fuel pump diaphram

[mhanewich]

I am replacing my fuel pump diaphram due to what I observed as a loss of pressure at high rpm. I have about 3 psi at idle and it drops to zero at high rpm. I tryed running it off a protable tank and had the same results. I took the fuel pump apart. I found no tears in the diaphram. My question is, will the pressure still drop from a bad diaphram if there are no tears in it?

 

[backdraft]

Re: fuel pump diaphram

The diaphragm gets stiff and fails to move back and forth pumping the fuel .Check valves in the pump get tired and will leak back causing the same result. nvjb

 

[eurolarva]

Re: fuel pump diaphram

If that fuel pump is the same one that is in a chrysler there should be 3 fuel pump valves. One is held in by two screws and the other 2 are press fit. The press fit ones can be tough to get out without damaging them. Look at the gaskets before removing the valves to see if they are torn. The rebuild kit I got the gaskets provided were too big and would not fit without tearing them. I had to buy gaskets and 2 new valves. The valves were only 4 dollars and the gaskets under a buck but shipping was 20 bucks.

 

[backdraft]

Re: fuel pump diaphram

Mh: How did you test for fuel pressure at high speed? Were you having fuel starvation problems? A flow of less than a quarter pound should be enough to maintain speed. Thats just a guess! nevjb

 

[mhanewich]

Re: fuel pump diaphram

Eurolarva, I have the 2 stage fuel pump that looks like a figure eight. I can see one valve that is screwed into the housing but I don't see any others.

 

[mhanewich]

Re: fuel pump diaphram

Nevjb, I used a fuel injection test guage to measure fuel pressure. I tested the outboard with a tank under the lower unit. The pressure dropped to zero without being in gear when I ran it up to about 50% throttle.

 

[force01]

Re: fuel pump diaphram

At low speed and idle your needles are closed or nearly closed. at high speed all of your needles are opened so with this in mind can you see the pressure loss? especially with a tired fuel pump replace your 3 check valves diaphram, gasket and the gasket around the one check valve. this will make your fuel pump like brand new, eliminating it from whatever problem you are having. Check iboats for the parts if they cant help you we can. thanks, bret<br /><br /> If you need further assistance please email me @ forcepower01@yahoo.com

 

[backdraft]

Re: fuel pump diaphram

Buy a complete new pump. nvjb