Fuel Pressure Guages

[BillLipson]

 I would like to fit a fuel pressure guage to my Rotax 582. Does anyone know where I can obtain a guage and how to go about fitting it?

 

 

[Thruster88]

 I would like to fit a fuel pressure guage to my Rotax 582. Does anyone know where I can obtain a guage and how to go about fitting it?

 

I use a VDO mechanical 100KPa or 15psi gauge. The line is teed in between the diaphragm pump and one of the carbureters. A 1/8 inch OD nylon line about 4 metres long is used to dampen pulsation that will otherwise destroy the gauge. It is reassuring to be able to check the operation of both pumps, electric first then diaphragm only then both together. In the good old days I got all this a repco, now a truck or automotive performance shop may be able to help. There are cheap 0-15psi fuel pressure gauges on eBay. 

 

 

 

[skippydiesel]

I use Speco gauges and seem to get excellent service life & operation at a much lower cost then VDO. If you go this rout be sure to purchase sender/sensor & gauge from Speco (do not try to mix brands)

 

 

[Thruster88]

Agree with Skippy, electric sender type gauge would be safe and easy to install.

 

 

[Yenn]

I use an electric sender in the engine compartment, connected to the fuel line and with a restrictor to damp down the pulsations. No fuel line in the cockpit area. I don't like the idea of nylon fuel line in the cockpit. My gear came from vans aircraft, but any automotive parts supplier should be able to supply suitable gear.

 

 

[Old Koreelah]

I got both my fuel pressure and fuel flow gauges from the late Maj Millard. Both have been dependable for a decade, despite some of the pump pulsations getting to the fuel pressure gauge needle.

 

I'd rather not have that fuel line running into the cockpit, but it should be okay if I leave it alone; that's one reason I haven't fitted a "T" extension to soak up pressure fluctuations.

 

 

[Downunder]

I imagine a with a 582 diaphragm pump you would get more pulsations in pressure over a 912 or Jabiru mechanical pump.

 

If going with an electronic gauge, you would definately need a restrictor or dampener of some sort to smooth it out I think.

 

 

[BillLipson]

Thank you to all those who responded to my query. All very helpful and reassuring.

 

 

[Bruce Tuncks]

I want a 0-5psi gauge. Most of them are 0-15 psi which is too much given that you are often operating at 2psi. NEVER over 5psi.

On the net, there is a Winter 0-5psi gauge. Are there any others in use? I have a digital pressure gauge which I wonder if it is compatible with fuel. Maybe there is something similar that is designed to work with fuel .

[Markdun]

This is what I use. 0‑15PSI /4" Pressure Transducer Sensor Output 0.5‑4.5V/0‑5V for Water Gas Oil | eBay Output is linear....0.5V is 0psi, 4.5psi is 15psi. It Does need a regulated 5V supply. I tried a 0 to 10psi model but it failed almost straight away, so hence the 0 to 15psi one, which has given 100hours of no fault operation on a Jabiru engine with mech pump and facet boost pump. My display range is 0 to 7.5psi. (And there we go again with archaic units of measurement,)

I know of one problem caused by fuel pressure monitoring on Jabiru and Rotax 4 stroke installations — when the electric facet pump is switched off the fuel pressure drops close to zero for a second or two until the poppet valves in the mech pump on the engine start working. No-one without fuel pressure monitoring has reported this issue. It’s the same logic as Trump has when claiming that increasing testing for Covid increases the incidence of the disease.

[Kenlsa]

I was suffering with flooding problems on the Jab at idle, so attached a gauge and found 2.6 psi for the electric pump and over 5 for the engine pump. I had a spare pump anyway and pushrod and after contacting the factory I found that one was about 0.8mm ( from memory) shorter and used the shorter one on my pump and this dropped it to 4.35 psi. Problem solved.

Ken

[Bruce Tuncks]

Once at Gawler a pilot turned on the electric boost pump on pre-landing checks and the engine stopped! He turned off the electric and restarted the engine and he hasn't used the electric pump on landing ever since. This is exactly the situation where a good fuel pressure gauge would help.

If the mechanical pump has a higher pressure than the electric, as yours has Ken, in theory there should be no more fuel pressure at the carby with both pumps on. The fact that engines can flood-stop can only be that there is in fact a higher pressure and this forces the float-valve to open when it should be shut.

[Markdun]

Once at Gawler a pilot turned on the electric boost pump on pre-landing checks and the engine stopped! He turned off the electric and restarted the engine and he hasn't used the electric pump on landing ever since. This is exactly the situation where a good fuel pressure gauge would help.

If the mechanical pump has a higher pressure than the electric, as yours has Ken, in theory there should be no more fuel pressure at the carby with both pumps on. The fact that engines can flood-stop can only be that there is in fact a higher pressure and this forces the float-valve to open when it should be shut.

Seems a good argument to go back to no fuel pumps, mech or electric, and no pressure gauge, relying only on Newtonian gravitational forces for fuel transport from the tank to the carby, which I did for over 700 hours without a problem. If gravity fails there are much bigger problems to worry about.

[Kenlsa]

Did a test on a J170 last week and only got a gravity flow of 36 lts/hr. Not enough for WOT. This was with an old fuel filter. Electric pump was 42 lts, so that is ok when on mech pump. When a new filter was used, Gravity was 40lts and elec was 46lts.

The next J170 flowed 60lts on elec. So looks like each a/c needs to rely on each of the 3 systems, Gravity, Elec, Mech somewhat differently. I suppose gravity would work in S/L flight but unless you have a full tank with a good head working for you, it may not be enough on climb out.

I know that it is all tested on the factory proof plane, but on yours? Best check the actual figures.

The jab has a lot of pipe work and 15lts (?) behind the seat and all that imparts a fair bit of friction in the system, as compared with a Sonex where the tank practically feeds directly into the carb.

Ken

[Markdun]

Did a test on a J170 last week and only got a gravity flow of 36 lts/hr. Not enough for WOT. This was with an old fuel filter. Electric pump was 42 lts, so that is ok when on mech pump. When a new filter was used, Gravity was 40lts and elec was 46lts.

The next J170 flowed 60lts on elec. So looks like each a/c needs to rely on each of the 3 systems, Gravity, Elec, Mech somewhat differently. I suppose gravity would work in S/L flight but unless you have a full tank with a good head working for you, it may not be enough on climb out.

I know that it is all tested on the factory proof plane, but on yours? Best check the actual figures.

The jab has a lot of pipe work and 15lts (?) behind the seat and all that imparts a fair bit of friction in the system, as compared with a Sonex where the tank practically feeds directly into the carb.

Ken

For a Jab 2200 I would have thought 36lph would be about 150% of max fuel flow and ok? I was getting 40lph in my Cygnet, and 33 in a Corby Starlet (both Vw 1835, which drinks a max of around 20lph). Both just had a paper filter in the gascolator. When I upgraded both planes to the Jab2200 I kept the gascolator filter and installed the recommended inline filter....and gravity flow rates diminished to a tad over 30....not good enough, and I blamed the valve springs in the Jab fuel pump rather than the filters. I get over 60lph on both with electric. Still the max flow I’ve seen climbing out at WOT at 3100rpm with the Jab is 24lph except the 30lph ‘indicated’ when the facet pump is turned on....but that is a lie caused by pulsing. I do wonder just how many people test fuel flow rates....it’s not hard to take off the float bowl and collect the fuel in a large measuring cylinder.

[facthunter]

I think it would be wise to check them frequently. Tank pumps help prevent vapour lock on hot days. The engine pump valves may well cause the pressure drop you had. The fuel cap vent may also be an issue.. Nev