High oil temp/CHT's

[Frankh]

Hi,

Went flying for an hour this morning and everything was fine...Came out of the FBO fired up the airplane to go back home.

On climbout D10 showed alarmingly high #4 CHT and oil temp....The other CHT's were high too but the #4 is the hottest.

Thinking we had a serious engine problem we returned to the airport and pulled the cowl and plenum and found nothing obviously wrong...epected to see a dead rat on tp of the #4cyl blocking the air to the oil coller...Nothing all baffles in place, it was perfect.

Took off again and I seemed to be able to keep the temps stable but at redline

Then the tach started jumping around and the CHT's came down but not the oil temp...After a scary but uneventful landing (IMC) we taxied off and one of the EGT's went suddenlt nuts, like 2000F...clearly impossible.

So I'm thinking this is an instrumentation issue and I don't have an engine problem (hard to see how the high CHT and oil temp would be related unless I holed a piston or something...all cyl's had good compression) at all.

Have you any clue?...I was thinking maybe a bad ground but the unit has been working perfectly for 45 hours...I did do firmware upgrade (1.08)before I flew it today.

Thanks

Frank

 

[vinhvinh]

HI,
I had the same problem and it was the wire of a CHT probe that was nearly broken near an attatchement point on my engine mount. My cht was gooing to hight and too low in a mather of second but wasn't alwaiys high

take a look

vinh

 

[Frankh]

Another symptom is that the fuel pressure has now jumped from 28psi to 35psi...Now I have 2 independant electric fuel pumps and two relief valves that set the pressure..If one valve was sticky then that would raise the pressure, but the high pressure is noted with either pump running....

The battery voltage is noted as normal i.e 14.2V, as is oil pressure.

So far the errors (assuiming my engine is not really about to blow up) appear to be oil temp, all CHT's...Noticed an occasional erratic jump in the tach signal and the #4 EGT on the ground, suddenly spiked to 2000f and immediatly back to 900F.

All very odd dontcha think?

 

[dynonsupport]

My first guess on the symptoms you are seeing is a bad ground between the engine and the EMS. If the ground on the engine isn't really well tied to the EMS, a lot of sensors can act strange. I'd check your ground strap to the engine first. It would also be interesting to see if the symptoms go away when you shut down your alternator. The alternator is the thing on the engine that puts lots of current through the ground strap, so shutting this down will change the load there and if you see stuff change, it's an indication that your ground is poor. You can do this on the ground if you wish.

Let us know how that goes and we'll keep looking. It doesn't directly sound like the EMS, but I guess anything is possible. I'd expect all the values in the EMS to go totally crazy if something in it failed.

 

[Frankh]

Hey thanks,

Will do the groundstrap check...Do you happen to have the calibration curve for the oil temp sensor?.....I was thinking I could directly connect an ohm meter to the sensor and if it acts up again see if the reading it is getting is real.

Just scratching for ideas at this point.

Thanks

Frank

 

[dynonsupport]

The curve isn't linear, so it's hard to just tell you what it should be.

It's 1500 ohms at 50 deg f, 750 ohms at 75 degrees F, 420 ohms at 100 deg f, and 53.5 ohms at 212 degrees.

Remember, you need to measure this at the back of the EMS. If it's correct at the sender, the ground may make it inaccurate at the EMS.

 

[Frankh]

Thanks...Yes I was going to fly, see if it gets hot and changeover to ohmmeter at the snder to check to see if the reading is real (unlikely but possible)...If not then we at least know for sure its an instrumentation issue.

Cheers

Frank

 

[Frankh]

Found nothing.

Flew again and everything was fine...of course I wiggled all the ground conections and who knows if I seated something. Thinking I might cut the ground wires and maybe make a single dedicated ground to the engine block and battery to the EMS.

If the engine had done something serious it certainly would not have gotten better.

Beyond that I guess its wait till it acts up again, if it ever will.

Frank