Nautique GT-40 Missing/Rolling Idle
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=30567
Printed Date: October-08-2024 at 11:20pm
Topic: Nautique GT-40 Missing/Rolling Idle
Posted By: camprnik
Subject: Nautique GT-40 Missing/Rolling Idle
Date Posted: July-04-2013 at 6:51pm
So I have a 2001 Air Nautique that has started to have issues. At the end of last season, the boat was missing slightly under load. The miss would come and go.
This season, after de-winterizing the boat, it is missing while at idle (No Load) and also while under a load. Right now it seems like its only one cylinder missing (#2). It has also started to have a rolling idle (rpm goes up and down 100-200 from 750 and will occasionally kill the boat).
Doing a tune up on it, I noticed that the interior of the distributor (the metal cap with the teeth for the hall effect sensor) was extremely rusty. I took it out and cleaned it up the best I can, and replaced the rotor and cap. Also replaced spark plugs and wires. Took the Idle Speed controller off and tried cleaning it up as much as I could (didnt look too dirty). swapped the two ECM relays to see if it changed anything (it didn't though both could be bad). Did a compression check (130-140 on all cylinders).
I tried going through the PCM Diagnositc manual but I don't have all the testing equipment so I tried to do all the resistance checks and what not.
Any ideas? It may be two different problems (rolling idle and missing)
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Replies:
Posted By: ac505
Date Posted: July-04-2013 at 7:19pm
Replace the FCC filter and the small 2 inch hose in the filter body. It can develop a crack,,often too small to see which can cause this problem.
Had a very similar problem on my GT40', replaced the hose just a week or two ago.
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Posted By: camprnik
Date Posted: July-05-2013 at 3:05am
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Thanks for the info! I will check and see what condition that hose is. I do know that the previous owner replaced the whole FCC unit a couple years ago as they wrenched it trying to remove it. I am not sure if that is the cause of my miss though. I seem to be missing at the distributor.
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Posted By: bigwavedave
Date Posted: July-05-2013 at 10:18am
Are you tell me what the FCC filter is? Thanks
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bigwavedave
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Posted By: TX Foilhead
Date Posted: July-05-2013 at 11:10am
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Fuel Control Cell (fuel filters and pumps)
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Posted By: Bri892001
Date Posted: July-05-2013 at 12:06pm
Take a look through this thread:
http://http://www.correctcraftfan.com/forum/forum_posts.asp?TID=25584&PN=1&title=poor-mans-gt40-diagnosis" rel="nofollow - http://www.correctcraftfan.com/forum/forum_posts.asp?TID=25584&PN=1&title=poor-mans-gt40-diagnosis
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Posted By: camprnik
Date Posted: July-07-2013 at 8:59pm
Update:
So I inspected the FCC internal hose (looks ok, ran some fuel through it and didn't get a leak)
Changed the TFI (no change in missing)
Changed the Idle control valve (no change in rolling/loping).
Another couple bits of info to throw out there. When I take the SPOUT plug out (forcing the boat to run at base timing with no advance) I lose the missing. However the Tach is jumping all over the place and eventually just pegs at its max RPMs (The boat's actual RPMs are not jumping around). Also the Rolling/Loping is soo bad that it will actually kill the engine after a couple minutes (makes setting the timing a pain).
Anyone have any other ideas? the Missing seems to be located to one cylinder only, and when I put a light on it, it acts like its not getting enough voltage, or has a bad connection. I have swapped wires around and it has no effect.
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Posted By: lewy2001
Date Posted: July-07-2013 at 11:20pm
Just checking that hose and running fuel through it does not really prove much. That hose has 40psi fuel pressure when supplying the fuel rail.
Have you tested fuel pressure??
It does not really sound like a fuel pressure problem. But testing pressure will rule that out.
The tach fluctuating has me thinking it may be the stator sensor (PIP) in the distributor.
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Posted By: Tim D
Date Posted: July-08-2013 at 2:58pm
Check the distributor cap for cracks.
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Tim D
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Posted By: camprnik
Date Posted: July-10-2013 at 1:42pm
UPDATE:
So it appears I have found the problems. The low pressure fuel pump had debris in it (just on the little screen inside it) and between that and a new fuel filter in the FCC, it eliminated the rolling/looping.
For the missing, I went through the distributor again, and the Stator (specifically the magnet for the hall effect sensor) and the round cap with the teeth were pretty rusty. I cleaned those up and the miss has disapeared.
I am plannin on replacing the stator (have a new one in a box) but the round cap with the teeth I havent been able to find a good replacement unit for that. It's pretty pitted on the inside of the teeth.
Took the boat to the lake last night, idles and runs great.
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Posted By: ac505
Date Posted: July-12-2013 at 7:07am
how does the LP pump seal? Can you take it apart, clean the mesh and put it back together without a seal kit?
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