350 dies after short runs

[Winner74]

I have a 1974 Winner with a 350 Mercruiser, still running points. It will idle forever, but when you bring it up off idle it runs for maybe 100 yds. then dies. Sometimes it is very hard to start, other times it will start right back up. Has a electric fuel pump inline before the filter, and still has the mechanical pump also. Need to know if anyone has any ideas.

 

[achris]

Re: 350 dies after short runs

When was the carb last cleaned?

Chris.........

 

[Winner74]

Re: 350 dies after short runs

Replaced Carb also, no change

 

[JustJason]

Re: 350 dies after short runs

why do you have 2 fuel pumps?

get rid of the electric pump and change the fuel filters (if not relatively new) and see how you do. Don't forget you may have a fuel filter in the mechanical fp and in the carb inlet as well

 

[wca_tim]

Re: 350 dies after short runs

choose one fuel pump or the other... and make sure it works... then change filters. if you still have the problem, add a cheap fuel pressure gauge (less than $20) right in front of the carb to see that you've got at least 4 or 5 psi... and not more than 6 1/2 or 7. (sorry, don't know the real specs, I'm sure someone else will chime in and correct it). Sounds like you're starving for fuel, and that can be the filter, or next (once fuel filter thing is straightened out) the tank screen or ball check valve, etc...

just my two cents...

 

[Winner74]

Re: 350 dies after short runs

changed all the filters, added the electric as a quick fix last weekend to get going. Seemed to help for a little while. Is there a screen on the pick up in the tank?

 

[searay3]

Re: 350 dies after short runs

Check to make sure the tank vent is clear...

 

[wca_tim]

Re: 350 dies after short runs

as he mentions above, there's an air vent to let air in, make sure it is clear and that the hose running to the tank is not kinked, than there is usually also a scfeen on the end of the pick-up in the tank - typically a little harder to get to, and finally there's a ball check valve (anti siphon) valve where the fuel line connects to the tank, etc...

 

[Winner74]

Re: 350 dies after short runs

The vent is clear, I will check the screen in the tank. Appreciate the help.

 

[jerryjerry05]

Re: 350 dies after short runs

Check coil.J

 

[CharlieB]

Re: 350 dies after short runs

Has a electric fuel pump inline before the filter, and still has the mechanical pump also.

Some manufacturers used an electric pump and filter before the Merc manual pump which also has a filter. I suspect they felt that the added restriction of the additional filter was too much for the manual pump, hense the electric pump.

Prior advice to change BOTH filter may correct your problem, HOWEVER, test both fuel pumps flow is recommended to ensure correct diagnosis and possible future reliability.

Taking the time to properly test ensures proper diagnosis.

Disconnect the fuel line AFTER the electric pump, assuming this pump is before the manual pump. Attach suitable hose to direct fuel to a safe container. Turn key ON to energize pump and observe flow, good solid stream or wimpy dribble?

Same test for manual pump, may be easier to disconnect at carburator. Ground coil wire to prevent starting, crank engine and observe fuel stream.

 

[180shabah]

Re: 350 dies after short runs

....added the electric as a quick fix last weekend to get going.

Is this a marine pump, and has it been wired properly so that it does not pump if the engine is not running????

 

[Winner74]

Re: 350 dies after short runs

Found the problem, it was in the pick up inside the tank. Pulled the tank out and replaced. Thanks for all help.