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Hermes SMTP Server) with ESMTPA ID 4e220eb825caca2fb6ae32f1b6c275b6; Tue, 24 May 2022 13:01:43 +0000 (UTC) Subject: Re: [FlyRotary] Re: Fuel pressure trending lower. To: Rotary motors in aircraft References: Message-ID: <13051b69-da4f-51b2-11e2-7bdec4e78abd@verizon.net> Date: Tue, 24 May 2022 09:01:38 -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="------------BC11FCCD3AA1DB38C23033BF" Content-Language: en-US X-Antivirus: Avast (VPS 220523-6, 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: 38144 This is a multi-part message in MIME format. --------------BC11FCCD3AA1DB38C23033BF Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Dave, I have a filter just before pumps. The after pumps filter is on top of the engine. Then a Y to primary and secondary fuel rail. Pressure sender is at end of the secondary fuel rail. In your installation it would seem that the regulator would compensate for a clogging filter? Anyhow, this is amazing pump info. I thought pumps would last for thousands of hours. Amazingly I now can't find the official flow rate specs for the GSL414. Only the testing on https://vansairforce.net/community/showthread.php?t=168793 which gives about 42gph near 0 psi. The GSL393 is rated at 155lph or 38gph. The allure of the GSL414 is the three times lower current draw. Seems a good way to monitor the state of the pump is to monitor current draw. From my recent testing, looks like my pump is still OK. But the conclusion must be that the GSL414 is weaker and is likely to hit end of useful life quicker than a GSL393? I'll take a new look at possible air leak on input side as well as better grounding. Finn On 5/23/2022 4:37 PM, David Leonard wdleonard@gmail.com wrote: > Finn, > Where is your fuel filter located?   Mine in downstream of the pump, > but before the fuel injectors.  Fuel pressure gauge is just upstream > of the filter for me, which I now realize is sub optimal but does > provide good info about the state of the fuel filter.  The pressure > starts going up as the filter clogs. > > I also have a fuel flow sensor on my return fuel line, which has > turned out to be a great troubleshooting tool and reflects the overall > health of the fuel system. > > I am using the walbro pumps that Tracy recommended.  I bought 10 of > them once to have a supply on hand because I never again want to delay > replacing them when I see the performance start to degrade.  For me, > the first sign would be decreasing return flow.  It more or less seems > to linearly decrease with the total time on the pump.  For me, the > pressure starts dropping as the return flow gets closer to zero.  I > have taken to replacing the pump earlier in the process, like 50% > reduction in return flow.  With pumps like the walbro, current demand > to the pumps goes up as the flow goes down.  At some point the current > demand will blow the breaker and terminate the flight.  I would guess > that fuel pumps seem to last 400 hrs or so.  This is an improvement > since I installed a larger fuel filter to keep down the pressure > differential. > > If your pumps are similar and your fuel pressure is dropping at the > injector, and the problem is not a clogging fuel filter, then I > suggest you replace the pump ASAP.  They seem fairly susceptible to > damage from particulate contamination or being run while dry. > > Cheers, > Dave Leonard > > On Mon, May 23, 2022 at 9:04 AM Steven W. Boese SBoese@uwyo.edu > > wrote: > > Finn, > > What the fuel pump should be flowing and what it is flowing may be > two different things and needs to be evaluated before being > "comfortable"  That is why I would encourage you to measure the > actual flow rate if you can do it safely. When I left MS71 in May > of 2017 following Charlie's rotary fly-in, my 13B burned 18 gal/hr > on take-off and initial climb at 5800 RPM and initial OAT of 80 > degrees F.  Your set-up likely would require this much or more.  > This was the indication from a Flowscan turbine type sensor which > has been demonstrated to be accurate.  The flow measurement would > just be a next step in the investigation.  If the flow rate is not > what is what it should be, then determining why would follow. The > replacement pump should be helpful in this regard. > > If you recover the fuel being bypassed by the regulator, bubbles > in that fuel will not necessarily indicate air leaking into the > fuel drawn into the pump.  The process of dropping the pressure > when the returned fuel passes through the regulator, causes > dissolved air in the fuel to separate.  Bubbles in this flow will > be obvious.  If fuel is drawn from a small reservoir (< a gallon > or so) and returned to that same reservoir where the bubbles are > allowed to escape to the surface, the bubbles will eventually > disappear as the fuel is degassed.  Degassing all the fuel from > the wing tank is unlikely to occur due to the large volume of fuel > and the large surface area of the fuel in the tank.  This is why > returning bypassed fuel directly to the fuel pump intake or to a > small unvented header tank (where the separated air is allowed to > accumulate) may not be the best practice. > > FWIW > > Steve Boese > > > > ------------------------------------------------------------------------ > *From:* Rotary motors in aircraft > on behalf of Finn Lassen > finn.lassen@verizon.net > > > *Sent:* Monday, May 23, 2022 6:25 AM > *To:* Rotary motors in aircraft > > *Subject:* [FlyRotary] Re: Fuel pressure trending lower. > https://vansairforce.net/community/showthread.php?t=168793 > > The GSL414 should be flowing more than 30 GPH at 40 psi. More than > double of what I need. Does that qualify as "a comfortable amount"? > > I have a new one on order. I'll try to hook up my own test. > > Finn > > On 5/22/2022 11:00 PM, Sboese sboese@uwyo.edu > wrote: >> Finn, >> >> It seems to me that the problem you’re seeing is consistent with >> the capacity of the pump not being sufficient for the max flow >> required by the engine and the pump flow capacity is decreasing >> with use  You appear to have checked everything but the flow >> capacity of the pump under normal system pressure which is what >> you really need to know.  If you can divert the returning fuel >> flow from the pressure regulator to a measuring vessel and and >> collect that fuel for an accurately measured time, the pump flow >> rate can be calculated.  This flow rate should be greater than >> the maximum required by the engine by a comfortable amount. >> >> My apologies in advance if this is obvious. >> >> Steve Boese >> >>> On May 22, 2022, at 8:05 PM, Stephen Izett >>> stephen.izett@gmail.com >>> >>> wrote: >>> >>>  >>> >>> ◆ This message was sent from a non-UWYO address. Please exercise >>> caution when clicking links or opening attachments from external >>> sources. >>> >>> >>> Hi Finn >>> >>> Thanks for the reminder of my pump issue. >>> Yes, you chose more wisely the pump capacity. Mine were way >>> overkill. >>> >>> So I’m thinking options are: >>> 1. Fuel Pressure transducer fault - No - as this was confirmed >>> by the mixture monitor and tune going out. >>> 2. Power supply to pump via fault in termination or switch >>> current path - Unlikely, given the slow reduction - I would >>> imagine a faulty connection would create a less uniform symptom. >>> 3. Alternator Battery voltage/current reduction over time - No - >>> You would see this in the log. >>> 4. Significant Fuel leak - No - Would think this would have >>> become obvious on inspection and not intermittent. >>> 5. Fuel Regulator - They are pretty simple but unsure if they >>> can fail with this symptom? >>> 6. Fuel filter blockage - Certainly this would have to be an >>> obvious, but I take it you swapped this out. >>> 7. Pump internal failure - >>> Electrical - ? >>> Mechanical breakage - ? >>> Flow Path - blockage - unlikely if filtered effectively >>> >>> Where is your pressure transducer in relation to Reg/Any post >>> pump filtering/Flow Transducer/Rail? >>> >>> If fuel regulator and filters can be discounted, I’m struggling >>> to trust the pump. But your test had it sounding in good shape >>> and to spec. >>> >>> So frustrating. >>> >>> Cheers >>> >>> Steve >>> >>> >>> >>> >>> >>>> On 23 May 2022, at 8:44 am, 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 3.04 to 286 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 >>>>>> >>>>> >>>> >>> > --------------BC11FCCD3AA1DB38C23033BF Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 8bit
Dave,

I have a filter just before pumps. The after pumps filter is on top of the engine. Then a Y to primary and secondary fuel rail. Pressure sender is at end of the secondary fuel rail.

In your installation it would seem that the regulator would compensate for a clogging filter?

Anyhow, this is amazing pump info. I thought pumps would last for thousands of hours.

Amazingly I now can't find the official flow rate specs for the GSL414. Only the testing on https://vansairforce.net/community/showthread.php?t=168793 which gives about 42gph near 0 psi. The GSL393 is rated at 155lph or 38gph.

The allure of the GSL414 is the three times lower current draw.

Seems a good way to monitor the state of the pump is to monitor current draw. From my recent testing, looks like my pump is still OK.

But the conclusion must be that the GSL414 is weaker and is likely to hit end of useful life quicker than a GSL393?

I'll take a new look at possible air leak on input side as well as better grounding.

Finn

On 5/23/2022 4:37 PM, David Leonard wdleonard@gmail.com wrote:
Finn,
Where is your fuel filter located?   Mine in downstream of the pump, but before the fuel injectors.  Fuel pressure gauge is just upstream of the filter for me, which I now realize is sub optimal but does provide good info about the state of the fuel filter.  The pressure starts going up as the filter clogs.

I also have a fuel flow sensor on my return fuel line, which has turned out to be a great troubleshooting tool and reflects the overall health of the fuel system.

I am using the walbro pumps that Tracy recommended.  I bought 10 of them once to have a supply on hand because I never again want to delay replacing them when I see the performance start to degrade.  For me, the first sign would be decreasing return flow.  It more or less seems to linearly decrease with the total time on the pump.  For me, the pressure starts dropping as the return flow gets closer to zero.  I have taken to replacing the pump earlier in the process, like 50% reduction in return flow.  With pumps like the walbro, current demand to the pumps goes up as the flow goes down.  At some point the current demand will blow the breaker and terminate the flight.  I would guess that fuel pumps seem to last 400 hrs or so.  This is an improvement since I installed a larger fuel filter to keep down the pressure differential.

If your pumps are similar and your fuel pressure is dropping at the injector, and the problem is not a clogging fuel filter, then I suggest you replace the pump ASAP.  They seem fairly susceptible to damage from particulate contamination or being run while dry.

Cheers,
Dave Leonard

On Mon, May 23, 2022 at 9:04 AM Steven W. Boese SBoese@uwyo.edu <flyrotary@lancaironline.net> wrote:
Finn,

What the fuel pump should be flowing and what it is flowing may be two different things and needs to be evaluated before being "comfortable"  That is why I would encourage you to measure the actual flow rate if you can do it safely.  When I left MS71 in May of 2017 following Charlie's rotary fly-in, my 13B burned 18 gal/hr on take-off and initial climb at 5800 RPM and initial OAT of 80 degrees F.  Your set-up likely would require this much or more.  This was the indication from a Flowscan turbine type sensor which has been demonstrated to be accurate.  The flow measurement would just be a next step in the investigation.  If the flow rate is not what is what it should be, then determining why would follow.  The replacement pump should be helpful in this regard.

If you recover the fuel being bypassed by the regulator, bubbles in that fuel will not necessarily indicate air leaking into the fuel drawn into the pump.  The process of dropping the pressure when the returned fuel passes through the regulator, causes dissolved air in the fuel to separate.  Bubbles in this flow will be obvious.  If fuel is drawn from a small reservoir (< a gallon or so) and returned to that same reservoir where the bubbles are allowed to escape to the surface, the bubbles will eventually disappear as the fuel is degassed.  Degassing all the fuel from the wing tank is unlikely to occur due to the large volume of fuel and the large surface area of the fuel in the tank.  This is why returning bypassed fuel directly to the fuel pump intake or to a small unvented header tank (where the separated air is allowed to accumulate) may not be the best practice.

FWIW

Steve Boese

 


From: Rotary motors in aircraft <flyrotary@lancaironline.net> on behalf of Finn Lassen finn.lassen@verizon.net <flyrotary@lancaironline.net>
Sent: Monday, May 23, 2022 6:25 AM
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: Fuel pressure trending lower.
 
https://vansairforce.net/community/showthread.php?t=168793

The GSL414 should be flowing more than 30 GPH at 40 psi. More than double of what I need. Does that qualify as "a comfortable amount"?

I have a new one on order. I'll try to hook up my own test.

Finn

On 5/22/2022 11:00 PM, Sboese sboese@uwyo.edu wrote:
Finn,

It seems to me that the problem you’re seeing is consistent with the capacity of the pump not being sufficient for the max flow required by the engine and the pump flow capacity is decreasing with use  You appear to have checked everything but the flow capacity of the pump under normal system pressure which is what you really need to know.  If you can divert the returning fuel flow from the pressure regulator to a measuring vessel and and collect that fuel for an accurately measured time, the pump flow rate can be calculated.  This flow rate should be greater than the maximum required by the engine by a comfortable amount.  

My apologies in advance if this is obvious.

Steve Boese 

On May 22, 2022, at 8:05 PM, Stephen Izett stephen.izett@gmail.com <flyrotary@lancaironline.net> wrote:



◆ This message was sent from a non-UWYO address. Please exercise caution when clicking links or opening attachments from external sources.


Hi Finn

Thanks for the reminder of my pump issue. 
Yes, you chose more wisely the pump capacity. Mine were way overkill.

So I’m thinking options are:
1. Fuel Pressure transducer fault - No - as this was confirmed by the mixture monitor and tune going out.
2. Power supply to pump via fault in termination or switch current path - Unlikely, given the slow reduction - I would imagine a faulty connection would create a less uniform symptom.
3. Alternator Battery voltage/current reduction over time - No - You would see this in the log.
4. Significant Fuel leak - No - Would think this would have become obvious on inspection and not intermittent. 
5. Fuel Regulator - They are pretty simple but unsure if they can fail with this symptom?
6. Fuel filter blockage - Certainly this would have to be an obvious, but I take it you swapped this out.
7. Pump internal failure -
Electrical - ?
Mechanical breakage - ?
Flow Path - blockage - unlikely if filtered effectively

Where is your pressure transducer in relation to Reg/Any post pump filtering/Flow Transducer/Rail?

If fuel regulator and filters can be discounted, I’m struggling to trust the pump. But your test had it sounding in good shape and to spec.

So frustrating.

Cheers

Steve





On 23 May 2022, at 8:44 am, 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 3.04 to 286 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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