Fuel pump problem

[Dunromin]

1985 OMC 3l.
Boat was standing for 2 years with stern drive problem, so I turned the engine over to see if it was free. No problem there, but found fuel was not being pumped from the tank. Pump bottom was full of what I can only describe as tar, so I cleaned it out and got it pumping by hand, no apparent damage to the diaphragm but when I re-installed it, it was still unable to pump gas. At this point I decided to remove tank in case it was gunged up too, but it looks fine, at least from what I can see through the filler hole. I poured some paint stripper in to remove any gunge I can't see, and left it soaking while I replaced the fuel line from the gas tank,, which was brittle. I tried pumping gas from a gas can, through the new line, but again, with no luck. I'm on the point of ordering a new pump, unless someone has any ideas? I've read mention of an anti siphon valve, which isn't fitted to mine, do I need to fit one?

 

[Scott Danforth]

You ignored the fuel pickup tube and the anti siphon valve

 

[Dunromin]

Pickup tube is clear, but I asked if I should have an anti siphon valve?

 

[Scott Danforth]

you have an I/O, your tank came with an anti siphon valve.

 

[Dunromin]

OK. I'll be getting a siphon valve, I understand it's primary function is to prevent gas siphoning into the bilge, but does it give any assistance to the fuel pump priming a bone dry fuel line, or is this down to the fuel pump alone?

 

[444]

I would replace the fuel pump just as a normal matter of maintenance after an engine has been sitting. But for what it's worth, it takes a lot of cranking for a mechanical fuel pump to get fuel back up to the carb.

 

[Dunromin]

I would replace the fuel pump just as a normal matter of maintenance after an engine has been sitting. But for what it's worth, it takes a lot of cranking for a mechanical fuel pump to get fuel back up to the carb.

Strongly suspect your right on both counts. I knew it might take a while to fill a 3/8" x 20 foot hose, and spent several minutes cranking the engine over, while dreading what I was doing to the starter motor. I'm going to get an anti siphon valve first, followed by a carb.

 

[Scott Danforth]

I would replace the fuel pump just as a normal matter of maintenance after an engine has been sitting. But for what it's worth, it takes a lot of cranking for a mechanical fuel pump to get fuel back up to the carb.

why, would be a waste of money unless the fuel pump is bad

 

[Dunromin]

why, would be a waste of money unless the fuel pump is bad

I installed a new anti siphon valve hoping it would help prime the fuel line, but no difference. Removed pump again for a closer inspection and realised that although it is working to some extent, just not enough to do the job. Bullet is bitten, I have ordered a new one.
On a different note, I'm changing all the oils, and upon removing the drain plug in the tilt gearbox, out poured water-no oil at all. I put some air pressure to the fill hole while pouring soapy water all over it, but no bubbles. I had assumed water must enter through a faulty gasket, or gear seal, is there another way for it to enter?

 

[Dunromin]

New fuel pump arrived today, but still can't get it to pump fuel from the gas tank. To recap, I have had the gas tank off to check for varnish, but found it to be pretty clean, washed it out anyway. New anti siphon valve, new fuel line, and now, new fuel pump. I spun the engine over for what seemed a long time, but I'm guessing probably about 2 minutes. I have 5 gallons of gas in a 12 gallon tank, so not scraping bottom. I am wondering if 2 minutes is enough to bring fuel through, but it seems a while to spin the engine on the starter motor. It's been a long time since I played around with a mechanical pump on old cars, but I don't remember it taking that long to prime. Anyone got any suggestions?

 

[Scott Danforth]

Have you pulled the pickup tube and checked it? If tou have a hole, you are sucking air. If there is a filter in the tube, its probably clogged

 

[Dunromin]

The pickup tube is welded onto the tank, so could not really examine it, but I can blow through the fuel line and hear it bubbling in the tank. I'm going to hook up a line from a gas can to the pump, over a short distance just to confirm the pump is working. If it is, I will have to consider the possibility of a crack in the fuel pickup as you suggest.

 

[Dunromin]

Have you pulled the pickup tube and checked it? If tou have a hole, you are sucking air. If there is a filter in the tube, its probably clogged

Scott, turns out you were on the money regarding the pickup tube. I had not looked at it when I removed the gas tank, but remembered it being welded around the base, not realising it could be unscrewed from the top of the mounting tube. Anyway, it was a plastic pipe pushed onto the fitting, and it had become a loose fit, and was letting in air. I fixed it, pump primed quickly, and engine started easily. Stern drive is rebuilt & back on, just have to sort out the shift mechanism mounted at rear of engine.