gt40 EFI HELP
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Boat Maintenance
Forum Discription: Discuss maintenance of your Correct Craft
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=47527
Printed Date: November-15-2024 at 11:56am
Topic: gt40 EFI HELP
Posted By: Don W
Subject: gt40 EFI HELP
Date Posted: May-28-2019 at 8:32pm
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At the strt of the season my boat would crank, run a few seconds and shut down. After a lot of trial and error, luck and help from folks on this forum I found that the problem was that it was not getting enough air for combustion. I could pull off the pcv hose and it would run great just at a higher rpm. I ran it around the lake then hooked the pcv back up and it runs great,,,, as long as you don't idle too long. I have been trying to teach some grand kids to ski and that requires a lot of idling. After a few minutes it starts to run rough and shuts down when in gear. The only ;solution is to run it aroung the lake for a few minutes at 34-36mph then it idles fine for another few minutes. I feel like it is not getting enough air at idle to fully combust the gas so it builds up. I can smell it sometimes.. I have repaced the pcv valve and cleaned the spark arrestor . Any nuggets of wisdom will be appreciated, Thanks Don W ------------- DON W |
Replies:
Posted By: gt40KS
Date Posted: May-29-2019 at 1:23am
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Don, I offered a possibility on your other post but in a nutshell, check your spark plugs to start - see if they are wet (unburned fuel). If so it could either be bad plugs or your injectors may be failing - they will drip, sometimes a pretty heavy drip, after engine shut-down and even during operation. This can also cause a hard start condition. But the dripping fuel can fowl the plugs and even 'load up' the cylinders as you say and cause the same symptoms you describe. Plenty of folks on the forum with GT40's, most with a problem at some point. I'm sure there will be several thoughts on the matter. ------------- JCCI 1995 Ski Nautique GT40 |
Posted By: KENO
Date Posted: May-29-2019 at 8:38am
I guess it was "cured" for a month  I still think you have IAC related issues like maybe the passage around the throttle plate that the IAC regulates the air flow through is plugged or restricted and your throttle body needs a good cleaning especially that passage. |
Posted By: Don W
Date Posted: May-29-2019 at 8:40am
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Thanks for that. The plugs are new so this very well be the problem. But I keep coming back to the air and it solving the problem when I took the hose off of the pcv valve. What controls the air intake into the engine? ------------- DON W |
Posted By: KENO
Date Posted: May-29-2019 at 8:44am
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It's going in through the throttle body and at idle the IAC valve meters the air through an internal passage in the throttle body when the throttle blades are closed. The valve gets a signal from the computer telling it how far to be open but if the passage is plugged it won't matter how far it's open. |
Posted By: JoeinNY
Date Posted: May-29-2019 at 10:37am
The IAC itself may be busted, or stuck, as the problem is you are not getting enough air into the engine to allow it to idle and the Idle Air control valve is the thing that allows air into the engine at idle so it will run it does seem like that would logically be the place to start. Although I like the dripping fuel injectors as a backup idea, as with way too much fuel eventually the IAC circuit wouldnt be able to provide enough air... but firstest things firstest. |
KENO wrote:Posted By: KENO
Date Posted: May-29-2019 at 11:44am
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Don Quit naming all your threads the same, it gets confusing Now you have 3 with the same name Here's a link to the thread from about a month ago for reference http://www.correctcraftfan.com/forum/forum_posts.asp?TID=47388&PID=569110&title=gt40-efi-help" rel="nofollow - link It looks like he replaced the IAC valve, not sure how voltages were checked or what they were at different positions. as the manual talks about. |
Posted By: zwoobah
Date Posted: May-29-2019 at 12:03pm
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Joe makes a good point - wet plugs means it's getting too much fuel. Pull out the fuel rails with the injectors still attached. Position a couple layers of paper towel under the injector nozzles and let them sit for a few hours (cycle the ignition to prime the fuel pump). If they leak fuel you'll see it on the paper towel. Be a bit careful starting the engine in this condition. If an injector leaks badly enough, you can hydrolock the motor. ------------- 1968 Mustang 16 - 351W powered |
Posted By: Don W
Date Posted: May-29-2019 at 7:43pm
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All good suggestions. I replaced the IAC valve early on and it was not the problem.It was then that I found out about the air because when I removed the IOC it ran fine, but when I put the new one on it did the same thing. How would I check for restricted airflow and clean it- injector cleaner? From what I have learned there are only three vaccuum hoses: one to the PCV, one to the map gas- (there is a filter here, white, about 3 inches long that I need to get off and check- and one to the fuel pressure regulator, which appears to go through the above filter and to the map gas sensor. Does that sound right? ------------- DON W |
Posted By: KENO
Date Posted: May-29-2019 at 10:29pm
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Here's a link to the GT40 manual. Lots of good info, but some of it doesn't pertain to a PCM GT40 like anything talking about a fuel reservoir vapor separator and any associated lines or any reference to a 10 pin round engine connector which on the PCM's is 8 pins and rectangular. These engines were also used by OMC/Volvo and the manual is more accurate for those engines. There is a whole section of abbreviations that could really use your review For one example your map gas sensor is really a Manifold Absolute Pressure sensor The IAC passage is internal to the throttle body. Maybe with the IAC valve removed you could spray cleaner through the passage or blow compressed air through it to see if it's clear but I think I'd remove the throttle body and soak it in cleaner and use compressed air. The manual will show 4 vacuum hoses but one is associated with the fuel vapor separator which isn't on a PCM GT40 so three like you came up with is a good number http://correctcraftfan.com/Downloads/Pro_BOss_GT-40_Service_Manual.pdf" rel="nofollow - link |
Posted By: Don W
Date Posted: May-30-2019 at 4:28pm
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Thanks. I like the idea of removing the throattle body and soaking it. There is a new wrinkle. Tried to ski this morning but The boat started surging and check engine light is on.Maybe if I can determine what is causing the light to come on.... ------------- DON W |
Posted By: Don W
Date Posted: May-30-2019 at 4:35pm
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Thanks. I like the idea of soaking the throttle body. There is a new wrinkle. I tried to ski this morning and the boat started surging and the check engine light came on. Maybe if I can figure that out... ------------- DON W |
Posted By: tryathlete
Date Posted: May-30-2019 at 8:26pm
I had the stumble and surging when my LPP started to fail. I replaced it and the issue went bye bye. I do think your throttle body or IAC is acting up too. KENO is like a remote surgeon for this stuff. |
Posted By: lewy2001
Date Posted: May-30-2019 at 9:38pm
****Moved post to this location. It does make it confusing when you have the same info in different locations.***** Symptoms sound like you have a rich mixture. Maybe the ECM still thinks the engine is cold and is using the warmup fuel tables. Check ECT and ACT sensors.    ------------- If you're going through hell, keep going http://www.correctcraftfan.com/diaries/details.asp?ID=2999" rel="nofollow - 89 Ski <a href="http://www.correctcraftfan.com/diaries/details.asp?ID=5685" ta |
Posted By: MrMcD
Date Posted: May-31-2019 at 3:59pm
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With the IAC removed you can first blow some WD40 into the throttle body at the IAC mounting hole and then blow high pressure air hoping to clear the passage. Finish by blowing Carb cleaner to remove any trace of the WD 40. IF you leave oil/WD40 in the opening it will attract dirt and clog again but I think the slippery WD40 may help clean out any crud in the passages. You can hook up a Fuel Pressure gauge and watch pressure while you run the boat. I use a pressure gauge with a 5' hose so I can hook it up and place it somewhere to observe while it is running. A second person can help and record what you witness. It is a quick way to establish fuel pressure and rule it out as a cause. For many years now, 20 at least, I have been using a quart of ATF, automatic transmission fluid in my fuel injected cars and this boat. Put one quart in to a full tank and it lubricates and cleans the fuel injectors pretty well. I use it about once a year. Learned this trick from Diesel mechanics years ago. It is cheap compared to FI cleaner and has smoothed out a few cars that had sticky injectors. Some of the early FI cleaners were hard on the Orings but ATF has worked with no issues. I am sure the EPA would not want it used as it is not approved. But it works. ------------- |
Posted By: Don W
Date Posted: June-01-2019 at 4:17pm
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Sucess!! well at least partially. I decided I would try cleaning the throttle body first because I was afraid I would screw up the linkage hook-up. I took off the IAC and removed the gasket as fell. there is a wire screen there. I took it out and cleaned it good. I also removed the pcv valve and there is the same type screen under it, I cleaned it . It now purs at idle and I let it idle twenty minutes and it never loaded up or even sputtered. HOWEVER it still surges after just a few seconds if you go over 3000rpms. I put on a new MAP sensor and disconnected the Idle speed control and it is still doing it. I have ordered a new oil sender and oil pressure switch because the oil pressure gauge was pegging 80. Any thoughts? ------------- DON W |
Posted By: KENO
Date Posted: June-01-2019 at 4:37pm
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Sounds like the original problem may be fixed but the new issue you first mentioned a couple of days ago is still there. I think I'd check that all the connectors for the sensors are plugged in properly as a start and look at Lewy's post from yesterday. |