhetorical question: why are the CHT probes' connections troublefree?  (Or maybe they're not.)

In any case, it's the best time of year for flying so I'll be doing it with only 3 channels of EGT rather than work on this thing now.

--
Joe

 

[jakej]

Joe
Do a search on this subject, my experience is that I've only had to replace 1 x EGT probe out of scores installed. Types of terminals AND crimping can have a big impact & cause most of the problems found IMO despite some having good success in the early engine hours

Jake J

 

[mmarien]

If you look at the EGT sensors available a lot have connectors other than the push together type. Contrary to good sense, I didn't use the connectors that came with the new sensors and went with the crimp type push on connectors that matched what I already had on the EMS harness. I haven't had any problems in the last couple of years. I did purchase a more expensive crimp tool.

My problem wasn't a connector problem. I fried my EGT sensors with heat when I upgraded to electronic fuel injection. I was running my engine at peak EGT and the EGT's were in the 1600F range. After I fried the Dynon probes I bought probes advertised to 2000F but I've been running a lot leaner with my new cylinders. First screen shot shows EGT's over 1600F. The second screen shot is a cooler LOP setting and lower EGT's. You can tell by the AFR gauge at the top. 14.7 is peak EGT. Larger is leaner.