12.2.4 Pressure lines

This entry is part 23 of 50 in the series 12 - Engine / Propeller

There are three pressure sensors that have to be installed. Fuel pressure, oil pressure and manifold air pressure (MAP). There’s also an oil temperature sensor but that’s installed on the oil cooler.

The rule is that you don’t install sensors directly on the engine. The vibration can cause them to crack or break and then you’ve got fuel or oil running all over the place.

There are a few different approaches to how the sensors are mounted.

One way is to mount the sensors to the firewall individually. Like this:

One of those is the fuel pressure sensor and the other is the oil pressure sensor. (I don’t have a picture that shows the MAP sensor.

But my buddy Brooke has his sensors consolidated.

On the left is the fuel pressure sensor, the right is the oil pressure and the center line connects to the MAP on the inside of the firewall.

This manifold was made from a piece of 3/4″ x 1″ x 5″ solid aluminum. I couldn’t find any 3/4″ x 1″ but I did find some 1″ x 1″  at McMaster-Carr (I love that place!).

Here’s my plan.

Here’s the 1 foot piece of aluminum that I bought.

I marked the location of the five holes on one edge (three for pressure and two for mounting).

I made a decision to move the fuel and oil feed lines from the side to the bottom. Here’s it is with the holes drilled.

And the finished product with cut down to 5 inches long with the holes taped and fittings & sensors installed.

Looking at it now, I should have put the MAP feed line on the bottom too. Since I’ve got enough stock left, I may make another with the three feed lines on the bottom.

Update…

I decided to see where I would mount this masterpiece. The three lines will all be coming from the right (co-pilot) side so that seems to be the logical location. But once I placed it on the firewall I noticed something.

This thing sticks WAY out. Which means that when I change the oil filter, it’s going to be in the way and in danger of getting bumped into.

I could try a vertical orientation. With the sensors on the top and feed lines on the bottom. But then I’ll still have to run the long feed lines all the way to the firewall.

Another method that I saw which I’m now giving serious consideration to is mounting the sensors to brackets that then mount on the engine with a short feed line. That way, instead of a couple 1/4″ feed lines going all the way to the firewall, I’ll only have four wires. Here’s an example that I found on a Cessna 350:

Still not sure how I’m going to resolve this.

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