Racor 120-Series Fuel Filter/Water Separator

Good morning all.

I have a Racor 120 fuel filter in the engine compartment and it is the model that has the dual NPT inlets and outlets. Only one of the inlet/outlet pairs are used and the other pair is blocked with the plastic plugs that I assume came with the unit when it was new. The original vent plug was also plastic and it broke off a few years ago and I replaced it with the brass one. I have read the installation instructions and there is no mention of replacing the plastic plugs with metal.

Are the unused inlets a possible source of air getting into the injection system, if the plugs are leaking? I'm thinking about replacing them with metal plugs when I get into the fuel system later this month to chase an air leak.

Since shortly after my last filter change I have experienced hard starts and this has morphed into the engine stalling about 30-60 seconds after a cold start, about 3 out of 4 times, if the engine has not been started for a couple days or longer. After a quick prime and it starts right back up and clears the rest of the air and runs smoothly. This has been mildly annoying, but we've learned to make sure it will accept a good bit of throttle before starting out. I loathe working with the fuel system because I always make a mess.

I have found several clamps loose and tightened them. Then I replaced the two short hoses on the spin-on filter because they were clearly spongy and a likely source of air. The situation today is that the engine occasionally stalls shortly after startup and has to be primed, then runs fine. No water or sediment in the Racor bowl. The fuel is clean and have had two re-fuelings since this problem started.

The engine has 1600 hours. The fuel supply hose has a loop that goes above the waterline and then goes into the Racor. Out of the Racor it goes through an electric pump that is only used for priming the system. Then to the mechanical low-pressure lift pump (?) on the engine, to the spin-on filter and then to the injector pump.

Any advice would be appreciated. The next thing I plan to do is re-seat the Racor filter and replace those plastic plugs with metal.

Cheers,

I feel your pain

IIRC, one of the main reasons that sailors convert to the larger 500 $erie$ Racor is that there is only one ring gasket at the top of a bowl. Your series, like mine, has the spinn-on element with gasket at top and a second gasket at the bottom for the sediment bowl.
That's a lot of gasket area total for a miniscule vacuum leak to happen.

Then there's the little plastic pump plunger at the top, if yours has this. Then, as you have noticed, there are ports with plugs and ports for the fuel in and out.
That model has a LOT of places for an air seepage under vacuum.
You may recall my older thread on how I finally replaced the original Racor with a new one when we reformatted the fuel system. One reason, other than that old model being out of production, was that we had a lot of problem keeping it tight under vacuum. We figured that it finally could have been the primer pump plunger, but never were sure.

So, as per grim usual, I cannot diagnose your problem... but some of the symptoms do sound familiar!

I have a good friend who has a Racor (think the same model as you) that had an air leak from a split nylon plug, as you suspect. He contacted Racor, and obtained a replacement, which was metal.

I'm guessing you have a 5432 Universal? I went crazy looking for a reason for a hard starting problem on mine. The problem ended up being the bleed valve on the IP was leaking air. It would allow the fuel to pull back from the IP, a vacuum leak after shutdown. Take a close look at that bleed valve, could be the problem. FWIW, I have a Racor 500 turbine series. Its great! Filter is expensive, the elements are cheap though. RT

5432

Yes, I have the 5432 diesel. Thanks for the tips. I will proceed with the plug replacement and filter re-seat on the Racor and see what happens. I think I have a maintenance manual for the 5432 that might show the details of the bleeder screw. Is that a difficult repair, Rob?

If it turns out to be one of the possible Racor issues, I'll probably never know what the problem was, unless one of the plastic plugs is split. But one problem in 7 years isn't so bad.

Thanks guys. I'll report in a couple weeks about what I found.

PS - All that bottom blister repair from the '08-'09 layup looked real good on this haulout, about 20 months since we put it back in the water. No new ones popped up in the 8 days it was out. The cutless bearing looked good, and the shaft alignment out of the log and though the strut was excellent - just like I left it.