1996 GSX Fuel Pump

[Grags]

Hi All,

Looking for a little feedback from someone a little more knowledgeable than me. My brothers 96 GSX has always been a little temperamental. When it runs, it runs great. The ski has had the carbs rebuilt when the ski was first purchased, I want to say a new fuel pump was put on as well, and the electrical system was gone through and brought back working as it should. The one issue that has seemed to be a consistent issue is it being a hard start. It seems to have an issue that when off, the fuel flows out of the lines to the carb. I have checked for fuel leaks and have not found any. To get past this problem I put together the below diagram coming from the tank.

My question is, while the shutoff valve works great to isolate the electric pump output from the mechanical pull of the fuel, it is a pain in the ass to access to turn it off. Would putting a check valve in place of the shutoff valve cause the mechanical pump to work harder than it needs to? Right now the electric pump is really just to prime the system to start again.

 

[burtshaver2021]

Are you sure that this machine has an electric fuel pump? I don’t think it does. I’m no expert so I could definitely be wrong. I have a lot of these old 2 strokes and except for the RFI’s and DI’s which do have elle truc fuel pumps, all the carbureted models have a diaphragm pump built into the carburetor that works off the air pulse created by the engine. If your machine is a 96 GSX then it is carbureted. I would say your hard start could be caused by a couple different things. 1 thing to look at would be your rotary valve to rotary valve cover clearance, if it’s worn a lot past it’s limit it will cause hard starting.As for the fuel flowing when it’s off, pressure test the carburetor with 10 pounds of pressure to see if the needle and seat is leaking or if the diaphragm is pushing on the lever holding the needle open a bit. This is described in @mikidymac carb rebuild thread which can be found on his profile. You could also have a look at your pressure relief valve that would be located under the rub rail and goes to a T and then to the fuel tank, if this relief valve is not opening and realizing pressure that could building up from sitting in the heat it could be forcing fuel into the carburetor.

 

[Grags]

Are you sure that this machine has an electric fuel pump? I don’t think it does. I’m no expert so I could definitely be wrong. I have a lot of these old 2 strokes and except for the RFI’s and DI’s which do have elle truc fuel pumps, all the carbureted models have a diaphragm pump built into the carburetor that works off the air pulse created by the engine. If your machine is a 96 GSX then it is carbureted. I would say your hard start could be caused by a couple different things. 1 thing to look at would be your rotary valve to rotary valve cover clearance, if it’s worn a lot past it’s limit it will cause hard starting.As for the fuel flowing when it’s off, pressure test the carburetor with 10 pounds of pressure to see if the needle and seat is leaking or if the diaphragm is pushing on the lever holding the needle open a bit. This is described in @mikidymac carb rebuild thread which can be found on his profile. You could also have a look at your pressure relief valve that would be located under the rub rail and goes to a T and then to the fuel tank, if this relief valve is not opening and realizing pressure that could building up from sitting in the heat it could be forcing fuel into the carburetor.

The Ski did not have an electric pump originally, It was added as a workaround to avoid killing the battery turning over the ski. I never though to check the pressure relieve valve. Originally a new petcock was installed only to find out later that the system would draw air in through the faulty petcock. To get him out on the lake that day the petcock was bypassed and the "On" nipple off the fuel tank was connected directly to the input of the fuel filter. He has lost interest in the ski since it takes a little tinkering before going out on the lake.

 

[burtshaver2021]

I’m confused with the fuel pump you’ve added, it’s a carbureted 787 correct, does it not have a pulse line from the crankcase going to the fuel pump integrated into the carb?

 

[burtshaver2021]

I had another look at your schematic , so you put an electric fuel pump online in the reserve line and you use it to basically start the ski only and then switch over to on that’s also running directly to the tank, well through the fuel filter but bypassing the fuel selector valve. That’s some serious ingenuity but to answer your question about hard starting, I would just go with the basics, get ride of the electric fuel pump and put it back to stock and figure out why it’s hard to start, probably either low compression or a fuel issue that a back to OEM carb rebuild kit with new needle and seat from OSD marine would likely solve.

 

[Sunsport]

Best bet for this is to put it all back to original and then troubleshoot and fix the original issue that led to this work around in the first place. I have a 96 GSX - stock. Starts easy peasy.

 

[POPPS]

I’m with sunsport,,, return the setup to original and proceed from there, even the race motors of that CC do not have electric fuel pumps!

 

[Venturian1]

You should follow those suggestions! The only reason someone would put on an electric fuel pump, I think, is because they didn't know how to replace the check valves in the fuel pump that's part of the carb. So then what about the rest of the carb, like needle and seat, pop-off pressure, and what was done with the return fuel hose nipple on the carb, and the pulse nipple on the crankcase? Don't neglect cleaning out the fuel tank too. any foreign material in there is at the bottom, and the electric fuel pump suction is connected to the reserve nipple, if there is crap / water in the tank, there's a chance its entering the carb through the reserve line. The ON nipple on the tank doesn't go as far down as the RES.