1956 Johnson fuel pump conversion

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SuperUnknownMC

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Jun 23, 2011
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I was wondering what you thought about this.....................What's stopping me from mounting this pump on the transome and using the original outlet for the crankcase pressure ( the one that presurized the tank ) to power the new diaphram pump. then simply run a fuel line from the tank to the pump, and another fuel line from the peump to the carb. This way I wouldnt have to mess with the bypass cover and worry about clearance issues. Im gonna give it a shot this weekend and see what happens

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1946Zephyr

1946Zephyr

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Re: 1956 Johnson fuel pump conversion

If it was me, I would just get a bypass cover and fuel pump from an old 28hp. No muss, no fuss and it'll look factory. There won't be any clearance issues either, because it's one of the smaller square ones.
 
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Daviet

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Re: 1956 Johnson fuel pump conversion

The outlet you are talking about that pressures up the tank is not a pulse type surge and will not power the new style pump. That is why you have to drill and tap the bypass cover.
 
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SuperUnknownMC

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Jun 23, 2011
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Re: 1956 Johnson fuel pump conversion

AHHHHHHH.........thank you sir. Is that because that pressure doesnt come from the crank case? If not, how is that pressure created.
thanksfor the input.
Jim
 
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Daviet

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Re: 1956 Johnson fuel pump conversion

There is a little valve in the intake manifold and only creates pressure out.
 
nwcove

nwcove

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Re: 1956 Johnson fuel pump conversion

...correct me if im wrong.....but the purpose of blocking off one of the pressure outlets is to allow a pressure...then vacuum pulse to operate the diaphragm in the new fuel pump.
 
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Daviet

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Re: 1956 Johnson fuel pump conversion

The pulse type pumps require a use the piston going back and forth to make the pump work.
You cannot use the original hose fittings, that's why you have to drill and tap the bypass cover.
If you would run a search, I think you will find a lot of information on the conversion, there are several posts on it.
 
wbeaton

wbeaton

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Re: 1956 Johnson fuel pump conversion

Actually, you can use the pulse from the intake manifold, however, you must first remove the manifold, remove the two check valves behind it and then plug one of the holes. The pulse will be weaker than the bypass cover. Its easier and better to use the bypass cover for this modification.
 
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