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185 throttle adjustment

Tom3holer

Registered User
Cape Cod
My mechanic was doing an annual on the 185 and broke a wire on the micro switch where the throttle connects to the fuel control unit that controls the fuel pump speed. I also asked him to replace the worn the throttle cable and rod end fitting as they were worn. Had to leave early due to obligations. The other mechanic and I took up where he left off with a new micro switch and rod end fitting. The problem is that he is not sure of where the throttle arm is supposed to be positioned on the shaft at full throttle. In the service manual diagram 11A-5 it shows it at about 90deg to the fuel control unit which seem about right but wanted to be sure.
Tom
 
I forgot what uear your airplane is

Short answer to your question is: orient your throttle arm so you can get full travel and not go "over center" or near it.

Other things to look for while u are doing this job:

1 the bracket that holds the end of the throttle and mixture cable sheaths....are the tabs under the induction hose worm clamp still there?

2 is the micro switch cam worn? (The eccentic thing miunted behind the throttle arm)

3 are the throttle body braces broken? (They go from the bottom of the air horn on the theottle body up to the oil sump bolts)


having fun yet???
 
Like Dave said.

You will also also want to check and reset the position of micro switch as needed. And check the electric pump flow/ resistor settings. Important things if the mechanical pump takes a dive....
 
Thanks Mike and Dave,

I will make a copy of this and bring it with me tomorrow when we get started again.
As I recall the cam is in good shape and braces are in good shape. The engine has only 180hrs SFREM in 09.
We have the specs for setting/checking the resistors and fuel flow.

Tom
 
When you say over center do you mean to orientate the throttle arm to be 90 deg to the rod end fitting at mid throttle?
The diagram on page 11A-5 of the SM shows it oriented that way but does not say what the throttle position is, mid or full.
Tom
 
When you say over center do you mean to orientate the throttle arm to be 90 deg to the rod end fitting at mid throttle?
The diagram on page 11A-5 of the SM shows it oriented that way but does not say what the throttle position is, mid or full.
Tom

that is a good place to start. Then see if your throttle cable rod-end/Heimjoint gives you adjustment enough to maintain that.

Your "new-ish" engine throttle body has a "knurled" throttle shaft, so the arm orientation (and micro switch cam) is nearly infinite, and captured by the clamping force of the nut. The old throttle bodies had a peened-over pin that fixed the throttle arm location FYI
 
those parts are not included in OH....

yes, the cam is a Cessna part.

I did a 550 two years ago and the throttle body braces were included. I think they were Continental branded. I kindof recall the same parts available with Cessna part numbers??
 
We finished it up this afternoon.
All went well after tweaking the adjustment to get the arm to have equal movement.
Had to ballpark the called for 20" MP. There were two marks on the cam that seemed to relate to throttle closed and switch activation.
After trying to determine what was meant by the many inconsistencies in the repair manual will have to see if its close when we get it outside and run it.
Thanks again for all the advice.

Tom
 
Since you had the torque off the throttle shaft nut, the cam was able to rotate so those "marks" (wear?) on the cam will no longer relate to the arm orientation nor to the manifold pressure value at which the electric pump speed should reduce. A couple of test runs and you will nail it down no problem.
 
The marks were put on with black felt pen it looks like.
Ran it today and found the cam will need adjustment to get it to switch at 20" of MP.
We think it can be done with the cowling on through the right cowl flap.
 
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