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F9V9hJtLH780Rngg_MojeprmT8quaxG5HgIpQU0FOWNi1OLpEVOdxka_7GmJDPsj8SNdlERoSoCy yhulF54u9n6iRCrkZILi1JLg416O54aMGsIRH8v0WK16uBwJstYFavkXKLw-- X-Sonic-MF: Received: from sonic.gate.mail.ne1.yahoo.com by sonic306.consmr.mail.ne1.yahoo.com with HTTP; Mon, 23 May 2022 12:29:37 +0000 Received: by hermes--canary-production-bf1-5d4b57496-wjd85 (Yahoo Inc. Hermes SMTP Server) with ESMTPA ID 9837e845bc486ad691c21f5616468ffc; Mon, 23 May 2022 12:29:31 +0000 (UTC) Subject: Re: [FlyRotary] Re: Fuel pressure trending lower. To: Rotary motors in aircraft References: Message-ID: <7b5333e3-7bbe-4cc9-5565-14c358f25546@verizon.net> Date: Mon, 23 May 2022 08:29:24 -0400 User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/alternative; boundary="------------6D887B57DA672FD28F91063A" Content-Language: en-US X-Antivirus: Avast (VPS 220523-2, 05/23/2022), Outbound message X-Antivirus-Status: Clean X-Mailer: WebService/1.1.20225 mail.backend.jedi.jws.acl:role.jedi.acl.token.atz.jws.hermes.aol Content-Length: 10691 This is a multi-part message in MIME format. --------------6D887B57DA672FD28F91063A Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Air leak is definitely a possibility. I did have a slow leak. Tightened some fittings and the problem appeared to go away briefly. So the theory is that the stronger pump can overcome a tiny air leak, but it becomes an issue with the weaker pump? Finn On 5/22/2022 10:49 PM, David COOK hoursaway1@comcast.net wrote: > Hey Fin, quick thought, how about air on the low pres. in-side of the > pump via leaky fitting ect. ?   Draws air in during op. but not > leaking enough to find or show witness marks when static ?   David R. > Cook RV6A Rotary >> On 05/22/2022 8:44 PM Finn Lassen finn.lassen@verizon.net >> wrote: >> >> >> Thanks Steve. >> >> From your March/April 2017 posts it was a GSL392 that failed (high >> current draw/low pressure, even after you removed the insect you >> found in the inlet). >> >> So this afternoon I ran the pump for about an hour. Amp draw from 304 >> to 2.86 depending on voltage. Pressure between 43 and 40 psi (also >> depending on voltage). No noticeable degradation. Of course the >> difference with this test is that no fuel went to engine -- all >> recirculated through pressure regulator and back to tank. But no >> signs of a failing pump in terms of higher current draw and less >> pressure. >> >> I guess I should put a temp probe on the pump and see what it reads >> during flight to see if that could be a factor. >> >> Finn >> >> On 5/21/2022 9:01 PM, Stephen Izett stephen.izett@gmail.com wrote: >>> Hi Finn >>> >>> I had from memory a 393 fail. Can’t recall the symptoms sorry. >>> >>> I test before takeoff and then run both pumps below 2ooo ft incase >>> of failure. >>> I plan to instal a comparator relay board in fuel pressure circuit >>> to automatically bring on backup pump and failure indicator. >>> So testing before flight becomes - switch off and back on main >>> engine pump. This will save amps and wear of backup pump. >>> When I switch off a pump at WOT the engine dies pretty much >>> instantaneously and don't want to be fiddling with a restart in the >>> Glasair which glides like a brick with the gear out in the breeze. >>> >>> Regards >>> Steve Izett >>> >>> >>> >>> >>> >>>> On 21 May 2022, at 10:30 pm, Finn Lassen finn.lassen@verizon.net >>>> >>> > wrote: >>>> >>>> Recently I noticed my fuel pressure being low. Noticed because >>>> engine did not come up in power when advancing to full throttle. >>>> Noticed mixture real lean. Checking fuel pressure as low as 28 psi >>>> (normally 35 and up to 40 at full throttle). >>>> >>>> Going over my engine logs since first flight I now see that fuel >>>> pressure has been trending lower through each flight -- more >>>> pronounced on longer flights (40+ minutes). More and more >>>> pronounced over the months and became really noticeable over last >>>> month. Could explain why mixture tuning /appeared/ to have changed. >>>> Nice to have engine logs from practically each flight. >>>> >>>> But why? Pump getting weaker? >>>> >>>> My primary fuel pump is a GSL414. I figured it was wasted energy to >>>> push way more fuel than needed through the pressure regulator back >>>> to the tank. >>>> >>>> My secondary (backup) pump is a GSL393. When turning that on, fuel >>>> pressure comes back up to where it needs to be. >>>> >>>> Anyone have experience with failing or weak EFI pumps, particularly >>>> the GSL414? >>>> >>>> Finn >>>> >>> >> --------------6D887B57DA672FD28F91063A Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 8bit
Air leak is definitely a possibility. I did have a slow leak. Tightened some fittings and the problem appeared to go away briefly.

So the theory is that the stronger pump can overcome a tiny air leak, but it becomes an issue with the weaker pump?

Finn

On 5/22/2022 10:49 PM, David COOK hoursaway1@comcast.net wrote:
Hey Fin, quick thought, how about air on the low pres. in-side of the pump via leaky fitting ect. ?   Draws air in during op. but not leaking enough to find or show witness marks when static ?   David R. Cook RV6A Rotary
On 05/22/2022 8:44 PM Finn Lassen finn.lassen@verizon.net <flyrotary@lancaironline.net> wrote:


Thanks Steve.

From your March/April 2017 posts it was a GSL392 that failed (high current draw/low pressure, even after you removed the insect you found in the inlet).

So this afternoon I ran the pump for about an hour. Amp draw from 304 to 2.86 depending on voltage. Pressure between 43 and 40 psi (also depending on voltage). No noticeable degradation. Of course the difference with this test is that no fuel went to engine -- all recirculated through pressure regulator and back to tank. But no signs of a failing pump in terms of higher current draw and less pressure.

I guess I should put a temp probe on the pump and see what it reads during flight to see if that could be a factor.

Finn

On 5/21/2022 9:01 PM, Stephen Izett stephen.izett@gmail.com wrote:
Hi Finn

I had from memory a 393 fail. Can’t recall the symptoms sorry.

I test before takeoff and then run both pumps below 2ooo ft incase of failure.
I plan to instal a comparator relay board in fuel pressure circuit to automatically bring on backup pump and failure indicator.
So testing before flight becomes - switch off and back on main engine pump. This will save amps and wear of backup pump.
When I switch off a pump at WOT the engine dies pretty much instantaneously and don't want to be fiddling with a restart in the Glasair which glides like a brick with the gear out in the breeze.

Regards  
Steve Izett





On 21 May 2022, at 10:30 pm, Finn Lassen finn.lassen@verizon.net <flyrotary@lancaironline.net> wrote:

Recently I noticed my fuel pressure being low. Noticed because engine did not come up in power when advancing to full throttle. Noticed mixture real lean. Checking fuel pressure as low as 28 psi (normally 35 and up to 40 at full throttle).

Going over my engine logs since first flight I now see that fuel pressure has been trending lower through each flight -- more pronounced on longer flights (40+ minutes). More and more pronounced over the months and became really noticeable over last month. Could explain why mixture tuning appeared to have changed. Nice to have engine logs from practically each flight.

But why? Pump getting weaker?

My primary fuel pump is a GSL414. I figured it was wasted energy to push way more fuel than needed through the pressure regulator back to the tank.

My secondary (backup) pump is a GSL393. When turning that on, fuel pressure comes back up to where it needs to be.

Anyone have experience with failing or weak EFI pumps, particularly the GSL414?

Finn




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