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Fuel Pump Failures

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Ron C

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2000, 5.0L, Mercruiser Alpha. Have owned for seven years with no problems until 2011 season. Engine started just fine at start of season. Shutdown for about an hour and would not start again. Mechanic checked the usual and determined the fuel pump was bad. New replacement did not work. Re-installed the old pump and it worked fine for a month until engine quit while running. Would not restart. Checked the inlet screen in the tank, inlet screen in the carb, changed the separator. Finally installed a new fuel pump. OK for another month or so and then the same - quit while running. Removed the anti-syphon valve at the tank pickup, changed the hose from the tank to the separator. Finally in desparation because of grandkids here changed the fuel pump again! Ran OK for a month or so and then quit while running again. Put away for season.

Just now starting 2012 season. Decided to change the float valve and seat just in case. No luck, no start. Carb dry. Seems like the fuel pump again. 10.75V at the connector during cranking, 12+ with the ignition on and the oil pressure sensor jumped. Tomorrow I'm going direct from the battery to the pump but based on past experience, I think the fuel pump is not working again. Any thoughts on what could be "taking out" fuel pumps or stopping it from running?

Thanks.
 
Lack of fuel will burn them up. Is it a Merc. pump? Make sure the vent is open. Loosen the fuel filler cap and see if the problem goes away. Fuel line routing can affect the pump...do want dips in the fuel line.
 
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Welcome aboard !

If this were my boat i would remove the fuel water sep. Go straight from the tank to the fuel pump then to the carb. Make sure your pump is not drawing air. Bypass the sender switch.

What i would do is install a switch at the helm for the pump you flip the switch straight power to the pump keyswitch... start and run the engine.

You want to cut off the engine you flip the switch.. power off to the pump, keyswitch off for the engine.

See if this fixs the problem at the end of the season go after the problem with more resolve. Meaning no grandkids around that want to go boating grandpa.

Post back at the end of the season and we all together will try to help you resolve the problem.

You have a pm.
 
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Thanks for the input. I'm assuming there is nothing wrong with the fuel system design as it has worked fine for several years. Something is broken, plugged, etc. to be causing this problem. I just can't seem to find it. Again, added stabilizer in the off season, fuel tank screen seems clean, anti-syphon valve out, new hose to separator, new separator, screen at carb clean, new float valve.

First I'm going to determine if the existing fuel pump works at all by bypassing everything and connecting it directly to a battery - only for testing. If the pump is dead, no choice except to buy yet another and wonder what's taking them out.

The last pump was a Mercruiser. I think the vent on the tank is clear but I'll check. Thanks for the suggestion.

Ron C
 
Ron C said:
Thanks for the input. I'm assuming there is nothing wrong with the fuel system design as it has worked fine for several years. Something is broken, plugged, etc. to be causing this problem. I just can't seem to find it. Again, added stabilizer in the off season, fuel tank screen seems clean, anti-syphon valve out, new hose to separator, new separator, screen at carb clean, new float valve.

First I'm going to determine if the existing fuel pump works at all by bypassing everything and connecting it directly to a battery - only for testing. If the pump is dead, no choice except to buy yet another and wonder what's taking them out.

The last pump was a Mercruiser. I think the vent on the tank is clear but I'll check. Thanks for the suggestion.

Ron C
Click to expand...

Ayuh,... Those Merc electric fuel pumps have a funky electrical connection at the top of it that many times is a Problem...

The old 1 on my motor was a problem, that wigglin' it abit at the start of the day, cured it, for the day...
Only to repeat itself the next day...

I changed the pump, 'n had the same problem...
After I took the top apart, 'n refit the connector fitting, it's been workin' Perfect for a few years now....
 
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