Bleeding a Racor Filter / Water Separator

[richardabeattie]

I have a fairly new Racor (120 I think) and have tried to bleed it after inadvertently running the tank too low. Having half filled the tank I opened and indeed removed the bleed screw and some fuel seeped out - but I was expecting a proper flow of fuel. Is this because the level of fuel in the tank is still too low?

Once I have bled the Racor I then need to bleed the fuel filter on the Yanmar using the little lift pump handle but if the fuel line from the Racor to the filter is currently empty I assume I'm going to have to pump the lever for a long time.

 

[prv]

What were you expecting to propel the fuel from the tank into the filter?

Some people have tanks mounted high up, in which case the answer is gravity, but otherwise you will need some kind of pump. I have an outboard-style bulb pump, but there are a couple of other options.

What are the relative heights of your tank and filter?

Pete

 

[ip485]

Yes, you will have air between the Racor and tank.

Does your fuel pump run when the ignition is switched on? If so this will prime the Racor. If not, some other means of expelling the air is required.

Yes you will almost certainly need to bleed the engine as well as air will have entered the engine filter. As you correctly say if you have a seperate electric lift pump, open the bleen screw and use that. If not use the diaphragm pump on the engine fuel filter.

With luck you havent got air further into the engince. In the worst case you may need to bleed the injectors, but hopefully not.

None of us do it intentionally, but well worth knowing the minimium fuel level before you start picking up air - and taking into account any heel. We all know the stories of the engine quitting at the worst possible time. With mine I know the Genset is likely to quit a little less than a quarter of a tank and the engine not too far behind, so I never allow the tank to get below a quarter.

Every engine setup is potentially a bit different so just some general thoughts from me.

 

[[70521]]

I have a fairly new Racor (120 I think) and have tried to bleed it after inadvertently running the tank too low. Having half filled the tank I opened and indeed removed the bleed screw and some fuel seeped out - but I was expecting a proper flow of fuel. Is this because the level of fuel in the tank is still too low?

You may find this of use?

 

[richardabeattie]

Thanks. My Yanmar engine mounted fuel pump is not electrically powered so does not run until the engine is running.
The Racor filter/water separator is gravity fed - provided the fuel in the tank is high enough. As the fuel level falls I assume the engine mounted pump sucks - provided there is no air in the system. So I think the answer is to fill up the tank and bleed everything again. Perhaps I should also reposition the Racor lower down.

But my original question boiled down to whether when I open the bleed screw on the Racor I should get a continuous flow of fuel, not just a trickle.

 

[Dull Spark]

"But my original question boiled down to whether when I open the bleed screw on the Racor I should get a continuous flow of fuel, not just a trickle."

If the Racor is just below the fuel level in the tank, you may get a very low flow.

If the Racor is above the fuel level, it may suck air in.

Could I suggest that you close the isolating valve between the tank and the Racor and re-prime the Racor as shown in the above video clip. (If you have a valve downstream of the Racor, close that as well.) Once the unit is primed with fuel, then you can open the valves and use the manual lever on the engine-mounted fuel pump to prime the line to the injectors.

On mine, the Racor is above the fuel tank AND the engine. There are valves upstream and downstream of it. I close these, drain down, change the filter and re-prime as shown on the video. Before I put the top back on the Racor, I open the valve to the engine and bleed the engine fuel pump. It re-fills the pipe and pump under gravity. Then I top up the small amount that has left the Racor and put the top back on. No need for extensive use of the little manual lever on the engine pump.

It all depends on the level of the bits of kit relative to each other - and whether you have isolating valves. Good luck!

 

[nemodreams]

Is you tank a top feed out - with a dip tube ? If so - if the filter is below the level of the fuel in the tank it should keep the syphon intact ( fuel has to go uphill out of the tank and then down again )
If its not you can't use a bleed screw on the filter housing - it will destroy syphon and allow fuel to run back into the tank emptying your dip tube.
A top feed tank - if an electric fuel pump is not fitted - really needs primer bulb between tank and first filter. Establishing the syphon from empty is very difficult with a small lift pump lever.

I have a Yanmar 1gm10 - I fitted an ASAP type banjo fitting primer bulb that pumps IN to the pre- filter head (simply fits into the inlet of the filter ) Not only does this make priming the fuel into the lines from empty so easy - it make bleeding every thing simple - as it pressurise's everything in front of it.
https://www.asap-supplies.com/pumps/fuel-pumps/fuel-primer-pumps
I should get a spare while they still sell them - they are very good quality.

 

[macd]

I fitted an ASAP type banjo fitting primer bulb that pumps IN to the pre- filter head (simply fits into the inlet of the filter ) Not only does this make priming the fuel into the lines from empty so easy - it make bleeding every thing simple - as it pressurise's everything in front of it.
https://www.asap-supplies.com/pumps/fuel-pumps/fuel-primer-pumps
I should get a spare while they still sell them - they are very good quality.

Probably no use to the OP and his Racor set-up, but exactly the same pump can be bought integrated into the head of a CAV filter housing. Much more effective that the engine's fiddly primer pump. Worth considering if you have priming issues with a basic CAV housing.

 

[prv]

re-prime the Racor as shown in the above video clip.

But that's not the kind of Racor he has. The 120 is a spin-on with a bowl attached to the bottom of the cartridge.

I guess you could pour diesel into it before screwing it onto the head, but you'd still end up with an air bubble in the top.

Pete

 

[prv]

But my original question boiled down to whether when I open the bleed screw on the Racor I should get a continuous flow of fuel, not just a trickle.

If you took it right out, and had gravity or pumped feed from the tank, you'd get a flood of fuel from the hole . With it in, and just loosened a little, there should be a good flow of air from the hole drilled in the side of the screw, followed by a bubbly mix of air and fuel, followed by a solid squirt of fuel at which point you close it. A good handful of rag or paper is needed to catch the escaping fuel.

Sounds like you're right about needing the tank to be more full, so that the head of fuel is above the filter. I'd recommend a pump in-line between tank and filter, though, so that you can change the filter even if the tank is low. Otherwise what happens if the filter blocks at sea when the tank happens to be low?

Pete

 

[richardabeattie]

If you took it right out, and had gravity or pumped feed from the tank, you'd get a flood of fuel from the hole . With it in, and just loosened a little, there should be a good flow of air from the hole drilled in the side of the screw, followed by a bubbly mix of air and fuel, followed by a solid squirt of fuel at which point you close it. A good handful of rag or paper is needed to catch the escaping fuel.

Sounds like you're right about needing the tank to be more full, so that the head of fuel is above the filter. I'd recommend a pump in-line between tank and filter, though, so that you can change the filter even if the tank is low. Otherwise what happens if the filter blocks at sea when the tank happens to be low?

Pete

I'd pour some more in from the reserve jerricans! Thanks everyone - I've lived and learned.