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97 Sport Nautique GT40 smokes and misses at idle

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BobinIL View Drop Down
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    Posted: July-29-2018 at 7:17pm
I started up my 97 Sport Nautique this summer and noticed that it seems to smoke more than it used to. I get blue/white smoke (like I am burning seafoam through it) and a nice sheen on the water behind my boat if I let it idle for a while. It seems to run fine and has no loss of power and no missing at higher speeds. At idle I get the smoke and it shakes a little bit like it is missing.   I just changed the plugs, wires, dist cap, and rotor and changed the oil. I put 10w30 mobile 1 in and I think I am going to change it again to 20w50 and a motorcraft filter. I noticed the oil pressure runs at 40psi until it warms up then it drops to 20psi at idle but goes back up to 40psi when I run it at speed. Any ideas what may be going on.   
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: July-29-2018 at 9:34pm
Blue smoke, your burning oil, black smoke you are running rich, too much fuel.
White smoke usually shows you have a blown head gasket or somehow water is entering your intake manifold.
My GT-40 runs perfect but if I start it on a cold day on the water it will have white smoke in the exhaust.   I think that is just condensation till the system warms up.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BobinIL Quote  Post ReplyReply Direct Link To This Post Posted: July-31-2018 at 12:27pm
I think it may be a fuel issue. I am going to check the fuel pressure and go from there. A few things I do know.
1 it does not use oil with only 400 hours
2 there is no water in the oil or crankcase
3 It is getting good spark just changed all electrical components
4 it is running cool at 150-160
5 it only misses at low idle smooths out at higher RPM runs a strong 46-48mph wide open

This caused me to deduct that it is loading up on fuel at idle or it may have a sticky injector or possibly bad fuel. I stored it with 1/2 tank of old fuel and added another 10 gallons this spring. May drain the fuel, or dump a can of seafoam in and run it out.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: August-01-2018 at 10:05pm
Another trick for cleaning injectors it to run a quart of ATF, tranny fluid with a tank of gas.
It does a good job cleaning and lubricating injectors, without causing any damage.
Many Truck Drivers used it for years to lubricate the fuel system.
Nothing against Sea Foam, I think it is pretty good stuff but for injectors I use the ATF.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: August-01-2018 at 10:19pm
Originally posted by MrMcD MrMcD wrote:

Another trick for cleaning injectors it to run a quart of ATF, tranny fluid with a tank of gas.
It does a good job cleaning and lubricating injectors, without causing any damage.
Many Truck Drivers used it for years to lubricate the fuel system.
Nothing against Sea Foam, I think it is pretty good stuff but for injectors I use the ATF.

Personally, I'd rather see this in the gas since it's designed for it:



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Post Options Post Options   Thanks (0) Thanks(0)   Quote gt40KS Quote  Post ReplyReply Direct Link To This Post Posted: August-01-2018 at 10:55pm
Originally posted by BobinIL BobinIL wrote:


... This caused me to deduct that it is loading up on fuel at idle or it may have a sticky injector ...


The stock factory injectors are fairly robust. But when I rebuilt my engine I had them rebuilt and found out as they age they can start dripping when you turn the engine off and can get worse over time. Fuel system cleaners work well but nothing is going to replace the level of cleaning a rebuild will do. At the same time they can replace worn O-rings and caps and flow match the set, which can make the world of difference if they were in bad shape before.
While 400 hours on the engine isn't a lot, injectors do not go by this clock - some may be good for 1000 hours and never have to touch them, others start failing within a few hundred hours. If all else seems good and you still feel it's a fuel problem, I'd pull the injectors and have them rebuilt/ flow matched at a reputable shop.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BobinIL Quote  Post ReplyReply Direct Link To This Post Posted: August-05-2018 at 3:41pm
Just an update. I put a fuel pressure gauge on the fuel rail and the pressure shoots up to 40 when I turn the key on but immediately drops back to zero. If I start it the pressure tops out at 35 then drops back to zero immediately when I shut the engine off.. If I take the vacuum line off of the Fuel pressure regulator the fuel pressure jumps up to 41 and stays there and the engine smooths out and idles a little faster. I guess I will be ordering a new fuel pressure regulator.   
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gun-driver Quote  Post ReplyReply Direct Link To This Post Posted: August-05-2018 at 4:47pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BobinIL Quote  Post ReplyReply Direct Link To This Post Posted: August-06-2018 at 11:41am
This is the correct fuel pressure regulator for my GT-40
https://www.autozone.com/fuel-delivery/fuel-pressure-regulator/gp-sorensen-fuel-pressure-regulator/79674_594834_0?fromString=search&make=&model=&year=


I replaced it and it helped slightly but my system is still not holding fuel pressure. It pumps up to 40psi they leaks back down to 0 PSI in about 10 seconds. It leaks down slightly slower with the new regulator. Could I have a fuel pump problem or an injector stuck open?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary S Quote  Post ReplyReply Direct Link To This Post Posted: August-06-2018 at 12:12pm
Short answer is yes it could be either. Are you following the manual? section 3H.
The Ford regulator is part number F3DZ-9C968-B, does your replacement cross reference to it?
I'm guessing your engine smoking and missing at idle could be an injector problem. Have you pulled plugs to see which cylinder/cylinders could be running rich?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gun-driver Quote  Post ReplyReply Direct Link To This Post Posted: August-06-2018 at 1:25pm
You can use a stethoscope to listen to the injectors after pumps stop to see if its leaking.
As Gary said checking plugs first could help narrow the search.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BobinIL Quote  Post ReplyReply Direct Link To This Post Posted: August-13-2018 at 2:46pm
I put the Fuel pressure regulator on and finally used my boat this weekend. It ran ok for about 15 minutes but when we started wakeboarding and it did a lot of idling and stop starts the missing and fuel smell /smoke got progressively worse until I could barely pull a boarder out of the water. Checked the oil and it is very clean and full so I would say it is not using oil and there is no water in the oil. the oil pressure hovered around 40 PSI and the temperature was around 140 with no anomalies. I must still have a fuel issue and the fact that it would not hold fuel pressure makes me think fuel is an issue.   
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: August-13-2018 at 5:13pm
Sounds like a leaking injector. If you pull the spark plugs you should see the one that is burning rich. It will be carbon coated black compared to your other cylinders.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DVskier Quote  Post ReplyReply Direct Link To This Post Posted: August-13-2018 at 6:28pm
Sea foam once per year keeps my injectors clean, Nautique dealer recommended it back in 97 when I had a 97 SN with GT 40 engine. I bought a case many years ago and still have a few cans left.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gt40KS Quote  Post ReplyReply Direct Link To This Post Posted: August-14-2018 at 1:37am
Originally posted by MrMcD MrMcD wrote:

Sounds like a leaking injector. If you pull the spark plugs you should see the one that is burning rich. It will be carbon coated black compared to your other cylinders.


+1 - Might add that a severe as yours seems to be you may also notice a "wet" spark plug and/ or may have several leaking injectors not just one. Again, when mine were rebuilt they told me there's really no fix to the leaking ones once they get that bad, just have to replace them. Only other thing I can think is a few of them might be clogged at the nozzle bad enough that you aren't getting a spray at idle - more of a rapid drip. I think this could cause the uneven firing and also explain the smoking issue as well. If that's the case and the internals of the injector(s) haven't been damaged they might be salvageable.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BobinIL Quote  Post ReplyReply Direct Link To This Post Posted: August-27-2018 at 3:09pm
I finally got around to pulling the spark plugs and sure enough the front cylinder on the drivers side the one behind the water pump was black and carboned up. All others were like new.

Now my next question is how to pull the fuel injectors out?? Also should I send it off to be cleaned or just buy a new one?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary S Quote  Post ReplyReply Direct Link To This Post Posted: August-27-2018 at 9:28pm
You would first have to release the fuel pressure,then remove the two bolts that hold each fuel rail on to the manifold. The injectors are held in place by the rail. I can take a couple of pictures if you need them. Your call on replacement or cleaning, I guess it depends how deep your pockets are. If you have gone thru all that work to remove the rail for one you might as well take them all off and have them cleaned,you may have others not up to spec's. If you have them cleaned they may find others that need replacement too,a good rebuilder will have a source for others
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: August-27-2018 at 11:20pm
With 400 hours I would replace the one and make sure your fuel filter is new at the same time.   400 hours in a car would be less than 30,000 miles and not many mechanics would replace fuel injectors at that age.
Something most likely came through the fuel system and has it hung open.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gt40KS Quote  Post ReplyReply Direct Link To This Post Posted: August-31-2018 at 3:06am
I might add that cleaning/ refurbishing and flow matching all of your injectors at this point would be a good idea. If one is fouled badly enough to warrant replacing chances are at least some of the others may be partially blocked as well. There is a rebuilder close to me in Valley Center (KS) that does an excellent job, ships all over the country and is very reasonable - rebuilt all 8 of my injectors for $119 including some new tips.

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