fuel issues

[CaptH00k]

I have a 1991 or 1992 Mercury 175 black max. Once it is warmed up it will run wonderfully at max speed until the carbs run out of gas. If i let off then give it the gas again it runs fine until it again runs out of fuel in the carbs. Where is the fuel filter located at and has any one else experinced this problem:

 

[Chris1956]

Re: fuel issues

If you pump the primer bulb, will the motor stay running? If so, you have an air leak, clogged filter, A-S valve or bad fuel pump.

That motor may have an inline fuel filter under the cowling. Did you check your fuel line for air leaks? Did you check the antisiphon valve in the boat tank for clogging? Finally, you might rebuild the fuel pump.

 

[Silvertip]

Re: fuel issues

When the engine begins to lose power, is the primer bulb in the fuel line being sucked flat?
If so, then there is a restriction between the bulb and the bottom end of the fuel pickup tube in the fuel tank. Surging like you explain however is very likely a fuel pump going bad. Fix it before your high speed runs turn into an engine rebuild due a lean condition.

 

[j_martin]

Re: fuel issues

When the engine begins to lose power, is the primer bulb in the fuel line being sucked flat?
If so, then there is a restriction between the bulb and the bottom end of the fuel pickup tube in the fuel tank. Surging like you explain however is very likely a fuel pump going bad. Fix it before your high speed runs turn into an engine rebuild due a lean condition.

I bought an XR4 that balked like that. I think I shot 6 or more distinct measurable problems out of it before I got it fixed. Search the forum, you'll find it.

John

 

[CaptH00k]

Re: fuel issues

I have not checked the primer bulb when this happened, just didnt think about it. Not a real good motor mechanic is the fuel pump hard to replace? Thought I would change all the fuel lines and primer bulb and any filters I could find before I let some one work on fuel pump or carbs. Any suggestions or pictures would be helpful. thanks

 

[Willie Nel]

Re: fuel issues

Make sure that the vent on the fuel tank is open, it seems as if you are creating a vacuum on your fuel tank. Some tanks have a vent on the cap which has to be opened manually, others open automatically when you connect the fuel line. If this is the carb model, the only filters which I am aware of is on the carb inlet, it is actually a fine sieve which should not block up easily unless you had some very dirty fuel.

 

[Silvertip]

Re: fuel issues

You apparently feel throwing parts at a problem is a reasonable way to fix a problem when it is a foolish waste of money. Diagnose, then repair. There are lots of things you can do before you spend a nickel on the repair.

1: Remove the fuel line at the engine. Now squeeze the primer bulb using a jar or jug to catch the gas that may or may not come out. If the gas shoots out in a good stream when you squeeze the bulb you just saved yourself the cost of the line and the bulb. If no fuel or just a trickle, check for a sticking anti-siphone valve which is the fitting on the tank to which the fuel line is attached. It has a spring loaded check ball in it and it can get sticky.

2: Attach the fuel line and then disconnect the line that comes out of the fuel pump and goes to the carbs. Again, using a jar or jug (and a longer piece of hose if necessary) have a helper spin the engine to see if the pump is moving fuel in a good stream. If not, you now know the problem is likely the pump or the fuel filter but more likely the pump. If the filter has not been changed recently, change it if only for preventive maintenance purposes.

See how this process goes? Diagnose - then repair.

 

[CaptH00k]

Re: fuel issues

Thanks for the help on troubleshooting the fuel system. One of the main reasons I joined the forums was for the expert and experience that can be gained from others. Unforunatley being a novice at these issues money is the only avenue I have outside these forums. Thanks for all the help I will try your susggestions. CaptH00k