Boat stops on the lake Fuel pump or What?

[Chaparral220]

I have defined that I have a fuel problem with my boat. After running an hour or so it will start, idle, then die and not restart. This time I verified that I have spark and that it is a fuel issue.

It is a 5.7 with throttle body.

While trying to get it going it clearly was starving for gas. I could pour a little gas down the throttle body and it would at least try to run.

I pulled the line from the tank and ran it into a small gas tank. After a bit is it started and ran.

I idled a bit toward the dock and then put the line back on the tank and it then kept going. Not sure what to think.

I did read about fuel testing in the adults only. At present, I don't have a device to test fuel pump pressure. I was wonder if pumps can be this intermittent and if it is a tank issue. I have replaced the water separator filter and syphoned the tank recently thinking bad gas could be an issue. This is the third time the boat has left me on the lake. At least this time I got it in.

I read about the antisyphon valve being possibly clogged. Where exactly is it if I need to inspect or replace it? How do I get to the screen on the end of the fuel line inside the tank. There are no gas tank diagrams in the shop manuel given it is not an engine or outdrive component.

I don't mind replacing the fuel pump if I have to but it is expensive.


My experience with a car fuel pump going bad was basically all or nothing. It worked or it didn't.

I could go out now and it would start and run seemingly fine.

Any suggestions would be appreciated.

 

[Chaparral220]

Re: Boat stops on the lake Fuel pump or What?

I forgot to mention that I remove the gas cap and did blow back in to the tank and could hear some bubbles.

 

[TilliamWe]

Re: Boat stops on the lake Fuel pump or What?

Fuel pumps can indeed be intermittent. In cars too.

The anti-siphon valve will be at the top of the fuel tank, where the fuel line to the water separator attaches. The screen is up there, not inside the tank.

Have you tried to run your bilge blower while idling? This reduces the heat in the engine compartment. You may have a bit of a vapor lock issue.

 

[Chaparral220]

Re: Boat stops on the lake Fuel pump or What?

I thought about vapor lock as well. We have been boating for years and have never had that problem with this boat. We have over 400 hours on it and it has been terrific up to this point. Even if it it vapor lock, wouldn't low pressure contribute to that? If so could still be tank or pump.

I went to a local auto parts store to put together a rig to test the vacuum on the pump. They looked at me like I had two heads! I have a vacuum gauge off of an old A/C charging system that may work for me.

When I disconected the fuel line to run out of the gas can, I did it at the point where the fitting then goes down into the tank. Can I unthread the fitting on top of the tank and pull the pick up tube, anti syphon valve and screen all out through there?

 

[TilliamWe]

Re: Boat stops on the lake Fuel pump or What?

The tube that sticks down into the tank should have a square head on it. Sticking out of that square head (making the 90 degree angle) should be the fitting that your hose goes over and clamps to. (This should also be your anti-siphon valve) Unscrew that fitting and the screen should be right there. It should NOT be in the bottom of the tank or at the bottom of the pickup tube. These aren't cars, where while still a pain, the fuel tank can be unbolted and dropped out. In a boat they are usually fiberglassed in. So they put the screens and the anti-siphon valve at the top.

Got a picture of your set up?

 

[gadget73]

Re: Boat stops on the lake Fuel pump or What?

Have you replaced the fuel filter? Usually the filter is located before the pump, so if its clogged, it will cause low pressure.

antisiphon valve is usually located at the top of the tank where the fuel hose attaches. Pull it off and check for varnish or other dirt buildup. SHould be able to clean it out with carb cleaner. Be sure the ball moves freely in there and does not stick.

 

[Don S]

Re: Boat stops on the lake Fuel pump or What?

I forgot to mention that I remove the gas cap and did blow back in to the tank and could hear some bubbles.

Not sure what you mean by "I remove the gas cap and did blow back in to the tank"
When you removed the cap, did you hear a hissing noise? If yes, then you probably have a plugged up fuel vent. When you are out running on the lake, you use gas and create a vacuum in the tank that the fuel pump can't overcome.

Might head up to the Adults only sticky at the top of this forum and look at the HOW TO check your boats fuel system.

 

[Chaparral220]

Re: Boat stops on the lake Fuel pump or What?

Don, I started at the adults section and have followed what I read there up to testing for vacuum.

I blew back down the fuel line when I disconnected it at the water separater filter. Wanted to make sure not just clogged line.

I did not get a big hissing sound when I removed the cap but will be more aware of it in the future.

Can low fuel pressure lead to vapor lock? I am going to go out and check vent tube as well as the screen will report back.

 

[Dshow]

Re: Boat stops on the lake Fuel pump or What?

I had a similar issue with my 2001 Mercruiser 5.7L TBI. I attributed that to heat in the engine compartment/fuel vapor lock. Now, when running hard, l leave my blower running and haven't had any more issues.

Here was my post on the subject:
http://forums.iboats.com/showthread.php?t=256257

About half was down, there is a picture of my throttle body. I believe there is a valve to measure my fuel pressure to the right of the fuel pressure sensor. If it happens again, I will start by measuring my fuel pressure there.

 

[Chaparral220]

Re: Boat stops on the lake Fuel pump or What?

Vent tube is clear and flows freely.

I removed the antisyphon valve and cleaned it. It did not have any apparent blockage. The pick up tube was fine. I do not have any type of screen filter.

I have not had a chance to get my rig together for a pressure test. Will report back once I do.

 

[Chaparral220]

Re: Boat stops on the lake Fuel pump or What?

Did the vacuum test as outlined in the adults only section. Ran engine for a couple of minutes for warm up. Took it up to 1500 RPM. Crimped gas line behind gauge to test. I got 9 - 10 on the gauge.

According to the posting that is exactly what I should be getting. Have inspected all lines. Everything seems to be in good shape. Yet I still was out of commission on the lake.

If it is Vapor Lock what can I do and why does it show up now after 4 seasons with this boat? Could the pump still be faulty?

All suggestions deeply appreciated!

 

[Chappy216]

Re: Boat stops on the lake Fuel pump or What?

Chaparral 220, if you find any solutions to this please post them. It sounds exacly like my problem.

See my story http://forums.iboats.com/showthread.php?p=2165985&posted=1#post2165985

 

[Chaparral220]

Re: Boat stops on the lake Fuel pump or What?

I sent an email to Mercury on this. This is what I got back. Can anyone help on the Service Bulletin.

I am thinking Vapor Lock but still don't understand why all of a sudden I have the issue now after years of solid service.

What mechanisms are in place by Mercruiser to prevent this problem?

What about the pressure regulator. I am not sure how all that part works.


This is what I got from Mercruiser.
"Good Morning. Thank you for choosing MerCruiser. The issue you are describing sounds like a vapor lock condition. Please have your dealer review service bulletin 99-7. The bulletin address issues such as fuel line routing, fuel pump pressure and engine temperature inside the engine compartment. You may also want to consider , when safe operation allows to use your bilge blower as often as possible to remove the heat from the engine compartment and also leave the engine hatch up to get more ventilation. "[/B]

 

[Chaparral220]

Re: Boat stops on the lake Fuel pump or What?

"About half was down, there is a picture of my throttle body. I believe there is a valve to measure my fuel pressure to the right of the fuel pressure sensor. If it happens again, I will start by measuring my fuel pressure there."


What can you do to prevent it other than open hood and blower? I never ever had this issue before.

 

[Chappy216]

Re: Boat stops on the lake Fuel pump or What?

Chaparral220,

I agree with you 100%. I have had this boat for 4 years and never before have I ever had a "Vapor Lock" issue. There has got to be a reason for this besides that.
I think i may start with replacing the fuel pump. It is an expensive trial but the current one is 9 years old so it can't hurt. There seems to be several post regarding the exact same issues. Got to be a culprit.
I will post any info I find out. Thanks for your post.

 

[Chaparral220]

Re: Boat stops on the lake Fuel pump or What?

I found the service bulletin on line.

http://www.boatfix.com/merc/Bullet/99/99_07.pdf

Too big to up load.

I probably will go the fuel pump route as well. It is 9 years old and must be a bit weaker. However, I sure do hate to spend the money! The service bulletin is somewhat useful so take a look.

It looks like it will be a pain!

 

[Chaparral220]

Re: Boat stops on the lake Fuel pump or What?

One other thought. What about placing an in line fuel pump for outboard motors in the line as it comes out of the fuel tank. Could we not then hand pump gas through the line and push out the air in some manner?

Any thoughts on that?

 

[Fun Times]

Re: Boat stops on the lake Fuel pump or What?

If I was you I would hook up a fuel psi gauge in line with the throttle body inlet fuel line hose and get a fuel psi reading before and after the new pump. And on the vaper lock heat reading under the engine hatch, mercruiser dose not want it over 176 degress under there max. Where you running on a hot day? When you looked at the gas tank fuel pick up tube in the tank did you see any cracks in the tube, That would suck in air if damaged. Also pull the filter off and make sure it dose not have too "o"rings too it, And it is tight with fresh fuel in it and make sure you fill it up before you reinstall it so the pump will not have to prime it so hard. Then see if the engine will try to start. Then after it dies pull the filter to see if it is full or almost emptey.

 

[Chaparral220]

Re: Boat stops on the lake Fuel pump or What?

The Adults Only section indicated that you test these pumps by vacuum. Should I do it differently?

It was not a horribly hot day. I have certainly run in hotter weather. This situation has occurred on three different occasions in May and June. I have never had any issues and now three in one season. The blower seems to function properly and I have replace the gas filter twice with no difference. I am going to take a spot meter to test heat next time out just so I know.

When it runs it runs great. Then we wait and have issues with restart.

Any thoughts on the in line hand pump to prime it if it happens?

 

[Viking...]

Re: Boat stops on the lake Fuel pump or What?

Any thoughts on the in line hand pump to prime it if it happens?

I've seen that set-up on a couple of boats. One in particular was a Mercruiser 140, older Starcraft. The owner said it worked beautifully.

As for it not happening in the past...400 hours of glorious un-vaporlocked goodness!
Things wear out, seals and O-rings shrink and harden, flexibility is reduced, and performance diminishes. And that's just the operator, imagine the poor old boat