1958 Johnson 5.5 Mikuni fuel pump problems

dockrat100

Petty Officer 2nd Class
Joined
Mar 22, 2011
Messages
144
I have a 1958 Johnson 5.5 that I put a Mikuni pump #808492 on, and I am leaking fuel from the little copper colored disc on the top of the pump.

1. Is there particular orientation that the pump is made to work in? Flat, sideways, etc...

2. What is the little copper disc for?

The pump can be seen here:

808492 | eBay
 

nwcove

Admiral
Joined
May 16, 2011
Messages
6,293
Re: 1958 Johnson 5.5 Mikuni fuel pump problems

Is this a new conversion? Or have you used the motor with the pump?
 

Crosbyman

Rear Admiral
Joined
Nov 5, 2006
Messages
4,914
Re: 1958 Johnson 5.5 Mikuni fuel pump problems

that disc is likely a smalll mesh to balance air pressure.... likely culprilt if leaking is a bad diaphram inside the pump
 

nwcove

Admiral
Joined
May 16, 2011
Messages
6,293
Re: 1958 Johnson 5.5 Mikuni fuel pump problems

DSCF1726.jpg

heres a pic of a b&s pump mounted on a 7.5 johnson, the pulse line is obviously coming from a different location than it does on your 5.5, but for this pump, the top connector in the pic goes to the fuel in line, the bottom connector goes to the carb. if you are sure your lines are on right ( suck blow test), your problem could be as mentioned, a ruptured diaphragm.

edit: the part # for the pump shown in the pic is 808656, so your lines may attach differently, but the suck blow test still applies.
 

dockrat100

Petty Officer 2nd Class
Joined
Mar 22, 2011
Messages
144
Re: 1958 Johnson 5.5 Mikuni fuel pump problems

The motor will run with this pump, but it is dripping gas through the copper colored disc. Stinks, because the pump should be brand new, off fleabay, so not worth returning.
 

HighTrim

Supreme Mariner
Joined
Jun 21, 2007
Messages
10,486
Re: 1958 Johnson 5.5 Mikuni fuel pump problems

If it runs it has a bad diaphragm.
 

dockrat100

Petty Officer 2nd Class
Joined
Mar 22, 2011
Messages
144
Re: 1958 Johnson 5.5 Mikuni fuel pump problems

I will swap out to another pump. Thanks.
 
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