Excessive throttle pumping required to start
 

When my engines have not been run for a week or so, it takes many, many throttle pumps to get as into the engine to start. Once it's been running, the rest of the day it takes no throttle to start - just turn the key.

Is this indicitive of bad fuels pumps or are there check valves in the system leaking back over time? If it's check valves leaking, where are they, in the carbs?

Engines are 1989 454 Mags, bone stock.

Thanks
Dave

Re: Excessive throttle pumping required to start
 

I have the same situation with 350 Magnums. Mercury developed small fuel bowls in the Weber carbs to reduce varnish formation during storage and they drain back into the tank over time as well. Mercury said the fix is:

Without touching the throttles, on a cold start, turn the engine over for 5 seconds to fill the fuel bowl. (Some boats may need a second 5 second cranking, for the loading of the bowls, if the next step didn't result in immediate starting.) Then, and only then, pump the throttles back and forth twice to prime the engine now that the fuel bowls are full and the next cranking should start it immediately. If not, the next time you know you have to do a 5 second cranking, then wait a couple seconds then another 5 second cranking then pump twice and it should start up.

Once you get it right it's a breeze. But don't expect immediate start ups after a pumping because of this design. I hear changing to a different carb and probably you would need a different manifold as well would get you into an instant pump then start situation. Maybe going to a Holley 600 CFM. It's the design and now that things are "efi" it's a moot point anymore. But that's the rational and "fix". My feeling is that as long as I know there is nothing wrong and it's just an inconvenience of design I can live with it. But you are right in that if you came back a day later it probably would start right up with a pumping but a week and the fuel bowl is empty. It's a dry start situation everytime time after a few days storage.

Re: Excessive throttle pumping required to start
 

Cant wait to try this ....my 454's esp the port motor are hard to start cold .....but after they have been run ....start instantly .....

Re: Excessive throttle pumping required to start
 

Mine too as well as most everyone I know with this starting situation. Once I did the priming with 2 five second cranks without touching the throttles and then pumped twice and turned the key they started every time immediately. Always start instantly when warm or recently started and it seems that the bowls empty after a couple days and then this procedure is the only answer other than going to a carb with a big non draining bowl.

Re: Excessive throttle pumping required to start
 

My 454 was like this and everybody else's that I know of too. I replaced with a Holley and now I pump twice and it starts right up. It seems to run better too.

Re: Excessive throttle pumping required to start
 

HOW I SOLVED THIS SAME PROBLEM

















I changed to HOLLEY carbs. HP 950's

Re: Excessive throttle pumping required to start
 

Hot Damn .....it werks ....

Re: Excessive throttle pumping required to start
 

In my experience Holley has always been a better cold start carb.

Roby

Re: Excessive throttle pumping required to start
 

Our rig has secondary elestric fuel pumps with switches.

Run those for a few seconds before a cold start and they crank right up. Just ask all the neighbors!

Re: Excessive throttle pumping required to start
 

I thought you weren't supposed to use electric fuel pumps on a marine engine. Anyway, besides starting better my engine with the Holley is more responsive and seems like it uses a little less gas (unless wide open).