Fuel presure sender unit location

[Ironman Al 35]

Howdy folks! Happy New years!! Well, Ive installed an electric Faucet back up fuel pump to my plane now Im installing a fuel presure gaudge in the panel, its electric, from Vans, only about 30$ with the proper range, anyway now to install the sending unit. Would either side of the two fuel lines from mechanical pump have the same presure? Or would a cross over line with the sending unit have to be included? Thanks for your advise in advance! Al!

[EDMO 1078]

Excuse all my babble - Needed another cup of coffee to wake up - Of course, you are asking about the sender, and not the line from the Facet pump!  I would put the sender in the pump to carb line - that's where you want to know what the pressure is -  I am not deleting the below in spite of it not answering your question - You may want to think about it too.

Al,  a couple of questions on this:  assuming you mean one input line to mechanical pump and one line from pump to carb:   Excuse my poor memory, but I cant remember which engine everyone has.  Thinking about car engines, most mechanical fuel pump failures either block fuel flow, or with the diaphragm type, dump fuel into crankcase - of course, these did not have a back-up electrical fuel pump in the system.

1.  If your mechanical pump fails, can the Facet pump still get fuel thru it to carb?  If there is a possibility that fuel cant get thu, then the Facet line should be directly attached to the pump to carb line.

2.  If possibly, your Facet pump may put out more pressure than the mechanical pump, and is plumbed to the pump to carb line, then how would it affect your carb?  Maybe this is a non-issue? 

My Subaru engine has no mechanical pump, and relies on the electrical pump(s) or gravity for fuel flow.  That gauge sounds like a good deal.   

EDMO

Edited 31 Dec 2016 by EDMO

[Av8r3400 1178]

Just prior to the carbs would be best.  That is the only place you care about fuel pressure.

 

 

 

[EDMO 1078]

That $37 price is not the whole cost - You have to buy a $40 transducer to supply the signal to the gauge.  EDMO

[Ironman Al 35]

Yep Ed, you need that transducer! I called it a sending unit! Its what tells the presure to the gauge. Every thing Ive heard or read about the 912 mechanical pump and people answered me about that here as well, was the mechanical pump fails open! If it does fail, therefor the electric pump can be in the line prior to the mechanical pump.  So after the mechalical pump Ive put a presure regulator, then the line is a T one side goes to each carb. Cant put the sender before the regulator, can it be on one leg of the line to one carb? Or conect the both lines, include the sender in that line after the regulator.I think it will need it to be in a cross over line conecting both carb lines.

[EDMO 1078]

Once the fuel line T's off of the regulator you should have the same pressure to each carb, so I think you could put the sender on either line.  If it was a fuel flow instrument it would have to be put before the line T, otherwise you would only be measuring the flow to one carb, or 1/2 the total flow.   EDMO

Edited 2 Jan 2017 by EDMO

[Ironman Al 35]

Thank Ed! Its electric transducer!