Fuel Pump Problems?

N

nvracer

New member
My fuel pressure on the Franklin 150 has been pretty steady at around 4 PSI. Recently the pressure on the gauge has started to fluctuate higher and lower than the 4 PSI with each stroke of the pump. So the needle is covering quite a bit of distance now. What do you think the cause is?

Ray

Cruisaire 14-13-2
N33GM
 
You probably have an air leak causing the needle fluctuation, it may be tough to find. Remember all of the flexable hoses on any airplane shoud be changed at least every ten years. Look at your exhaust and see if your stacks are cream colored or white. White indicates to lean. If you find a problem with the pump shoot me an email, cglucas@cox.net. Greg
 
I removed the pressure relief valve, dissassembled it and cleaned it. It didn't look dirty. Guess what? Everything is back to normal without the large needle fluctuation.

Thanks,

Ray
 
Ray,
I have been having the same indications in regards to my fuel pump..could you please give me information on the pressure relieve valve and how you went about cleaning it?...
Mike
N86744
 
The pressure relief valve was added due to a factory service bulletin a long time ago. It is to prevent high fuel pressures from unseating the float needle in the carburetor. Mine limits fuel pressure to 5psi. The valve is located at a Tee in the fuel line from the fuel pump to the carburetor. It allows excess fuel to return to the tank. It is easily removed and will come apart using 2 wrenches to unscrew an end. It is a spring loaded valve and very simple.

Cruisaire N33GM

Ray
 
Ray,
thanks for the reply. I knew the relief valve was in the system and why, but, wasn't too sure about cleaning it. I too had fluctuating fuel pressure. when I went to check the relief valve, I found a loose connection in my fuel line after the wobble pump on the engine side of the firewall. I was able to find it by leaving the mixture in idle cutoff and pressurising the system with the wobble pump.
Mike
N86744
 
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