Air in fuel system

[Squanderbucks]

What model Racor do you have. Some of the larger ones have a float ball that can cause problems as they befome fuel logged and no longer float. Racor sent out a builtin about this a few years ago.
Also if it has the T-handle or similar with O-ring and larger square rubber o-ring I have seen the upper rim become rough from paint chipping and going over it with 400-600 sandpaper makes for a better seal. With a little grease.
You mentioned pressurized the fuel system - usually the lift pump creates a vacuum as it is mounted on the engine or at least after the Racor. Racor does not recommend "pushing" fuel through their systems.
Also, if your fuel tank is well below the engine and low on fuel it is more prone to pulling back on fuel in the lines.

[Mike Banks]

I use a simple trick, I have a small day tank which is mounted midships and above the engine, wj=hich is fed from the main fuel tank by an electric diesel pump from a rtruck wreckers, but any good impulse type fuel pump should suffice. When the tank is full, it overflows via a discharge pipe back into the main fuel tank, so that the fuel by passing through filters, is continually circulating and polished. Because there is only a straight length of pipe above the engine, any bubbles in the fuel escape via the be breather on the day tank, which holds about twenty litres, although one could get away with ten litres or even less--but more is safer.

[ebsail]

First make sure you're using the correct filter. Someone may have used an incorrect one. Came across this twice, one time in a trawler's fuel filter and one time when Jiffy Lube changed my car oil filter

[Smooth Move]

Check the spin on fuel filter to make sure not an oil filter . Easy to get mixed up and restricts fuel flow

[beirutsailor]

I once spent two weeks looking for leaks, replacing fuel lines, etc. etc.
Then found that the final fuel filter was blocked up. Engine cuts out when the standing fuel runs out.

[a64pilot]

Originally Posted by Kenomac

A very light coating of grease would be my choice, not silicone.

I assume silicone grease was what was meant, not silicone caulk.
Silicone caulk is not fuel proof, fuel will soften it and make it swell up.

[model 10]

[QUOTE=a64pilot;2947751]I assume silicone grease was what was meant, not silicone caulk.


It used to be DC4 compound, but they all look the same now. I can buy squirt cans of silicone grease in Rio Dulce now.

[Mickeyrouse]

Okay gang, the problem has been solved. While the fuel lift pump was on, (not necessary for engine to run, defeated oil pressure switch by jumping around it) noticed a steady stream of air bubbles flowing into the bowl from two sources: the plug where the water sensor would be if fitted (it’s not) and the drain plug. Closer inspection revealed air bubbles were traveling through the threads on both plugs.
So apparently once the bowl was adequately filled during pre-heat, more than enough fuel was continuously entering the system to offset the air entering the system. The air in the system was being passed via the bleed-off back to the tank, so the injectors received adequate fuel.
However, once the engine (and lift pump) stopped running, minute amounts of air continued to enter the filter bowl and the siphon of the fuel in the bowl returning to the tank via the feed line caused air to displace the filter bowl fuel. Obviously the O-Rings weren’t seating properly after 8 years of use.
Solution: tightening the fittings did no good. I took the o-rings that act as seals for these two fittings to my local hardware store, who had exact matches. They were black, (neoprene?) though, not red,(rubber?) so I am sure Racor would contend they are not correct replacements. Anyway, replaced them and the air problem cleared up.
Total cost: $1.45, they’re in stock, and easy to carry as spares.
I should point out that not even tiny amount of fuel seeped out- air was seeping in. I imagine if the placement of the filter was below the tank (it’s above, like most filters are) it would have seeped fuel.
I must admit, though, that it seems like the check valve should have prevented the back-siphon. Gunk in the valve seat?

[Mickeyrouse]

I never mentioned the filter model: It’s a Racor 500 series turbine filter, using a 2 micron element. I usually, not always, pre-filter with a Baja. I have bought fuel from Brownsville Texas to Jonesport Maine. It has always (pretty much) done its job. Sometimes I get sold water at diesel prices, but the filter does its job. It does pay to check it.

[sailingchiro]

Glad you found your problem. It seems vacuum on the Racor has caused some problems. The Racor is a great product but must be vacuum checked. But if you are creating a vacuum at the Racor, something is limiting fuel flow. Mine was the gunk in the pick up tube. If you have a pick up pump, you should have no vacuum.
Rebuilding the Racor and vacuum checking the Racor is a very good idea.
I use the 10 micron for the Racor then 2 micron for the engine filter.
I do recommend Power SErvice products to clear up gunk on the fuel tank.

[skipmac]

Thanks for posting. Always nice to hear the solutions.


Had a similar problem, leaking around the drain plugs and fittings) with the system on my boat when I first bought it 10 years ago. Came with a very old Racor 500 which I determined was slightly different than newer models and some of the parts (drain plugs and similar bits if I recall) were not interchangeable with newer models. By the time I figured it out I was so frustrated and parts weren't available locally so I just bought a new one.


By the way, the dealer where I bought the new 500 recommended 30 micron in the Racor and 2 micron in the secondary filter on the engine. The reason he said was the Racor is there to stop the water and just the bigger particles and the secondary will catch the small stuff. Also you're less likely to plug the Racor at an inopportune moment if you catch some bad fuel.

[sanibel sailor]

As others mentioned, the air leak is a symptom of another problem, excess vacuum in the pickup line or a clogged filter. if you fail to address whatever that is, the problem may reoccur at a different spot. Whatever is impeding flow from the tank to the filter will tend to get worse. I battled this problem on another boat, the engine would run well, then seemed to quit when most needed.

PS those hardware store ORings are nitrile and they are fine with diesel