Waverunner GP760 fuel starvation

[charleswmoore]

I replaced the fuel pickup / sending unit last year end of season. (Not knowing if this is contributing to my problem) first trip out this year the unit ran good then started loosing power just like it was running out of gas. Changed fuel filter then went back out. With a full tank it ran great but after tank got to below 1/2 it started starving for fuel. Problem was worse when switched over to reserve where the pickup is even longer? Does anybody know what the vacum should read on the input to the dual fuel pumps? Has anyone tried carb cleaner<br />down the suction hose or will it eat the diafram? Will failure of one fuel pump still allow unit to run good but not achieve enough vacuum to pull all the fuel out at lower levels?

 

[BiXLL]

Re: Waverunner GP760 fuel starvation

Sounds to me more of a vapor lock problem. Check your vent to see if it is clear.

 

[charleswmoore]

Re: Waverunner GP760 fuel starvation

Bixll ,<br /> I wished it was that simple. The tank vent has a one way check valve on it going to a fuel trap I guess to keep the fuel system closed. Also I noticed that the ski use to hold tank pressure and now it doesn't? Otherwise when opening fill cap it would hiss as fuel vapor was releasing? I removed the return line off carbs and started the motor and fuel was just barely comming out? Also I blew into the fuel return line pointed at tank and the tank seems to be holding pressure that is why I think gum may be clogging up one of the check vales on one of the two pumps? Maybe not pumping well. If nobody knows the vacuum level the two paumps in Parrallel should <br />have I guess I'll read the vacuum, spray carb cleaner down the fuel line and see if it changes.<br />Charlie

 

[BiXLL]

Re: Waverunner GP760 fuel starvation

The check valve retains certain amount of pressure in the tank which pushes the fuel down and forces it up thru the fuel lines. Its main porpuse is to assist in the delivery of fuel to the carbs.

 

[charleswmoore]

Re: Waverunner GP760 fuel starvation

BixLL<br /> I just downloaded a breakdown of Carbs and I see<br />item number 30 is labeled as a strainer. Are you familiar enough with the GP760 to know if it can be gotten to without any disassembly? And are you famliar enough to know if it should retain tank pressure or is it blead off through the carb.?<br />Charlie

 

[BiXLL]

Re: Waverunner GP760 fuel starvation

My experience is with the 1200s. I can tell you though, those check valves can really play havoc with performance when bad! You mentioned you are no longer holding tank pressure, and that is a sign of bad check valve!

 

[charleswmoore]

Re: Waverunner GP760 fuel starvation

Yeah thats the concern. I don't feel the check valve is bad because with the tank selector in off position I can blow into the return line and the tank will pressurize. If the check valve was bad it would vent directly to outside? That also eliminates fuel filler hose, cap, sending units etc etc. It only leaves fuel pumps or carb so i'm back to origianl question how to test fuel pumps.<br />Charlie

 

[BiXLL]

Re: Waverunner GP760 fuel starvation

on the 1200, it is 1-2 lbs in the water at idle, 4-5 lbs. in the water at WOT. If you have vacume tester with gage, check the entire fuel system. I have heard of both fuel shut-off, and fuel pick-up getting cracks in them causing loss of presure also. You mentioned problem occured after 1/2 tank? Fuel pick-up could be cracked?

 

[charleswmoore]

Re: Waverunner GP760 fuel starvation

Thanks for the assistance. I'm going at it this evening. My intention is to start motor bring up to temperature then check vacume. Then clean flter on side of each carb (If i can get to them), Spray in some carb cleaner let soak for five minutes or so then pour in some gumout carb cleaner in gas run motor then recheck vacume to see if any increase. My intention is to do this prior to addressing tank pressure issue.<br />Again thanks for help I'll keep ya posted<br />Charlie

 

[charleswmoore]

Re: Waverunner GP760 fuel starvation

Well the tally is in. Now I'm more confused.<br />I placed a vac gauge t'ed into the line from the fuel tank. It pulls aprox 14 inches at idle. Then<br />goes to 18 inches at throttle. Placing the t on the return line reads no pressure but further checking I find the check valve like you said is not closing at low pressure but only when you blow into it hard. With all that said I go to another brd and find that people are removing this valve so they can regulate thier fule pressure. I can only assume this is being done<br />when they install external performance fuel pumps. So the majic question is: Can the tank check valve effect the ability of the fuel pump<br />to feed adequequate fuel to the carbs at below half a tank? Thanks<br />Charlie<br />Ps the local parts store say they have never ordered or replaced one??? From other message brds that seems hard to believe?

 

[Tech SBT]

Re: Waverunner GP760 fuel starvation

I would bet your fuel selector switch is bad. It should turn like a knife throug butter - if it's notchy at all or sticks - it's bad. Pull off your return line from the carbs and blow through it to pressurize the system. Not ethe flow of fuel out the carb fitting on the RES and ON settings - both should be equal and strong.

 

[charleswmoore]

Re: Waverunner GP760 fuel starvation

Changed the check valve, Sprayed carb cleaner down the hoses towards fuel pump, replace fuel line (In case it was colapsing) checked the selector as you said. Sent the kids out on it saturday and they indicated it ran great. Since ski came back on 1/4 tank and I assuming its good to go. (Other than the compartment door they ripped off the hinge) Kids will be kids <br />Thanks <br />Charlie

 

[BiXLL]

Re: Waverunner GP760 fuel starvation

charleswmoore, glad it worked out for you!