uniflite 42 ft question

[john hitchcock]

I have the above boat.  The engines have not run in months but are in good shape. Now that I am trying to start them I have a problem getting fuel to them.  I know I have to prime the filters but my question is...The supply line comes from the TOP of the tanks, not the bottom.  Therfore by the force of gravity the fuel sould run back into the tank and leave a airblock...right?? This would then be a constant problem.  Anybody suggest anything??

 

Thanks

 

John

[e b]

the supply outlet is on top of the tank but inside the tank there is a dip tube that goes to the bottom, sometimes on the bottom of the tube thee is a mesh strainer, usually the strainer and / or bottom of tube is slightly above the bottom to prevent dirt / water from being sucked up if there is any. depending on tank location / fuel level the fuel might be above or bellow the engine the fuel pumps should have no problem priming the line unless the check valve in the pump is dirty or sticking.

eric

---

Date: Sat, 7 Apr 2012 09:10:02 -0400
Subject: [UnifliteWorld] uniflite 42 ft question
From: evange...@gmail.com
To: unifli...@googlegroups.com

I have the above boat.  The engines have not run in months but are in good shape. Now that I am trying to start them I have a problem getting fuel to them.  I know I have to prime the filters but my question is...The supply line comes from the TOP of the tanks, not the bottom.  Therfore by the force of gravity the fuel sould run back into the tank and leave a airblock...right?? This would then be a constant problem.  Anybody suggest anything??

 

Thanks

 

John

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[berni...@aol.com]

Eric is correct and John's question is valid because it would seem
that having a gravity fed fuel system would work better, but then all
the sediment would be sent through your engine and that's not good at
all. I have Cummins 903 naturals on my boat and they are very easy to
bleed. There's a bleed screw at the top of the engine in the valley,
it's on the fuel pump. The few times I've had to bleed the engines I
just cracked the screws open a little and turned over the engines
until fuel started flowing from the screw. While you're still turning
the engine over, tighten the bleed screw and the engines will run just
fine. If the fuel lines have a cronic problem of air in them then you
may want to check the connections from the pick-up tube to the fuel
pump. If any of the fittings are loose, air will be sucked into your
system and stop the engine. There shouldn't be too many fittings and
should only take a few minutes to go through and tighten everything
up..

Also John, note that you have another fuel line that returns to your
fuel tank from the engine. That is called the fuel return line and it
returns unused fuel back to the tank. You may ask, why send more fuel
than the engine will burn and then return it back to the tanks. The
answr is, it ensures that enough fuel is getting to the engines but
just as importantly the extra fuel acts as a coolant and lubricant for
components on the engine.

On your boat you probably have a grouping of ball valves that have
fuel lines running in and out of them. They are there so you can
choose where the fuel is coming from and going to. If you need to
transfer fuel from port to starboard or forward or aft you can open
and close the appropriate valves to move the fuel around and transfer
weight. Remember the fuel return line? You can pull fuel from one tank
and return it to a different one effecting the boat's trim, list and
running attitude.

All the best,
Bernie
1973 42' Aft Cabin
Cummins 903

On Apr 7, 6:41 am, e b <gon2...@msn.com> wrote:
> the supply outlet is on top of the tank but inside the tank there is a dip tube that goes to the bottom, sometimes on the bottom of the tube thee is a mesh strainer, usually the strainer and / or bottom of tube is slightly above the bottom to prevent dirt / water from being sucked up if there is any. depending on tank location / fuel level the fuel might be above or bellow the engine the fuel pumps should have no problem priming the line unless the check valve in the pump is dirty or sticking.
> eric
>

> Date: Sat, 7 Apr 2012 09:10:02 -0400
> Subject: [UnifliteWorld] uniflite 42 ft question

> From: evangelfi...@gmail.com

[Bernie Meisinger]

Hello John,

 

Eric is correct there is a pick-up tube that reaches to almost the bottom of the tank and suction from of the fuel pump draws fuel to the engine. If you need to bleed your system it may be easier than you think. You’re also correct that the fuel filters have to be full before you bleed but unless you ran the fuel out of the filters there’s probably enough to get the engines started.

 

I have a 42 aft cabin with Cummins 903 naturally aspirated diesel engines and they are very easy to bleed. The fuel pump is on top of the engine in the valley, (they are V8 engines) on the forward part of the fuel pump is a bleed screw. I just open that bleed screw and turn the engine over (this works better with two people) and when the fuel starts flowing I close the bleed screw and the engine runs just fine.

 

If you often find yourself bleeding the fuel system then there is air being sucked into the fuel lines before the fuel gets to the pump. There are a few fittings between the tank and the pump and it should only take a few minutes to check for any loose fittings.

 

Something else that you may have noticed is that there is another hose or tube running from the engine back to the fuel tank. That is called a fuel return hose and that returns unused fuel to the tank. Why have so much extra fuel flow from the tank that it has to be returned? The answer is that these engines are designed to use that extra fuel flowing through internal parts to act as a coolant and lubricant. There’s also a residual benefit from the return hose.

 

Having fuel returned to the tank allows you to decide where that fuel goes. On you 42 there should be a series of ball valves with fuel and return lines running to and from them. This allows you to take fuel from one tank and return it to another therefore changing the weight distribution of the fuel. By moving fuel around while underway you will be able to control list, attitude and trim of your boat. Transferring can only be done while the engines are running unlike other fuel transfer systems which use electric pumps dedicated to the task.

 

All the best,

Bernie

Southern California

1973 42 aft cabin

Cummins 903

-----Original Message-----
From: john hitchcock <evange...@gmail.com>
To: unifliteworld <unifli...@googlegroups.com>
Sent: Sat, Apr 7, 2012 6:10 am
Subject: [UnifliteWorld] uniflite 42 ft question

[john hitchcock]

Thanks EB and Bernie.  I have the twin Detroit Diesel

 6 71s and its a terrible job opening up the floors, and having to move all the furniture to get off the fuel filters.  Then I have had to remove the injector covers and brake them loose to bleed.  I dont believe I have a priming valve or bleed screw  as you mentioned. A problem Ive had in the past is that the port engine fires up immediately but the starboard just keeps cranking. I took in the starter and they found it was a 24 volt whilst my system is 12 volt.They corrected it to 12 volt and  I put the starter back on but it still seems to be cranking slower than the port engine.  Do you think this may be the problem why the engine wont start up?

[M/V Arrluk Homer Alaska]

Hi John,
I have a 42' with twin 671's. They run great. My fuel filters are in
locations that are easy to get to and I think that previous owners
have upgrade the original system. I would suggest you do the same and
mount your filters in the engine room in a place were you can get to
them easily.

As for your starting problem, I had a similar problem last year. The
port engine fired right up, but the starboard engine would crank over
good , and try to fire. I am a mechanic by trade (aircraft), but
don't have much diesel experience. After calling several friends that
do have diesel experience, I was told about the emergency air cut
off. If this valve is stuck closed, as mine was, the engine will not
fire up.

This is an important part of a diesel engine and must be working
correctly. This would be your only means of shutting down a run away
engine. If a diesel engine goes out of control, it can actually
continue to run even if you shut off its fuel supply. This is because
it will suck its own oil supply and that is 5 gallons or better. If
your emergency air shut off vale is stuck, you need to fix it to were
it will work freely.

Also, one time I had a fuel problem to the starboard engine. I could
not get the thing to fire and went through the bleeding process
several times. I finally found the problem was a cracked fitting on
the line going into the secondary filter. It was not leaking but was
sucking enough air to keep the engine from firing up.

Thanks,

Arlen Zacharias
42' Sport Fisherman Extended Cabin
Homer, Alaska

On Apr 7, 2:58 pm, john hitchcock <evangelfi...@gmail.com> wrote:
> Thanks EB and Bernie.  I have the twin Detroit Diesel
>  6 71s and its a terrible job opening up the floors, and having to move all
> the furniture to get off the fuel filters.  Then I have had to remove the
> injector covers and brake them loose to bleed.  I dont believe I have a
> priming valve or bleed screw  as you mentioned. A problem Ive had in the
> past is that the port engine fires up immediately but the starboard just
> keeps cranking. I took in the starter and they found it was a 24 volt
> whilst my system is 12 volt.They corrected it to 12 volt and  I put the
> starter back on but it still seems to be cranking slower than the port
> engine.  Do you think this may be the problem why the engine wont start up?
>

[john hitchcock]

Dear Arlen,

Thank you for your input, but my emergency shut off valve is correctly set.  I will check the lines but don't quite know how to check if it is sucking air.  One very important thing I have learned with a diesel engine is that the starter motor has got to put out enough revolutions to start up, it is not like a gas engine which can fire up on half revs.  It is just a job removing it in such confined space.  Thanks for your input, I really appreciate it.

John

[e b]

John,

in theory both engines should should spin the same speed when cranking, the 6-71's require decent starter speed to fire up being a two stroke diesel, if your starters were easy to interchange i would swap them and see if the starter speed is now on the other engine.  at least start the easy engine first which will charge the batteries and give some boost to the other when you start it.

if you swap the starters and the problem now has changed engines, check you cables, diesel starters require alot of amps and any corrosion hurts, also, you can have someone crank and touch the terminals, if they seem to get abnormally hot then there is an issue.

i know alot of this is theoretical and can be frustrating, we are just typing words, you're the one actually getting dirty, be systematic and eliminate one problem at at time, on your fuel line,  any oily residue around a fitting or valve can be a sign that something is loose, things are easier to check with an electric fuel pump, you can simply turn the ignition on, disconnect the fuel line and dump it in a container, if you see little bubbles then you're sucking in air somewhere... with a mechanical pump the engine has to be running... obvioulsy you cant disconnect the fuel line..

you can use the return line and see if you're getting air..

of course, im in arizona , its going to be 92 today, any diesel starts in this weather...lol....

hope some of what i said helps.

Eric     

---

Date: Sun, 8 Apr 2012 09:23:28 -0400
Subject: Re: [UnifliteWorld] Re: uniflite 42 ft question
From: evange...@gmail.com
To: unifli...@googlegroups.com

[M/V Arrluk Homer Alaska]

Yes John I found the cracked line purely by accident and had no idea
it was there or even cracked. I was amazed that such a little crack
could make such a huge difference. I put on a new line and the engine
fired up and has been running without a problem since.



Arlen

On Apr 8, 6:12 am, e b <gon2...@msn.com> wrote:
> John,

> in theory both engines should should spin the same speed when cranking, the 6-71's require decent starter speed to fire up being a two stroke diesel, if your starters were easy to interchange i would swap them and see if the starter speed is now on the other engine.  at least start the easy engine first which will charge the batteries and give some boost to the other when you start it.if you swap the starters and the problem now has changed engines, check you cables, diesel starters require alot of amps and any corrosion hurts, also, you can have someone crank and touch the terminals, if they seem to get abnormally hot then there is an issue.i know alot of this is theoretical and can be frustrating, we are just typing words, you're the one actually getting dirty, be systematic and eliminate one problem at at time, on your fuel line,  any oily residue around a fitting or valve can be a sign that something is loose, things are easier to check with an electric fuel pump, you can simply turn the ignition on, disconnect the fuel line and dump it in a container, if you see little bubbles then you're sucking in air somewhere... with a mechanical pump the engine has to be running... obvioulsy you cant disconnect the fuel line..you can use the return line and see if you're getting air..of course, im in arizona , its going to be 92 today, any diesel starts in this weather...lol....hope some of what i said helps.
> Eric
>

> Date: Sun, 8 Apr 2012 09:23:28 -0400
> Subject: Re: [UnifliteWorld] Re: uniflite 42 ft question

> From: evangelfi...@gmail.com
> To: unifli...@googlegroups.com
>
> Dear Arlen,Thank you for your input, but my emergency shut off valve is correctly set.  I will check the lines but don't quite know how to check if it is sucking air.  One very important thing I have learned with a diesel engine is that the starter motor has got to put out enough revolutions to start up, it is not like a gas engine which can fire up on half revs.  It is just a job removing it in such confined space.  Thanks for your input, I really appreciate it.
> John

> For more options, visit this group athttp://groups.google.com/group/unifliteworld?hl=en.