GT-40 stalls after quick shutdowns

[peteSki]

I've got a 1997 SN with GT-40 fuel injected engine and have had this problem the last couple of times out. The boat will start first time, every time and run great for the day no matter what speed we may be towing. There is no apparent loss of power or performance. The problem only happens if after skiing for some time and the engine is turned off for a very short amount of time, like 15-20 seconds while a skier gets out of the water onto the deck. Starting back up again the engine fires and starts at a very low rpm and then stalls. Attempting to start again the engine just cranks and does not fire at all. If I continue this a few times, each time it cranks and usually doesn't fire but may fire for a second and then stall again. Using full throttle for a flooded engine really doesn't seem to make a difference. Ultimately if I do nothing for about 5 minutes, it will then start up straight away like nothing was ever wrong and run fine. Whatever is causing the problem seems to be happening withing 30 seconds after shutting down the engine and corrects itself after some time.

I had it with the dealer and they couldn't find any problems with the ignition system based on the computer read outs, but from other posts here I've learned that the computer does not monitor the fuel pressure.

I can confirm that I hear the fuel pump running when turning the key to run each time.

Could this be a fuel pressure regulator problem or possibly a leaking injector?

Any help is greatly appreciated.

Pete

[boatech]

RE: GT-40 stalls after quick shutdowns

sounds like fuel perculation. to test this cycle the key on five seconds off 5 seconds three times each then start if it starts up and is fine its a fuel perc. problem.

[peteSki]

Will give it a try tomorrow as we will be out.

What exactly is fuel percolation?

[peteSki]

The problem changed last time out. This time it wouldn't start cold after launching until a few attempts. It ran fine for some time and then cut out but always would restart after a minute or so.

I couldn't duplicate the problem when running the boat on the trailer a day later, but did notice that the fuel pump would sometimes not run when turning the key from off to run position. This led me to think that one of the relays was bad, and noticed that one of them got very hot after a few minutes of idling. I replaced the relay and the fuel pump no longer failed. Hopefully this was the issue, will find out next time we're on the water under normal operating conditions.

Pete

[johnsugar]

Boatech,
Just joined and read all the threads that dealt with an issue I have. I have a 95' GT40 that doesn't start (cranks good) after the engine is warmed up. It will restart after cooling. You were the only person to say this on any of the threads:

"sounds like fuel perculation. to test this cycle the key on five seconds off 5 seconds three times each then start if it starts up and is fine its a fuel perc. problem."

I did this and it will start when warm now. I have had the boat for over 10 years and it never did this before with the same use pattern. Do you know what really needs to be fixed? Is Percolation same as vapor lock?
Thanks, John

[M3Fan]

johnsugar, your 95 does not have the Fuel Control Cell so yes, it is prone to vapor lock. It's not an apples to apples comparison to the 96+ GT40s.

[DanielC]

Do this:
http://www.planetnautique.com/index....highlight=fuel
It just assumes the fuel pressure is correct.

[johnsugar]

OK. checked the fuel pressure. 39psi prior to start, 35psi idle and goes up to 39 again for acceleration. The times it doesn't start the pressure is next to nothing. Most the time turning the key 1 click from off the pumps pressurize to 39psi. Sometimes they only go to like 15 and it won't start. One time it didn't pressurize at all. I'm guessing the relay. Opinions?

[DanielC]

Intermittent problems are the worst to find. When the engine does not start, we now know is because of insufficient fuel pressure. The pumps could be bad, and unable to supply the required fuel pressure, or the pumps could not be getting enough voltage, and current, from a weak connection. A bad relay is one possibility, a bad connection in the harness is another possibility.
This is what I would do next. Hook everything up for the fuel pressure test again, but also back probe a fuel pump connector, and check the voltage at the fuel pump.
If the voltage remains around 12, and the pressure drops for some reason, that is the problem. On the other hand, if the voltage drops well below 12 volts, the fuel pumps cannot supply sufficient fuel pressure.
If you have not done it yet, download the GT-40 service manual from this site.
The 39 psi pressure is normal for an engine with the fuel pumps on, and the engine not running, and it is normal for the pressure to drop when the engine is running at an idle.

[peteSki]

I agree with what DanielC says. I also put a voltmeter at the fuel pump to test whether the connections to the pump was good. In my case there was either sufficient voltage or no voltage at all, indicating a complete break which supported bad relays in my case. The relays are cheap so changing them as a first point is no big deal.

Pete

[johnsugar]

Thanks guys. I'll check and report back here. John

[johnsugar]

Ok, Looks like the high pressure pump. Gets good voltage every tme. Pump seems now to only partially pressurize each time I cycle the key (once engine is warm). It takes about 3 cycles or so to get enough pressure for starting. Seems the pump is going. It's also a possiblity I suppose that I'm getting some vapor lock and it takes a few key cycles to pump out the air and refill with cool fuel. My engine runs and stays cool so it couldn't be the engine causing vapor lock. If it is vapor lock, I would think it's because the pump is still going bad....working harder and overheating itself. I ordered a new one. For anyone else who needs this pump (95' GT40), I found it for $189...much cheaper than any other place. Here is a link. http://bpi.ebasicpower.com/pc/CARP60...tage%2C+GM+MPI
john