Fuel Filter Problem?-gctid366571

[Guest]

We are in the process of moving our 4550 from Shreveport LA back to our home in Green Cove Springs, FL and had a little problem on the Gulf of Mexico crossing. Departed Apalachicola FL yesterday morning for Steinhatchee Fl, about 80nm on a very confused sea. Our course Eastbound, we had 10 to 15 kt winds from the south west with a 3' or better swell from the south. Needless to say, it stirred the fuel tanks pretty good. I had filled up the day before but obviously there was a whole lot of sloshing going on.

About 30 miles out from Steinhatchee we lost the starboard engine. I have the original style racor canister filters and changed it out without too much grief (hot engine room, a loud port engine running at 1800 rpm very close by and still a lot of rockin and rollin, not feelin the best after that one.) Engine cranked ok and ran for about 30 minuites and started losing rpm's again. This time I decided to shut her down and continue on the port engine alone. After about 30 minutes, I recranked the engine and decided to run her at a reduced rpm (1200 on starboard, 1800 on the port) This lasted about 20 minutes and she started to die again. Ran the rest of the way on one and cranked her for docking, no problem.

This morning I changed out the filter while tied to the dock (much easier!!!!!) and drained the water separator and changed the engine fuel filter. All looked good with a little trash in the new racor that was installed underway. This is what has me puzzled. By my best estimate, we should not be loosing the engine due to that filter, just was not that dirty.

We will be continuing the trip in a few days.

Any thoughts?

Rod

[p91473]

Check the tank fitting. Some of these have anti-siphon valves, a little ball check valve. Mine has clogged there. Also check the tank pickup tube. Hope you have good access.

[jmcannonball]

+1 on the pickup tube. With all the sloshing around it's pretty safe to say some crap may be clogging the screen. With good Racor filters (mine have the plastic bowls with drain plug), you can probably remove the screen over the bottom of the pickup tube and let the filter catch everything. Just a thought.

[mmichellich]

jmcannonball wrote:
+1 on the pickup tube. With all the sloshing around it's pretty safe to say some crap may be clogging the screen. With good Racor filters (mine have the plastic bowls with drain plug), you can probably remove the screen over the bottom of the pickup tube and let the filter catch everything. Just a thought.

+1

[LTCret]

Have you checked/changed the on-engine filter?

[boatworkfl]

A temp. fix at best is to clean the screen, have the tanks professionally cleaned.

[Guest]

Yes I did change the engine mounted fuel filter, looked ok.

So if I am understanding correctly, there is a screen on the bottom of the pickup tube?

Having not seen this assembly, just wanting to be sure.

There is easy access to the top of the starboard tank so this should be an easy to check.

Rod

[cosmo777]

Do you have crossover valves?

Maybe try running both engines off the port tank and see if the starboard engine runs fine.

This would rule out your filters and isolate the issue to upstream of the valves.

[Guest]

Is there any way that you can isolate the pickup fuel line, and then have air shot down to have some of the "stuff" blown off the screen. Would putting w large amount of "Fuel Doctor" into the tank/s, help break it down, so it will pass the screen, and then be picked up in the filter?

Cheers

[Guest]

Pat

I was thinking this same thing late last night. I will be able to run both engines at the dock off of the starboard tank and if they continue to run for 20 minutes or so, I would think there is not a problem.

Also late last night I was wondering if in fact there is a screen at all. When removing the canister filters, I too have the clear bowls on the bottom of the filter and both bowls had a bit of junk in them. Does not make a lot of sense to have a fine screen on the bottom of the pickup tube that would clog if you have a filter, bowl, water separator and engine filter that are supposed to do this job and are accessible?

I can easily remove the fuel line off of the pickup side of the racor and back blow the line but it was mentioned there is a backflow valve? I did have this valve on an old Mainship that I owned but I am not sure on this application.

Rod

[boatworkfl]

Should be easy to identify the type of fitting at the pick up tube.

The hex portion between the hose barb abd the threaded portion in usually longer and most are made of aluminum.

Anti-Siphon valves are an integral part of the marine fuel system. There main function is safety related. They prevent a ruptured or leaking fuel line from filling your bilge with explosive fuel.

How an anti-siphon valve works is actually quite simple. Attachment 427The valve which is really a fitting has an orifice through which fuel passes, on the downstream side of that orifice is a small steel ball. The steel ball is held against that orifice with a spring. If their is no suction from a fuel pump on the downstream side, the spring presses the steel ball against the orifice effectively blocking the fuel flow. Once the fuel pump develops sufficient pressure the steel ball compresses the spring and unseats allowing fuel to flow.

Debris or corrosion due to water in the fuel are the two most common culprits that cause these Attachment 429valves to malfunction. If you suspect you have a malfunctioning anti-siphon valve you can remove it and install a threaded nipple into the fuel line to see if the problem goes away. If this resolves the problem you can try cleaning the valve with carburetor cleaner or by blowing air through it with an air hose. If it is clean you should be able to blow air through it in one direction only. If the valve is bad don't leave the fuel line unprotected without an anti-siphon valve, replace the faulty one with a new one immediately.

[Foster]

Check the air vent on the tank to see if it's blocked. In the Diesel class I took, that was one of the "exam" problems. Engine would run for 20-30 mins, slow and then stop. After 20 mins it would start back up and run for another 20-30 mins. Issue was a clogged air vent. It would not let air flow into the tank, and at the 20 min mark it the pump could not draw the fuel out. If you opened the fuel system to change the filter, that would release the pressure.

Matches pretty much what you described in your post.

[ksanders]

Foster wrote:
Check the air vent on the tank to see if it's blocked. In the Diesel class I took, that was one of the "exam" problems. Engine would run for 20-30 mins, slow and then stop. After 20 mins it would start back up and run for another 20-30 mins. Issue was a clogged air vent. It would not let air flow into the tank, and at the 20 min mark it the pump could not draw the fuel out. If you opened the fuel system to change the filter, that would release the pressure.

Matches pretty much what you described in your post.

Thats a really good idea!

Just open up a fuel fill and see if the problem goes away.

[johnrupp]

A blocked or partially blocked fuel return line will cause the problems you are having.

[Guest]

I agree that the vent would cause the problem but I do not think that is it in this case. We have been running for about 8 days now and I bought fuel at the start of the trip and 2 times since. I have the suction cup vent overflow bottles that are attached to the hull over the vent during fueling and I have gotten a good indication that the lines are clear at all fuelings, both tanks. I will check this again as we will top off the tanks before leaving Steinhatchee in route to Tarpon Springs.

Can't think of a good way to check the return line other than pull the line and crank the engine catching the flow with a portable fuel jug?

All of these suggestions are great, please keep it coming. I am for sure checking the pickup tube and then running both engines at the dock off of the starboard tank for a bit. Of course I will do this before filling the fuel tanks so as not to create another problem with overflowing the port tank.

Rod