Fuel supply issue

[FishHunt23]

I have a 2002 merc 15 that starts and idles great. At high RPMs, it seems to not get gas quickly enough and will fall off plane for a minute while it seems like the fuel catches up ... then I'm good to go for a couple minutes before the cycle repeats itself. When this happens, the bulb goes soft, but pumping it doesn't seem to help much. I've tried two different fuel lines, and it doesn't make a difference. And both lines appear to be fine, so my thought is that the problem is inside the engine. The fuel filter seems to be OK. Any advice on what to look for? I really appreciate any help. Thank you.

 

[aussieflash]

Re: Fuel supply issue

First check fuel lines for cracks, leaks or loose connections.Is tank vent open?Then id be looking at fuel pump and carb service.

 

[FishHunt23]

Re: Fuel supply issue

First check fuel lines for cracks, leaks or loose connections.Is tank vent open?Then id be looking at fuel pump and carb service.

So far I have cleaned the fuel filter (looked almost spotless even before cleaning) and inspected all hoses. Everything looks great. The intermittent nature of the problem has me confused ... could it be fuel pump or carb? When the motor seems starved for gas, the bulb goes soft (not flat, just soft/empty) on the fuel line, but it firms right back up soon thereafter and I'm good to go for a few minutes before it repeats. Seems like there must be air getting in there somewhere, or the fuel is getting blocked somewhere in the motor? It seems like it should be an issue with the external tank or fuel line, but the problem happened with two different tanks/lines that both seemed fine. It's driving me nuts!

 

[CharlieB]

Re: Fuel supply issue

O-rings inside quick connections can fail when under vacuum, allowing air to suck in, yet when pressurized while squeezing the bulb will seal and appear fine.

Test by temporarily installing a clear hose between the fuel pump and carb, run the motor and observe for any air bubbles passing thru the clear hose.

Remove the clear hose once finished with your repairs as it is NOT rated for continuous use.