Backup fuel pump for IO-240 engine

[SkyPirate]

actually ,..thinking about it,.. the pressure control valve I used had an off position,..it was a requirement in case of fire,.. one of the nascar rules for sanctioned tracks

[PapuaPilot]

Jeff, I think you are right about the Holley Blue being marginal and a 30+psi pump working. Good pressure will definitely give you better priming for starting.

The engine data sheet from Continental that came with my IO-240 shows it needs 35-53 psi of unmetered pressure for full power. During the full power run they had an actual 53.0 psi unmetered pressure that yielded 16.3 metered pressure. Unmetered pressure is what is coming out of the engine driven fuel pump, therefore I have to believe that you must have the same pressure from any backup pump (if you want full power).

I have a lot of experience working with Cessna TU-206s that have the Cont. TSIO-520. They have a 3 speed boost pump (Emergency, High and Low) that MUST be setup properly so the engine can run in case the engine driven pump fails. It uses the lower speeds with a throttle microswitch so the engine can run OK from cruise power to idle. The emergency position is incase you need full power, but you have to hold the red switch on as it is spring loaded to off. If the fuel flows are misrigged for the other two positions it can cause the engine to die because it is too rich or lean.

I looked online and think I found a Holley pump that should work great with the IO-240. The Holley model 12-920 inline pump shows specs of 67 gph @ 45 psi. It weighs 2.6 lbs. They say you must use a 40-100 micron filter before the pump (for warranty). This seems like a good idea to have the filter. I would put one at the outlet of the header tank and then tee it to a bypass valve and the Holley pump. I don't think it would need a regulator. Amazon has this pump for $176 and the filter for $64 which is a lot less then a Dukes or Weldon pump.

I like the Cessna 206 system but it is complex. There is another option. If you have enough fuel pressure for full power then you can keep flying if your engine pump fails. You would need to turn on the aux pump and open to full throttle; the engine will run. After that you can reduce power slowly (till it is getting rich/rough) and lean the mixture the engine runs smoothly again. If you do the power/mixture reduction in a few steps you can make the engine run all the way down till landing. At MAF,where I work, we used to have a standby emergency fuel pump system in our TU-206s that did exactly that. It used a second Dukes pump.

If I can't find a used (free) 12 volt pump at work I will most likely get the above mentioned Holley setup.

[n85ae]

Yep, that's exactly what I think. Continental used to have a chart that showed the unmetered pressure up to 2800 rpm, but I can't find it now. I have a couple
that show the metered pressure. The priming pressure issue, was one that a
Continental tech rep explained to me. I think if you get 30 psi or more, then
you should be able to tweak everything to make it run at least long enough
to get close to an airport.

I also found a note that the engine driven pump does have a built-in bypass for
exactly this reason.

Regards,
Jeff Hays

[N981MS]

After reading Jeff's account I went with a Weldon. Much more comforting than the Facet. It is warm enough in Georgia that I really never noticed any trouble starting with the Facet though.

[PapuaPilot]

I thought it would be good to follow up on what I have done so far. I was able to get a used Dukes pump where I work. Actually I put one together out of several green tagged pumps that came off of C-185s. I picked the best running motor I could find and mated a very low time pump assembly and got a "like new" boost pump. The nice thing about this pump is that is doesn't require a bypass line and check valve, it is already built into the pump.

I just finished making a mounting bracket and fuel lines from the header tank to the firewall. I kept the fuel line run as straight as possible and put the pump under the right seat and mounted the bracket to the bottom airframe tubes. I ended up buying an aluminum header tank from KF after reading all of the issues with the poly header tank that came with my plane.

I will need to set the correct fuel pressure/flow later on, but this pump should give me got atomization for priming and the ability to keep the engine running should the engine driven pump fail.

I will make a drain line later for the aux pump case drain. I think I will have it come out the bottom at the same place as the header tank sump. This line is one that should not have fuel draining out. If it is dripping you have leakage at the seal of the pump.

[airlina]

Nice job Phil, looks like a good clean setup with the backup pump. I had to have a parallel fuel line with a check valve because my holley didn't have the internal bypass that yours has . My IO-240 installation has 3 drains exiting at the lower mid firewall 1) eng driven case drain if the seal fails (there is a service bulletin to check the integrity of the seal) 2) manifold drain from the spider 3) cylinder drain for overpriming to prevent hydraulic lock. Bruce N199CL