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99 Nautique GT 40 Fuel Delivery issue high RPM

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    Posted: August-20-2023 at 2:39pm
Hi all. I have a 1999 sport Nautique with GT. The engine was having trouble at high rpm and shutting down over 20 MPH. I have tried the following in order to try and resolve the issue and still having problems. Any insight would be appreciated.

New fuel filter
New spark plugs
New fuel filter
New fuel pick up
Removed anti siphon valve
New fuel modules
New high pressure fuel pump
New low pressure fuel pump
New ignition module
Drained fuel tank and filed new fuel
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Jonny Quest View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jonny Quest Quote  Post ReplyReply Direct Link To This Post Posted: August-20-2023 at 6:15pm
Could be the ECM going into "limp mode".  Have you noticed the red cyclops light between the speedos being illuminated?  Limp mode happens when the ECM senses a high temp or low oil pressure event and shuts down all but 2 cylinders and allows you to "limp home".  Usually, the engine won't turn over 2,000 RPMs in limp mode.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jhenrichon Quote  Post ReplyReply Direct Link To This Post Posted: August-20-2023 at 7:09pm
Thanks JQ. Haven’t seen the light come on. Also after boat stalls out from high rev cutting out is hard to start up again.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bwinn Quote  Post ReplyReply Direct Link To This Post Posted: August-20-2023 at 7:26pm
You should be checking for fuel pressure or spark while it’s hard to start.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: August-20-2023 at 9:55pm
Originally posted by Jonny Quest Jonny Quest wrote:

Could be the ECM going into "limp mode".  Have you noticed the red cyclops light between the speedos being illuminated?  Limp mode happens when the ECM senses a high temp or low oil pressure event and shuts down all but 2 cylinders and allows you to "limp home".  Usually, the engine won't turn over 2,000 RPMs in limp mode.


So you think a gt40 will run on 2 cylinders? Come on now Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mpost Quote  Post ReplyReply Direct Link To This Post Posted: August-21-2023 at 8:57am
Originally posted by jhenrichon jhenrichon wrote:

Thanks JQ. Haven’t seen the light come on. Also after boat stalls out from high rev cutting out is hard to start up again.
Does the check engine light come on when you turn on the key but dont try to start it? It should. If not your bulb may be burnt out or wire disconnected. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jhenrichon Quote  Post ReplyReply Direct Link To This Post Posted: August-21-2023 at 5:54pm
Thanks guys for the input. Check engine light is operating. One person mentioned the check cleave in the tank. That make any sense to try next?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jonny Quest Quote  Post ReplyReply Direct Link To This Post Posted: August-21-2023 at 6:54pm
The fuel tank has an anti-siphon valve and a tank vent.  Both must be operating properly for fuel to flow out of the tank.  You really should verify that both are working properly in your trouble-shooting efforts.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jhenrichon Quote  Post ReplyReply Direct Link To This Post Posted: August-21-2023 at 7:10pm
Thanks JQ. Both are. I did replace the anti siphon and we tested the vent
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: August-21-2023 at 7:28pm
Originally posted by jhenrichon jhenrichon wrote:

Thanks guys for the input. Check engine light is operating. One person mentioned the check cleave in the tank. That make any sense to try next?

I don't know what a check cleave is, but what the hell, why not check it out Wink

I figure you typed check valve and got bit by autocorrect or something like that.

The anti siphon valve that you already replaced is probably what that person was referring to.

I'm not sure from your first post if you replaced the suction line in the tank or the suction hose for the LP pump, but the tank suction is a plastic line with a small strainer at the bottom that can get gunked up

Back in the first post where you mention fuel modules, do you mean you replaced the 2 relays for the ECM and the fuel pumps?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jhenrichon Quote  Post ReplyReply Direct Link To This Post Posted: August-25-2023 at 5:07pm
Thanks Keno. Yes I did typo and replaced the anti suction valve as well as new pick up line, both relays by the ecm and then both fuel pumps. Still having issues. Could it now be the injectors?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jonny Quest Quote  Post ReplyReply Direct Link To This Post Posted: August-25-2023 at 9:10pm
Inside the FCC (fuel control cell) there is a short rubber hose connected to the high-pressure fuel pump.  These hoses can develop cracks and cause fuel delivery problems.  Several threads on this site have discussed the hose cracking.  SKIDIM sells a fix kit:

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Post Options Post Options   Thanks (0) Thanks(0)   Quote bwinn Quote  Post ReplyReply Direct Link To This Post Posted: August-26-2023 at 8:19am
I think it would be helpful to check fuel pressure at the rail while the problem is occurring before you change any more parts. Do you have a fuel pressure gauge?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: August-26-2023 at 12:11pm
Originally posted by bwinn bwinn wrote:

You should be checking for fuel pressure or spark while it’s hard to start.

You should do what he says Wink

Fuel pressure at idle with high engine vacuum should be about 31 psi plus or minus a little and at full throttle Little to no vacuum) it should be about 39 plus or minus a little.

Cruisin' around it'll be somewhere in between those numbers

I'd hook it up and leave the engine box open so you can see the gauge and go for a ride.

Same with an in line spark tester, hook it up to  #5 if you have a helper to watch the spark tester. Should be able to see it pretty easily sitting in the observer seat
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