Accelerator pump travel in 2 BBL. Mercarb

[bobafett]

Rapid Idle to full throttle stalls engine, but not if done slow.<br /> I disconnected the linkage from the throttle to the acc. pump and then turned the pump by hand. I did not feel any spring resistance for say 30 degrees of rotation, and then I did and at the same time saw fuel being injected into carb. When I connected back to throttle the fuel doesn't enter carb until vlvs are cracked open a good bit. Does this mean the stallout is because there is too much air and not enough fuel in the first part of acceleration because of the pump "lag" in spraying?<br />Just a note .. when i slowly inc the throttle to say 2000 RPM and then quicly go to full throttle there is a slight hesitation but no stallout. <br />Anybody got any ideas to fix? The pump is new from a rebuild kit but this problem existed before rebuild with old pump too.<br />Wrong size pump? Is it true that Merc later made a new pump with 100% capacity inc over old design for mid 80's mercarb?<br />Is it

 

[Trent]

Re: Accelerator pump travel in 2 BBL. Mercarb

Just pulled my hair out with this one a few months back. It was the timing of the engine. If you have two good streams of fuel when you pump the throttle its not the accel pump. You did not say your year model? Their were a couple of service bullitins on "bogging" due to the mercarb. Usually needle and seat or accel pump.<br />Their are two differnt size accel pumps for the mercarb. You have to measure the bore to know. web page

 

[bobafett]

Re: Accelerator pump travel in 2 BBL. Mercarb

If it was a timing problem won't I still stall out even when I accelerate to full throttle really slowly? It doesn't do that. It will hold higher rpm without missing or knocking. Idle seems seems in range. The Merc is an 1986 140 HP with Mercarb.<br />At what rotation of the pump linkage should the 2 spray shot begin?<br /><br />What is an active web page for service bulletins? All I find are dead ones

 

[Don S]

Re: Accelerator pump travel in 2 BBL. Mercarb

It may be you just need to "rebuild" the carb. this isn't just taking apart and hitting the parts with some spray carb cleaner then sticking a new "Carb Kit" in it. It requires dipping the carb into a carb cleaner so all the passages get cleaned. The passages have to be cleaned with compressed air and verified they are clean. Corrosion in passages and places you can't see will cause a "regasketed" carb to act just like it did before. How about the throttle shafts? Bushings worn out???? Then ALL of the adjustments have to be checked and set properly. Don't miss any.<br />And even if the carb is perfect, if the engine has mechanical problem (vacuum leaks, low compression, etc.) the rebuild won't work either.<br />Then you have the electrical system. Points, Condenser, Cap, Rotor, Plugs. Those are tuneup items and on boats, that is a yearly thing.<br />Dwell, timing, advance timing all has to work together with the carb.<br />The fuel system with air leaks, partial clogs in fittings and lines. Water in the tank, weak fuel pump. <br />Everything has to work together.

 

[bobafett]

Re: Accelerator pump travel in 2 BBL. Mercarb

Rebuild was a good soak soak on all parts followed by flush and compressed air. Fuel anti syphon vlv clean and vent line clean to carb.<br />Any thoughts on timing of acc pump spray?

 

[bobafett]

Re: Accelerator pump travel in 2 BBL. Mercarb

The guy I bought the carb kit from seems to think that the pump is the problem. He says it should be shooting in gas as soon as the throttle is applied. Anyone agree or disagree? If so, what could cause a new pump not to start spraying at the correct time? check ball? wrong spring? linkage to the pump connected wrong?

 

[bobafett]

Re: Accelerator pump travel in 2 BBL. Mercarb

Anyone nknow how to make the acc. pump start spraying earlier when the throttle is applied?