Thread: fuel bleeding procedure

I have had to bleed my system many times on the side of the road due to a blocked CAV pre filter.
I only ever crack the return line on top of the filter. works every time.

Why so many dirty filters? Because of the crap fuel we pay top dollar for.

Originally Posted by JDNSW

I find you can bleed it by hand without opening anything - you can feel when fuel is picked up and the primer is pumping fuel not air.

It is definitely not self bleeding (unless you have a very good battery and a complete lack of sensitivity to the effects on the starter.

John

depends on how unsympathetic you are when it comes to running it out of fuel or how smart/lucky you are when it comes to where you do your servicing....

the dual tank vehicles if you run them till they first start to drop power (as opposed to putting the boot in) or have their first miss will reprime at idle as soon as you change tanks. If you run them till they stop well, not so much, but from 60kph on tank change over with the engine not making power they usually self prime and keep going..

about a 500m down hill run in 3rd is enough to get them to go if not get them close enough that I wouldnt call it abusing the battery or the starter getting it to run again.

If Im changing the fuel filter Its usually the last thing I do on the service, with the filter changed and the fuel cut out in the off position I crank it untill the oil pressure light goes out. wait one minute, crank it for another 15 seconds (it seems like a bloody long time) fuel to run position, foot flat to the floor and then kick it into life.... 90% of the time they will get the fuel up for you unless you have a fault elsewhere in the fuel system.

IF you've gone to the effort of plugging on a servicing harness (which gives you control of the fuel cut off and starter) inside engine bay while you service the vehicle

Originally Posted by rocket scientist

I have had to bleed my system many times on the side of the road due to a blocked CAV pre filter.
I only ever crack the return line on top of the filter. works every time.

Why so many dirty filters? Because of the crap fuel we pay top dollar for.

only if

1. you've been using military fuel,
2. filling from jerries
3. have had a dose of diesel snot that has never been cleaned out of the fuel system properly
4. have the paint inside the tank coming off
5. have rust in the tank
6. have an injector thats letting combustion pressure back into the fuel lines

I dont have anywhere near that many dramas and a lot of the time Im not using "crap fuel we pay top dollar for"

Trust me on this if you're continually blocking the CAV prefilter filter your most likely cause is diesel snot + contamination from something...

**********techy bit here you can ignore if you like************
the dissapearing snot routine

when the prefilter picks up the snot it sits and lines the fittings orifices, these then pick up any sediments and contamination that comes through...

the flow of the fuel leaves the contaminant stuck in the line and the eddying moves the snot on in the fuel system (or it gets removed when you treat the fuel system) leaving the sediment behind the sediment creates a restriction as the fuel tries to flow past the restriction it deposits more and more residuals at the lead up to the restriction and the total flow rate drops off.

The killed all the bugs routine

Youve had diesel snot, youve dosed the system and killed the bugs, over the next 5 or ten tanks of fuel the sloshing action of the fuel shifts all the bug corpses from the tank into your filters. (which are perfect breeding grounds for any survivors) in and of itself this blocks your filters. BUT worse if you have any survivors the filter chamber and filter medium is the perfect growth site for diesel snot, lots fuel, lots of water and lots of surface area.

MY solution once a snot contamination is confirmed is to ALWAYS, completely over haul the fuel system, drop EVERY line off and blow it out backwards, remove every filter housing and clean them meticulously (including scrubbing out the seal seating rungs, the threaded fittings), drain and meticulously clean the fuel tank fillers and breathers. then reassemble using new seals rubber hoses (if you have retrofitted flex rubber hose on the lines).

IF its really bad it also pays to have the IP, injectors and high pressure lines sorted as well.