14-13-3 Fuel System Question and Engine Mount Rubbers

G

gfhawker

New member
I am replacing fuel lines in my 14-13-3 and have noticed that the fuel system after the fuel selector valve differs from the schematic in the parts manual for the 14-13-2 (I know a different model but the only manual I have right now). I hope the following description is clear enough for someone to understand and be able to help me. Just after the selector valve there is a T fitting. The run of that fitting is from the selector valve to the wobble pump. The branch of that T fitting is to accept fuel returning from the engine driven fuel pump. I am assuming that when the float in the carb has the needle valve seated that the engine driven fuel pump is just pumping fuel back to the line between the selector valve and the wobble pump. That return fuel is being delivered through a check valve between the engine driven pump and the T fitting between the selector valve and wobble pump. The parts manual for the 14-13-2 shows no such return line and only shows one line from the selector valve, through the wobble pump, to the engine driven pump onto the carb. Can anyone see a reason for the return fuel? To me it seems that some of that return pressure can be directed backwards through the system causing issues. This airplane has a history of in-flight engine failures. Looking for thoughts.

Also, are the engine mount rubber bushings the same as those used in C65/85 engines on cubs? They look as such. I have a cub as well and comparing what was on the Bellanca and the Cub's they look identical.

Thanks all.

Cheers.

RT
 
RT, The extra line was the result of an AD that came after the 14-13-2 manual was printed. I dont know if there is any literature on the -3 Cruisair. The check valve you mention is actually an over pressure relief valve. Some Cruisair,s developed engine trouble from too high fuel pressure and an AD was issued. Check your AD list for the proper pressure and then check the valve for proper function. Many of them have leaked causing low pressure or seized shut which defeats its purpose. If any of your engine failures have been from flooding or running too rich, you might check the dash number on the carb and see if it is a Stinson carb. I believe they are set up to run on the very low gravity pressure that a Stinson has, and ours are set to run on the higher pressure that our fuel pump gives. At least it was explained to me that way. Good Luck_____Grant.
 
Thank you Grant. I now see the AD and understand why the system is modified in that way. I will definitely verify the proper operation of the relief valve.

Cheers
 
Grant, thank you once again. I removed the relief valve today and tried to activate it with compressed air. I applied the full 120psi of my compressor (coming up from zero in increments of 20) and it did not actuate. You ht the nail on the head. The relief valve is stuck closed. I will be disassembling it to see if I'm able to salvage it.

Tanks again.

Cheers to all.

RT
 
One more thing to add on this relief valve, and the entire fuel system for that matter. This airplane was operated almost exclusively on auto fuel. Every fuel system component I have touched is completely covered in varnish and gunk. I have restored a number of airplanes that spend years sitting and by far those that have used auto gas have had the most damage to fuel systems. Just wanted to share.

Cheers.

RT
 
RT, dont be surprised if you find a glob of solder or a screw sealing the valve. The valve has a very tiny O ring in it, and they are prone to leaking so if the plane had low fuel pressure a quick and dirty fix is to plug the valve in hopes of fixing it. Pin holes in fuel lines , and leaky relief valves are common causes of low fuel pressure. Good Luck____Grant.
 
I disassembled the valve and found it completely gummed up with auto gas varnish. All cleaned and working well now. Does anyone happen to know the pressure with which it should relieve the output of the engine driven pump? The AD references Bellanca Service Letter 23, so I assume it would be listed there. I have ordered all the service letters from the web site but won't receive them for a bit and I would like to go back together with the fuel system. Any input would be greatly appreciated.

Thank you again to all.

Cheers.

RT
 
I am still working with Southland on the engine mount cones. Does anyone out there have a Franklin print for them? I think the Continental A and C series rubbers could be used if you whittled the cylindrical end down. I don't know if they are the same durometer value- hardness. Dan
 
RT, I just found my book of SBs and SB 23 doesnt give the pressure that the valve is supposed to regulate to. It may be in the actual AD note which I dont have with me. Maybe someone else can chime in?_____Grant
 
I just looked up the type certificate data sheet for the engine itself and it states that the inlet pressure for the MA3SP for pressure feed is between 1 and 7 psi. For gravity feed inlet pressure is between .5 to 5 psi. So for the Bellancas a good range is 1-7 psi. Hope this helps more than just me.

Cheers.

RT
 
I have now reassembled and tested the pressure relief valve and it releases pressure between 6 and 7 psi, so all should be good with that part of the fuel system. I also disassembled the fuel selector valve and cleaned and resealed. No more leaks.

Cheers.

RT
 
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