ZZ13
Well-Known Member
ttmott you were right on the money. The leak is coming from the fuel tank return line fitting. I just gotta remove a few lines in the way so I can get a wrench to it. Thank you.
Diesel fuel line fittings and selector valve questions
- Thread starter ZZ13
- Start date
ZZ13
Well-Known Member
One question. I have to remove some lines on the valve that are in the way of getting a wrench on the target fitting. This will introduce some air in those lines i take off. These are fully mechanical Cummins 6cta 450 Diamonds. Do I need to do anything special to clear the air from the line, other than pumping the manual primer pump next to the injector pump?
my3sons
Well-Known Member
- Feb 24, 2009
- 3,046
- Boat Info
- 2004 400DB, Onan 9 kw Generator, Highfield RIB,
- Engines
- Cummins 6CTA M-3
You could drain the racors then refill them after your lines are all hooked up, any air in the lines should pass through while they fill (under gravity from 1/2 full tanks or better) . I would just start them up and they might stumble a bit but will most likely be fine. If they stall, pump the plunger.
ZZ13
Well-Known Member
I finally got around to isolating this today. Both fittings on the return line from the tank to the valve are leaking at the crimp. The port hose has no slack and is actually under tension. Either someone already cut it back to refit it, or the factory cut it short. My mechanic is going to replace that entire line. The starboard line has plenty of slack to for him to cut it off and refit it.
ZZ13
Well-Known Member
So my initial analysis was wrong. The leak is not at the hydraulic fitting end as I originally thought. It's at the tapered end of the coupler where the tapered end screws into the valve. Looks like I have three options. 1)just tightened it, 2)loosen it and put sealant on it before tightening, or 3) replace the coupler. It's the third fitting from the front that is black and has shiney fuel on the upper threads.
Bill
That is actually a tapered thread or better known as National Pipe Taper (NPT). Remove the fitting clean and either apply a fuel compatible thread sealant or put three wraps of teflon tape around the threads and put back together. Tighten securely. Make sure there are no cracks in the valve body as that may be where the leak is actually coming from. If someone over-tightened the NPT fitting that can crack the valve body.
Tom
That is actually a tapered thread or better known as National Pipe Taper (NPT). Remove the fitting clean and either apply a fuel compatible thread sealant or put three wraps of teflon tape around the threads and put back together. Tighten securely. Make sure there are no cracks in the valve body as that may be where the leak is actually coming from. If someone over-tightened the NPT fitting that can crack the valve body.
Tom
ZZ13
Well-Known Member
Thanks Tom. That's exactly what I did. There were no cracks. It was clearly under tightened. I got several more threads into it when I tightened it without too much effort. It only took me 6 months to get around to doing this one. Ha!
