GT40 Fuel Delivery Issue

I could use some help from the GT40 gurus here.

The last 3 times I’ve had the boat out I am experiencing the same issue: I put the boat in the water and for the first run of the day it runs like a scalded dog. Then we stop to hang out for a while. It will start back up fine, but a few minutes later will die and not restart. It sounds like it’s not getting fuel, so today I brought a pressure gauge and sure enough there is no fuel pressure on the rail.

I have checked connections in the line leading up to the low pressure pump. All look clean as a whistle including the anti siphon valve. I am getting 12 volts to the fuel pumps and I can hear/feel them turn on when I turn the key. I pulled the outlet hose from the low pressure pump to the FCC and it’s dry/no fuel pumping when Ii turn the key.

I read on here that a failing low pressure pump may still power on despite being bad. Given that it’s first in the line and I’m not getting anything out of it, is it safe to assume it’s bad?

Gary has giving good advice for the Low Pressure Pump. My boat is a 95 but has an in line filter in the fuel line right under the rear of the engine cover on the passenger side.
Your 99 may have one also.
You can also pull the Low Pressure Pump supply line and see if fuel will vacuum out of that line. It should flow freely to feed the LPP.

cboland wrote: I have checked connections in the line leading up to the low pressure pump. All look clean as a whistle including the anti siphon valve.

Did you pull the suction line out of the tank and see if there's a little screen at the bottom of the suction line or did you just unscrew the anti siphon valve and check that it was clean?

You didn't specifically mention it like you mentioned the anti siphon valve, so I figured I'd ask

See the thread in the link below for a picture of a plugged little screen that caused similar symptoms. It keeps junk from getting into the anti siphon valve

link

Thanks, everyone. All very helpful.

I didn’t even think to try and suction the LPP supply line. That would be an easy check. I tried pulling the suction line out of the tank, but it’s location in the tank is directly underneath the cross member of the deck of the boat. I could pull it out about 6 inches but couldn’t bend it enough to get it all the way out. I did blow compressed air down it to try and unseat anything that could be stuck to the bottom. Given the specific fact pattern of all 3 days and how the issue keeps happening, it seems highly likely that it’s a pump issue. After looking at some other threads, it looks like my symptoms of failing when hot are typical of a failing LPP.

KENO wrote: cboland wrote: I could use some help from the GT40 gurus here. The last 3 times I’ve had the boat out I am experiencing the same issue: I put the boat in the water and for the first run of the day it runs like a scalded dog. Then we stop to hang out for a while. It will start back up fine, but a few minutes later will die and not restart. It sounds like it’s not getting fuel, so today I brought a pressure gauge and sure enough there is no fuel pressure on the rail. I have checked connections in the line leading up to the low pressure pump. All look clean as a whistle including the anti siphon valve. I am getting 12 volts to the fuel pumps and I can hear/feel them turn on when I turn the key. I pulled the outlet hose from the low pressure pump to the FCC and it’s dry/no fuel pumping when Ii turn the key. I read on here that a failing low pressure pump may still power on despite being bad. Given that it’s first in the line and I’m not getting anything out of it, is it safe to assume it’s bad? So you're saying that if you pull the hose from the LPP to the FCC, it will pump when the pump is cold and won't pump when it's hot? What if you don't stop and hang out, will it eventually quit?

Good question. I can’t say for sure if it would eventually go out if I just kept running, but each of the 3 times it’s happened we have been riding around for a lengthy time. Probably 45 min at least and it ran great. It just happens that the one time it wouldn’t start and I pulled that hose off there was no gas pumping. When i pulled it and it would start there was gas. The very first time it happened I pulled the hose off the anti siphon valve thinking that was clogged and when I connected it back up it started. Maybe just a coincidence on that one.

Don't waste that valuable time drivin in circles alone- pull a tube.....

MrMcD wrote: Or take a friend in a nice Bikini! Could help time go much faster!

Ah the old Sorry babe I didn't know what happened it seems like my fuel pump just died trick - take the fuel pump apart and clean it out - before you burn out the motor.   

You guys are true experts. Even going so far as to suggest I bring Pete to tube and a bikini clad woman. Thank you.

I’ll get to work this weekend. Though for $70 I’m inclined to just start fresh with a new pump.

KENO wrote: I want to see you pulling bikini clad Pete in a tube

I've always wondered about your SO!!

LOL !
Sounds like you are on the right track Bud......with the pump issue that is.
Not so sure about Pete and the tube.
Better leave the bikini part to your beautiful wife !

For the benefit of others facing a similar issue, I want to close the loop on this and provide the solution.

I ended up replacing the LP pump. Despite hearing the old pump power up when key was turned on, the fuel pressure gauge indicated no pressure and when I pullled the output hose off the LP pump there was nothing coming out.

So, moral of the story is do not assume a pump is working just because you hear it power up.

Good job troubleshooting. Logic prevails and you did the work!