Symptoms of Clogged Racor

[osd9]

I just finished reading Quality Time's post in another thread where he had to change his Racor Filter while he was out on the bay away from the dock.

I know I shouldn't say this, but I've not yet experienced a clogged Racor/fuel filter.....(I can hear Gary laughing already).....while under way, or at the dock for that matter. In my limited time/experience with diesels, I've changed the filters in the begining of the season and nothing in between.

I have all the necessary spare filters (primary and secondary), necessary tools and my 'emergency' 1 gallon can of diesel fuel on board.

My real question is....what are the symptoms of a clogged filter? How does the boat react? Do you change out the filters on both sides when one is clogged or wait to get back to the dock to the other side?

 

[quality time]

Dom,
This was only my second time changing a Racor ever. Luckily the first time was at the dock with no pressure. When we left for Still Pond I felt a lag when getting on plane. After a second it passsed and I flipped on the sync. I saw the sync gage dip then come back and it cleared out. I had never experienced this before and just kept an eye on the tachs on the way down, didn't happen again. I was nervous that I would see the same thing when leaving to return home and I did but way worse. Couldn't get on plane and the port tach was diving all over the place. I started limping home at about 1500 where I didnt notice any RPM changes. After about 15 mins the port started to drop 30-40 RPM and then come back. I was a few hours away from the marina at this speed so I decided to go for it. Shut them down out of the channel and told my wife to tell me when I had a clear window as far as wave action. Got rocked around bad a few times but, shut the valve off, yanked the old (black and funky) filter out and slapped the new one in. New o-ring in the lid and added a little fuel from my 1 gallon can that I carry and prayed that I wouldn't get any air in the system. Fired up and got back home alot faster than 8 knots. I will change the other one this weekend. All this action and never even woke up the toddler!

 

[fwebster]

Dominic,

On your Caterpillars, the system is tight enough that you won't suck air into it, but you will have fuel starvation when the filter gets so clogged that it won't flow as much as the engines require. Depending upon which Racor and how many of them you have, the flow rate may mean that the engines just slow down to some sustainable RPM or they may slow down to something like a fast idle. I have dual 900MA's on each engine and my engines will slow to about 2300....then to 2100.....then to 2000, but I usually have plenty of notice so I can get to calm water or the dock to change elements. It usually happens to one or the other but not both at the same time.

For non-Caterpillar diesel owners, I don't know if other systems can handle starvation without ingesting some air, but that isn't a good thing since purging air from a diesel can be a real job.

 

[Jaws]

I had a similar experience and the Racors were just changed in April, 43 engine hrs. ago. Trouble getting the one motor up to speed and on plane.
Took the Racors out and they were black. It's only a 10-15 minute job per side with the twin canisters and I will change them faithfully twice per season from now on, at the dock!Check Frank W. recommendation on online ordering; they're inexpensive and easy to do; just make sure you prime, prime, prime. Then fire the motors up on a fast idle for a couple of minutes. (Actually I change out the on-engine 2 micron primaries at the same time but fill them with diesel first before priming. You don't have to with the Racors unless you slop a lot or drain off some water.)

 

[quality time]

(Actually I change out the on-engine 2 micron primaries at the same time but fill them with diesel first before priming. You don't have to with the Racors unless you slop a lot or drain off some water.)

Not arguing with you, but I thought I've read on here not to pre-fill the 2 micron filters because the fuel has not been filtered. I use the priming pump to fill them once installed. :huh:

 

[Jaws]

Yes, I was under that impression as well so I spoke with the mechanic. If you have Cummins like I do, the priming plunger is a little thumb-operated plunger that takes forever to fill the on-engine filter if it is empty. I think CAT's have a better priming pump. So, I simply purchased a bit of "road" diesel from a station that sells a lot (thinking the supply is clean and fresh) and I hope that there is not much to worry about. Either you take the chance or prime for fifteen minutes (the starboard engine is a bear to get at) and lose all feeling in your thumb.

It's worked out fine for me.

 

[never monday]

Dominic,
For non-Caterpillar diesel owners, I don't know if other systems can handle starvation without ingesting some air, but that isn't a good thing since purging air from a diesel can be a real job.

Frank,
This is more a testament to the quality of the SeaRays. With the pressed flare fitting on the fuel system. It's almost never a problem. With other installations that use hose clamps air can be ingested rather easily.

Not arguing with you, but I thought I've read on here not to pre-fill the 2 micron filters because the fuel has not been filtered. I use the priming pump to fill them once installed. :huh:

I can go both ways on pre filling. If you have an older mechanically injected engine. Don't worry and pre fill. If you have an electronic engine. Use the priming pump. Now, I have seen 31 series Cat's installed in a few other boats that did not have priming pumps installed. Most notably these boats were built in Wisconsin and New Jersey.

 

[fwebster]

Caterpillar does have a good priming pump, but they also have a ball valve with which you take the priming pump in or out of the system. It works very nicely except when the knurled knob slips on the shaft and you cannot tell whethere it is open or closed. Open and the pump leaks all the time but you can prine the filters; anywhere less than open and you will pump your butt off trying to fill a filter and it still leaks all the time. Correspondingly, if the valve is closed, it doesn't leak, but if it is slightly open, it still leaks all the time.

While the design is good and the pump works, if they get a little age on them and the knurled knob slips any, it becomes a guessing game to find open and closed. I don't mess with the priming pumps; I manually fill my filters and get on with the program.

Pat,

My point on other non-Cat engines is: I've never had one run out of fuel so I just don't know and I don't post stuff here I don't know about.

I do know that Cat's unit injection has only one fuel line feeding the fuel chamber where others like Cummins, Kubotas, Perkins, etc. have individual fuel lines from the distribution pump to the injectors and it stands to reason that there is more potential for leaks. But, I do agree that properly attached and torqued flare fittings should be trouble free.

I also know (the jhard way!) that air will leak into a fuel system in a place where fuel won't leak out.

 

[never monday]

Pat,

My point on other non-Cat engines is: I've never had one run out of fuel so I just don't know and I don't post stuff here I don't know about.

I'm kind of weak with Cat, so it's all yours. LOL

I do know that Cat's unit injection has only one fuel line feeding the fuel chamber where others like Cummins, Kubotas, Perkins, etc. have individual fuel lines from the distribution pump to the injectors and it stands to reason that there is more potential for leaks. But, I do agree that properly attached and torqued flare fittings should be trouble free.

I also know (the jhard way!) that air will leak into a fuel system in a place where fuel won't leak out.

I think what your describing is more the difference between a mechanical system and a electronic unit or common rail system. Am I on target?

The steel pipes from the injection pump to the injectors are almost never a problem. They are pretty thick walled. Having to carry fuel around 2500 PSI to the injectors.
The newer CR engines also use the single line from the high pressure pump to the fuel rail. Then most will use a smaller steel pipe to the injector.
Most commonly I find leaks on the boat side of the system. Upstream from the lift pump. The engine builders have gotten so go at what they do. Failures are just not common.

 

[never monday]

Dom,
To answer your original question.
You'll notice a decrease in power and max achievable RPM. Then there might be just the slightest stumble at idle. If you look in the filter bowls they should be black.

 

[fwebster]

Pat,

Think of the Cat unit injection system as a precurser to common rail. It is a purely mechanical systm. The Caterpillar pump delivers the fuel at injection pressure to a chamber located in the head thru a single fuel line. The injectors padd thru that fuel chamber and are opened and close by cam action, push rods and rocker arms, just like overhead valves. The system is expensive to produce but is supremely simple. Since timing and duration are controlled by how the injectors are set and by cam action, Cats can be adjusted with a little more precision than a regular mechanical system like Cummins uses which is why they are typically smoke free and start so easily.

 

[Jaws]

Dom,
To answer your original question.
You'll notice a decrease in power and max achievable RPM. Then there might be just the slightest stumble at idle. If you look in the filter bowls they should be black.

I lost some WOT rpm 2650 down to 2550 and thought it was some bottom fouling but I checked the Racor bowls. They were clear, just red diesel. It wasn't until I took the filters out that I could see how fouled they were.

B.T.W. From now on complete filter changes with Racors X 4 and on-engine fuel filters should take no more than an hour and about $50-55 total.

James

 

[Blown284]

Thanks, this thread is helping me with a fellow SR owner who has one engine that has done something similar to what is explained about (up/down rpm). He's going to change all filters and see if that helps. Next step will be fuel polishing if needed.

 

[BlueYonder]

Not arguing with you, but I thought I've read on here not to pre-fill the 2 micron filters because the fuel has not been filtered. I use the priming pump to fill them once installed. :huh:

If you have an older, non common rail diesel you can fill pre fill the filter with clean fuel. If you have a newer, common rail diesel, do not pre fill the on engine filter. There is a reason that filter is 2 micron, the tiniest piece of grit can trash an injector and cause significant damage. My QSC has an electric pump that will fill the filter by turning the key on and off activating the pump (the instructions are in the manual).

 

[Almightys]

Anyone know what kind of PITA this is for a boat with Detroit’s?
I just purchased this summer and part of my plan for maintenance is to change all the filters so I have a baseline for a schedule. It appears to be a dual filtration system