Marlin Diesel tank

[Angler Management]

This is a can of worms that I don't want to feel bad dragging you guys into, so I think I can get my answer if I just ask one question to Marlin 300 owners from my era (2007) who have a diesel tank installed in the aft bilge that supplies their Mini4+ Fischer Panda Generator:

Here's the question, I'm hoping it answers many others as I am in the middle of replacing the external filter and pump.

In your setup, is the hose that enters the TOP of the diesel fuel tank (mine has a gauge here, the top of the tank), is this a fuel DRAW or RETURN.

?

I think I know, but want to see what everyone has. Pictures if possible. You show me yours, I'll show you mine type situation.



Real Randy

 

[Fishtales]

i'll try to check this weekend.

 

[DennisG01]

If that line goes to the pump and filter, then it is the draw, right?

 

[Angler Management]

If that line goes to the pump and filter, then it is the draw, right?

Maybe....?

Yes, as it looks from the outside, the line coming from the top of the tank leads to the filter, then the pump, then leaves the pump to disappear behind my genny housing to hook into one of the two ports in the back. One would assume the unobservable return hose flows from the other port on the back of the generator to the tank somewhere.

So here's where the can of worms starts. Short story is sometime in the month since I removed the old pump and installed the new, I lost the instructions.
I ended up installing the pump with the INLET facing downstream toward the genny, and the OUTLET facing upstream toward the filter and top of tank.
(I get no data in my little hole of a marina or I would have looked online, prior pump was a cylinder with no readable IN or OUT, new pump is a cone and I assumed the small end was the OUTLET, also previous positions of filter and pump were in the same order as I was installing.)

Regardless of this pump being installed to pump fuel the opposite direction I had assumed, when I ran the genny she cranked right up and purred under load for 45 minutes with no issues whatsoever. It was only when I arrived home to double check the install instructions that I read the small end of the cone is the INLET side.... (Walbro FRD-1) and theoretically I'm running fuel the wrong direction...?

This raises questions, no?
-Does the genny run no matter which direction the fuel flows from the tank? In my current situation you'd think the genny would be drawing from the return line and returning from the intake line. Besides the obvious filtration issue, does it matter????
-Is the internal pump working overtime compensating for the external pump trying to push fuel the opposite direction?
-The installer(probably Grady, maybe prior owner) installed the system in this same order (tank, filter, pump, genny but unknown pump direction), Did they mistakenly put the filter on the wrong side of the pump (downstream from pump instead of upstream from pump)???

Bottom line, if the schematic is correct from Walbro, I've installed a pump that is moving fuel from the genny to the filter and into the top of the tank. So I'd like to know if
a) I need to turn the pump upside down to reverse the flow, or
b) move the filter to the opposite side of the pump

It's either one or the other, thus I'd like your input. Let me know your thoughts, which direction does your fuel flow for youf FP setup, and is your order of parts the same as mine (i.e. top of tank to filter to pump to genny)

???

R

 

[Angler Management]

Here's a photo of the pump

 

[Angler Management]

Here's the schematic I read AFTER installing the pump.... showing direction of flow as opposite of how I intended to install, and how one would imagine the correct flow to be based on relationship of tank, filter and pump positioning in the line.

 

[Angler Management]

Why does my generator run perfectly if the pump is cycling fuel this direction? Should I reverse the flow, or move the filter, or don't do anything because despite the filter being on the wrong side, the internal filter is doing it's job and diesel is basically being polished each time around, so if it runs fine don't sweat it???? :hmm

 

[journeyman]

First, I haven't done much work on the genny except change oil and filter. I will also check when I get to the boat but that may not be til next week. Hope you can resolve this before then but if you don't, I will post my findings.

My FP manual is on the boat. My diagram from the Marlin owner's manual shows pump suction from the tank. It looks like it takes it from the top but it is only a diagram. Pump discharge goes to the filter then to the genny. There is no indication for a return to the tank from the genny. I didn't know/think there was one. Another system I need to learn more about.

When you changed the pump, did you also replace all the fuel lines? Is that how things may have gotten jumbled up?

Good luck. Again, I will poke around and reply if you still haven't figured this all out.

 

[Angler Management]

Thanks, Jim.

I did replace all the lines and barbs except for the one that leads from my replacements to the generator itself, which is the lowest hose there I never touched other than to attach a hose clamp to the new barb. Regardless, I put the filter and pump back in place where the originals were mounted, and don't recall any crazy overlapping tubing when I dismantled it. However I could have forgotten since I figured this job would be easier! When will I learn.

If this genny burns all of its fuel with no return to the tank then I'm really confused....!!!

 

[DennisG01]

If that line goes to the pump and filter, then it is the draw, right?

Maybe....?

Well, what I meant was... "YES, the line that goes to the filter then the pump is DEFINITELY the draw". But I see why it's confusing since it's running with the pump supposedly backwards. My "guess" is that the genny is being gravity fed by the tank/return line and the pump is then pushing the "extra" fuel back to the tank. If this is the case, then the genny is pulling strong enough so that fuel pump doesn't starve the genny by pulling too much fuel away.

You absolutely want the order to be: tank-filter-pump. Otherwise you run the risk of running crap directly into the genny without first being filtered. You don't want the genny to be the "filter".

 

[journeyman]

From Fisher Panda - Tank / Pump / Filter / Genny

From GW - Tank / Pump / Filter / Genny


FP does show a return line so I guess that is what we need to identify.

 

[Angler Management]

Awesome, Journeyman! Can I get that URL so I can scroll the GW schematic?

I will reverse the pump, as I would prefer (so would Walbro) to have the filter upstream of the pump...

Anyone disagree that it’s preferred to have the filter ahead of the pump?

Again, Thanks.

 

[journeyman]

The second pic is right from my owner's manual. It's an 08 and I downloaded it right from Grady's site when I bought the boat. I keep a hard copy on my boat.

The first pic is from Fischer Panda and the link is below, Page 45. It probably is not for our year genny but for what we are talking about, it is relevant. I have the original manual for my genny on my boat.

https://fischerpanda.com/go/wp-content/uploads/2015/06/Panda_4K_PMS_eng.R01.pdf

 

[Angler Management]

Copy. Both of my printed manuals are on the boat. I

 

[DennisG01]

I will reverse the pump, as I would prefer (so would Walbro) to have the filter upstream of the pump...

Anyone disagree that it’s preferred to have the filter ahead of the pump?

Again, Thanks.

Some pumps are designed such that they are OK to pump unfiltered fuel. I prefer, whenever possible, to have the filter be the first thing in line after the tank (why not, right?). But, if the pump can't pull the fuel through the filter, then it needs to be before the filter so it can push the fuel through. Since FP shows it before the filter, I would install it that way... EXCEPT, I would first give them a call and ask if it's OK to switch the pump/filter order. If they say it's fine, then I would switch the order.

 

[Angler Management]

Funny you should say that DennisG01, as I first started this procedure I called FP, they said they weren’t responsible for anything outside “the box” and to call Grady. Grady said call FP. The Walbro pump instructions said (before I misplaced them) to place a filter before the pump. I’m sure this is what all pump manufacturers say and in most circumstances these pumps will run fine on standard unfiltered fuel systems.

Since the entire system is doing fine now, running backwards, I assume we are talking about “best practices” not “what works” here, and I’m good having prefiltered fuel pumping the intended direction into “the box”. I think I will just undo the hoses to the pump, unbolt it and turn it 180 and reattach hoses and bolt it back in and be good with it.

Thanks guys! Always up for more input. Great chat room.

 

[journeyman]

It MAY not matter that the pump is before or after the filter... But the filter could be designed to pass a specific volume of fuel under pump discharge pressure versus pump suction pressure, especially uner load. Just sayin'.

My filter separator is a Racor Filter Housing Model 110A ,element # R11 / O-Ring kit # 10527.

 

[Angler Management]

Good point, Journeyman, I have the same filter and these instructions I have not lost. They say the filter is designed for both pressure side or pull side up to 100gph. I think the Walbro pump is 15gph max...

Looks like I’m covered. I’ll report back on my success at the boat tomorrow!

 

[journeyman]

Good to know! 8)