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454 Starving for Fuel

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NautiqueJeff View Drop Down
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    Posted: March-24-2018 at 9:55pm
Ok, time to bring in the experts on this one...

I am working on the 454 in my winter beater, my 1988 Martinique (Ol' Sparky).

It has been running fine for the last few weeks, but all of a sudden it developed an issue where it seems to be starving for fuel. It runs OK at idle, but when you try to accelerate, it dies. Also, if you let it run long enough at idle, it dies then, too. If you wait a few minutes, it will start up and run at idle for a few minutes again, but still won't run long at all above idle.

I have changed the fuel filter, checked the fuel tank vent line (all clear), and tested the fuel pump by connecting the output to a hose running into a gas can (pumping plenty of fuel).

The carb was rebuilt by PCM less than a year ago.

In the videos below, I bring the engine up to about 1,600 RPM's and it runs for a few seconds, then seems to starve for fuel. I never reduce the throttle at any time.

Any thoughts on what's happening?

Here's a video.

454 Video

Thanks!
Current Boats: 1998 Ski Nautique, 2000 Sport Nautique, 1985 Sea Nautique 2700 (twin-engine), 1981 Fish Nautique (twin-engine), 1980 Fish Nautique (twin-engine)
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Gary S View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary S Quote  Post ReplyReply Direct Link To This Post Posted: March-24-2018 at 10:13pm
Anti syphon valve at the outlet of the tank. It's part of the hose barb where the fuel line connects. They can get clogged up. Take it off and look in both ends make sure the ball and spring are free to move
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8122pbrainard View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: March-24-2018 at 10:23pm
Jeff,
Besides checking the anti syphon that Gary mentions, I'd "T" in a pressure gauge in the line between the fuel pump and carb. Yes, you mention the pump delivers fuel but at what pressure? Did you check the inlet screen on the carb?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: March-24-2018 at 10:24pm
sounds like the anti siphon valve to me too but why don't you hook up a temporary tank to the fuel pump suction and see if it runs OK.

That'll tell you if the problem is before the fuel pump or if it's fuel pump / carburetor related.

If you use a clear line and you see lots of bubbles in the line and the line starts shaking rather violently as it's quitting, you have a fuel pump check valve problem allowing the pump discharge to go back thru the suction and the carburetor gets starved

If it runs good then the anti siphon valve is a likely culprit.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote NautiqueJeff Quote  Post ReplyReply Direct Link To This Post Posted: March-24-2018 at 10:30pm
Thanks! I will try hooking up a spare tank tomorrow and report back.
Current Boats: 1998 Ski Nautique, 2000 Sport Nautique, 1985 Sea Nautique 2700 (twin-engine), 1981 Fish Nautique (twin-engine), 1980 Fish Nautique (twin-engine)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: March-24-2018 at 10:33pm
Make sure the temporary tank is vented too.

And don't forget that old saying that half of all fuel issues are ignition related
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Post Options Post Options   Thanks (0) Thanks(0)   Quote NautiqueJeff Quote  Post ReplyReply Direct Link To This Post Posted: March-25-2018 at 7:07pm
Ok, Ol' Sparky is fixed!

Hooked up the spare tank, and it ran fine.

Checked the anti siphon valve, and it looked and operated fine.

The only thing left was to replace the fuel line itself, so that's what I did. It must have been swollen on the inside or something. The new fuel line seemed to fix it. I put an hour on it this afternoon, and it ran great.


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Nautique2001 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nautique2001 Quote  Post ReplyReply Direct Link To This Post Posted: March-25-2018 at 7:10pm
I had the same issue happen with my '86. Pulled the fuel supply line going to the carb and the screen leading into the carb was clogged with junk. Cleaned it all up and that did the trick. I'm guessing that the ethanol doesn't help the cause! Ken
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: March-25-2018 at 7:16pm
Originally posted by NautiqueJeff NautiqueJeff wrote:

Ok, Ol' Sparky is fixed!
The new fuel line seemed to fix it. I put an hour on it this afternoon, and it ran great.

Enjoy the water!!


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Post Options Post Options   Thanks (0) Thanks(0)   Quote NautiqueJeff Quote  Post ReplyReply Direct Link To This Post Posted: March-26-2018 at 12:02am
Originally posted by Nautique2001 Nautique2001 wrote:

I had the same issue happen with my '86. Pulled the fuel supply line going to the carb and the screen leading into the carb was clogged with junk. Cleaned it all up and that did the trick. I'm guessing that the ethanol doesn't help the cause! Ken


I did check the screen too, and it was pretty clear. I completely cleaned it, but I don't think that was the cause of my issues. I was kind of surprised it was so clean, but I was glad it was.

I have no idea what fuel was run in this boat before I got it. It was up in Wisconsin, and whatever was in the tank had been in there for the last ten years without the boat being used at all! I pumped it out when I picked up the boat last year, and ever since then it has had ethanol-free gas. The ethanol that was likely in the gas that sat in the lines for those years probably caused the lines to swell.

Took it out again this evening, and it is running great now. Thanks for the help everyone!
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