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Jan 23rd, 2013
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Loss of fuel pressure #13216569 07/16/19 06:32 PM
Joined: Mar 2018
Posts: 41
basscatmo Offline OP
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Joined: Mar 2018
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2018 Merc Pro XS 250 loses fuel pressure when idling and stops/won't start until I prime the bulb. After it gets some fuel, runs ok. Seems to run fine when on plane. Any ideas?

Thanks

Re: Loss of fuel pressure [Re: basscatmo] #13216606 07/16/19 07:15 PM
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Bruce's Online Content
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Mine does the same thing. It does not like to idle long ways. It will do the same thing unless i idle it up faster.


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Re: Loss of fuel pressure [Re: basscatmo] #13218627 07/18/19 05:39 PM
Joined: Apr 2014
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Fishcharmer Offline
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I have seen a bad primer bulb be the cause of the same problem several times.... Replaced the bulb and that fixed it..

Re: Loss of fuel pressure [Re: basscatmo] #13219494 07/19/19 03:23 PM
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DFW-fisherman Offline
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Most primer bulbs have an internal check valve inside - sounds like it could be leaking allowing fuel pressure at the engine to flow back to the tank. Or, it could be the one at the fuel pickup line at the tank that is leaking back; I would check them both.

Re: Loss of fuel pressure [Re: basscatmo] #13219610 07/19/19 05:14 PM
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Gamblinman Offline
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Make sure fuel lines and primer bulb are made of the newer ethanol resistant materials. If you haven't, change all fuel lines and primer bulb from tank to engine.

Check screen in top of VST to make sure its not plugged with trash.

May be time to rebuild low pressure pulse pump. Fairly easy to do...just make sure you get the valves and springs in the correct position.

Re: Loss of fuel pressure [Re: basscatmo] #13224267 07/24/19 04:06 PM
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OPTI Offline
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The low pressure fuel pump is the problem the optimax uses a vacuum operated fuel pump and with the new style pressured fuel tank system the fuel demand valve will cause the fuel pump to work harder and stretch the diaphragms or tulip the mylar check valves. How I solved this problem was to replace the fuel demand valve and rebuild fuel pump. I got Mercury to pay for a few fuel pump but the technician needs to call Mercury and explain the situation but to be honest they may or may cover it. Had this problem quit a few times. boat builder covers the valve and Mercury the pump........OPTI

Last edited by OPTI; 07/24/19 04:07 PM.
Re: Loss of fuel pressure [Re: basscatmo] #13225126 07/25/19 01:08 PM
Joined: May 2003
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gary purdy Offline
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Have seen lots of problems with the fuel demand valve.


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