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life of fuel pump?


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My Jabiru was bought as a kit in 1998. I have just done a carby overhaul job and now I am worried about the fuel pump. The factory only replaces the whole unit at a price of $260 which I think is a lot of money and I don't even know if the old fuel pump needs replacing.

One aspect is that there is a backup electric fuel pump, so maybe the best thing to do it wait until the mechanical pump fails.

What have others done?

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I reckon you've had a good run for your money out of it. Duff pumps can often leak fuel into the motor. Your pump regulates the fuel pressure if I remember correctly by the pressure of the diaphragm spring. Nev

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Yes that's the worry Nev, if the diaphragm leaks, will the fuel go into the engine? I think that it could. But I have never heard about problems due to fuel pump malfunctions with Jabirus. Does anybody have an example of this happening?

Here's an irrelevant but true story about after the fuel pump on our Falcon failed on the Hume Highway near Wangaratta. The repair guy was intrigued to hear about how planes had two fuel pumps. He considered this then said that all of his customers would just drive as usual on the second pump for as long as that went.

( The Falcon has just the one pump, with a cheap brushed motor, inside the fuel tank, where you would think it would cause an explosion but the air/fuel mix is too wrong for that to happen.)

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My Jabiru was bought as a kit in 1998. I have just done a carby overhaul job and now I am worried about the fuel pump. The factory only replaces the whole unit at a price of $260 which I think is a lot of money and I don't even know if the old fuel pump needs replacing.

One aspect is that there is a backup electric fuel pump, so maybe the best thing to do it wait until the mechanical pump fails.

What have others done?

Bruce, pay the money and have peace of mind.

As you say, you have backup but why rely on that?

I dont think $260 is exhorbitant. I replaced mine a while ago with the Jabiru updated model with no issues since.

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Jabiru & Camit had a problem with a batch of mechanical fuel pumps at one stage & all had to be replaced though not before some of them stopped but the electric pump resolved the issue at the time in all cases AFAIK. Most engines will go to TBO without any maintenance to the fuel pump. If it weighs on your mind just get a new one. Then you can pull the old one apart & see if there looks to be any wear or stressed parts and if you find something your expenditure will have been completely justified. If not then you will at least know how it works and how robust it is.

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$260 is too expensive?

What's your life worth?

I just spent $1700 on a five year rubber replacement kit from Rotax, fuel pump included. Even though the rubber bits all look OK to me, that is what the manufacturer specified and they spent a lot of money and time figuring that out. It's part of the reason Rotax engines have a reputation for reliability.

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$260 is too expensive?

What's your life worth?

I just spent $1700 on a five year rubber replacement kit from Rotax, fuel pump included. Even though the rubber bits all look OK to me, that is what the manufacturer specified and they spent a lot of money and time figuring that out. It's part of the reason Rotax engines have a reputation for reliability.

$260 is about the price of a box of half decent Shiraz.

Some people have no idea on just how tight of a budget some of us fly on....

Also, Who drinks Shiraz when you can fly?:yuck:

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You'll do a lot more than $260's worth of damage if the fuel pump gives up the ghost at 3500'.

 

Fuel pumps in cars, at least, are pretty reliable things. How many have you had to change in the cars you have owned over your life? I think that the biggest problem for aircraft fuel pumps is the fact that they are not used enough, and this leads to deterioration of the diaphragm. Compare the number of hours per year your aircraft's fuel pump works with the number of hours your car's one does.

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What ACTUALLY wears in the Jabiru pump ?

 

Is there some way to test the performance ?

 

IE: fuel pump pressure, flow, leak test ?

 

Gaskets are cheap.

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What ACTUALLY wears in the Jabiru pump ?

 

Is there some way to test the performance ?

 

IE: fuel pump pressure, flow, leak test ?

 

Gaskets are cheap.

The risk with old fuel pumps is a split in the diaphragm's, if the drain tube has been blocked by a mud dauber insect (common occurrence, there is an insect for every size orifice including static ports) fuel can enter the crank case. Fuel nowadays is hard on rubber parts. Another possibility is corrosion causing the spring to break.

1201381165_images(4).jpeg.c94e6760f81ce957f0cb9eb350bd64a8.jpeg

Edited by Thruster88
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$260 is too expensive?

What's your life worth?

I just spent $1700 on a five year rubber replacement kit from Rotax, fuel pump included. Even though the rubber bits all look OK to me, that is what the manufacturer specified and they spent a lot of money and time figuring that out. It's part of the reason Rotax engines have a reputation for reliability.

 

Wow! My last 5 year was about 1/2 yours (I only purchase Rotax items that I can not find elsewhere) and I replaced absolutely everything however the pump had been purchased some years befor (so cost not included) :- When the Rotax fuel pump 5 year replacement recommendation came in, I purchased a new unit and put it on the shelf. My 2000, 920 hr 912 ULS has fuel pressure & flow gauges so that I can monitor fuel delivery performance. The origination fuel pump was still delivering expected flow/ pressure & no evidence of crankcase contamination/leak and continued to do so right up to the 900 hr service, when I bowed to my own guilt and replacing it (put it on the shelf)

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You Rotax guys are wealthy, but I always knew that. Here's what I'm planning.. If , on removing and inspecting the fuel pump, I reckon that a hole in the diaphragm will not lead to fuel running into the crankcase, I will continue to use that fuel pump.

Gosh, this grumpy old guy who was working on a 60 year-old gypsy engine told me that he reckoned the fuel pump in that plane was 60 years old and still going fine.

BUT if a hole in the diaphragm will lead to fuel contamination of the engine, then I will reluctantly find the money.

On reflection, if the mechanical fuel pump can do this, then the electric backup is only good for getting you safely down immediately, unless you did some plumbing so that the faulty mechanical pump could not put fuel from the electric pump into the crankcase.

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It DOES go into the sump oil of an Auster. They duplicate the pumps. on that engine. A perforated diaphragm will flood the entire body of the pump which is not sealed as it has a bleed hole as a minimum somewhere. Those diaphragms are a canvas and rubber thing and just fall to pieces eventually. Every diesel has a similar thing for what they call a lift pump and I consider 7years about enough for them. Over 20 years in service is RIDICULOUS Bruce. Oh and IF you do replace the diaphragm tighten its lightly and evenly then flex it over the full stroke then tension the screws to the proper amount. You have one way valves in there as well but often they are not designed to be rebuilt and the body is only diemetal muck.Nev

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Rotax fuel pumps have a drain hole between diaphragm and engine to drain fuel from any leaks.

Maybe your pump has one Too?

My concern with the diaphragm would be deterioration in the context of time in service.

Heat and time are the enemy of any rubber or synthetic flexible material.....discounting the long term effects of the fuel used.

If the pump is "branded" and disassembly is possible, you may be able to source parts or get one cheaper than an aircraft manufacturer can supply.

But.....

If it's 22 years old unfortunately I would recommend complete replacement and be grateful for it's long and reliable service.

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With a Jab engine using the Jab pump and an electric booster I would leave the pump alone unless there is evidence of it failing. Any leak through the diaphragm should exit via a drain.

If you start the engine using the booster pump to fill the carbie, then shut off the booster, then if the Jab pump is failing the engine will run short of fuel. You just have to ensure that there is enough time to drain the carbie bowl of fuel, before you attempt to take off. At take off you start the electric boost pump going so now you have two pumps. Once you are up and away turn off the boost pump and if the Jab pump is failing you will lose power. Turn on the boost pump and land. If you only use the boost pump at take off and go around, the failure of the Jab pump will be apparent and you will not be in major danger.

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A fellow I know says the jabiru has the best fuel pump ever made, gravity. Should run fine without any pump.

Prior to flight testing a new aircraft a fuel flow test is required at climb attitude to prove a 150% flow rate of full power requirements. I made sure mine could do 60 litres an hour with gravity alone.

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A fellow I know says the jabiru has the best fuel pump ever made, gravity. Should run fine without any pump.

Prior to flight testing a new aircraft a fuel flow test is required at climb attitude to prove a 150% flow rate of full power requirements. I made sure mine could do 60 litres an hour with gravity alone.

I have a J3300 with an Aeroinjector in a Sonerai and have removed the mechanical fuel pump. Fuel is gravity fed through the electric Facet pump and it works well for me. The max flow rate is 50 litres per hour with the Facet pump off and 70 litres per hour with the pump on. As best I can recall the "fuel head" in the Sonerai is similar to the early model Jabiru that I used to own. But it was a long time ago so I may not be right about the head available in a Jabiru. In my experimentation I found that there is a significant difference in the flow rate depending upon the fuel filter used.

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The standard starting procedure on all Jab engines is Master On, Electric Fuel Pump On for 10 seconds, Electric Fuel Pump Off, Throttle Idle, Choke On, Mags on, Start. If the mechanical pump isn't working the engine will stop during warm up. If the engine is warm just the choke part is not required and the throttle cracked a couple of mm. You will still run out of fuel taxying to takeoff unless you are already there. BUT takeoff checks include Electric Fuel Pump On. At top of climb Electric Pump Off. Now if the mechanical pump has failed during takeoff the engine will quickly lose power & then stop. If you react when there is a power loss & turn on the Electric pump all is good again. Otherwise just a restart is required. Now you just go around & land. This assumes no gravity feed.

 

Even without the mechanical or electric pump in the high wing Jabiru as Tasmag says there is enough gravity feed for the engine to easily make full power. I imagine then that you may have a mechanical pump that has failed but there as are no symptoms you are none the wiser.

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But all the fuel has to flow through the engine pump and if the diaphragm is perforated you will have fuel leaking and some debris going through the fuel. The diaphragm is usually multi element but they still end up in a bad way sometimes.. Todays fuel is funny stuff. and it IS an aeroplane after all.. You don't run a timing belt till it breaks either . Nev

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The standard starting procedure on all Jab engines is Master On, Electric Fuel Pump On for 10 seconds, Electric Fuel Pump Off, Throttle Idle, Choke On, Mags on, Start. If the mechanical pump isn't working the engine will stop during warm up. If the engine is warm just the choke part is not required and the throttle cracked a couple of mm. You will still run out of fuel taxying to takeoff unless you are already there. BUT takeoff checks include Electric Fuel Pump On. At top of climb Electric Pump Off. Now if the mechanical pump has failed during takeoff the engine will quickly lose power & then stop. If you react when there is a power loss & turn on the Electric pump all is good again. Otherwise just a restart is required. Now you just go around & land. This assumes no gravity feed.

 

Even without the mechanical or electric pump in the high wing Jabiru as Tasmag says there is enough gravity feed for the engine to easily make full power. I imagine then that you may have a mechanical pump that has failed but there as are no symptoms you are none the wiser.

Fuel pressure gauge may be a worthwhile investment. I have one and it shows pressure by electric and mechanical engine pump, good for verification.

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It's easy to sit here and write about mech pump failures and "simply" turning on the electric pump.

And it's easy to discuss that the engine "should" keep running under gravity feed.

 

We also talk about engine failures and how easy it "should" be to glide to a suitable landing area, however the dead and maimed results indicate it may not be as easy in practice as in theory.

 

The aircraft was designed WITH a functioning and servicable mechanical pump.

I'd stick with that.

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Today I took out the fuel pump and had a good look at it. As has been said, the diaphragm is a double thing with a drain in between. If the top diaphragm got a hole, fuel would exit at the spacer between the diaphragms.

To get to the crankcase, the fuel would have to get past the second diaphragm and also the fuel-pump drive-pin, which is a working fit in the side of the crankcase.

These things explain to me why we have never heard of the fuel pump system causing a failure. And the official "life" of the fuel pump is the TBO, at which time the pump is replaced.

The pump itself is a " made in Italy" CD brevettato and it works by a drive pin against a lever mechanism which pulls a diaphragm-piston down against a spring. If no fuel is being used, the drive pin misses the lever as the lever stays depressed. The depressed lever corresponds to the chamber above the piston being full of fuel and pressurized by the spring.

If fuel is being used, the spring sets the pressure and the lever mechanism moves toward the pin and gets some pushing.

When I removed it, the lower part of the fuel pump was full of oil. This may have come in from the drive-pin, but I can't see how it gets out again. Does anybody know?

The pic shows the 2 diaphragms with a vented plastic spacer in between. The biggest vent is facing the camera.

IMG_0010.thumb.JPG.7e2d55bd83e7cc84269157932497ef5f.JPG

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Well, the original electric fuel pump on my 56 year old Airtourer is still ticking away quite happily.

 

I have fun telling the apprentice who has to disasemble it to clean the filter what the consequences are for not getting it to seat well when it gets put back together again!

 

I think I remember years ago being told a suitable replacement was what went into some early Range Rovers. Nev can you help? Facit?

 

The mechanical fuel pump is of CAV make, same as went onto Chamberlain tractors. The fuel filter is also CAV and what was fitted to Chamberlain Countryman 6 tractors. The local John Deere agency is a port of call before a 100 hourly! If you can't find it there it is surprising what can be found for an Airtourer at Coventry's.

 

Sadly both Chamberlain tractors and Victa aircraft are a demonstration of what we were able to manufacture in the 1960's, but somehow lost along the way. Somehow this mature farmer well into his seventh decade, and a prolonged exposure to both these Australian products, maintaining reasonable audio functions is something a bit short of a miracle!

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