Fuel Pump Diaphragm

[willieandralphsdad]

I don't get it. I took apart the fuel pump (type A, 2 part, I think) and observed a diaphragm in between the valves and the hose elbows? What gives, the manual says it should be there and not perforated or overstretched but um, doesn't it block dispersal of the fuel oil mix?

Any other tips on getting an old fuel pump straightened out? Gas doesn't seem to be making it into the engine. 1969 Chrysler 55hp, #5555.

 

[jerryjerry05]

Re: Fuel Pump Diaphragm

The diaphram should be a smooth piece of rubber.
Pics of the pump?
Profile? Location? You might be close to someone who can help??

 

[Frank Acampora]

Re: Fuel Pump Diaphragm

The pump has three valves in the top half. This is the only side that sees fuel. The diaphragm separates the crankcase from the fuel. The back side of the pump (or top, depending upon which one it is) has holes for crankcase pressure and vacuum to alternately push out the pull in each half of the diaphragm. This alternate movement of the diaphragm first sucks fuel into the large chamber then pushes it out to the next chamber. The second smaller chamber does the same except it pushes fuel to the carbs. The valves are one way and keep the fuel flowing in the correct direction.

 

[willieandralphsdad]

Re: Fuel Pump Diaphragm

Thanks Frank! I figured that out after digging into it a little deeper. I assumed, before removing and cleaning the fuel pump, that the air and gas combined and were injected into the motor from the top hoses. Now I see that those hoses are intended to allow the air from the pistons to compress the diaphragm and by doing so propel the fuel oil mix to the carb. I removed and cleaned the carb too. In neither instance did I have any new gaskets so I coated the old ones with a light coat of gear oil and replaced as carefully as possible. I guess ill have to replace the gaskets but I didn't have the time to get up to the marine parts store today (30+ miles).

So now its all back together and I can get it to start. But it runs fast then it dies. Blows some white smoke. I ve been fiddling w/ the throttle and I guess the prop director? But it won't run for more than about 10 seconds? Any ideas? Fuel mix? Id like to get it to idle for a minute or so w/o it smoking me out. Any help is much appreciated.

I'm not taking it to anyone. I either figure it out or I don't.

 

[IamCanadian]

Re: Fuel Pump Diaphragm

sounds like it may be starving for fuel did you set the idle mixture screw out 1 turn from fully seated?

What I think is happening is this, you choke it, it starts and runs till it burns off the extra fuel from the choke.

The top screw right above he carb inlet should be screwed in all the way till you feel it bottom out, and then you unscrew 1 full turn from there. that will get you close to the right air fuel mix at idle.

 

[jerryjerry05]

Re: Fuel Pump Diaphragm

Starting and dying after initial pump up, usually means the pump isin't delivering.
Or the unit's sucking air somewhere.
They have Ethanol in Africa? In the US we are pretty much forced to buy it.Where are U?? Profile? Location?
It makes old hoses soft and the inner lining will delaminate,causing it to collapse.
It destroys seals too.
The needle seat clogged,water in the system.

Check valves put back in right?

 

[foodfisher]

Re: Fuel Pump Diaphragm

Lots of white smoke could be a clogged fuel recirculation system. Cleaning it out worked for my 125. Don't know if the 55 has one.

 

[willieandralphsdad]

Re: Fuel Pump Diaphragm

Africa?. I'm in Colorado.

Could be sucking air. I didn't replace the gaskets and they're very old and not at all limber.

Second valve was loose, other two were in real tight.

I cleaned out the needle seat. No water in the system.

I've checked the fuel circulation system for clogs. All hoses look good. No leaks that I can tell. New clamps.

I'm going to find some gaskets, mix some fresh fuel mix, adjust the carb idle screw as canadian noted and give it another shot.

Not really sure of the correct starting procedure. The throttle and prop line are confusing. Changed lower gear unit oil yesterday.

 

[jerryjerry05]

Re: Fuel Pump Diaphragm

Kidding about Africa. Sometimes you can find help right around the corner.
Pump it up.water on.Unhook the fuel line to the carb.then start it.See if it pumps fuel.
Not pumping? Valve in pump/bad or in wrong.
Pumping? Then the float might be sticking?


Start,pump ball till firm,then fast throttle all the way forward(fast throttle is pulling the silver button on the shifter and advancing the throttle) key on,key pushed in to choke,turn key all the way to engage starter. Then it might start or cough? If it coughs,then try starting without the choke.

 

[willieandralphsdad]

Re: Fuel Pump Diaphragm

Two hoses come out of the box/right behind the carb. They both have some hard piece of metal in them at about the same place, nearest to the nozzle. One has air flow, the other, not nearly as much. They both connect to a coupler then another short hose, then down into the gear case. I'm assuming exhaust? What should I know about these hoses? Should they be replaced? If so with what? I can't identify these hoses using the manual. What is that piece of hard metal ?(looks kind of like a nozzle). Could the disparity between the flow rates be causing the engine to stall out? Thanks so much for all your help.

 

[IamCanadian]

Re: Fuel Pump Diaphragm

The lines you are asking about is just an excess fuel drain if it gets flooded or the carbs leak fuel into the reed blocks, you should be able to blow into them but not suck any air from them (there is a one way valve in the lines) They just empty into the water/exhaust outlet.

 

[willieandralphsdad]

Re: Fuel Pump Diaphragm

Ok so that is part of the recirculation system then and those metal pieces are the "puddle valves?". They both blow in both directions so I guess they need to be replaced. Are these common or do they need to be special ordered? While I'm at it I guess ill have to find a bunch of new gaskets too.

 

[willieandralphsdad]

Re: Fuel Pump Diaphragm

Garh. Cleaned a bunch of stuff up today. Fuel system is airtight. Fiddled w/ idle screw. No luck. Fires up on ether, then dies. No more white smoke though.