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  #61  
Old 01-04-2015, 06:44 AM
Ivan Kristensen's Avatar
Ivan Kristensen Ivan Kristensen is offline
 
Join Date: Mar 2008
Location: Guelph Ontario
Posts: 267
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Quote:
Originally Posted by RV10inOz View Post

Hot fuel, sucking uphill in the climb and lowering outside pressure. Hot pumps too.
I think this statement from David sums it up best.

After all the research, anxious moments and cancellation of a trip followed by the installation of a new fuel pressure sender, a new Fuel Pump and a cooling shroud I come to find out that decreased fuel pressure in the climb is not at all abnormal.

The one nagging question that remains is how can I fly for over 500 hours and never have this happen. Why now???
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Ivan Kristensen
Guelph, ON. Canada
RV-10 (C-GMDV) 1355hrs.
Dual GRT 8.4" HXr EFIS, VP-200, TT A/P, Avidyne IFD440, uAvionixX ADS-B out, Sky Radar WX and Traffic, Dual EI's (one Lightspeed & one SDS CPI)

RV-14A under construction.

Link to my build site:
https://ivankristensen.smugmug.com/B...ENTAL-aircraft
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  #62  
Old 01-04-2015, 07:47 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 5,516
Default Does this make sense?

Quote:
Originally Posted by Ivan Kristensen View Post
I think this statement from David sums it up best.

After all the research, anxious moments and cancellation of a trip followed by the installation of a new fuel pressure sender, a new Fuel Pump and a cooling shroud I come to find out that decreased fuel pressure in the climb is not at all abnormal.

The one nagging question that remains is how can I fly for over 500 hours and never have this happen. Why now???
David seems to have nailed the variables, but the summing needs numbers. "Why now?" you ask. 500 hrs and off shore fuel. No data, but since this has not occurred in 500 hrs, you ask why now - really appropriate question.

So lets see,

1. angle of climb - no change - Check
2. Temperatures, fuel, ambient, etc. - well, if it was just coming out of Bahamas, then the tank temps with ambient, could have been a major factor, but you have repeated this, right? - probably not the root cause.
3. System suction pressure loss from tank to mechanical pump - well, we don't know this one. Let's explore

3.+ since the system has not changed, it is not a configuration,
But - the pressure drop may have increased - how? - fuel filter.
or a minor tube facture, or a loosening fitting.

You did not say if you have checked the suction screens and the fuel filter. You could have gotten a bad batch of fuel, or just shaken loose a connection that is sucking a minute about of air. These factors might be your best place to start getting some data of why now.

Good Luck. Fly Safe
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RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”

Last edited by BillL : 01-04-2015 at 08:14 PM.
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  #63  
Old 01-04-2015, 09:56 AM
N427EF N427EF is offline
 
Join Date: Oct 2005
Posts: 1,516
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Good points made by David!
Like all of you I am curious to find out as to why Ivan's fuel pressure problem
Showed up at 500 hours?
A cavitating mechanical fuel pump or vapor lock resulting in fuel pressure loss is often the result of cumulative factors.
While a fuel delivery system might tolerate a number of less than ideal components "gascolator" or installations where fuel is allowed to heat up, adding just one more factor "unknown at this time" can be enough to push pumping ability over the edge.
BillL is probably on the right track, pointing out a developing small leak somewhere along the fuel delivery system. Additionally a mechanical fuel pump that may have deteriorated just a bit over time and no longer develops 100% of its rated pumping ability could also be considered.
While I always keep my boost pump on for landing and take off, I can confidently take off on the mechanical fuel pump only showing 20 plus psi fuel pressure all the way up to 14000 feet on a hot day over 100F using 91 octane gasoline.
My guess is that if you "need" your boost pump on for your climb to keep fuel pressure up you have a fuel system that is not far from vapor locking and cannot tolerate any other negative factors such as small system leaks, very hot temperatures, substandard gasoline, or even a slightly deteriorating fuel pump.
Just food for thought.
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  #64  
Old 01-04-2015, 12:44 PM
Jackm Jackm is offline
 
Join Date: Feb 2012
Location: Prosser,WA
Posts: 272
Default Good thoughts

I would be curious to know how many of you having issues, have the Tempest pump installed vs Lycoming pump.
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  #65  
Old 01-04-2015, 08:07 PM
RV10inOz's Avatar
RV10inOz RV10inOz is offline
 
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Location: Brisbane Qld. Aust.
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Thanks for the compliments but I just learned this stuff from George Braly and from the unleaded Avgas project.

What could have changed? Slight clogging of the breather lines in your tanks. A bit more butane in the avgas blend you have?
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  #66  
Old 01-07-2015, 03:03 PM
Strasnuts Strasnuts is offline
 
Join Date: Jan 2009
Location: Salt Lake City, Utah
Posts: 554
Default Another data point

While I was building my 10 Scott S told me about the breather vent line possibly getting fuel in it when the tanks are full while climbing. I tried my best to install the line as close to the top of the tanks as I could. My fuel pressure will drop way down to 5 psi if I top the tanks completely and stay on a long climb. Of course I'll turn on the pump but I've seen 5 psi before I do. The engine has never stumbled during this phase. If I don't fill the tanks all the way it will not happen. Sometimes it doesn't happen with full tanks, just when I am doing long climbs with topped off tanks?? Just another reference.
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  #67  
Old 02-17-2015, 06:24 PM
jchang10 jchang10 is offline
 
Join Date: Nov 2005
Location: San Francisco, CA
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Interesting, i had no idea others were having this issue. After 400 hours, i am experience a similar issue. I have tried to tighten lines up and cleaned the obvious fuel filter in the tunnel as well as the wing tank screen.

Another question: are there any other fuel screens in the fuel flow path? IE, i am wonder if the mechanical fuel pump has a screen or filter? Also, does the Silverhawk throttle body have one?

Stock plans. Just like Ivan, i find it interesting that this fuel PSI issue has come up all of a sudden. Literally, one flight was fine. The next one the problems have all started.

Thanks!
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  #68  
Old 02-17-2015, 06:57 PM
Wayne Gillispie Wayne Gillispie is offline
 
Join Date: Apr 2009
Location: USA
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Quote:
Originally Posted by jchang10 View Post
Interesting, i had no idea others were having this issue. After 400 hours, i am experience a similar issue. I have tried to tighten lines up and cleaned the obvious fuel filter in the tunnel as well as the wing tank screen.

Another question: are there any other fuel screens in the fuel flow path? IE, i am wonder if the mechanical fuel pump has a screen or filter? Also, does the Silverhawk throttle body have one?

Stock plans. Just like Ivan, i find it interesting that this fuel PSI issue has come up all of a sudden. Literally, one flight was fine. The next one the problems have all started.

Thanks!
Yes, there is one in the Silverhawk fuel control.
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  #69  
Old 02-17-2015, 08:56 PM
jchang10 jchang10 is offline
 
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Location: San Francisco, CA
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Quote:
Originally Posted by Wayne Gillispie View Post
Yes, there is one in the Silverhawk fuel control.
ok thanks. i see that now. it says it's a filter of last resort if the main one fails. i guess i will take a look next time cowl is off. thanks!
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  #70  
Old 02-18-2015, 06:18 AM
rleffler's Avatar
rleffler rleffler is offline
 
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Location: Delaware, OH (KDLZ)
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Ivan,

You've had the shroud on now for a month. How has it been performing since the change? The same or was there an improvement?

Hopefully, the RV-10, Diane, and you are all basking in the Florida sun and not all the winter weather in Guelph.

bob
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