Fuel pumps

[Bruce Tuncks]

Well there we were, Grandma and me, driving our 6 year-old Falcon on the Hume Highway when the car just stopped going. The 50 psi fuel-pump, inside the fuel tank, had stopped. It is not a maintenance item, you just replace it when it stops. How amazing that a brush-motor is inside a fuel tank.

 

In contrast the Jabiru operates at about 4psi and has 2 pumps. But I have wondered if it is a good idea to replace the diaphragm on the mechanical pump on a time basis, and also I have wondered if it is possible for the mechanical fuel pump to fail in such a way that the electric pump output is either blocked or diverted.

 

.. Bruce

 

 

[facthunter]

I would replace the diaphragms at a set interval. Some of the fuels available would have an unpredictable effect, I would think, so what is a good time to inspect?? 2 years? I wouldn't let a car that I had to keep reliable going more than 4 years.( old type pump with carburetter) If you are only hacking it around the local town it is a different matter.

 

As to the blocked or diverted, check by blowing through it. The one way valves shouldn't stop the fuel flowing through. Nev

 

 

[fly_tornado]

Don't Jabiru use Chinese knock offs of Facet pumps?

 

 

[damkia]

... The 50 psi fuel-pump, inside the fuel tank, had stopped. It is not a maintenance item, you just replace it when it stops. How amazing that a brush-motor is inside a fuel tank.

You need a roughly 14:1 mix of air and fuel vapours to allow for combustion. Most fuel tanks would have too much fuel vapour pressure for combustion (too rich) with the available air.

 

 

[fly_tornado]

sshhh, let the nanny staters feel a sense of foreboding, every time they drive their cars.

 

 

[Bruce Tuncks]

Thanks Facthunter, I will order a pump overhaul kit . The existing diaphragm has been in use for 12 years.

 

On the Falcon fuel pump, I am still trying to work out if the electric motor is full of petrol or not when it normally operates. How would you seal it off to stay dry inside after years? The commutator was badly worn after 140,000 km. Maybe fine grit in some fuel did this? I don't know.

 

On the nanny state, I couldn't agree more! We are losing our liberty in the name of protecting us from ourselves.

 

Bruce

 

 

[facthunter]

Bruce, I have one that has done 647,000. kms in an EA and still going. They all run immersed and I have never heard of a problem unless they are run empty or low, usually when on gas in a dual system where it is recommended to keep at least 1/4 tank of petrol. The pumps run all the time essentially.

 

12 years is a long time for the diaphragm. Some diaphrams when they leak let fuel into the crankcase. Gypsy Major etc (engine driven). Bad fuel and ethanol worry me. Avgas should not be a worry. Nev

 

 

[xair1159]

Might have said it on here before, but when you rebuild the Jab mechanical pump fit the 6 (8?) screws holding the two halves finger tight at first.

 

Then fully flex the diaphragm by pushing the operating lever right in and only then fully tighten the screws. To quote the original article I read, "failure to do this will result in high and erratic fuel pressure". They are dead right as I found out the hard way. The screws only need to be tightened firmly, not until they squeak as this will only crush the diaphragm edge and damage it.

 

Fuel pressure is set by the spring strength and if the diaphragm isn't flexed, the load from stretching it gets added to the spring, plus it will also shorten the life of the new diaphragm.

 

 

[jetjr]

Jab have 2 fuel pumps, either is enough to run engine. Prospect of both stopping has to be pretty slim.

 

Part of 100? hrly service is fuel pump check where back up electric pump flow and pressure is checked. Pretty important check as the back up unit could fail without you knowing it and then not be working if the mech ever chucked it in.

 

In saying that mechanical one is very reliable. Probably cheap insurance to overhaul or replace every 10 yrs?

 

Good advice from Xair, how much is a entire new one?

 

 

[xair1159]

Despite living on the other side of the world, I sourced my replacement pump from an online car parts shop in Australia. Even with carriage costs it was still half the price of our local dealer!

 

The Jabiru fuel pump is a Goss 875 (BCD 1875) which fits the Peugeot 404, 504 and 505 up to 1979. Jabiru have modified it somewhat.

 

 

 

The spring is lighter and the plunger shorter to reduce the pressure to suit the Bing, but these can be swapped over and the main parts likely to give trouble are the diaphragm and valves.

 

The fuel-in spigot is the same but the fuel-out is vertical, not the 90deg to horizontal type, so the answer is swap the top covers.

 

The vent in the nylon spacer, between the two diaphragms, is just a hole and has no small hose nipple. Again, the answer is to transfer the other one, or insert a suitable fitting.

 

It was about this point I discovered the trick in my post above.