Fuel draw problem can't figure out

I have a single engine trawler. The engine is a Cummins QSB 5.9 480hp. My problem is I cannot draw fuel from my Starboard tank. I close all valves from my Port tank (inc. returns) and still draw from there. I checked to make sure that the lines were marked correctly and they were going to the correct tank. I am totally confused why this is happening?

Anyone with a possible solution please let me know as that fuel in my Starboard tank must be used soon. I keep Biodiesel in it but it is getting old.

Thanks!

Maybe the outlet opening is blocked with crud inside the tank?
But if you close all the valves on the port tank how can it still draw from there? Are they Gate valves, which can malfunction?

jwinner said:

I have a single engine trawler. The engine is a Cummins QSB 5.9 480hp. My problem is I cannot draw fuel from my Starboard tank. I close all valves from my Port tank (inc. returns) and still draw from there. I checked to make sure that the lines were marked correctly and they were going to the correct tank. I am totally confused why this is happening?

Anyone with a possible solution please let me know as that fuel in my Starboard tank must be used soon. I keep Biodiesel in it but it is getting old.

Thanks!

Click to expand...

You need to go back and recheck your work. Somehow fuel is getting from your port tank to the engine. If you can't figure it out, get someone else to check it. It's not something that can be done over the Internet.

Yes, I will recheck my work as I know this is "Impossible". The next time out (if I still come up with the same conclusion) I am going to close the Starboard valves and leave the Port valves open. I don't believe there is crud in the Starboard tank. I know when I bought her (new) in 2010 I took her 650 miles around Florida and I had all valves open and she did eventually draw from both tanks. That is what confuses me? I realize (like most problems posted here) that it cannot be fixed on the Internet. I was just hoping someone might have some ideas. Thanks again!

You may have a bad valve on the port tank. . Is it higher than the starboard tanks?? Make sure you don't have a cross over fuel line between the tanks. Some manufactures will use these as a method of ensuring self leveling. I have four tanks, two port and two starboard, with a cross over line between the two sides. My crossover is separate from the engine feed lines, but they don't have to be.

On a side note, it is not uncommon that debris blocks the fuel pickup inside the tank, sporadically. Especially newer vessels where construction crud was not policed.

I don't know if I have a crossover line. When I get back to the boat I am going to go through it and make sure I followed the fuel lines correctly. The boat Port tank is slightly higher than the Starboard. I forgot to check the vent as there might be a Mud Dobber or a wasp nest there. We do have a problem here in Florida with them. I don't think it is the vent unless there is a crossover that I am unaware of. I know it is something I am overlooking and a crossover line is one of them. I am going to have another person double check me as God knows I have screwed up before!!

I do thank all of you guys with being patient with my stupidity.

Thanks Sunchaser but if there was crud in there I think I would have run out of fuel with the Port closed. One possibility... there might be a crossover line which would account for only drawing from the Port tank if Starboard were blocked. I wonder what would happen if I closed both tanks (returns also) I assume I would run dry but the way it is acting I would still draw from the Port tank. If that is the case then I do have a faulty gate valve.

First you must determine if you have fuel flow from the bad tank to and through your gate valve. This is easy to do if your fuel level is above the gate valve, is it? Is so, take some spare fuel hose and fittings with you so you can drain into a bucket.

Double check that you know where all lines and valves are including fuel tank pickups and returns. As previously stated, internet trouble shooting is a guess at best since we are all in dark. Is the vessel still under warranty?

My guess is one or more of your gates valves are not actually opening or closing. The handle turns but the valve is not working.

If that turns out not to be the case then you may need to start taking things apart and blowing air through the lines. Or run a line right from the tank to your filter to see if you can at least draw from it that way to answer whether the pick up is clogged.

Off hand I don't see how a cross over valve would create this issue.

Common for three way valves to be mis-positioned as aiming arrow does not always correspond to flow port. Also need to know if there is a crossover line. Time to do more homework!!

Thanks Sunchaser & Capt. Bill11,

I realize there is no way to determine anything on the internet. I have taken note of all the suggestions and appreciate them all. I have to get back to the boat (60 miles away) to really look at this again. I will have my friend who also has a boat take a look too. I have to think like you guys that something maybe blocking or a bad valve. Will let you know as soon as I know.

Thanks!!

Didn't mention what kind of tanks or where the fuel comes out...but if top feed...the tanks may have anti-siphon barbs at the pickups...I don't think they are required for diesel tanks but are sometimes used.

Could be a bad one that is sticking.

You close all valves to one tank and still draw from it???
Clearly something wrong there. I suspect a valving issue.

Greetings,
While I'm not ruling out a "valve issue", have you checked the fuel lines. The rubber lines have been known to de-laminate and appear fine on the outside but the inner liner sucks the line closed on fuel draw. Just sayin'....Fuel line is cheap.

When I bought my boat and brought it up from Florida, about 3/4's the way I notice we had a list to starboad. I went below to check and found the starboard tank was full and the port was at a 1/4. Turns out the crossover valves were open and all the fuel was being pulled from port and the returns were going to starboard. I adjusted the valves and stopped and got fuel to balance the tank. We caught it just in time, any longer and we would of been dumping out the overflow.

Agree with the others. I would go further and say that for fuel manifolds, you should plan on building yourself a diagram and a valve placement chart. The chart should be a cheat sheet that says in plain English which tanks you want to run and the associated valve placements.

I don't know why, but every time I get in a hurry and try to eyeball these things, I end up doing something wrong. I've caught myself verbally stating what position a particular valve should be in, then upon a recheck 5 minutes later I find I did just the opposite, even though I verbally had the right answer. I just don't get it. I'm just saying to figure it all out, write it on a chart and then follow the chart when you need to make a change use the chart instead of trying to visualize it.

I'm pretty good when it comes to mechanical visualization, yet I still screw this up without the chart. I suspect others have the same problem.