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).

Re: Excessive throttle pumping required to start
 

Mine started hard with the Weber also. I put a Holley 800 on it and it starts right up every time. It also picked up almost 2 mph. Much stronger throughout the rpm range. Gas mileage is just as good, too.

Re: Excessive throttle pumping required to start
 

[QUOTE=BajaBuddy]I thought you weren't supposed to use electric fuel pumps on a marine engine. QUOTE]

Many marine engines use electric fuel pumps. The mechanical pumps don't create enough pressure for EFI's.

They have been around for a long time. The pump in the bottom right of this picture came from a 1987 320 EFI, which I believe was Merc's first attempt at fuel injection.

Re: Excessive throttle pumping required to start
 

Glad it worked Offthefront.

Re: Excessive throttle pumping required to start
 

I have had several boats with the same problems that you have described. Set for a week then it takes all day to start. The problem was fixed by my mechanic very easily. My carbs were Quadrajets. He said that the fuel bowls leak down when they get older. He pulled the carbs off and sealed a small hole on the bottom of the bowl. (dont know details). When I got the boat back, WOW, just like new. Pump the throttles twice, and it fires up even after sitting for several weeks.

Re: Excessive throttle pumping required to start
 

Hydro, I will try also. Never heard that before. I pump mine 6-10 times when ice cold.
1993 502 Quad jets. It's not a big deal the way it is now but always looking for improvements. Tnks for your suggestion.

Re: Excessive throttle pumping required to start
 

I don't think I've ever seen a carb that had a bowl drain... I've seen leaky Holleys that drained... but I think what is happening is the fuel pump is allowing the fuel to drain back into the tank and the gas in the bowl is just evaporating. The last cars sold in this country that had carbs didn't have bowl vents that were open to the atmosphere.. they had to vent into a canister.. and that slowed down the evaporation rate. Fuel bowls on carbs are engineered to be as small as possible. In fact.. on quadrajet carbs there is a "spacer" made of plastic to displace some of the fuel. The reason for this is to maintain a more even level of fuel in the bowl at different angles. Boats of course don't have to start and run going uphill. If you were to look at a quadrajet,,, you will notice that it is a "centered" bowl.. the bowl is right in the center of the carb. If you look at a Weber dcnf... the bowl is in the front.. that way if the car is running up a steep hill.. the fuel is sloping toward the emulsion tubes and not away causing a lean condition. If you have ever driven an old Ferrari that had Webers... 275 GTB 6 carb version... 365 GTB.. or even the early carbed 308s... try backing up a steep hill.... every time you let the clutch out... the fuel runs away from the emulsion tubes and the engine stumbles... this was a common problem that was eliminated with fuel injection.

Re: Excessive throttle pumping required to start
 

I hear ya Reed but the bowls are empty in a couple days after standing in most applications and everybody has the same start up situation. Wierd eh?

Re: Excessive throttle pumping required to start
 

My electric pumps are secondary pumps the motors have a mechanical fuel pumps as a primary. The electric ones I use for priming.

Re: Excessive throttle pumping required to start
 

My Friend Bad Accelerator Pump In Carb Seen This Before .have Carb Rebuilt. I Have 30 Years Experience. And Make Sure The Choke Is Working.ps Trust Me!!

Re: Excessive throttle pumping required to start
 

Maybe so ....but sure as hell werks ....all these are bad Accel. pumps ?

Re: Excessive throttle pumping required to start
 

There are two well plugs below the main jets on a Quadrajet that leak. This is a well known problem. Rebuild kits even came with a foam block that you put in to stop the leak. The fix is to remove the throttle plate assy, and you will see the two plugs sticking down. Smear a good epoxy (Like JB Weld) on them, let it dry, and reassemble.
It's that easy.