GT 40 Fuel Issue

[A_B]

Last time I ran my '99 SN GT40, it ran great as usual for 4 passes, but on the 5th pass, it died as I gave it gas to accelerate. It would idle, but not take any rpms or imcrease in gas. Sounded like a gasping sound, then would die. I have replaced the fuel filter, which lead to replacing the entire FCC because it started leaking out the top of the FCC. I have also replaced the relays. The pumps are not priming when you turn the ignition on, and when it was idling in the driveway, I had a fuel pressure gauge hooked up, and it was reading 40 psi and then when I gave it gas, it dropped to nothing as the boat died off. The low pressure pump was replaced last year, so has about 50 hours on it. The hi pump is new, as the FCC came with everything in it.

 

I think the pumps should prime everytime you turn the ignition on, right? No matter if the FCC is full or not.

 

What else could be cutting power to the pumps?

 

I might be trailering this up the dealer on this one. Unfortunatley, its about 2 hours away.

[walleye]

Ab

Possible bad ground, Do you still have the large fuse by the battery.....if so check that connection. You are correct every time you turn the key you should here the pump prime.

[mylemsky]

Disconnect the oil pressure sensor, see if this works Sounds like the same thing we had. though it was fuel as well, ended up being something simple. Boats goes into "don't run me mode" Would actually run for a bit, halfway around the lake it would die and surge from 0-10mph. So frustrating, and you look like a jackass.

We waste 2 months trying to figure it out, finally called skidim.com, saviors.

 

Good luck.

 

 

[A_B]

Good points. I don't have the separate fuse on the battery, but I went out and double checked. When I turn the key on, the PP system goes through its test and the dash lights come on, and starter turns over.

 

I haven't tried the oil pressure sensor. Where is this located? It is odd that it would idle but not take any rpms, wouldn't that kill the engine completely? Mine acts like it is starving for fuel and then can drop back to idle if I move throttle back to idle and catch it so it doesn't stall. I think if I leave the gas on it stalls. Sounds like the engine makes a gasping sound, for whatever that is worth. The fuel pressure goes to zero, and then the boat idles or lugs at idle, but can't take any rpm on.

 

This is a pain in the knee (just had knee surgery).

[MJE]

Went through the same thing this summer with a 99 GT-40. It was a faulty oil pressure switch causing the ignition to go into "limp mode". The oil pressure sensor and switch are located behind the fuel filter canister. The sensor is dome shaped. The switch looks more like a cylinder. Unhook the wire that goes to the top of the switch. Then run your boat and see if that solves the symptoms. If that's the problem you can get a new switch here. http://www.skidim.com/prodinfo.asp?number=R020015A

[A_B]

I will give it a try. Thanks

[Jody_Seal]

AB,

If you have low fuel pressure the oil pressure switch is not the cure. The oil pressure switch can send the engine into power reduction but does not lower the fuel pressure. If you have low fuel pressure and low enough to starve the motor and make it die then you need to look at other sources for the problem. 1st 13 year old boat, a lot of people are having to run fuel with up to %20 ethanol. Ethanol will cause numerous problems in your fuel system. I would first try and run the motor off of a external fuel source such as a rigged up 3 gal outboard tank and see if your problem still is prevalent. If it clears up on the remote tank then you have a problem back thru the fuel supply system and or the pickup assy in the tank,( I have seen dead yellow jackets clogging the anti siphon valve ) if the problem persist's then you start at the low pressure pump and work up to the FCC and the fuel rail. Two immediate things to look at is take the low pressure pump apart and see if the Vains have rusted and or have Grawdew in the screen. The low pressure pump is a very easy thing to take apart just put it back together the way it cam apart! the second common cause is in the FCC the fuel supply tube that attaches the high pressure pump inside the FCC to the high pressure fitting. the hose can become split and suck air causing all kinds of fuel delivery problems.

Good luck.

 

[A_B]

My pumps are not priming when I turn the key on. They were running initially, now nothing.

 

Replaced relays, changed anti siphon valve, entire news FCC module with new internal pump and filter.

 

Any clogs I wouldn't think would shut down the pumps. They should at least run, right?

 

Sounds like the oil switch would limit RPM but not kill pumps.

 

I am stumped.

 

Looks like a 2 hour ride up to dealer.

[Jody_Seal]

Oh now we get the whole story! :)

Hold off on that two hour run to the dealer.

Did you check your emergency cut off circuit? You know the lanyard that is red has the clip on it right next to the throttle. Need to check that circuit also where it plugs together in the console if it is not the switch itself. You might want to temporarily bypass it with a jumper wire.

All your assumptions above are correct oil switch failure limits RPM, Limp mod/or power reduction. pumps will still run.

[A_B]

I tried jiggling it, but discarded it because I replaced it last year. While the relay was starting to fail last year, it was intermittant, and when we were at the far end of the lake the boat died. I jumped the kill switch and it started and ran so I thought that was it. It died next time out with the new kill switch. I can't feel either pump vibrating when I turn the key on. I am told both should run. I really listen for them after last year's relay problem. I am freaking pulling my hair out on this, I guess I am pig headed like my son always points out. I am thinking I should be able to figure this out!!!!

[Jody_Seal]

Did you check the 2 purple wire's at the console connection? Up stream from the kill switch.

Does the boat have a three way bilge switch?

Do you have 12 volts with key on at the engine 10 pin connector?

[A_B]

No, to all. I had knee surgery, so not getting around like usual, but will try to get up under the dash and follow the kill switch leads.

Bilge is just on/off.

 

I have access to volt meter. Where is 10 pin connector? Everything lights up when I turn key on, PP system goes through motions, dash display, etc... Starter turns engine over. Maybe there is some ECM bug, which I would have no clue to solve. I have the PCM Manual for the Boss GT40. May have to go through that again...

[Bill Gladding]

Probably should go ahead and get the Mastercraft out if someone hasn't stolen it already;)

[A_B]

Good one Bill! It's worth the effort to ski behind the best.

 

 

[walleye]

AB,

 

I think your fighting 2 problems. The original problem I don't have a clue. But the pumps not priming I feel is the positive control wire feed coming off the battery not making connection. From the Mfg it had a bayonet fuse about as big as a 4-10 shell. I would trace that wire to a CB. Without that feed the starter will roll, PP, & lights, but will not fire. I had a similar problem and I blamed the ECM board...Midwest told me they had not seen one of these boards go bad.

[Up North]

I realize that your pumps should still turn on with the key, but if you have not done so already, there is a semi hard plastic hose that goes down in to the fuel tank that has a screen in the end of it. Be sure to remove it and make sure it is clean. I had a similar cut out problem last summer and after replacing many of the parts you did, it was this small screen that was the problem. I have also had the oil pressure switch problem and it is easy to just disconnect the wire to check out the limp mode issue discussed above. I have the luxury of having 2 older nautiques with GT-40s, so I just keep swapping parts until I find the issue.