Racor Fuel Filters

[Capt Happy]

Good Day All,

Hope this note finds everyone well and healthy.

Fuel injected 350 Crusader XL

Getting ready to put in for the season. Noticed during engine run up, that we have what appears to be air bubbles in the Racor filter. I changed the fuel line, tank fittings, O-rings on intake side of filter. Removed and replaced the feed line from the inside of fuel tank. Switched the lines to the opposite filter for the other engine, issue still present. Does anyone have any suggestions on where to look next? I cannot think of anything else that could be causing this. Perhaps it may be normal, but never noticed before and the second engine is not producing any bubbles at filter. Thanks in advance for any suggestions.

[bud37]

Heh Cap.....are you saying those are the Racor filters that have clear sight bowls with drains, if so are they clear glass or clear plastic?

[Viper]

Glass or plastic, I don't think that's allowed in an inboard gasoline engine compartment. If it's the type of assembly with the removable bottom, it's supposed to be the solid metal bottom/bowl for gasoline engine rooms.

If you're confident you've eliminated the possibility of a leak letting air in, including the filter assembly itself, the other possibility is vapour lock. This can happen due to a hot engine compartment or excessive vacuum in the suction side due to too many bends, bad fuel lines, too many fittings and accessories in the line, etc. Anything that restricts fuel delivery on the suction side is suspect.

Do you get bubbles right off the bat from a cold engine start or only after she's been running for a while?

Do you have any accessories installed such as a flow meter?

Does your engine model have an Oberg fuel filter installed? This is a black hockey puck/pancake type filter assembly usually installed on the right side of the engine, low, toward the back. There are two halves that have a single bolt through the center. If you have these, check it.

Also, does your engine have a Racor filter on the engine itself?

Does this engine model have a fuel module (long vertical cylinder with fuel lines going to it)?

[Capt Happy]

Good Day,

Yes, from a cold engine start-up. Thought about the bends, restrictions of the fuel line. When I replaced it, I ran a straight section directly from the tank to filter to eliminate a potential problem, same issue. No Oberg filter or fuel module. There is a very small filter on the engine, these are replaced every season. I swapped from engine to engine, just to make sure it wasn't this. I will keep looking, but at a loss currently. Have noticed a slight surging of engine, assume this is related to improper fuel delivery....

[Capt Happy]

Sight bowls on Racor's are glass.

[bud37]

IMO air would only be seen at the filter if the air gets in between the filter and the tank. If you have a fuel shut off valve between the tank and the filter where you are seeing the air, check that valve especially if the valve is the type that has packing.....it can be adjusted by the way. You would be amazed at how air can be pulled into fuel lines under suction without leaking noticeably. Worth a look.

Does it change when the tank is more full?

Curious....Were the sight bowls mentioned on your survey, do they have the metal guards around them?...anyway....I am of the belief that those bowls should be metal as well.

[waybomb]

I also believe in metal. When I bought my Racors, they came with plastic bowls. I bought the metal ones before I installed them.

[Capt Happy]

They sight bowls are glass, protected by a metal guard. A recent survey did not identify any issue with the present setup.
I replaced all fittings including shut-off. Went back yesterday, disassembled them all again and reapplied everything with liquid thread sealant. Thanks to all who have made suggestions. Keep them coming as issue remains. Cheers

[Capt Happy]

Sorry, need to fully read all replies.
I wondered about different tank levels. Removed the suction line from inside of tank and pressure tested. Replaced the solder around fitting. Did not find anything concerning within the fuel tank.

[Viper]

Hook up a portable fuel tank directly to the filter and see if you get the same problem. If the problem goes away, you know the cause is before the filter. Don't forget to ventilate ventilate ventilate!! Not having the tank in the engine bay is best, outside is safer. Should be easier on your model I think.