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Old 04-07-2014, 13:45   #1
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Racor Assistance Please

In an attempt to fix something that wasn't broken in order to make it better, I've created an unknown. I'm getting air bubbles in my new Racor 75/500FGX dual filter system. Basically, it's a Racor system that permits switching between two filters in case one fouls.

When I run the engine, I can see small bubbles swirling in each clear plastic bowl, along with larger bubbles coming up from the white vortex guides. The bubbles have not made their way up to the engine, which is running fine even at higher revs, but I need to keep adding diesel to the filters in order to keep them topped up. The old single Racor I removed, did have a significant air bubble when I removed it, and it had always worked just fine, but now, I'm hesitant to head out of the anchorage alone in case of a major stall.

My thoughts: There's probably air in the line leading from the fuel tank up to the Racors (7ft long ,3/8 inch diameter hose with an 18 inch rise). I'm going to head out tomorrow to fetch an inline bulb pump to try and force out the air from the line using a small gerry can of diesel. I've checked and re-checked all my hose fittings. I've read online that some air bubbles are normal, but it concerns me that a large bubble will eventually find its way to the engine and cause a stall at just the wrong moment.

Any expert opinions would be most welcome. Another bit of information: The fuel tank was emptied and scrubbed clean 12 months ago, and all fuel since has been clean and pre filtered at the fuel dock and fuel treatment added. No water has ever been seen in the bowls.

Thanks

Ken
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Old 04-07-2014, 14:56   #2
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Re: Racor Assistance Please

Not sure this helps but most Racor filters work under a vacuum. Meaning the electric fuel pump is between the filter and the motor.it sucks the fuel through the filter causing a vacuum and compresses the filter causing the seals to tighten. If the fuel pump is on the intake side of the filter it pressurizes the filter and pushes the seals apart. Not sure how you did yours.
Just a thought.
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Old 04-07-2014, 15:00   #3
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Re: Racor Assistance Please

There is a chance that you could have a pin hole air leak in your pickup tube. Does it make any difference if the tanks are full?
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Old 04-07-2014, 15:12   #4
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Re: Racor Assistance Please

The new Racors have replaced the old Racor at the suction side of the pump. I've checked and rechecked the connections... even re-cut the hose ends and double clamped. Same bubbles. Does anyone know if I'm on track with suspecting air in the take up hose? I did forget to close the fuel shut off valve at the tank prior to disconnecting the hose from the old Racor. Probably dumped all the fuel in the hose back into the tank. Will the air not clear out until the fuel line is properly purged in the manner I suggested?

The fuel tank is 3/4 full with 150 gallons.
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Old 04-07-2014, 15:30   #5
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Re: Racor Assistance Please

The bubbles could be coming from the pickup line or from the filter housing itself. Are you sure they aren't coming from the drain cock on the bottom of the filter housing? I have heard of that causing problems without an obvious leak.
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Old 04-07-2014, 15:35   #6
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Re: Racor Assistance Please

I've had a leak from the little o ring at the base of the t handle cause something like that.
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Old 04-07-2014, 16:54   #7
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Re: Racor Assistance Please

Sounds like a vaccum leak to me, not trapped air. Vaccum leaks can be a bitch to track down...especially given that you just replumbed the system so have lots of new options.

One idea is turn it into a pressure leak which is much easier to find. Isolate and pressurize the new filter system and see where it leaks. You could pressurize with diesel using a hand bulb. For example, I have a bulb in-line just up stream of my filter, close the fuel shut off at the engine (using the normal shut down lever/solenoid), pump it up hard and see if diesel leaks anywhere. Let it sit pressurized (and maintain pressure) as a liquid may take more time to find its way out a small leak.
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Old 04-07-2014, 16:59   #8
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Re: Racor Assistance Please

Quote:
Originally Posted by DeepFrz View Post
The bubbles could be coming from the pickup line or from the filter housing itself. Are you sure they aren't coming from the drain cock on the bottom of the filter housing? I have heard of that causing problems without an obvious leak.
Ive also had shut off valves at the tank leak and cause similar symptoms.
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Old 04-07-2014, 19:44   #9
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Re: Racor Assistance Please

Ken
Keep focused on the basics,i.e. 1) there should be no air bubbles in the Racor bowls and 2) everything on the Racors and upstream of them is suspect no matter whether new or old. It is all under a small depression and therefore will suck air in at any weak point.
If you cannot find the leak by elimination then carry out a simple pressure test with air and a soapy water solution.
Drain the fuel out of the lines then pump up with air and detect leakage with the soapy water solution. Copper fuel lines can also develop pin hole leaks so everything has to be tested.
Good luck
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Old 04-07-2014, 20:37   #10
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Re: Racor Assistance Please

Quote:
Keep focused on the basics,i.e. 1) there should be no air bubbles in the Racor bowls and 2) everything on the Racors and upstream of them is suspect no matter whether new or old. It is all under a small depression and therefore will suck air in at any weak point.
If you cannot find the leak by elimination then carry out a simple pressure test with air and a soapy water solution.
Drain the fuel out of the lines then pump up with air and detect leakage with the soapy water solution. Copper fuel lines can also develop pin hole leaks so everything has to be tested.
Good luck
Great tip.
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Old 04-07-2014, 23:15   #11
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Re: Racor Assistance Please

Quote:
Originally Posted by belizesailor View Post
Sounds like a vaccum leak to me, not trapped air. Vaccum leaks can be a bitch to track down...especially given that you just replumbed the system so have lots of new options.

One idea is turn it into a pressure leak which is much easier to find. Isolate and pressurize the new filter system and see where it leaks. You could pressurize with diesel using a hand bulb. For example, I have a bulb in-line just up stream of my filter, close the fuel shut off at the engine (using the normal shut down lever/solenoid), pump it up hard and see if diesel leaks anywhere. Let it sit pressurized (and maintain pressure) as a liquid may take more time to find its way out a small leak.
This sounds like what I plan on doing in the morning. Hopefully, it's not the new Racor system leaking, but I do have the old working filter standing by just in case.

Thanks everyone for all the good suggestions.

Ken
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Old 05-07-2014, 04:13   #12
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Re: Racor Assistance Please

Quote:
Originally Posted by darylat8750 View Post
I've had a leak from the little o ring at the base of the t handle cause something like that.

and

as Acushla said: Keep focused on the basics.
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Old 05-07-2014, 08:44   #13
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Re: Racor Assistance Please

Quote:
Originally Posted by darylat8750 View Post
I've had a leak from the little o ring at the base of the t handle cause something like that.
Mine seems to be coming from the same place. how did you make your final determination? I've double checked and double clamped everything, purged the system, but when I use the front switch lever, I notice that I get far fewer bubbles when I use the filters together, than when I use the filters individually. The bubbles almost stop.

I'm almost ready to give up on this thing and switch back to the original.... except that I've traveled 4000 miles with this thing to get here, and have two days invested in trying to make it work.
Ken
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Old 05-07-2014, 09:06   #14
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Re: Racor Assistance Please

Am I right by assuming from your last post that you are getting bubbles from each of the filters when used individually? Then the problem is not likely in the filters, but in piping, valves, pickup. Each connection is suspect until proven good.

Have you tried the pressure - soapy water test?

I would suggest that you include the pickup tube/shut off valve when you do the pressure test. And keep the pressure low. About 4 psi is all you should need, IMO.

Edit: check to make sure you don't have a strainer on the bottom end of your pickup tube. If you do get rid of it.
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Old 05-07-2014, 09:39   #15
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Re: Racor Assistance Please

Put a cheap electric fuel pump between the tank and the filters. If bubbles disappear, you've got an air leak in that part of the system before the filters.
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