Fuel pressure

by Rich Provenzano in 912 / 914 Technical Questions 6 years ago

Good afternoon,
While flying from PA/NC my fuel pressure zeroed out. Put the aux on for 2 minutes, up went the pressure. Shut it off. Fuel pressure read fine on engine pump.
10 minutes later, a repeat of above. Finally it seemed to read correctly.
Any ideas?
Fuel sending unit? Dirt?
Something wrong with engine fuel pump?

Standard fuel sender mounted horizontally.

Tru Trac autopilot readout for pressure.

Plenty of fuel in header tank. Flying straight and level.

Newer engine fuel pump installed in September 2017.

45 hrs on new pump.

TIA for input.
Rich

Re: Fuel pressure

by Garrett Wysocki » 6 years ago

Garrett Wysocki

1 572 1.45k

It is an interesting problem because you can't really see it. No one seems to have a definite answer. I do not think any engine has quit or lost power. Ever since I verified my restricter in the fuel return line is not clogged I have not had a problem. Some think that it could be a vapor issue. I have had the same problem intermittently over the years on my Remos Gx and the next time it happens (hopefully not) I am going to check the fuel return restricter for flow.

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Re: Fuel pressure

by Rich Provenzano » 6 years ago

Rich Provenzano

20 59 30

Thank you for your reply.
I should have researched the topic before I posted.
When I get back to NC, and the airplane, I'll check the restrictor jet and hose to the sending unit for obstruction. Hopefully I'll not need to look further.

Another possible problem may be the venting from the bottom valve on the newer style pumps.
A vacuum may occur if the vent hose is exposed to low pressure air.

Also, vapor lock on the warm and very humid day I flew.

Some of these possibilities came fro Joe at Lockwood Tech.

Rich

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Re: Fuel pressure

by Roger Lee » 6 years ago

Roger Lee

128 5.28k 4.98k

Many have switched to a facet pump #40106 from Aircraft Spruce for the low wing guys. It has a higher pressure. The pump most use is only 3- 4.5 psi and it has a 12" draft maximum at 30 GPH. The newer pump is 4 - 7 psi and 32 GPH with a 12" draft.

http://www.aircraftspruce.com/catalog/eppages/facetpumps.php

I have personally used this pump with an increased pressure on a couple of planes with good results.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: Fuel pressure

by David HEAL » 6 years ago

David HEAL

23 192 440

Just as a point of reference and general information, Van's Aircraft has issued a Change Notification suggesting a slightly higher pressure Facet aux fuel pump for addressing low/fluctuating fuel pressure issues with the RV-12 (ROTAX 912 ULS). I gather that your aircraft fuel system is not the same as the RV-12 so this approach may not resolve your specific issue.

http://www.vansaircraft.com/public/Notification-2018-07-12.htm

ps -- Are you using auto fuel and/or 100LL? As noted above, vapor lock could be an issue for you. Auto fuel is more susceptible to vapor lock issues, particularly during seasonal fuel supply changes.

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Re: Fuel pressure

by Roger Lee » 6 years ago

Roger Lee

128 5.28k 4.98k

I have used this higher psi and flow pump on 3 different type aircraft including the RV12 and all low wings. So far all is good. Vans is usually a little behind in solutions and probably because they have to do testing on all their mods.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Fuel pressure

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