Is my fuel pump leaking?

[NatySailor]

After a month away from my boat, I've had trouble starting and running the engine. The problem seemed like a fuel issue because I could get it to ignite for a moment using starter fluid, and also because I could eventually get it to run weakly. Also, a few weeks earlier I had done a weekend trip where the engine ran fine for something like 15 hours. Perhaps some water had gotten into my tank?

So I pulled off my racor fuel filter which I hadn't done for a while, and there was a lot of sediment in the bowl. So I replaced that with a new filter. While I was at it, I also had my old monel fuel tank cleaned by a professional tank cleaning service, put in five gallons of fresh fuel, and cleaned out the old fuel from the fuel lines, fuel pump sediment bowl and my new Racor filter. I should now have nice clean fuel all the way to the engine.

BUT -- it still wouldn't start/run well. Argh...

I did a quick check of the fuel pump by pulling the hose off the carb and squirting some fuel into a glass jar. The pump seemed to be working fine, but the fuel looked cloudy and separated into two layers. Hmm.. How could that be?

Came back the next day with a fresh can of gas and ran a new fuel line directly from a gas can in my cockpit to the fuel pump. (I wanted to eliminate bad gas as a source of my issues) The engine still wouldn't start and again I noticed the fuel coming out the fuel pump looked cloudy. What the hell, I thought?

I've attached two images to this post showing fuel in a glass jar. The clear stuff is straight from the gas can, the cloudy stuff passed briefly through my fuel pump before going into the jar (bypassing the rest of my fuel lines, Racor, gas tank, etc).

So... what's going on here? I'm thinking there must be a hole in my mechanical fuel pump diaphragm that is letting some oil in. I don't think there is a way for water to get to the fuel pump (is there?)

Really curious to hear what you all think of this mystery!

Thanks
Dennis

[Al Schober]

The fuel in your tank has gone two phase - gas phase on top, water/alcohol on the bottom. Ain't alcohol fuels great!?? The water phase has gotten large enough to get up to the level of the pickup tube for the engine. You're going to have to pump the water phase out of your tank.
With my boat, I can get a tube from the fill connection to the very bottom of the tank. A small hand pump will remove the water phase - in my case, it might be two or three quarts. You'll have to see what access you have with your boat - pumping from the supply line to the engine will NOT get the stuff from the bottom of the tank.
Get the water out of the tank and keep it out. How's the O-ring on your fill cap? You want to add a Spring tank pump-out to your maintenance schedule until you KNOW you don't need it.
I went through a LOT of grief one season - water was corroding the steel components of the fuel filters. My final polishing filter (filter of last resort) was corroding downstream of the element and sending corrosion debris to the float valve - not a pretty scene.
Moral: Keep your tank clean and replace your filters - before you have troubles.

[edwardc]

Sorry to disagree, Al, but Naty stated that he re-ran the test with clean fuel in a fuel can in the cockpit, and new fuel line from it to the fuel pump, and got the same results. He literally has eliminated everything but the fuel pump, so it can't be from phase separated gas in the builtin tank!

And since the only other liquid anywhere adjacent to the fuel pump is crankcase oil, I think he's got a leak in his diaphragm that's allowing fuel and oil to mix.

[tenders]

Unless that stuff is a combination of garlic, red pepper, rice flour, and sea salt, like it says on the label (perhaps the recipe for New and Improved Marvel Mystery Oil - Kimchee Edition), I'd like to assume the mechanical fuel pump's diaphragm needs to be replaced.

I have an electric pump, so what do I know, but I had thought oil tends to dissolve in gasoline, and vice versa. And isn't the usual symptom of a failed diaphragm gas in the oil instead of the other way around?

Are there any signs of gas in the oil, i.e., an unexpectedly high oil level?

[edwardc]

Another thought.

Naty, did you drain and clean the fuel pump sediment bowl, or merely flush clean fuel through it? If the latter, there could still be water contaminated fuel collected in the bottom of it, poisoning the new fuel going through it.

[NatySailor]

Another thought.

Naty, did you drain and clean the fuel pump sediment bowl, or merely flush clean fuel through it? If the latter, there could still be water contaminated fuel collected in the bottom of it, poisoning the new fuel going through it.

I did indeed pull off the sediment bowl and dump everything out of it before running this test.

Thanks all for your replies.

What do you think of running a line from the fuel can directly to the carb? Perhaps I could put a little primer bulb in the line. This would further eliminate issues upstream of the fuel pump....

[ndutton]

What do you think of running a line from the fuel can directly to the carb? Perhaps I could put a little primer bulb in the line. This would further eliminate issues upstream of the fuel pump....

Yes, excellent test except you'll be testing a dirty carb. The krap that is your fuel sample is what's been running through the carb and all its tiny passages. The carb should be cleaned as part of the troubleshooting process.

[capnward]

Right, clean the carb also, if there is any crud in the gas. The cloudy stuff in the jar looks too stratified to be oil in the gas. Water can only get into the fuel pump if there is water in the gas. If there is no sign of gas in the crankcase, (dipstick smells like gas) your diaphragm is likely ok. Maybe you just need to pump more gas thru the pump and it will get clearer. I wonder if your professional tank cleaners didn't just stir things up. You may be clogging and replacing filters for awhile. As the owner of a trouble-free mechanical fuel pump, I await anxiously the determination of the condition of the diaphragm. It is my belief that using non-alcohol fuel with MMO keeps the diaphragm healthy.

[NatySailor]

Right, clean the carb also, if there is any crud in the gas. The cloudy stuff in the jar looks too stratified to be oil in the gas. Water can only get into the fuel pump if there is water in the gas. If there is no sign of gas in the crankcase, (dipstick smells like gas) your diaphragm is likely ok. Maybe you just need to pump more gas thru the pump and it will get clearer. I wonder if your professional tank cleaners didn't just stir things up. You may be clogging and replacing filters for awhile. As the owner of a trouble-free mechanical fuel pump, I await anxiously the determination of the condition of the diaphragm. It is my belief that using non-alcohol fuel with MMO keeps the diaphragm healthy.

Thanks. I'm kicking myself for not smelling the dipstick before leaving the boat. I can't imagine there would still be water in the fuel pump, but I will try pumping some more fuel through there before I drop $200 on a fuel pump.

The tank cleaners use the gas in the tank to power wash the inside of the tank, and then they take all the gas away with them and leave the tank empty. So I don't think they stirrred things up. Also, the gas in the photos came from a fresh gas can which I temporarily hooked up directly to the fuel pump.

Anyway, appreciate all the feedback here. Will report back to the team in a few days!

[NatySailor]

SUCCESS...

Got her running yesterday after a thorough inspection and purging of my fuel system.

I was getting cloudy gas out of my fuel pump and so I checked the fuel tank.. gas looked perfect. Checked the gas coming out of the lines before the fuel pump....also looked fine. Gas coming out of the fuel pump was still cloudy. Took off the sediment bowl again, dumped it out, still was getting yucky gas.

Finally figured out that a big part of the problem was my polishing filter! Clean gas went in, cloudy gas came out! I guess enough water and crud had gotten past my Racor in the past to turn the polishing filter into whatever the opposite of a polishing filter is.

Took that filter out of the system, slapped on my clean spare carb, and she started right up.

Now I just need to figure out where all the water came from in the first place. Do I have leak somewhere or is it just the ethanol in the gas and/or condensation. How quickly will ethanol fuel collect water? If you all are away from your boat for an extended period, do you check and/or pump out the old gas before running your engine?

Thanks for all the help!
Dennis

[roadnsky]

Now I just need to figure out where all the water came from in the first place.

Dennis-
First congrats on making progress!

As Al asked earlier way upstream in this thread, "How is the O-ring in your fill cap"?
I think he also correctly pointed to changing the filters as well.

[NatySailor]

Dennis-
First congrats on making progress!

As Al asked earlier way upstream in this thread, "How is the O-ring in your fill cap"?
I think he also correctly pointed to changing the filters as well.

O-ring looks perfect. Filter is new. Owner of my boatyard suggested that he had seen water get into the short section of hose between the fill cap and the tank though. I know my cockpit floor is a bit soft and there's likely some mushy core in there, so that could be an access point (gas tank is directly under the cockpit floor to be clear, and the fill cap is in the cockpit)

[sastanley]

NATY, I religiously replaced my o-ring on the fuel fill each season and then realized it was a problem with the threads and not seating/sealing. I had to replace the fuel fill.

Every suggestion here is good..any spot could allow water in. You need to eliminate each of those until fuel is not contaminated.