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GT-40 rough starting when warm |
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Shooter 
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Joined: April-30-2019 Location: Florida Status: Offline Points: 28 |
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 Topic: GT-40 rough starting when warmPosted: August-19-2020 at 9:57am |
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My 2000 SN generally runs great.. Except - When the engine is warm or hot, starting is very rough. I also get a strange reading ("low voltage" and warning beep) on my Star Gazer. After several starting attempts, it runs fine, but I have to coax it to life. Cold starting is no problem. Any suggestions? Thx, Shooter
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KENO
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Joined: June-06-2004 Location: United States Status: Offline Points: 11112 |
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Posted: August-20-2020 at 6:37am |
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I think a better description of "rough starting" would be helpful
 Does that mean you have to crank it a long time before it starts when the engine is warm? Do you turn it off and after it sits for a period of time like 10 or 15 minutes, it turns over at normal speed but takes a while to start? Or is it sluggish turning over.? Do you have to have the throttle wide open to get it to start when this happens? Some people have thrown lots of money and about every part they could at the problem with not much luck on their gt40.
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KENO
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Posted: August-20-2020 at 6:48am |
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Here's a link to a pretty recent thread about longer starts when hot that's maybe not quite finished yet |
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Shooter
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Posted: August-20-2020 at 2:47pm |
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Thanks, Keno, for your interest. Definitely I would like to avoid spending tons of $$$, especially as this is not a serious problem, more of an inconvenience. Well, also a little embarrassing, when I'm starting up at the marina in my pride and joy and the engine keeps dying making the takeoff less than smooth...
The issue arises yes, after turning it off and it sits for a period of time. 10-15 min, or also maybe 2 hours. Turns over at normal speed; not sluggish. Does not need to crank for a long time. Starts, but runs rough (RPM oscillates low, high, low, high, low) then dies. It usually takes a few tries of that, and if I shift into gear at the right time (when RPM high) it runs and keeps running. I do not need to have the throttle wide open to get it to start. After I get it running then all good.
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3749 |
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Posted: August-20-2020 at 4:41pm |
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For a starting point you might put a fuel pressure gauge on it and see what it reads while you run good and when it acts up.
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Shooter
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Posted: August-20-2020 at 5:02pm |
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Trying to diagnose a problem a couple of years ago, I ordered a Detool pressure gauge kit from Amazon ($35). Came with a bunch of adapters, but none seemed to fit the fuel system on my GT40. Maybe our marinized systems are different? I just checked on the Discount Inboard Marine website, but didn't see a gauge.
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Gary S
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Posted: August-20-2020 at 6:38pm |
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You sure save alot of money buying on amazon
. Here is a gauge including the adapter you need- nothing to do with marine,for 30 bucks. Think I bought mine one at one of the local box auto stores. Take your gauge with you to an parts store and see if they have an adapter that fits your gauge and a Ford. If they ask for a year say '93 Mustang don't confuse them with boats...... You say it's not a serious problem but how do you know until you find the trouble? You could be flooding the engine with a leaking injector/injectors and washing those cylinder walls of it's protective oil film causing that cylinder to wear. Dropping it into gear with the rev's up could damage the trans as well. |
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8122pbrainard
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Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Posted: August-20-2020 at 6:52pm |
Gary, Your link didn't work for me. Here's one I found at Summit but it's $50 Jeff, As Gary mentioned, it's not a marine fitting. All it is, is a Schrader valve. |
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MrMcD
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Posted: August-20-2020 at 7:31pm |
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I bought the adapter to fit my Ford GT40 off Amazon last year, just a simple screw in adapter that allows me to connect the GM style to the Ford. It was around $10, no big deal.
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Gary S
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Posted: August-20-2020 at 11:02pm |
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Fixed.... I've seen that "Pro" model listed for double that price but the one I listed works for us just fine
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slmskrs
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Joined: January-03-2012 Location: SF bay area, CA Status: Offline Points: 522 |
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Posted: August-21-2020 at 2:52am |
Classic idle control valve issue. I fought it for years on my 96 before i figured out some tests to do. Ended up being obvious it was the ICV. Dont know if i wrote the tests i did or not, but there are several tests you can do with the ICV off. Let me know and ill dig them up or re write them from my laptop. On my phome and thumb is getting tired.. |
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Gordon '97 Ski Nautique, GT40
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KENO
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Posted: August-21-2020 at 7:28am |
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Here's a link to Gordon's loping issues and what worked for him ...................... But not for everyone with the same symptoms.link
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slmskrs
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Posted: August-22-2020 at 7:00am |
Dang, I was long winded.... ;) Good thing about that thread is several of us were having similar issues, so a lot of test suggestions came out of it. So a slew of things to try in that thread.
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Gordon '97 Ski Nautique, GT40
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Shooter
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Posted: August-28-2020 at 1:00pm |
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Sorry to disappear for a bit. Wouldn't you know, my boat is running better after enlisting the help of this group!
It seems from some responses that the inlet idle control valve may be suspect. Even when I don't have the stalling, if often idles high (1300 RPM?) after starting, even when warm. But for starters, is this the inlet idle control valve:  Can I just remove it (2 bolts + wiring harness) and clean with carb cleaner for a possible easy fix? |
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Gary S
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Posted: August-28-2020 at 3:54pm |
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Yes pull the screen out and soak it as well. You might need a new gasket too.
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gun-driver
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Posted: August-28-2020 at 4:00pm |
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I would clean the air cleaner/spark arrester while you’re at it.
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Gary S
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Posted: August-28-2020 at 4:10pm |
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Here is the Felpro part number for the gasket and a picture of the screen that should be cleaned. It is in a port under the valve when you remove it.
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Gary S
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Posted: August-28-2020 at 4:26pm |
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slmskrs
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Posted: August-28-2020 at 5:41pm |
If you remove the idle control valve and start the engine, it will idle I think somewhere in the 1300-1500 range (should be in my previous write-up) because all the air that the ICV was blocking is now flowing. Just FYI, I cleaned the snot out of my original one and didn't get any improvement (bad idle). As I mentioned previously, when it was having the loping issue, to test, when it was loping bad, I shut it down, very quickly removed the ICV and started it again (within a minute or less). I then used my finger to block the air to drop the idle from the 1300 or so down to 650 or so. I got no loping when I manually closed off the air with my finger. So I just bit the bullet and bought one hoping against hope it would solve it (everything pointed to it at that point). I was estatic since that was it after all of that hassle..... ;) Note that when the engine first starts, it will initially idle high (over 1k), but should drop back down to normal idle within 5-7 seconds (haven't timed it, just seems that long). That is normal. Hopefully you clean yours and that solves it. Mine ended up being bad, so cleaning didn't change anything. But in the end, replacing it was the only way to absolutely confirm it was the problem. But after all the testing, etc. I did, there really wasn't any other possible fault (and using my finger to control idle speed was a good indication the problem was the ICV. After all the hassles with it, the time troubleshooting, etc., springing for a possibly not needed ICV was a no-brainer for me..... ;)
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Gordon '97 Ski Nautique, GT40
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slmskrs
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Posted: August-28-2020 at 5:45pm |
Dang!! That's clean!!! I've only had my current GT40 for a year and a half but since I haven't had the loping issue, I haven't taken the IVC off yet.
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Gordon '97 Ski Nautique, GT40
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gun-driver
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Posted: August-28-2020 at 7:49pm |
Yea ever since Gary retired all he does is sit around and polish his parts
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Gary S
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Posted: August-28-2020 at 8:53pm |
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I actually pull it out of the boat after every use just to clean it off
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gun-driver
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Posted: August-28-2020 at 9:43pm |
Make sure you put it back in the middle of the boat where it belongs, not "backards" in the rear.
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slmskrs
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Posted: August-28-2020 at 10:07pm |
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[QUOTE=Gary S]I actually pull it out of the boat after every use just to clean it off
Wow!!! I thought pulling the ICV out each time would be a bit of a hassle (although really easy), but pulling the engine after each outing like your picture? Impressive!!!!
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Gordon '97 Ski Nautique, GT40
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slmskrs
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Posted: September-23-2020 at 9:43pm |
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So Shooter, did you find out what the problem was?
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Gordon '97 Ski Nautique, GT40
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Gary S wrote: