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Fuel flow and fuel pressure

John Foy

Member
We did our first ground runs yesterday and have only 2.2 psi fuel pressure with no fuel flow showing. The engine runs fine so we wonder if anyone else has had that problem. All other engine parameters seem to be o.k. so far and no leaks in the tank after installing the mechanical gauge.
John Foy
 
Did you remove the orifice in the banjo fitting per the plans revision (this will affect the fuel pressure indication)? You should see a fuel flow of about 3 gpm (a potential wiring issue?)
 
Revision 46-09

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Marty and all:
We had removed the restrictor in the picolo - banjo fitting. We have checked the gascolator screen after running 40 gallons of fuel through the system and it was whistle clean. The lack of fuel flow has us stumped. We have checked the wire connections to make sure the right colors matched. also the low fuel pressure while the engine was running doesn't add up. Is there another restrictor in the fuel system? Flowscan unit? We have set the K factor to 30000. It was originally set at 68000 for the other type of fuel flow indicator. Thanks to all
John Foy
 
Outside maybe

Are you sure the main shut-off valve is down all the way ? Try taking the drain out of the gascolator, and put a gas can and funnel, or what have you, under it, and turn on the pump. It should flow fairly fast. That should eliminate everything from the tank to the gascolator. It will not have high pressure, but a serious flow should be seen.

John Bender
 
K factor setting

John:

There is another thread that addresses the K factor for the different flow meters (FT-60 vs FloScan). Several who have the FloScan have posted that they are using K factor values between 50,000 and 54,000 and that this seems to be working for them.
 
We have two holes drilled in the gas cap. The shut off valve is fully in the on position. I should have said that the fuel flow indication never showed. The flow is more than enough for the engine, it's just the indications that are wrong. We're waiting for feed back from Dynon and Van's. We may dissasemble the piccolo fitting to make sure that it is o.k.
Thank you all for the input. When we find the cause we will be sure to let all know.

John Foy
 
Fuel pressure

We had wildly variable fuel pressure and flow after a few hours of flight to the point that the low fuel pressure alarm came on repeatedly. I drilled two more holes in the top of the cap and two more in the bottom (total 6). Problem went away. Fuel pressure and flow very solid.
 
We reinstalled the Floscan unit and a new fuel pressure transducer from Dynon. Both units now work fine and we have done several runups with four or five at full throttle. All indications are now normal. Dynon said that they could not duplicate the problems that we were having with the Floscan so who knows what we did to correct the problem? Anyway we are now awaiting the DAR inspection as an EAB. One thing I would like to note-if it is possible to run the Dynon unit before installation to actually see the setups and get to all the pages, it would prevent a lot of callbacks to the company because of unfamiliarity. A downloadable simulation or disc sure would help a lot!
Thanks to all who offered soultions!
John Foy
N7771
 
John,

Just out of curiousity, what kind of psi does your Dynon show when the pump is on and no engine. Mine never goes above 2 but when the engine is running the Dynon is solid in the mid to high 4's.
 
Pete:
We haven't flown yet so I don't know how the numbers will be under real conditions. 2.9 psi with only the electric pump. 3.9 with the engine running.
John
 
Fuel Pressure

We got our engine started and everything ran pretty well. We taxied it down the taxiway and back and we smiled ALL THE WAY!
:DWe've got plenty of fuel flow, the engine runs fine,but we're only showing .9 psi. ALSO, our computer shows that we have 26 gallons of usable fuel after running the engine for about 1/2 hour...not bad fuel economy...
Meade and George
#16
 
We got our engine started and everything ran pretty well. We taxied it down the taxiway and back and we smiled ALL THE WAY!
:DWe've got plenty of fuel flow, the engine runs fine,but we're only showing .9 psi. ALSO, our computer shows that we have 26 gallons of usable fuel after running the engine for about 1/2 hour...not bad fuel economy...
Meade and George
#16

Do you have the fuel scanner installed backwards? The is the only way I know of to add fuel.
 
Fuel Flow

Dear Paint-Shop-Looker, maybe it was dumb luck, but I went to a local paint shop and found that they had a plane in their shop and said that they had painted several planes at their shop. We're taking ours there after we get the hours flown off and the auto pilot and lights installed.
We'll check about the scanner, but we're getting plenty of pressure; I think it's just a bad reading and is probably related to the display showing that we've got 26 gallons remaining...
Thanks
Meade
 
Dear Paint-Shop-Looker, maybe it was dumb luck, but I went to a local paint shop and found that they had a plane in their shop and said that they had painted several planes at their shop. We're taking ours there after we get the hours flown off and the auto pilot and lights installed.
We'll check about the scanner, but we're getting plenty of pressure; I think it's just a bad reading and is probably related to the display showing that we've got 26 gallons remaining...
Thanks
Meade

I guess we are not understanding each other. The -12 only holds 19.8 gallons. We are suppose to set that (or 20 gallons) as the "FULL" mark for the Dynon D180. If you start out with 20 and when you land you have 26 that means the sensor may be in backwards. Right? Maybe I'm not understanding the problem?
 
Fuel pressure

Hi Larry, we went through the calibration process and set the tank up for 20 gallons but on one of the displays, it says that we have '26 gallons usable fuel remaining'...or something to that effect.
We'll mess around with it some more on Tuesday, if the weather cooperates. We are also having issues with not being able to stop the engine; it worked well here at the house before we carried it up to the airfield but now, neither turning off the mags or the master cuts the engine off. We just cut off the fuel flow and it starved the motor.
Meade
 
I think Larry's point is that if the transducer is installed backwards, it may "add" fuel to the initial 20 gallons instead of "subtracting" it.
i.e. You would end up showing 26 gallons instead of 16.
 
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Hi Larry, we went through the calibration process and set the tank up for 20 gallons but on one of the displays, it says that we have '26 gallons usable fuel remaining'...or something to that effect.
We'll mess around with it some more on Tuesday, if the weather cooperates. We are also having issues with not being able to stop the engine; it worked well here at the house before we carried it up to the airfield but now, neither turning off the mags or the master cuts the engine off. We just cut off the fuel flow and it starved the motor.
Meade

Check your grounding wires for the magnito boxes.
 
We had wildly variable fuel pressure and flow after a few hours of flight to the point that the low fuel pressure alarm came on repeatedly. I drilled two more holes in the top of the cap and two more in the bottom (total 6). Problem went away. Fuel pressure and flow very solid.

Interesting. I did exactly the same thing you did after much frustration and yielded exactly the same result. All is well now. Now I'm told that was a waste of time, and shouldn't have fixed the problem. Ya know, when it works, it works. Guess I'll just have to just get over the alarm coming on every two seconds. Anyway...thanks for the tip...you saved my sanity.
 
Low fuel pressure

OK, we found the solution to, maybe, both problems. We discovered a loose connector today and that solved the problem of the engine not cutting off when we turned off the ignition switches AND, we now have healthy fuel pressure. We would have made first flight today but we had about 25 knot crosswinds; maybe tomorrow.
Meade
 
Thought I had fixed it

Well, I thought I had fixed the fuel pressure warning by drilling holes in the cap. But now it is back. I have run out of ideas now. Looking for loose wires but can't find any. Any suggestions of where to look.
 
check the screen in your gasolator. I had all the same problems mentioned here until I checked my screen. It was coated with **** that was restricting flow. It was **** from left in from the tank build. Have flown 20 hours since I cleaned it and the low pressure warning has never returned. It fixed the problem.


Brad Stiefvater
 
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check the screen in your gasolator. I had all the same problems mentioned here until I checked my screen. It was coated with some kind of black film that was restricting flow. It was stuff left in from the tank build I think. Have flown 20 hours since I cleaned it and the low pressure warning has never returned. It fixed the problem.


Brad Stiefvater
 
I installed the transducer backwards on my -8..... Dynon D180 and Dynon sensor. When installed backwards you get readings about half or less than they should be. Reversed it and all was normal.
 
Low Fuel Pressure Warning

We did our first flight today in our RV-12, sn: 120141. All went well, but after putting 2 hours on it, my partner got a Low Fuel Pressure Warning. We removed the gasolator screen, and cleaned, however we did not find any thing on the screen.

Reinstalled and pressure came back up. He flew it another hour and he said the pressure came down a little, but still in the green. Will fly it again and keep an eye on the fuel pressure. We checked fuel flow and all seems good.

Jim Olson
Blairsville, Georgia
 
We did our first flight today in our RV-12, sn: 120141. All went well, but after putting 2 hours on it, my partner got a Low Fuel Pressure Warning. We removed the gasolator screen, and cleaned, however we did not find any thing on the screen.

Reinstalled and pressure came back up. He flew it another hour and he said the pressure came down a little, but still in the green. Will fly it again and keep an eye on the fuel pressure. We checked fuel flow and all seems good.

Jim Olson
Blairsville, Georgia

Jim,
Did you conduct your first flight from Blairsville or Andrews?
Bruce
 
Low fuel pressure

My friend, Ren, flew his RV-12 (120020) for first time on Friday. Today, Saturday, there was a low fuel pressure warning, 1.2 psi. He checked the gascolator but it was clean. A dial type gauge indicated good fuel pressure. He called me up and asked to borrow my fuel pressure transducer. After replacing his fuel pressure sensor with mine, the Dynon once again showed normal fuel pressure.
Joe
 
My friend, Ren, flew his RV-12 (120020) for first time on Friday. Today, Saturday, there was a low fuel pressure warning, 1.2 psi. He checked the gascolator but it was clean. A dial type gauge indicated good fuel pressure. He called me up and asked to borrow my fuel pressure transducer. After replacing his fuel pressure sensor with mine, the Dynon once again showed normal fuel pressure.
Joe

Try venting the air bubble that leads to fuel pressure transducer in the tubing and let us know.
 
Air in sensor port

It seems to me that pressure should be equal at any point within the line that goes to the sensor. Pressure is only dropped when there is flow; and no fuel flows through the sensor. The sensor should register pressure whether that pressure is from air or fuel. But I have been wrong before. (Do not tell my wife). Regardless, my friend intends to return his sensor to Van's and ask for a new one that he will return to me to replace mine that he borrowed.
Joe
 
fuel pressure problems

While doing taxi tests I have been getting low fuel pressure alarms. I cleaned the gascolator screen and drilled the 2 extra holes in the gas cap. This had no effect. I pulled the VA-216 hose just to make sure I had it in correct. (it was) After I reinstalled it pressure went up 1 psi. Not sure why. My pressure with engine running is now 3.3 psi. I am only getting .5 psi from the aux pump. It has a good flow, just low pressure. (75 seconds in the flow test to pump 1 gal. the limit is 180 seconds) I called Vans and they had no idea why the pump had good flow but low psi. Ken even went out to their 12 and it showed 1.5 psi with just the aux on. Anybody else showing low pressure from their pump?
 
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Mark,
If the fuel return line, VA-216, was manufactured with missing or oversize restriction, that could cause low fuel pressure. A good test would be to disconnect hose VA-216 where it attaches to the firewall fitting and measure the flow rate with the electric pump running (engine off). Of course one needs to know the expected flow rate from VA-216 in order to know if their fuel system is working right. Perhaps Vans or another builder has that info.
Joe
 
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