motor losing prime

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bassplayer1958

Cadet
Joined
Nov 8, 2012
Messages
6
I have 1989 johnson 88hp v4 new carbs, fuel pump and fuel lines. Will run on 6 gallon remote tank but not on built in tank (new pickup tube and sending unit). Thanks for any help
 
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boobie

Supreme Mariner
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Nov 5, 2009
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20,826
Re: motor losing prime

Have you checked the anti-syphon valve in the fuel line connector on the built in tank ??
 
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emdsapmgr

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Dec 9, 2005
Messages
11,551
Re: motor losing prime

Have you checked to be sure that the vent on the built-in tank is open/unobstructed? Same fuel line?
 
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Georgesalmon

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Apr 14, 2012
Messages
1,793
Re: motor losing prime

I hesitate to say this because it can be very unsafe, but,,,,,,,,,,,,,,back in the day I remember that there were some outboard engines that could not overcome the anti syphon valve. I even remember (I think) that there were some made differently for I/O engines and outboards. You might try using a hose barb in place of the anti syphon valve and test it. If it works then I would look for a different brand valve. I would never suggest that you leave the anti syphon valve out of the fuel system for normal operation.

Edit: You do have a bulb on the remote tank fuel line and have pumped the fuel till firm right ?
 
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Rmoore45

Seaman
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Aug 4, 2011
Messages
68
Re: motor losing prime

I had a similar problem with my 9.8 merc, I could prime it and it would run for a while but once I got going wide open it would starve for fuel and die. I found a small leak in one of my hoses which allowed the fuel pump to suck air and not fuel. I replaced the line and it solved the problem.
 
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emdsapmgr

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Dec 9, 2005
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Re: motor losing prime

Just to be clear, you are using the same fuel line when testing both tanks. With the tank end connector when you run on the 6 gallon tank, then you remove that tank end fitting and install it on the anti-siphon valve hose barb on the built-in tank. Correct? What happens if you install the hose on the built-in tank, then remove the engine end fuel fitting-then prime the hose bulb. You get plenty of fuel gushing out the engine end of the hose?
 
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emdsapmgr

Supreme Mariner
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Dec 9, 2005
Messages
11,551
Re: motor losing prime

The 6 gallon tanks don't have an anti-siphon valve. Your built in tank does. You could do another test of that valve. Either replace it with a regular (straight through) hose barb, or you could remove the retainer, ball and spring from your current anti-siphon valve. Same thing. See what happens.
 
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bassplayer1958

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Nov 8, 2012
Messages
6
Re: motor losing prime

emdsapmgr said:
The 6 gallon tanks don't have an anti-siphon valve. Your built in tank does. You could do another test of that valve. Either replace it with a regular (straight through) hose barb, or you could remove the retainer, ball and spring from your current anti-siphon valve. Same thing. See what happens.
Click to expand...

removed retainer, ball and spring from valve today with no luck. Still losing prime. Thanks for sugestion
 
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Outsider

Lieutenant Junior Grade
Joined
Apr 24, 2007
Messages
1,022
Re: motor losing prime

Blow through the fuel line into the tank. If it's clear, you have a fuel pump issue ...

FWIW, anti-siphon valve isn't required unless your fuel tank/line are above the carbs ...
 
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