The 2 stroke fuel pump

[cart around]

I have been a member for about a year, and have noticed that the same questions keep coming up. The most common problems are bad seals, dirty carburetor, ripped diaphragm in the fuel pump, and piston in backwards.

Since I just saw my old pump sitting there, I decided to take some pictures to show what is inside. Maybe someone will make this a sticky.

The fuel pump works on vacuum pulses from the engine, and must be airtight. The movement of the diaphragms move the fuel. The 2 check valves control where the fuel goes. A ripped upper diaphragm will result in weak or nonexistent fuel pressure. A ripped lower diaphragm will pull fuel into the crankcase, and cause a wet spark plug. You will think that you are getting fuel, and start looking for an ignition problem. Cleaning, or changing the plug will almost fix the problem for a few minutes driving you crazy. I believe that more than one unneeded HEI conversion has been performed because of a bad fuel pump.

[cart around]

This last picture shows the ripped lower diaphragm. The cost of a rebuild kit was so close to the cost of a new pump, I opted to replace the entire pump.

[Stone]

Originally Posted by cart around

This last picture shows the ripped lower diaphragm. The cost of a rebuild kit was so close to the cost of a new pump, I opted to replace the entire pump.

Curious? What should I expect to pay for a new pump?

[kgsc]

And second question, will a four stroke pump work?

[cart around]

This should answer both questions. http://www.golfcartking.com/SearchRe...l+pump&Submit=

[Stone]

Originally Posted by cart around

This should answer both questions. http://www.golfcartking.com/SearchRe...l+pump&Submit=

Thanks

[Stone]

Originally Posted by cart around

I have been a member for about a year, and have noticed that the same questions keep coming up. The most common problems are bad seals, dirty carburetor, ripped diaphragm in the fuel pump, and piston in backwards.

Since I just saw my old pump sitting there, I decided to take some pictures to show what is inside. Maybe someone will make this a sticky.

The fuel pump works on vacuum pulses from the engine, and must be airtight. The movement of the diaphragms move the fuel. The 2 check valves control where the fuel goes. A ripped upper diaphragm will result in weak or nonexistent fuel pressure. A ripped lower diaphragm will pull fuel into the crankcase, and cause a wet spark plug. You will think that you are getting fuel, and start looking for an ignition problem. Cleaning, or changing the plug will almost fix the problem for a few minutes driving you crazy. I believe that more than one unneeded HEI conversion has been performed because of a bad fuel pump.

Fuel in the crankcase is a problem I have seen in other things like snowmobiles, etc. Is there any simple fix better than pulling the plug and assisting in evaporation?

[kgsc]

Originally Posted by cart around

This should answer both questions. http://www.golfcartking.com/SearchRe...l+pump&Submit=

I know they make like 50 different pumps but I think they may be just different frames.. I have a Briggs fuel pump on my Robbins and it works fine. That $20 was better than the $50 for factory. Not saying it's right but it works.

[Stone]

What is the best way to get fuel out of the crankcase? My lower diaphragm is bad and while I wait to get the new kit I want to clean out the fuel in the bottom.

[cart around]

Stone,
There is no drain hole, so I would say pull the plug, and spin it like crazy.

Another option would be to pull the plug, and blow some compressed air into the fuel pump hole. If you decide to do that, make sure you don't build up any pressure that would blow out your seals.

Also remember that there probably isn't that much in there.