fuel problems

[rgirandola]

I am having major problem with my 5.7 mercruiser...the port engine is not pumping gas to the motor. I've changed up the fuel line system, replaced the fuel pump, replaced the fuel/water seperators,swithced the fuel line from the starboard engine to the port and the port engine keeps dying(the starboard engine runs great). The cam looks good on the port engine. If you manually put gas in the carb, it runs fine until the gas is all gone. Even isolated the fuel system with portable tanks and a clear hose and it still isn't pumping gas to the motor...someone help????

 

[Don S]

Re: fuel problems

Is that a mechanical or electric fuel pump? What year and model engine do you have.

 

[rgirandola]

Re: fuel problems

I have a mechanical fuel pump..the motors are 1986 5.7 260 hp mercruisers.

 

[Don S]

Re: fuel problems

Have you checked the filter in the carb? If it's plugged you won't get gas to the fuel bowl, could also be a stuck needle valve in the carb.<br />Did you check the the fuel pump push rod was in place and actually working. The cam could have the lobe worn off.

 

[waterone1@aol.com]

Re: fuel problems

If you disconnect the fuel line from the carb and stick the end of the fuel line into a container and crank the engine over....does gas flow into the container ? If yes, then problem is in the carb (such as what Don suggested, stuck needle valve, clogged filter). If no, problem is in the pump or towards fuel tank . Don't forget that any type of air leak in the line before the pump will cause the pump to "suck air" and will not prime itself.

 

[deputydawg]

Re: fuel problems

If you replaced the feul pump, test the new one and make sure it isn't bad. <br />Sounds like a float problem, or a plugged screen in the carb. Where the feul line enters the carb there is a small filter screen, make sure that is clean. <br />if this screen is clean, it would be a good time to pull the carb off and rebuild it. It may be clogged inside with buildup. It may be running way too lean, until you overfill the float bowl. It will then run when it is flooded until it returns to the normal float bowl level where it floods again.<br />One quick test to do, close the choke or use a clean rag and close off the carb. Is it runs smoother it is getting some feul but not enough. Be careful though, when running lean they tend to backfire through the carb.

 

[rgirandola]

Re: fuel problems

I have rebuilt the entire carb-if I fill one of the fuel seperators with gas and crank the engine, it will suck half the fuel out of the seperator and then shut off. I isolated the fuel line(I have a left and right pony tank and a nose tank). The starboard engine runs perfect, now if I take that same fuel line going to the starboard engine and attach it to the port engine, it has to be primed with gas through the carb, runs off the primer gas and then dies...no gas getting to that engine..very stumped...new fuel pump, cam looks fine(as well as the push rod), rebuilt carb, new fuel lines....when it has primer gas in the carb it fires up and runs quiet for about 10 seconds and then shuts off because of no gas...please keep coming with your thoughts on this...thanks!

 

[llerrad]

Re: fuel problems

I see you said you have replaced all the fuel lines, just want to check did you replace them all. The reason I ask is I had same problem and found a blockage in a fuel line of fuel filter particals would never have belived it but just a fluke chance to pull line and blow air through found my problem, was a real Bas#$@d to find as engine started and ran for a short time then died.

 

[rodbolt]

Re: fuel problems

now is about where a fuel vacum gauge test would come in handy. its to simple and always gets over looked. hook up the pump with a hose from the suction side to a remote tank. if it wont draw then its the pump,pushrod,cam lobe or ya missed the rod when you installed the pump. its a basic mechanical pump that works great never breaks . your making it to difficult. its very simple. if nothing else hook the vacum gauge Directly to the pump intake and crank for 10-15 seconds. if it pulls no vacum most likly the pump is bad. not the first quicksilver brand new pump I have seen bad. the last bad pump was a quicksilver but it would not regulate pressure. fire it up and in 10 seconds the carb would flood. finally attached a pressure gauge and it goes to 50 psi and the needle would peg. bad pump from the box. good mexican quality controls. cant wait for the higher quality chinese stuff.