Gas Tank Question

[bigdog]

Trying to trouble-shot a gas realted problem, which I strongly believe is my fuel pump.... Getiing marine mechanic assistance.

I do have a few questions though regarding the fuel tank,
1.Is there some type of pickup valve in the gas tank? Or is this function
controlled entirely by th e furl pump?
2. Do gas tanks have any type of screen installed. Something which could
get clogged preventing gas flow?


Thanks.

[dpg]

"2. Do gas tanks have any type of screen installed. Something which could
get clogged preventing gas flow?"

No.......Oh and not sure about the first question.

[chipj29]

Originally Posted by dpg

"2. Do gas tanks have any type of screen installed. Something which could
get clogged preventing gas flow?"

No.......Oh and not sure about the first question.

I am not so sure that the answer is always no. My Ski Doo and Sea Doo both have screens on the fuel pickup inside the tank, as does my Yamaha motorcycle.

To answer the first question, there is either a fuel pump inside the fuel tank, or somewhere else between the tank and the carbs. But I don't think there would be 2 fuel pumps.

[CL 240 LS]

BD
There may be a screen attched to a pickup tube in your tank. I had all sorts of fuel related problems before discovering a screen that wold clog with debris that was in the tank. Would run fine for hours then exhibit running out of gas symptoms, after an hour or so of drifting it would restart.

Marina mechanics had all sorts of solutions that did not work. I finally removed tank and drained out all gas and assorted junk that was clogging up the works. This all happened before ethanol gas.

[kchace]

Some fuel tanks *do* have a screen over the pickup and some do not. Also, depending on your boat, you may or may not have an anti-siphon valve located where the fuel line connects to the tank. The anti-siphon valve is very small and looks pretty much any other hose barb, but inside would have a spring-loaded check ball. In addition to a clogged pickup screen, anti-siphon valves can also cause fuel delivery problems by sticking or becoming clogged with debris.

I have never heard or seen any boat with a fuel pump of any kind inside the tank.

Ken

[SAMIAM]

Trace the line all the way back.......I have in line filters which are easy to clean......don't know what kind of an installation you have.

[bigdog]

Some background:
My engine is a Mercruiser 4.3LX, with an electric fuel pump mounted between my fuel tank and feeds directly into my fuel filter. Gas comes through a metal tube into the fuel pump from the tank.

CL 240:
Excuse my lack of knowledge, but when you say 'pickup tube' in my tank? Is the pickup screen inside the pickup tube?
Would this actually located 'in the tank' or external?

kshace:
You mentioned and 'anti-siphon valve' located where the fuel line connects to the tank. If this something visible which a hose line is attached to? Still confused on how I check if I have this anti-siphon valve as part of my fuel system?

Last.... I have tried unsuccessfully to siphon gas out of my tank and replace with fresh. Bought a 10' length of 1/4 plastic tubing and a hand siphon. I can get about 6-8' of tubing into tank, but seem to be hitting an obstruction, but may be hitting bottom of tank? Anyway, cannot get tubing primed and filled with gas, and let gravity do the work. Have looked around for one of those drill attachment pumps, but cannot locate anywhere?

Anyone have a good method to drain gas from tank? I'm open to any suggestions. BTW, tank holds 35 gal.

Thanks!

[chipj29]

To drain mine, I always use the same as what you have. 1/4" tubing and run it to a gas can. Make sure the gas can is lower than the bottom of the gas tank. I use a turkey baster (primitive, but it works) to get the flow started.

What can happen is if you push the tubing too far into the tank, it hits the bottom and curls up so the end of the tubing is out of the gas. In that case, what I do is tape the end of the tubing to a telescoping magnet tool (even a stick would work). That keeps the end of the tubing on the bottom of the tank.

[robmac]

I would disconnect the filter and connect a hose to the pump side and use the pump to drain the tank. Tis will also help narrow down where your problem area is. Just make sure you use a clamp on the hose if it is an FI engine as the pressure is much higher than a carb engine which only has 7-9 PSI of fuel pressure. If at that point you get nothing then it will be the pump or the p/u tube in the tank.

[kchace]

Lets take this step by step. First, let me say that I am very very familiar with your setup. You say you have a "gas related problem". Ok.

Starting at the tank, you will have a tube inside the tank that is called the 'pickup'. The pickup goes down to near the bottom of the tank. The pickup may or may not have a screen on it. That screen may or may not be clogged. Next, there is a fitting on top of the tank where the fuel line attaches. On your setup, the fitting where the fuel line attaches almost surely includes inside of it an "anti-siphon valve". Anti-siphon valves can and do sometimes start sticking or get debris lodged in them and cause fuel delivery problems. This valve usually can be unscrewed and checked/replaced.

Next, you have the main fuel filter which is between the tank and the electric pump. This of course could become plugged and should be changed once every year or two.

After that filter is the electric fuel pump itself. Its very important to understand that this pump WILL NOT RUN when the engine is not running - even with the key in the "on" position! This is an important safety feature. The exception to this is when the key is turned to the START position - in order to fill the carb for starting. Once the engine is running, an oil pressure activated switch supplies power to the pump so that it keeps running. If you suspect the fuel pump isn't delivering fuel, any part of that system (The START bypass or the oil pressure switch) may have a problem.

Lastly, there is often a fuel filter *in* the carb right under the fitting where the metal fuel line attaches. This filter is tiny (barely bigger than a thimble) and NEEDS to be changed regularly. It is THE MOST OFTEN forgotten item in this list. If this filter becomes clogged, your boat may start and idle ok, but will bog a few seconds after accelerating because fuel can't get through it fast enough to run the boat under load.

Well, that was long but I hope it helps you in your troubleshooting.

BTW - DO NOT use a drill mounted pump to pump gas from the tank! Drills have open brushes which continually produce sparks. The slightest fuel leak from the pump and you could go up in flames.

Ken

[CL 240 LS]

BD
The pickup tube extended into the tank almost to the bottom with a fine brass screen at the end. The tube was connected to the fitting that the gas line hose to the engine was connected.

The debris in the tank would accumulated on the screen as the fuel was sucked in. Eventually the restriction was enough to starve the engine of gas.
After a while some of the debris would falloff allowing fuel to flow again, but we would only be able to run at reduced speed back to the dock. After a few hours the boat ran fine again, after the suction was reduced the debris would fall away from the screen which was clean when removed from the tank. I then removed the tank and emptied it finding a lot of junk.

I tried changing filters, ignition components, manifold and carburetor gaskets and checked fuel flow. The tank pick up was the last thing to try after much aggravation and expense.

I do not know if the debris was from the marina gas or sabotage but there was a lot of junk in there!

[wifi]

Not sure how applicable it is to boats, but in my youth, fooling around with cars, I had one that wouldn't run under load or high revs. Turned out to be a small (almost invisible without close examination) crack in the hose leading to the fuel pump. The pump was sucking in air as well as gas, and the engine was starved when it needed larger amounts of gas.

[Dave R]

Big Dog, I can not recall all the details of your problem, but it seems like you have been battling it for awhile and, If I recall correctly, the motor inexplicably loses power under load, but idles and runs fine on the muffs.

I thought of another cause, the exhaust system contains a pair of anti-reversion valves called "water shutters" They go into the tops of the Y pipe, near the rubber couplers. They do wear out, and can break free and lodge downstream in the exhasut system, causing excessive back-pressure and power loss. It's something worth checking. To check, pull the elbows off the exhaust manifolds and look into the Y pipe. They should be readily apparent.

Here's a link with a bunch of different merc shutters, so you know what to look for: http://images.google.com/imgres?imgu...%3Den%26sa%3DG

[fatlazyless]

Lots of small to medium sized outboard engines use six gallon, red plastic, portable gas tanks which have a gasoline hose with a fine mesh screen at its' intake, inside the tank. To get at it, you need to disassemble the four screws on the six gal tank. If it uses two-stroke oil inside the tank, the black two-stroke oil can become stuck to the very fine, mesh screen, about the size of a dime, and clog it closed.

Simply, feed the outboard a Bayer Asperin and race over to the Y-Landing Marina for a beer or two while it gets fixed (smiley face)!

If you want to actually try to fix it yourself, it should clean up with a small, fine, brass scrub brush, like a tooth brush. On second thought, you'll probably destroy the whole boat or something, so better to head to the Y-Landing......for a repair beer

[bigdog]

CL 240 LS
I am experiencing the same conditions you did: I would only be able to run at reduced speed back to the dock. After a few hours the boat ran fine again but only at idle. What you said about the pickup tube screen clogged with debris, makes perfect sense. I also have experienced much aggravation, changing various components, at much cost, as a trial and error to eliminate the problem without success. VERY FRUSTRATING.

Question:: Can the ‘pickup tube’ be removed from the tank easily to inspect screen for blockage, or does one have to remove the entire tank? This would be a major effort and expense !


WiFi
A crack in the hose leading to the fuel pump, would definitely cause air to be sucked sucking in as well as gas. This may also cause the electric fuel pump to act erratically, and cause the engine to starve for gas when it needs larger amounts of gas under load.

Will check hoses, and probably replace as the boat is 1995, and has original parts. I have been told that old hoses can experience the inner walls to collapse from the inside, which would give these same symptoms. One cannot see inside the hose walls.....


DaveR
You make a very good point about the anti-reversion valves, and I value your opinions, but I think it’s more basic than that. Pickup-tube clog, or electric fuel pump, possible something electronic?


The Merc electric fuel pumps historically has had known problems for failure.
This however is an expensive replacement. Will start with the basics, and least expensive repairs/replacements, and work up from there.

Can’t thank everyone enough for all this valuable information.

Bigdog

[jst_4_kiks]

many good answers so far.

anti-siphon valve: mounted on top of 90* elbow on top of fuel tank. gets blocked with debris

pick-up tube screen: on very bottom of pic-up tube screen in tank. it may or may not be clogged. may not even be there at all.

in-line fuel filter: looks like an oil filter in line with the fuel feed line. mounted before FP. small filter inside them too.

carb fuel feed filter: fuel feed line into carb. 1" wrench loosens to get to filter.

exhaust flappers: in top of exhaust y-pipe. age deteriorates them and lots of use. can get loose and break off. fall into pipe to obstruct flow. also if the rubber comes off metal (flappers are covered in rubber. wears off) then the flapper can eventually wear through the y-pipe. $$$$ to replace it.


when all those are checked, check the fuel pump pressure to make sure it is in spec. GOOD LUCK

[CL 240 LS]

My pickup tube was threaded into another 90 degree barbed x NPT fitting which had the fuel line hose connected to it. These were threaded into the top of the tank.

Use care in removing this fitting as mine broke off as it was made of aluminum. This led to the removal of the tank and then finding all the dirt in it when drained.I could not find replacements and bought a new tank.
Never had any more problems, sold the boat and the buyers had no problems either.

[bigdog]

Hi... thought I'd report back on results of gas tank problem....

Was able to drain all but bottom of tank, maybe 5 gallons of my 35 gal tank, and what a pain in the ### that was ! Only way I could drain was to remove the cover of the pickup tube, and anti-siphon valve connect, then insert palstic tubing through cover hole.

Ran siphon tube from that point via 1/4" plastic tube, down through bilge,
out through drain hold at back of boat. Long and tedious task. Trust me I had the fire extinguisher beside me at all times. 35 gals of gas and one spark, and I wouldn't be writing this message. KABOOM! Hope I never have to do this again ! $($@&$(@&@)

BTW, I used every drop of gas in my vehicles without any problems.
I checked gas before using, and it all looked clean, and also checked for water... None!

At the advice of 'Just-4-Kiks', I added a can of 'Seafoam', then fillled tank with 'High-Test, at least 89 octane.

I started boat only after cranking a couple times, started right up !
Took the boat out for it's first run of season, and it appeared to run extremely smooth! No hesitation, coughing, or stalling. Ran the boat for 30 min, then brought her in without issue. Beleive me this is 100% better performance than my last few times out on the water. Almost need to get towed in from last Oct Fall outing.

Hopefully, my original issue I was battling was just bad gas from last year.
I may have had some water in gas, not sure, but could never identify in several tests. ETHANOL ! I HATE IT WITH A PASSION !!!!

I had to rule out the Carb in my problems, as this was just rebuilt, with all new parts, including float.

Anyway, hopefully all my problems are behind me now? TBD?
I still have to change my impellor over the next few weeks, and I should be set for the summer season.

Thanks everyone, I really value your opinions and suggestions, especially 'Just-4-Kiks' for recommending the 'Seafoam'. I'll be using this gas additive on a regular basis.

See you on the lake !

Bigdog

[jst_4_kiks]

glad you finally got the whole thing done and out boating. also glad that i could help you out in your repair via PM.

continue to run your tank of 89 octane fuel until you need to refill. then switch back to 87. also with every other tank of fuel, add the recommended amount of seafoam to treat 35 gallons of fuel. do that for 6 fuel tanks worth. should be no more problems.

heres to a happy boating to you bigdog. Kyle