1951 rd 12 johnson.

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rd12man

Recruit
Joined
May 24, 2009
Messages
1
Just finished rebuilding the carb, new coils, points,condesor. rebuilt the lower unit with new bearings and seals. Engine starts and dies, have pulled and pulled for about 4 hours, will not stay running. Some one installed a new fuel pump on this engine before I got involved, it has a pressurized tank with a primer bulb. I tried venting the tank but the engine strarts and dies. Finally just hung the tank above the engine and let gravity feed the carb, engine ran, idled, sped up and ran great. What is the proper way to hook up this sierra fuel pump? It is hooked up to the crankcase outlet that used to pressurize the tank, it not working at all. Please help.
 
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Okee Jimmy

Seaman
Joined
Aug 13, 2008
Messages
58
Re: 1951 rd 12 johnson.

Hi,The fuel pump works off of pressure, and vacuum. The original pressure tank used a twin hose, one hose pressurized the tank, and the pressure in the tank forced fuel through the other hose, and into the carb. The location where the fuel pump is connected to the pulse source is pressure only. I once installed a fuel pump on a motor designed for a pressure tank, the pulse hose was attached to the intake. All that was needed was to remove a small reed valve in the reed plate that lined up with the nipple, this allowed the fuel pump to get pressure and vacuum from the crankcase. Hope this helps, Jimmy.
 
F

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,226
Re: 1951 rd 12 johnson.

As okee said, simply hooking a fuel pump to the tank pressurizing fitting just won't work. You need to modify the reed plate or find another source of a pulse.

The simplest way is to drill and tap one of the two bypass covers on the side of the powerhead to accept a hose fitting. That is WAY far easier than going into the reed plate.
 
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