4.3L Alpha One runs 6 minutes on topped-off fuel filter only

[den458]

I'm hoping this is fairly simple. 22 year old 4.3L always reliable, but sat last 2 years (no stabil) due to illness. Today: initially wouldn't start except on starter fluid or carb cleaner. I topped-off a new fuel filter 3X, the engine starts & runs for about 6 minutes each time, then starves for fuel & dies. When I spin the fuel filter off, the fuel level is down an inch or so, so it's running on fuel from the filter, but fuel is not replenishing the fuel filter. My fuel tank is half-full, I trust the gauge, the needle wiggles around as we move around in the boat cleaning, like the gas is sloshing a bit in the tank. The pump is between the filter & the carb, so fuel is definitely going through the pump to the carb. How do I know if the pump is pumping? Is there a simple troubleshooting method to confirm the pump is running? There are no fuses involved anywhere, correct? Thanks in advance.

 

[den458]

I topped-off the fuel filter & started it again. The oil is new & proper level, oil pressure at idle reads 40 psi on the gauge, increases to 60 psi when I increase rpm. Ran until fuel starved. I reseated the 2 wires at the oil pressure switch. Should I be able to hear the fuel pump running? How do I disconnect the wiring connector at the fuel pump to confirm +12V & GND connections?

 

[Bt Doctur]

put a jumper across the 2 wires , with the key on you should hear the pump running.
Insert a paperclip into the connector for testing

 

[den458]

For clarification: are you referring to jumpering the 2 wires at the oil pressure switch to power the pump? And removing those 2 connectors & inserting a paperclip into them (bypassing the oil pressure switch) should force the fuel pump to run?

 

[den458]

OK, I made a jumper, bypassing the oil pressure switch, turned the ignition ON, now I hear a buzzing sound I hadn't heard before from the fuel pump, hooray. Tried to start the engine, no luck. Again, topped-off the fuel filter with fuel, engine started & ran a few minutes, fuel starved again & died. I"m a step closer, fuel pump powered now. I'm open to more ideas, but I think either the pump isn't really pumping or is clogged, or I'm out of gas. The fuel gauge has been reliably working 20 years, shows a half-tank now, but I'm fuel starved, so I'm going to go top off the gas tank with premium & try again. Bt Doctur, thanks for getting me a step closer.

 

[Scott Danforth]

make sure your anti-siphon valve isnt plugged.

 

[alldodge]

sat last 2 years
think either the pump isn't really pumping or is clogged, or I'm out of gas

Will agree, its one of those, and maybe bad gas. Pull the filter and dump everything in a baggie to see if there is anything there but clean gas.

Next, disconnect the fuel line at the tank and stick it in a can of clean gas. If it runs without issue then its the tank ,or antisiphon valve.

If it still will not run then need to get a pressure gauge on the line going to the carb to see if you can get 4 to 7 psi

 

[den458]

The fuel tank took 11.5 gallons to fill-up, premium (to help the older gas), so fuel tank wasn't empty, fuel gauge was correct showing about half-tank. Bad gas is not the issue yet, since none of it has made it up to the filter (then fuel pump then carb) yet. As for examining the gas in the fuel filter, all I ever see there is the perfectly clean & fresh gas I used to top it off, before I spun it on. The engine runs for 5-6 minutes depleting the gas level a few inches within the filter. No gas ever makes it up from the tank into the filter. Don't know yet where to find the anti-siphon valve. Will have to set this aside today, back to it on Monday, thanks to all.

 

[alldodge]

Antisiphon vale is the barbed fitting that the rubber fuel line connects to. Inside the barbed fitting is a ball and spring

 

[den458]

I see a black rubber fuel line appear from under the floor, which connects to a 90-degree brass-colored fitting on the edge of the fuel filter housing. The fuel lines exiting the fuel filter are all metal, first to the pump, then on up to the carb. Is my valve within that 90-degree brass fitting? I have the 96 Glastron GS-185 with the 4.3 LX mercruiser sterndrive. More ideas for where my anti-syphon valve is?

 

[alldodge]

The valve is in the link below, and is connected to the fitting coming out of the tank
https://www.iboats.com/shop/moeller-...b-3-8-npt.html

 

[alldodge]

Here is my tank and note the ends with the red caps, they are antisiphon valves

 

[den458]

I'll have another look on Monday. At a glance, it appeared both the larger diameter fuel filler hose & the smaller diameter fuel tank to fuel filter feed hoses, pull-tied together, disappear under the floor. Should the valve be in a serviceable location? I have the sport-interior, a wide bench seat in front of the rear sundeck. The rearward end of the fuel tank is under the bench seat. I hope I don't have to dig into anything.

 

[Bt Doctur]

post a better pic of the tank connections, the feed hose to the fuel sep should be the black one. If that hose is the feed to engin the hose it must be connected to the tank to draw fuel from the tank to the engine

 

[Bt Doctur]

 

[den458]

I have to chase some other things today, but was thinking about the anti-siphon valve.... the hose to fuel tank connection is out of sight, possibly even out of reach. If the valve is the issue, it's somehow stuck closed. What if I disconnected the fuel hose at the fuel filter housing end & ran a flexible coat-hanger metal wire through it to the valve. Maybe tapping it against the valve would free-up whatever is stuck & unsealing the fuel line?

 

[alldodge]

A wire should not be able to go thru it., its a spring a steel ball

 

[zellerj]

On my Larson there is a placard by the gas tank fill port that says that it is a USCG requirement to inspect your fuel tank annually. Therefore boat manufacturers are required to make the fuel tank fittings accessible. From the USCG regulations:

The fuel system must be installed and the boat must be designed and constructed to provide access to every fuel system fitting, joint and connection. This access must permit: (a) inspection of these items for leakage and deterioration (mirrors may be used to see the hidden portion), (b) removal of these fuel system components for repair or replacement, and (c) maintenance of these fuel system components to preserve the integrity and reliability of the fuel system. All fuel system fittings, joints and connections must be accessible for inspection, removal and maintenance. This requirement does not apply to fuel tanks, only to the fuel tank fittings. Long runs of fuel hose, likewise must be accessible for inspection, but only the fittings must be readily accessible. In a long run of hose, it is acceptable to disconnect the fittings and to pull the hose out to inspect it. The entire run of hose does not have to be immediately accessible. Access may be gained by means of removable panels, hatches, ports, doors, removable seats, removable consoles or other means designed for such access. It is intended that these items be reached without cutting portions of the boat. Bolts, screws and other fastenings may be removed in order to move panels, flooring, furnishings and other items to gain access. Caulking and sealants do not make a part permanently attached so long as it can be removed and replaced without destruction of boat structure.

 

[den458]

OK, thanks for some assurance that it should be accessible. Maybe with a mirror on a stick I'll see what I haven't so far. Will have an update tomorrow, thanks to all chipping in.

 

[den458]

Weather was a rainy mess here today, hope weather cooperates tomorrow for some progress finding & evaluating that valve !