Fuel issues.....heat sink???

[mo10biker]

Hope someone can help with this. It seems to have started after start up last year. Launched the boat (99 Air Nautique) and was driven about 1/2 mile, the fresh water impellor failed and clogged the coolant lines to the manifolds. It melted the pass. side 4" exhaust. Now it will start and run fine, couple passes around the lake, sit at the sand bar for a bit, take off, and within seconds it dies. Sit for a half hour or so it wil start up and run. My first guess was Ignition moduel but no. After taking some tools out and getting it to do it again we found no fuel pressure. Both the high and low pumps get initial key on voltage when it doesn't run. when removing fuel lines I found little or no gas in the output of the low press. pump. I tore into the supply line line, tank connection etc everything seems to be okay. Hoping that maybe the supply line was damaged in the exh blowout I replaced that when winterizing but have not had it out yet. Again,it will start right up and run, you can ski no problem, just sit for a bit and when you go again it dies until something cools down My first thought is to put a new low press pump un and try that. My thinking is there is only the high and low side pumps left???
Thanks for any help guys!! want to ski this long weekend!
Randy

[jaybird]

RE: Fuel issues.....heat sink???

Did I understand you that you have voltage to the fuel pumps but they are not running? Where are you checking for voltage to the fuel pump? After or before the fuel pump relay?

[mo10biker]

RE: Fuel issues.....heat sink???

Pumps will cycle when the key is turned to the run position for a few seconds. I had this thought. There is 10 % alchohol in our non premium fuel here in WI. Does anyone think vapor lock is a possibility? I usually put premium in with no alchohol but my sons put regular fuel with at least 10%.Voltage was checked at the disconnect for both pumps

[DanielC]

RE: Fuel issues.....heat sink???

Do this:
http://www.planetnautique.com/index....=fuel+pressure
It is very difficult to vapor lock the fuel system, it is designed to vent any vapor back to the fuel tank.
My boat did not vapor lock working a Summer camp on Lake Shasta in 115 degree heat, and I have used E10 gas in my boat for years.
There is a line that returns fuel back to the gas tank from your FCC. Disconnecting the line, and doing the fuel pressure check with the engine off, you should see a steady flow of gas.

[mo10biker]

RE: Fuel issues.....heat sink???

The supply line CAN vapor lock due to the anti drain back valve on top of the fuel tank. It is designed to stop fuel to keep from returning to the tank on shut off. The return line is used to return unused fuel from the pump to the tank. The thing that bugs me is that after sitting it will start up again, What changes?

[DanielC]

RE: Fuel issues.....heat sink???

Did you do the flow test for your low pressure pump? Again, look at the conditions I have ran my boat under at Lake Shasta.
If you suspect the anti drain back valve is clogged, it will show up because you will not get sufficient fuel doing the flow test.

[mo10biker]

RE: Fuel issues.....heat sink???

Did not do a flow test. It runs great till after you sit. I am going to try the test listed above to see if the pumps will run when I bypass it. I could do a flow test when its running good but I have to assume it flows well, or well enough because of the way it runs. I did have the anti drain back valve out, it is clean and seems to fuction correctly. I have had the riser tubes out of the tank too, all clear. the fact that you run E10 makes me think it shouldn't be it. When it quits, if you open the engine cover and just sit, it will start and run good again, till you sit for a bit. The heat from the engine affects what ever it is. I was concerned about the fuel line and vapor lock because the fuel lines run so close to the exhaust pipe. I will try ths weekend to run the LPP and check its output. Thanks for your help too!