Fuel pressure, sensor

[roger lee]

This has so many pages I don't remember if you have the newer oil pressure regulator parts installed? Mushroom, spring and taller oil plug screw?

[designrs]

This has some many pages I don't remember if you have the newer oil pressure regulator parts installed? Mushroom, spring and taller oil plug screw?

Never addressed that issue yet Roger.
Is it related to fuel pressure as well?

[roger lee]

Just oil pressure

[designrs]

This problem is seriously interfering with my enjoyment of my aircraft.

Status is:
http://sportpilottalk.com/viewtopic.php ... 105#p40195

Unless some of the Rotax experts here have other solutions,
At this point I'm thinking:
1) Supply side fuel lines & connections. Possibly just replace.
2) Test swap or replace mechanical fuel pump.
3) Replace electric fuel pump. (Might as well do that with the supply side line replace)
4) Test swap Dynon D-120 EMS. My past mechanic has one on the shelf that I can borrow.
5) Replace / rewire ground and sender line to sender.

... And that's the ENTIRE fuel supply & monitoring except replacing the carbs!
What an ordeal! Jeez!!

[designrs]

Thoughts on fuel lines vs. mechanical fuel pump being the cause of intermittent low fuel pressure?

[SportPilot]

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[bstrachan]

FWIW: I have verified that the main tank vent on my StingSport is unobstructed. Has no bearing on the intermittent low fuel pressure indication that I get.

The vent tube opening is part of the fuel pickup/level sensor assembly that goes into the top of the fuel tank. This opening is located about an inch below the top of the tank. If you fill the tank up to the top (no tabs of course) on a cool morning, the fuel and small amount of air in the tank will expand as the day warms up, and will start a syphon that empties three or four gallons of gas out the vent hose. The vent hose has an anti-syphon loop that goes all the way to the top of the firewall but obviously this is ineffective. The only way to keep the syphon from starting is to leave the fuel cap unlocked. This vents pressure out of the tank through the cap. Of course there would be dire consequences if you took off with it this way, so I put a flag on it when I leave it unlocked and make it a point to check it as part of the preflight.

You might think that the vent tube opening being below the level of the fuel in the tank when it's full could cause a restriction. However I've had the low fuel pressure light come on with the tank half empty.

[SportPilot]

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[bstrachan]

Yes, it happens. Checking the vent(s) for obstructions should be part of the preflight.

Ernest K. Gann tells an exciting story about some mechanic who forgot to take the masking tape off a vent in a C-87 prior to takeoff, which meant they couldn't get fuel out of that tank. Of course they had multiple tanks which is why he lived to write the story.

[designrs]

I'm sure you probably discussed this previously, but are the tanks vented properly with no clogged vents, etc?

Yes. Issue is both tanks. I will check the vents again more thoroughly.

[designrs]

My LSA instructor was killed last year when he was conducting a flight review. It is believed the fuel vent lines might have been clogged by dirt dobbers. They were in a Rockwell Commander 112 or 114 and crashed soon after takeoff.

I have dirt dobbers in my hangar!! Will get rid of them and check the vents!
Thanks.

[designrs]

What is the best way to check the tank vents? (Low-Wing SportCruiser)
It is just a matter of shining a light up to look?
Or does it actually have to be snaked out with something?

[bstrachan]

I use a 50cc plastic syringe (http://www.ebay.com/itm/50ml-Plastic-Sy ... 1119076907) - the tip is a push fit into my vent hose. I just push it into the outside end of the hose and pump the plunger in and out. It will be very obvious if the hose is blocked.

Snaking something through one of these vent tubes could be a problem. I wouldn't try it.

[designrs]

Thanks. I'll look for a syringe.

[SportPilot]

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