REFLECTOR: Franklin Oil Temp Probe / Primer

[Donald Royer]

Where you can place the oil temperature probe depends on the probe that you have. If you have a probe that was designed for a Lycoming engine, it is a largish lump of metal with a 5/8in. 16 thread, your choices are limited. If you have a physically smaller probe you may be able to do better.

Referring to Plate 7 of the Installation Instructions (the oil bypass plate), the ideal place to sample both the oil pressure and temperature would at port 7.3 as that is the point at which the oil reenters the engine after passing through the oil pump and the external oil cooler circuit. Some people have said that by using a small probe they measure both temperature and pressure there. If they really did, it is not clear to me how they did it. Another way to accomplish the same thing is to drill and tap the the oil pressure nut on the left side of the plan view on Plate 7. That is the large nut just above port 7.2. If the probe is small enough to fit there, to should give the same reading as port 7.3.

In my case, I have a VM1000 engine monitor which uses a Lycoming type sensor, and so I was stuck with it. The best that I could do was a custom built tee fitting in port 7.2. The side arm of the tee has a 5/8 16 thread to accept the Lycoming probe. I bought the tee from The Franklin engine people in Fort Collins Colorado. They are essentially out of business now and so I don't know whether they would still have them or not.  The last time I checked their web site was still up.

Regarding you question about a primer. I had two small carburetor fires while trying to start the engine before I installed a primer system. The engine can be very difficult to start in cool weather without it. If you try to add gas by pumping the throttle to use the accelerator pump, it dumps raw gas out the bottom of the carburetor where it is only about a foot from the exhaust pipe. The slightest backfire then gives you a fire.

I have been very happy with my primer system. Aircraft Spruce has everything that you need. If you would like, could send you a Spruce parts list off of the Reflector.

Don Royer

From: Hiroo Umeno 
Where did you guys mount your oil temp probe?  Is there a “favorite spot” for it?

Also, is Primer really needed?  
                                                                                                                                   
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