Lucas CAV fuel filter separator - again.

CaptainBob

CaptainBob

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As per my post a few days ago re my fuel filter.

I removed the screw at the bottom to let out some fuel (or water) and lovely clean fuel came out... but two or three tiny weeny bubbles went up from the screw, towards the filter element.

You all suggested that it was imperative that I "bleed the fuel system".

Now I've read my manual and seen what's to be done, but I'm confused. The thickness of pipe coming out of the fuel filter is quite a large diameter, and the hole I'd pump fuel up to and out of with the manual lift pump thing is pretty small.

I'd have to pump quite a large amount of fuel out before the amount of air which _might_ be in the pipe (and not in the top of the CAV filter thing) would reach the hole. I'm guessing I'd be there for ages, and never really know if I'd got the bubbles out or not, and waste a bit of fuel.

Also

On the top of my CAV filter thing, there are two screws. One in the middle which I assume is used when disassembling it, and another which is about the highest point on the top... is that not for bleeding air out of it?

The top of the filter looks to be below the level of the top of the fuel in my tank... if not below the bottom of the tank completely.

Sorry if I'm being dumb - and thank you for your replies!
 
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Ah, brilliant. So I just undo it and wait for fuel to spew out?

[/ QUOTE ] You should just have to loosen it and fuel will start to flow. That's the highest point in the filter so any air should collect there and bubble out as soon as you crack the screw. Then just work down the line bleeding at the next filter (if any) and the injector pump. Don't over-tighten the bleed screws.
 
Unscrewed it more and more... and it came out... and nothing happened. No fuel on the threads, no fuel coming out of the hole.

What am I missing? Should I be running the engine when I remove it, to make fuel flow?
 
You need to make sure there's sufficient 'head' of fuel for it to flow through the resistance of the filter, and that there is no valve closed between the tank and the filter. Filling the tank can make it a lot easier. I had similar trouble when I took over Border Maid and found that the fuel pipe from the tank to the primary filter was almost completely blocked with bacterial slime, which I sucked out using a Pela Pump. It does sound as though you might have some constriction in the system between the tank and the filter.
 
If your fuel line comes out of the top of the fuel tank, you will have to start the syphon by operating the fuel lift pump lever or turning the engine over. The only way it will gravity feed is if the fuel tank is higher than the filter AND feeds out of the bottom of the tank.
 
er, forgive the obvious, you have opened the fuel tap from the tank?

Also, if only a v few small bubbles enterd the fuel system, I would be tempted to start the engine and see if it stalled - if not then no problem. If it does stall then turning the engine over on the starter (for a max of 10 seconds) may well shift the air. If all that fails then you have to bleed the fuel pump (at least if it is a CAV pump), but it is an easy job
 
Some of those bleed screws are not, they are blank holes used for mounting the leakoff connector. If it was only a few bubbles just start the engine and pull it through, if it does not work you can always bleed the pump and injectors.
 
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er, forgive the obvious, you have opened the fuel tap from the tank

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Is there a solenoid valve at the tank end, that only opens when you switch on at the engine control panel?
 
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