How does the Fuel Flow Meter work on the PA-30?

My fuel flow meter was working well until I replaced the fuel boost pumps.
We tried bleeding the lines from the fuel distribution manifolds back to the firewalls.
The fuel flow meter still does not work.

The diagram in the service manual shows the fuel lines coming from the fuel manifolds to the Fuel Flow meter on the instrument panel. Then there is one vent line from the meter going to the right engine firewall. I can not imagine fuel being pumped all the way to the meter on the instrument panel. That would be a receipt for disaster.

I find nothing in the service manual explaining how the fuel flow meter functions; or how to adjust it.

Does anyone know how it works and/or how to make it function again?

Thanks for any help.
Nimrod

It is a pressure gauge. Check for something plugging the line from he flow divider (spider) on the engine to the gauge. I had a TC this winter with something in the copper line from the gauge to the firewall. It took 200 psi from a nitrogen tank to blow it out. We blew from the gauge end out.

Thanks Jim.

Agree. I just tore mine apart a week ago. The copper line comes from the spider, past the baffle and into the wing ultimately to the gauge on the panel. It is a very small amount of fuel.

Easiest thing is to remove the panel cover and disconnect the copper line on the gauge. Then on the engine, disconnect the.copper line that attaches to the spider. It is easy to determine since the other lines go to cylinders. Then blow it out from the gauge toward the engine.

I also disconnected the lines to the cylinder from the spider and blew them out. All this said the problem was a small crack in the line.

So..how did I discover this leak? After I attached everything I turned on the fuel pump and the gauge still didnt work. While the pump was on I walked around the engine to look at the spider lines and saw fuel leaking under an adele clam on the baffle. Fixed that and problem solved. I turned back on the pump and the gauge showed flow.

Took about an hour to two tinkering but no crawling around and all on top of the engine or panel.

My suggestion, turn on the fuel pump with your top and side cowlings off and walk around the engine. If you see a leak where there shouldnt be one then that is the problem. No need to blow anything out then.

As others have said you can blow the lines clear, just use caution that both ends of the line are disconnected. The second line from the gauge is a vent which is open to atmosphere in the engine cowl at the rear baffle.

I've seen the line from the flow divider to the rear baffle usually with a piece of safety wire inside it to act as a snubber or restrictor of some sort.

Clarence