Coincidence? EGT weirdness

[MARZ]

My stock one cylinder EGT went kaput or so I was thinking, bought a new (used) gauge and exchanged it - tested the probe, all seemed to be working - but still nada in the dash.   So I got a 4 cylinder egt new - got it put in and on the test number three cylinder registered a whopping 255 Degrees with the rest running normal. (1300 or so) 

Odd that the original was in number three and not registering and that the new egt shows a very low temp in number three - I say odd in that I've not noticed an appreciable loss of power nor appreciable vibration that I would assume would be there if I had a dead hole.

My annual is about to start and I plan on getting it resolved before I go up again - anyone have any experience with this type of occurrence?

[Shadrach]

Are you using all new thermocouples (probes) or reusing an old one? What kind of unit. Did you trim  the wire length? In some units the gauge will only work with a thermocouple of a specific resistance (ohm rating) and specific length wires.

[MARZ]

Quote: Shadrach

Are you using all new thermocouples (probes) or reusing an old one? What kind of unit. Did you trim  the wire length? In some units the gauge will only work with a thermocouple of a specific resistance (ohm rating) and specific length wires.

[Shadrach]

Time to call the factory...

[carusoam]

Mike,

[1] Assume: All EGTs should be running over 1,000 F even if the holes are very far down the exhaust tubes. 

[2] Mounting: The probes are usually simple thermocouples mounted through the exhaust tube, in a small drilled hole.  It is not possible for the original hole to be so different to cause such a variation of temperature.

[3] Check the obvious: check for any accidental shorting, broken insulation or broken wire. 

[4] The test: Can you swap adjacent probes / locations for cylinders 1 and 3 to see if the weird reading goes with the probe?

[5] Follow-up: If your EGT is really that low, then there is no spark or no fuel going to that cyllinder.

[6] As JL points out below,  the original EGT may still be mounted in its original spot.  It would take an STC for replacement.  This makes you ask what is the new thermocouple connected to?

Best regards,

-a-

[jlunseth]

Did the probe actually get replaced?  Very often, the factory probe stays where it was and new probes get installed in the other pipes.  Could be that the probe went bad and has not been replaced even with the installation of the new unit.

[danb35]

Quote: carusoam

[6] As JL points out below,  the original EGT may still be mounted in its original spot.  It would take an STC for replacement.  This makes you ask what is the new thermocouple connected to?

[MARZ]

Quote: carusoam

Mike,

[1] Assume: All EGTs should be running over 1,000 F even if the holes are very far down the exhaust tubes. 

[2] Mounting: The probes are usually simple thermocouples mounted through the exhaust tube, in a small drilled hole.  It is not possible for the original hole to be so different to cause such a variation of temperature.

[3] Check the obvious: check for any accidental shorting, broken insulation or broken wire. 

[4] The test: Can you swap adjacent probes / locations for cylinders 1 and 3 to see if the weird reading goes with the probe?

[5] Follow-up: If your EGT is really that low, then there is no spark or no fuel going to that cyllinder.

[6] As JL points out below,  the original EGT may still be mounted in its original spot.  It would take an STC for replacement.  This makes you ask what is the new thermocouple connected to?

Best regards,

-a-

[danb35]

Quote: maropers

The original was removed completely.  The new EGT came with an STC so no issue there even if it weren't required.  

[MARZ]

"You don't have an issue because the EGT isn't required"

Agreed -

The STC actually does allow for primary secondary new or replacement. 

[Shadrach]

Quote: danb35

You don't have an issue because the EGT isn't required.  If it were, though, the simple fact that you have an STC isn't enough--that STC has to specifically allow use of the engine monitor to replace the primary engine instruments, and most engine monitor STCs don't.  The only ones I know of are the new multicolor displays that show everything on a single screen.  What your STC most likely allows (as my UBG-16 STC does) is installation of the monitor as a supplemental instrument--it can't replace any required instrument, but you can have the extra information.

[MARZ]

And the survey sez.........   bad connection !!! 

Restripped the wire reattached and tada.....  it works great...  I can sleep well tonight.