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Alternate (temporary) fuel supply

am_dew

am_dew

Advanced Contributor
Volvo AQ130C

I am having "no power under load issues (see here for details: http://www.marineengine.com/boat-forum/showthread.php?395173-AQ130C-bogs-down-under-load) and I suspect I may have issues with the gas in my tank so I would like to temporarily attach an alternate fuel supply to the intake side of my mechanical fuel pump to see how things work using different gas.

I think my first step is to go out and buy a small portable gas tank like the ones small outboards use and then I need to make a hose connection between it and my fuel pump, which has either a 1/4" or 5/16" hose barb attached to the intake side. What I am not sure of is how much flexibility these external tanks have as far as customizing a hose to make it work with my setup. Also, does that external gas tank have to be pressurized to work? I see the typical setup on them uses a hose that has a bulb inline, which as I understand it serves two purposes...to prime and to pressurize the tank.

Does this sound right? Any other ideas or suggestions?

Thanks!​
 
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am_dew said:
Volvo AQ130C


I think my first step is to go out and buy a small portable gas tank like the ones small outboards use and then I need to make a hose connection between it and my fuel pump, which has either a 1/4" or 5/16" hose barb attached to the intake side. What I am not sure of is how much flexibility these external tanks have as far as customizing a hose to make it work with my setup. Also, does that external gas tank have to be pressurized to work? I see the typical setup on them uses a hose that has a bulb inline, which as I understand it serves two purposes...to prime and to pressurize the tank.

Does this sound right? Any other ideas or suggestions?

Thanks!
​
Click to expand...


Re: What I am not sure of is how much flexibility these external tanks have as far as customizing a hose to make it work with my setup.

Tanks come without hose. Typically you can get one of two different hose sizes as a separate kit item w/bulb (pay attention to arrow for fuel flow direction!). You would probably be better served with the larger size. Hoses are available without the engine end fitting, i.e., just a hose. So... find the correct fitting to mate to your fuel pump with a barb to mate with the hose size. Use a SS screw clamps on the hose ends.

Re: The bulb.... Only used to prime the fuel system, i.e., avoid drain on battery for the engine mounted fuel pump to suck fuel all the way from the tank at startup. Not used to pressurize tank. As a matter of fact, the tank MUST be vented to the atmosphere. Usually, there is some kind of vent valve widget on the fuel fill cap. This MUST be open for the engine to run ( for more than a few seconds.)
 
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Thanks Capt Bob. Does not sound like a need bulb, just a hose between the tank and the fuel pump, the proper fittings, and some hose clamps.
 
Those small tanks are a little spendy for just a test run so maybe you can borrow one? You can get an adapter to go on the tank end that has a 3/8" hose barb, which is what you want for that motor. The bulb does help to keep from cranking so much.

I think you are on the right track by eliminating the pickup tube, vent, fuel line, bad fuel, etc. Good luck, Mike
 
Thanks Mike for the suggestion to borrow a tank however I've asked everyone I know and came up empty.:(
 
How about a regular gerry can (plastic). Stick the correct size hose into it through the spout and secure the hose by putting a hose clamp around the spout and clamping it to the hose. Keep the can out of the engine compartment, secure it, and ventilate, ventilate, ventilate.
 
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Thanks but I want to be totally safe when I do this and to me, that does not sound real safe, especially since my girlfriend is the only person I can take out with me to assist as needed, while I drive the boat. I just don't want to take any chances, especially in that sort of situation. I'll just have to spring the $$ for a portable gas tank.
 
IMO, this could prove to be a waste of time and efforts for what the gain would be.
Two things only can be learned from this:
1... your OEM tank and system is not the issue.
2.... your OEM tank and system needs attention.

I'd spend my efforts on diagnosing, cleaning and making the OEM fuel tank operational.
Once done....., you will have eliminated the fuel tank as being the source of the issue.
I'll bet that you can do this in less time required to find, connect, add fuel, etc. to an external fuel tank..... and much safer too boot!

Take a fuel sample. If bad, drain and dispose of the old fuel.
Add fresh fuel to the fuel tank.
Prior to this, pull the dip tube.... examine the screen.
Check the anti-siphon valve. Replace if need be.
Make sure that the vent line is clear. .
Also make sure that the vent hose has a "High Loop" in it just prior to the vent fitting.
Pull all fuel hoses and examine the interior...... better yet, replace them with new USCG approved gasoline fuel lines.
Remove the existing fuel filter base..... examine all ports and passages.
Install new pre-filled fuel filter cartridge.

Now there's no need for an external fuel tank that may pose safety issues. :D

.
 
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Thanks Rick, but I am going to very safely attach a 6 gallon external tank I bought yesterday and try it before I go to the steps you kindly outlined. It could also be that a fuel delivery related issue between the fuel pump and the carbs (all inclusive) is causing the problem and I want to discount that as well. Getting to my gas tank to check the things you mentioned on it will require a significant amount of work, which I really don't want to get into unless I really have to.
 
Do you not have access to the fuel gauge sender and pick up tube area?
I don't recall working on any boat that did not offer this access!
Hmmm.

.
 
RicardoMarine said:
Do you not have access to the fuel gauge sender and pick up tube area?
I don't recall working on any boat that did not offer this access!
Hmmm.
Click to expand...

Not sure, will have to take a close look when I get the boat tomorrow. The gas tank is directly behind the port side jump seat right up against the transom. It's a very cramped and difficult working environment back there, with about 12" between the left edge of the tank and the engine/bell housing. I'll post a few pics when I get the boat and you'll see what I mean.
 
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Whether you use a jerry can or an outboard tank, the same rules apply; out of the engine compartment, secure it, and ventilate.
 
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