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  #1  
Old 09-18-2010
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Racor draining, where is the leak?

I've been trying to figure out where the leak is in my system.

I have a pacific seacraft 37. Last spring I had my diesel tank replaced, and I changed the fuel filter etc. My racor is about three feet above my tank, and there is a fuel pump pulling fuel through the racor. A line leads from the racor, to a shutoff valve at the racor, to a shutoff valve at the tank, to the fuel pickup, into the tank.

When the fuel system is primed, with no air, if I leave it for two weeks and come back, the racor is drained down to the fuel swirl inlet, about 1/2 way down the bulb.

There is no fuel leaking in the boat - which makes me think the fuel is returning via the fuel pickup line. If I close the fuel shutoff at the racor, the racor stays full. If I close the fuel shutoff at the tank, the racor stays full.

When the racor is empty, I can turn on the ignition and the fuel pump will fill the racor and prime the pump. So I can start the engine without having to bleed (which is sweet. thank you yanmar.)

When both shutoff valves are open, if I turn on the ignition the fuel pump never shuts off. It should shutoff when the system has pressure. While the ignition is on, if I shutoff the fuel line at the tank, the pump stops pumping - there is a click every few seconds rather than many per second. So it seems to me that the leak must be between the fuel shutoff at the tank and the tank itself?

I can't imagine how the racor would drain without air being introduced into the system somewhere.

As I haven't seen any diesel leaking in the boat anywhere - I'm assuming that the fuel pickup line, inside the tank must have a leak. Above where the fuel pickup enters the fuel itself.

Has anybody else run into this problem? Do any of you have any ideas on what the problem is?

I would hate to pull the tank, "fix" the pickup, reinstall, only to have the problem remain.


Thanks in advance,


Craig.

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Old 09-18-2010
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Did you check the ring gasket on the filter? It seems to me that the filter is seeping air in. And yes I had similar problem, it was fixed by resetting the cup on the filter and tightening it
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Old 09-18-2010
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Craig--

I think CrazyRu has nailed it. There is an internal check-valve in the Racor that prevents fuel draining back into the unit from the line to the engine that can come in handy when changing the filter as it eliminates having to bleed the system. If, however, the seal on the top of the Racor is not 100% efficient, it will allow air to bleed back into the filter body--however slowly--hence what you are seeing. If the O-Ring was pinched at some point, it may be allowing a tiny bit of air into the unit while there is insufficient pressure in the system to force fuel out.

FWIW...
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Old 09-19-2010
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Thanks for your replies. I had checked the gasket on the filter, but as both of you suggested this as the problem I went through it again. I have a Racor 500FG. The gasket that is in there now is the one I obtained in the filter kit I used. I took it out of the racor, and it looked good, no kinks or pinches. I covered it in diesel again and then reinstalled and made sure the top had a good seal and tightened it down. If it leaks again, I'll try a new filter/gasket. If if its a problem after that, I'll look elsewhere.

It makes sense that this would be the problem - it explains why there is no diesel in the boat. The top of the racor is the high point in the fuel system, so a leak there wouldn't cause diesel to come out of the filter.

Thanks again for your help. I'll report back when the problem is resolved. As it takes a while for the racor to drain, there may be a delay in my report... Also, I want to get out sailing rather than leave my boat for two weeks!


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Old 09-23-2010
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A little update. The Racor has drained again.

I bought a Racor seal service kit, which has replacements for all the seals in the unit. I'll go through it on the weekend, replacing everything. This boat is 20 years old, and I've found that all the gaskets have needed to be replaced (portlight, hatch, pumps, etc.) So perhaps that will work.

The seal kit also describes how to replace the o-rings. It suggested covering the gaskets in "Parker o-seal lube" or automotive oil. I had covered them in diesel - perhaps grease will provide an airtight seal.

I also found some other references to racors losing prime, or allowing fuel to bleedback. They suggested the problem could be the check ball. I'll look that over as well.
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Old 09-24-2010
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I'm not familiar with the set-up, but with the filter mounted that high, it is also likely to be higher than the injectors, and I wonder if the return line from the injectors/pump could be allowing for siphoning of the filter over time. Try blocking the return line to the tank and see what happens.
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Old 09-24-2010
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As far as your fuel pump continuously running...from what you have explained you have a return line that always will cause the pump to run...This is normal in a lot if not most diesel fuel systems.
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Old 09-24-2010
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Ah, the return line! I hadn't considered that, thanks.

Kary - the racor is above the injectors so it is possible for the siphon to be happening with that route. However I'm suspicious of that as this setup used to work perfectly before I had the tank replaced (with an identical tank.) Working on the principal of "when something goes wrong make sure the last few things you did didn't mess it up" I haven't ever touched the return line/injectors. But I'll add this to my list of things to go through if my next steps don't work.

When I block the fuel pickup line to the racor, it doesn't drain. This suggests to me that if the air leak is in the racor, that the fuel must be returning via the pickup line not the return line (as that route is still open when the pick up line is blocked.) Its a theory anyway.

Stillraining - thanks, I think the return line could explain why the pump runs continuously at a slow rate. I need to learn more about diesel engines! I had thought the high pressure pump would block the fuel getting to the injectors if the engine wasn't running. Cool.

I still like my current theory of the gaskets being bad inside the racor. The tank was out of the boat for about two months, during which the racor was empty. So any internal gaskets were exposed to air. If the gaskets were 20 years old (ie, have never been replaced before) then they could well have dried out and be in need of replacing...
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Old 09-25-2010
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The racor 500fg has a big ring seal, but it also has a smaller o-ring seal on the shaft. It could also leak air.
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Old 09-25-2010
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FWIW...Several of my engines will run without the electric fuel pump running once primed including my Perkins boat engine and it has no mechanical lift pump...so if you get tired of listening to the pump try it...but if ever in a tight spot were loosing power would be detrimental keep it on for insurance..
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