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This after a filter change.
I can see few bubbles popping for the middle on my racor, and I have hard time to prime it, or at least to create enough vacuum to make sure fuel comes to the inlet of the filter.
Symptoms are : I bleed, start the engine, it dies 5 minutes later after half of the racor is emptied. I fill the racor again, rebleed, restart, and again.
I am thinking replacing the racor by a new unit. Should I ?
Sounds like you have an obstruction in the fuel line someplace or an air leak. I would check that out before just replacing the whole filter unit. Since this occurred after the filter change I would start there. Gasket/O-ring leak?
If the Racor is lower (in altitude) than the top of the tank dip tube and/or the tank valve ... if you did not shut off the tank valve when you changed the filter .... you probably drained all the fuel in the tubing from the filter all the way back to the tank and now have a huge 'slug' of air in that section of fuel tubing, including the 'dip tube'.
Suggest you get a vacuum source (vac pump etc. .... a manual vacuum pump mounted to a portable tank used for removing used engine oil is probably 'the safest') and pull enough vacuum so that fuel oil starts to readily 'siphon' out of the disconnected connector on the tank side of the Racor. When the fuel totally refills that run of tubing between the Racor and the tank, have an assistant immediately close the tank valve ... which will enable the tubing to 'hold' most of the fuel oil and without (much) draining out while you close that 'upstream' connection on the Racor. Then, purge the Racor housing for any oil that did happen to spill out and partly empty the tubing ... allowing air in; .... and then, 'purge' the rest of the air out of the tubing between the Racor and also the small engine mounted filter (if your engine has one). Then, bleed all the air out of the engine's fuel oil circuits.
Note:- If the Racor is 'higher' in altitude than the top of the tanks 'dip tube', then pull the vacuum from one of the lowest sections of the fuel system between the tank and the engine lift pump.
Always close the tank valve when changing 'filters'; for less need to purge the entire fuel delivery system.
I had exactly the same problem and it bedeviled me for some time. In my case it was a clog within the filter, before the element.
Basically, if you can start the engine and run it for 5 minutes and the filter is 1/2 full when the engine dies, you have an obstruction between the tank and the filter element, if your tank is not lower than the filter as in the post above. No need to replace the housing (if you decide to do so, please send it to me), they come apart pretty easily. Do so and make sure there is no obstruction in it.
I use a fuel bulb from an outboard motor to prime my filter. Place it between the tank and filter, near enough to the filter to pump and watch the filter fill. If you can't pump fuel with that, then there is either an obstruction between the bulb and the pick up, or the pickup tube has corroded away above the fuel level.
If you install one of these bulbs, do keep an eye on it as it can deteriorate and fail, though ours is 6 years old and just fine.
I changed and pull apart that racor several times now. and I know there is no obvious plugging clog into the system. I was able to run the engine by inserting a small 12v utility pump in the circuit. I actually found a leak thanks to the augmented pressure. I just did not want to run with that pump on all the time, this was a liability. I have a manual pump on the engine, but I suspect it was not able to generate enough suction to pull air for the full circuit.
However, how do you explain small air bubbles popping in from the middle of the racor ?
I guess it could come from the inlet that is full of air, not necessarily a leak.
However, how do you explain small air bubbles popping in from the middle of the racor ?
I guess it could come from the inlet that is full of air, not necessarily a leak.
The flow direction in Racors is bassackwards of most common filters, the flow is from inside/ID to outside/OD with respect to the 'pleat pack'. That you have bubbles from the middle (core) of the pleat pack most probably means that the air came from 'upstream' from the direction of the tubing between the tank and the Racor.
If the bubbles were noted on the 'outside' of the pleat pack, then the possibility is that the filter was 'coalescing' very small bubbles into larger and more visible bubbles ... and if the fuel system, from the Racer to the lift pump, etc., was at a gradual 'rising' to that lift pump, those bubbles would eventually become trapped in that small engine mounted 'guard' filter, which is very easy to bleed.
Also and if time permits, its good practice to soak such filters in fuel before installing them, as oils do not readily 'wet out' the filter media/material and any 'dry spots' within the filter material will/can hold air, .... until full flow begins in earnest and those bubbles can migrate towards the lift pump and the engine mounted 'guard' filter, etc. etc. But NOT if the filter location prevents that gradual 'rise' in all system tubing 'away' from the Racors.
Picture is quite bad, but the original owner had all fuel lines running ABOVE, everything. The filter, the tank, etc... It sounds a real bad idea as you have air trapped everywhere that is almost impossible to bleed without a pump.
Would not make more sense to run the fuel lines downward, and go under the engine ?
The 'workhorse' Racor filters should be AT the very lowest portion of the entire fuel delivery system. The reason is that WATER will always drain back to the Racors, where it can be visualized, then removed/drained. Plus, any entrapped/entrained AIR (your probable present problem) will tend 'gravitate' away (in two directions), away from the Racors, and easily migrate to the small engine mounted 'guard' filter or back to the tank valve .... hence easier to be removed/'bled'.
Further, If the filters are not at the lowest altitude of the entire system; then, water will become trapped in the tubing 'below' the altitude of the filters and their 'sumps', until more water than the 'capacity' of that tube can bear finally 'releases', and you WILL eventually 'slug' the hot injectors with slugs of water, especially true during a 'heavy' sea state.
Even further, such non-drained/trapped, now stagnant, non-moving water is an ultimate/ideal place to grow the 6-7 common bacteria species that thrive in diesel oil + water mixtures. The most common of those is B. Aeruginosa whose 'colonies' in diesel/kerosene and other 'light fraction' oils are stringlike and variably compressible 'mats' (hairballs) that easily 'stick' to everything.
I has a similar problem, mine used to have a fuel level drop every so often in the glass portion, it seemed random. Until one day on a two hour motor the engine quit. It took a bit of trial and error but it was the o ring that separates the two halves of the filter. I found it by pressure testing the filter to 18 lbs. and putting soapy water around it. New o ring and good to go.
If the flow is inside to outside (w/r to the pleats) there will be a perforated structural 'cage' on the OD to help prevent such 'ballooning'.
Without the external 'cage' on the OD, the normal flow will normally be from outside to inside. Also without the perforated OD structural 'cage', the differential pressure (∆P) across the pleats from inside to outside the pleats must be limited to LESS THAN 5 psid (or 10"Hg max. vacuum or pressure)
All this is irrespective of any markings on the inlet/outlet nozzles of the filter housing.
In your offered picture, the flow is outside to inside; and therefore is the preferable pathway; although the tortious 'fluid routing' requires a comparatively expensive filter housing.
I replaced an old Racor 200 primary filter with a new Racor 120A primary filter and relocated the 120A for better access to see the bowl and change the filter. The Racor 200 was impossible to inspect and drain where it was located.
After the change over I did have air in the system, the engine would run for 2 minutes then shut down. It was priming through to the secondary filter cup and when that was dry the engine stopped. A "mystery" that Sailnet members offered good information to help solve.
The Racor 120A has matching ports on each side, so with the fuel shutoff from the tank CLOSED you can screw in a 1/4 inch fitting to the opposite input side (follow the arrows on the filter head) attached a fuel line with a squeeze bulb to a separate diesel tank on the cabin floor and give the bulb a few pumps. You will quickly find the leak by the bubbles of air.
My fix was to replace a "new " off the shelf shut off with a new Racor fuel shutoff and problem solved.
Good Luck
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