need to install 2 new supply and returns for the Heater and Polisher

[nyrussell]

I just found out the person that installed our diesel heater did not do so to manufacturer specifications. He was supposed to have put the supply and return lines into the fuel tank itself, not tapped the generators lines. I am now having flame outs and the company I brought in to fix this and a myriad of other hassles with the install says this should be the reason for the flame outs.

Question 1: How do I go about tapping the main tank under the queen bed in the aft cabin? And then make sure the tank is closed up again correctly?

Question 2: can i run regular fuel lines from the tap or do I need to use copper tubing.

I plan to run the same setup for the polisher as well. Hate to do the job twice.

Noel

PS this needs to get done soon as our 2 month old is aboard now

 

[Genesis]

You should be ok with a dual tap if you get a Walbro or other small continuous duty diesel pump to insure positive pressure to the heater when it is running.

Adding a tap is not terribly difficult, but its a major pain in the butt if you also need to add a new dip tube!

 

[nyrussell]

Please elaborate as the heater has a 15 gph fuel pump and the polisher has an 80 gph fuel pump. I was intending on tapping each seperately. Also, I do need to add the dipsticks etc....

Noel

 

[Genesis]

The problem you're running into is that diesel fuel when put under a vacuum will pull some dissolved air out - this, when it gets to the high pressure pump on the heater causes the atomized fuel flow to be momentarily interrupted and the flame goes out. The safety system detects this and (of course) shuts off the fuel flow.

Kinda like what happens in an engine but there's no rotational momentum so once its out - its out.

Inadequate supply pipe size or excessive restriction tends to cause this.

There's no inherent problem with sharing a supply feed, then splitting it off before the filter for each consumer, provided the pipe is big enough. Ditto on the return side. The problem occurs when you've got a pipe (or hose) just big enough for the original consumer of the fuel, and add another draw to it.

Check restriction so you know what's going on and aren't guessing.

 

[Trojan]

You probably need check valves in both lines after the split. You are most likely sucking air from the other unit. I would try check valves first before I operate on that tank. Remember You draw from the least resistance and that tank is probably a long distance from your units. If your tanks are in the stern like most. It's doubtful that your starving the unit from too small a line. You can also gain fuel flow by putting the tee right at the tank with a check valve in each line. You never put a tee in the vacuum side of a supply line without check valves. You also must consider the the height of the head that the pumps will draw.



BILL

 

[nyrussell]

Okay, I can tee directly off the tank using the dipstick already installed rather than cutting a new hole and adding a dipstick is what I understand. This might not be up to manufacturers specs though it is better than teed right in front of the generators racor I hope. I can then pull a rubber fuel line off the T still right?

Thanks and keep the answers coming as I need to solve this in the next 2 weekends. (without putting diesel all over the boat).

Noel

 

[Genesis]

Its just a matter of restriction and back-feed.... (pulling air back into the heater's feed)

A check valve might take care of it....

I'd measure before you start cutting things up...

 

[nyrussell]

Okay, check valves can be gotten at Boater's World? Also, how do i check the restriction? And then i install the check valve where in the line exactly, I can provide pictures.

Guess I need a diesel course or two.

Noel

 

[Trojan]

Put one check in each line right after the Tee and keep the Tee right close to the tank. Don't down size anything. If you can, get the Tee as large as the tank siphon tube and go from there. Don't get small checks ether. There is a restriction through the check. You didn't say what size the fuel lines were or what they were made of. Shut offs would be good also. But get the units running first. Good Luck.



Bill

 

[nyrussell]

i Know they are metel, not sure if they are copper or steel. Will check that and sizes tonight. Also how does one check restriction? and where can i get the T's and other items besides the fuel line? Might as well change all the lines as long as i am about this i think? After i get the heater and polisher going...

Oh yes, Thanks to all. And why can't any of you guys be up here in the NYC environs?

Noel

 

[Genesis]

Checking restriction can be done with a vaccum gauge - you should be able to get one at any decent auto parts store. Standard 1/4 or 1/8" threaded (NPT) - screws right into a "T".

If you put a piece of clear line in the middle temporarily you'll see if you're getting air in the line from the genset line backfeeding when its off and the heater is on. I bet that's what's happening, or, if its happening when both are running its likely air being pulled out of the fuel due to excessive vacuum.

"T"s and hose barbs can be bought anywhere - brass/bronze parts are fine for this (diesel fuel), you can get them at any decent hardware store. Get some fuel-rated pipe dope (Autozone or Carmax should have it) for sealing the pipe joints - teflon tape should not be used as if little bits of it get into the fuel you won't like what it does to the equipment on the other end! Yeah, I know you have filters to stop that but why take the chance?