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Old 07-15-2011, 03:32 AM   #1
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Default 3.0 Mercruiser not getting fuel

Hello, i have a '99 Maxum 1800sr with the 3.0 merc. I've had some sputtering,stalling,hard start issues for awhile and decided to rebuild the carb. Rebuilt carb with Mallory kit, set all adjustments to mercruiser specs. and reinstalled. Cannot get engine to start. After inspecting i have there is no fuel spraying through carb. while engine is cranking over. After cranking engine over for awhile and then breaking the fuel line loose, some fuel drips but not a whole lot. Mechanical pump by the way. I can pour fuel into the carb and engine starts fine but of course stalls once that fuel is consumed. I'm leaning towards fuel pump but always thought these mechanical pumps were pretty bullet proof. Just added a water/fuel separator kit a couple of months ago so i suspect the filter to be clean. (the carb was clean during inspection/rebuild). I removed the fuel line and fitted it to spray into a cup, it would spray fuel but not sure if enough. I'm not real sure how 6psi of fuel would look spraying out. Where would i tap in fuel pressure gauge? Any advice or tips would be greatly appreciated. Also, if fuel pump is faulty, has anyone had good experience wiring in an electric pump and deleting the mechanical one?
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Old 07-15-2011, 03:25 PM   #2
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When you pour fuel into the carb where do you pour it in - the float bowl vent tube?

Given the symptoms it almost sounds like the needle valve is stuck closed - not allowing any fuel delivered by the pump to enter the carb float bowl. If the float bowl is empty the needle valve should be wide open so any fuel delivered by the pump would get into the bowl. If the engine would start and run prior to the carb rebuild and now it won't, and you didn't do anything with the pump, I'd be taking the carb apart again to check the float.

The mechanical pumps are bullet proof. Yours could be weak. If you want to install a pressure gauge to verify it needs to go between the pump and carb. Not sure I would fiddle with that, though, I'd just replace the pump. I also would not install an electric pump - why complicate your life? You'd need a marine rated pump and then there's the wiring, location, etc.

Dan
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Old 07-15-2011, 04:42 PM   #3
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I just poured down the throat through the choke plate. I suspect the same thing Dan with the needle valve. I just keep 2nd guessing myself being the valve is inverted and gravity should have it open and it is new. But again, i have seen many new parts fail in the automotive business. Thanks for your fuel pump recommendation, i would rather replace it with a like pump if needed but just wanted some reassurance. I'm gonna pull the carb again and recheck the float and may swap out the needle valve and seat. "Fingers crossed".......................Thanks...Tim
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Old 07-15-2011, 05:11 PM   #4
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Good luck with it Tim. I've had my hands into a bunch of Q-Jets and still manage to learn something new each time I take one apart.

Having gone the "modified" route in my younger days I'm a big fan of keeping things factory/stock for reliability. I hate after market electric fuel pumps, and ya just don't need the flow for that 3L.

Let us know what you find out.
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Old 07-15-2011, 05:26 PM   #5
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Thanks Dan.....will do, hopefully some good news here in the next few days. The boat has seemed to have something going on every time i turn around here lately. Makes me wonder whats next.
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Old 07-15-2011, 06:00 PM   #6
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Fickle beasts, no?

Children can be less maintenance. LOL
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Old 07-16-2011, 08:05 AM   #7
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As symptoms you have mentioned here I think your Fuel valve which spray fuel to carb is stuck. You should check valve or if possible replace it with new one. If you still found any problem, you need a boat mechanic who will help you find out and solve the problem.
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Old 07-17-2011, 04:22 AM   #8
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Just wanted to update. After pulling the carb for the 3rd time and rechecking everything i found that the float drop adjustment did not hold for some reason. I readjusted to 1 3/32 and triple checked again before reassembling. I even squirted gas through the fuel inlet with a baby dropper to be sure the needle valve was open. Installed carb and she fired up no problem. So, i guess the lesson here is even when you know you've done it right- RECHECK YOURSELF.
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Old 07-17-2011, 02:59 PM   #9
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thanks for posting the results!!...glad it worked out......



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Old 07-18-2011, 03:08 AM   #10
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You rebuilt the carb yourself? Very impressive. That's the one thing I don't do. I use a specialty shop that only rebuilds carbs. Glad it's working now.
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