96 SN EFI well after warm up problem |
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96SNEFI
Senior Member Joined: March-23-2009 Location: Canada Status: Offline Points: 138 |
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Posted: August-29-2019 at 6:32pm |
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So now I have it running after replacing the coil and distributor. Go out for a ride. Maybe out for about half an hour. All good just puttering along.
Then I decide to cross some short distance with some more speed. Back comes the problem that started this whole friggin' adventure. It starts to miss and cut and be all kinds of trouble. I pull back the throttle and let it putter along at idle if not a little more and it settles down and runs fine like that. Add throttle again and a few moments later it misses and cuts and even a few popping sounds as I bring back the throttle. It seems to be a warm problem. I can run it for a bit after it has cooled. Have a ski and all. But to use it after it has become warm...dang. I doubt it's gas as this has happened now across a couple seasons with newer gas. And I pump out the tank at the end of the season. Would regular gas make this difference? I've run many years on regular. For other over-heating awareness I don't have a thermostat in. Would that cause this nasty miss/stutter? Why? It has straight lake water flowing through. I watch the exhaust and there's flowing water coming out so the water is circulating. I'm just frustrated as all get out. What parts should I be throwing at it now? (other than a chain saw :) ) I do still have a new LPP on hand that I bought for all this nonsense but I haven't installed it yet (whether I need to). Thanks for any insights. |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Well you do need a thermostat in it,a 160. The computer thinks the engine is cold so it's going to make it run rich. Then just don't go replacing parts on a guess. Go get a fuel pressure gauge set and start there. Sounds as if the pumps may not be able to keep up with fuel requirements. Read through the gt40 trouble shooting manual here on the site to get an idea how everything works together.
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96SNEFI
Senior Member Joined: March-23-2009 Location: Canada Status: Offline Points: 138 |
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Thank you for the reply. At this point I don't really care about running rich. I'm not guessing things. I read a bunch of stuff here and decided on a coil. Runs now. I read about the engine cutting out and that it could be the distributor. And I also read about the relays so I replaced those too. This happened last year as well and I put it off. It is after all a 23 year old boat. I've managed to barely put any money into it in the 13 years I've had it. So I guess it's all catching up to me now. I'm obviously hoping for you and all the other experienced people to chime in and say oh yeah happens all the time it's this. Replace that and you're golden. :) |
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MrMcD
Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3734 |
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My 95 did the same thing 4 years ago, I did some reading and got advice on this forum to replace the Oil Pressure sensor and the Coolant sensor.
At the same time in installed a new Thermostat and impeller. The boat has purred ever since. The computer has a limp mode if it detects low oil pressure or hot coolant. As a test it has been reported on here that you can remove the wire attatched to these to sensors and see if this fixes your issue prior to replacing any parts. My boat only had 99 hours on it when the sensor failed but was 20 years old. In my case, I wanted it to run right away so I just changed them both. Certainly put a thermostat in your engine. 160 is correct temp. |
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96SNEFI
Senior Member Joined: March-23-2009 Location: Canada Status: Offline Points: 138 |
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Thanks for the reply. What does the engine do when it's not getting a signal from these sensors? My oil pressure gauge works...how would that indicate that the sensor is in trouble? Coolant sensor...well...it's straight lake temp so the temp gauge does move up but barely. Are you saying you had these after-warm miss/stutter/cut/idle-fine issues and it was these sensors? I'm a little over 800 or so hours now. I've probably put just 150 or so in my ownership. Yes...barely using it. |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Part to far right is pressure sensor only for the gauge. Part in the middle is the low pressure sensor for limp mode- it signals the computer that there is low oil pressure. The computer then limits rpm. Engine uses same type setup for water temp too. |
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96SNEFI
Senior Member Joined: March-23-2009 Location: Canada Status: Offline Points: 138 |
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Thank you for this clarification. So the irritating as heck miss/stumble/cut only when warm is maybe indicative of it quickly tripping in and out of limp mode? Why would it work fine when not warmed up? Y'know...this may be something. Earlier in the season I was out cruising at a higher speed when it did this one single lunge down in operation...then picked itself up and continued on its way. (Although I turned everything off at the destination and then the thing wouldn't start which I attribute to the coil.) Are these sensors known to fail in old age? Are they proprietary to PCM or standard Ford automative? |
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96SNEFI
Senior Member Joined: March-23-2009 Location: Canada Status: Offline Points: 138 |
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Ah. Well then that explains that. One analog for the gauge and one sensor for the computer. Got it. Awesome. Thanks for that. Edit: Ok so I did a little more searching and found threads about these sensors. I can't say the miss/stumble started at 2800 revs. When I had pulled back the throttle to let it putter at idle or so and let it settle down I would then add throttle again. It seemed to me that it would start to miss/stumble again at around 1500 or so. Not very much but I was aware of it. In case it was missed above...are these the same sensors used in the automotive side like say a 95 F250 5.8? Kinda like the distributor? |
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MrMcD
Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3734 |
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When it kicks in and puts you in limp mode your engine runs so bad you think you will not make it back to the dock. Mine ran great for quite a while and then bam, ran terrible.
Sputtering acting like it was going to die and huge drop off in power. I seem to remember having trouble getting on plane to get back to the launch. I did not know at the time to unplug the two sensors to see if they were the cause. I can say I replaced them and 80 hours later all is still good. I legitimately overheated once and the system shut me down right away. It is nice when it works as planned. |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11045 |
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Limp mode limits your engine speed to about 2700 ish rpm if the sensors think your oil pressure is less than 5 psi or water temperature is over 200 degrees (some places list it as 210 degrees but let's just say it's getting pretty hot)
If one of the sensors is bad but your oil and water temp are normal, you can drive around all day long at under 2700 ish rpm and everything will be normal. Hit that magic number of 2700 ish though and it starts stuttering and misfiring until you reduce speed and things will go back to normal So............if you're sure that oil pressure and water temp are normal (in your case the water temp seems to be low but that won't put you into limp mode) then you find the oil pressure sensor and disconnect the tan/gray wire and find the water temp sensor and disconnect the tan/gray wire (tape the wire ends so they don't contact the block or any other metal on the engine) and the boat will never go into limp mode. You want to be sure you get the tan/black wires because there are 2 sensors for water temperature along with the sending unit for the gauge on the dash. One sensor feeds the computer to tell it what engine temperature is and the other is for activating the limp mode and has the tan/black wire hooked to it. Now, take the boat for a ride and see if your problem still exists This may or may not fix your issue but it'll at least rule out a limp mode issue. If MrMcD's engine ran like crap at any speed, he had more problems than just a bad sensor Based on your edit a few posts back, it's probably not your problem, but it's easy to rule out. |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11045 |
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Here are a couple of links to threads about going into limp mode.
In the first one, you'l find a good explanation from the GT40 manual of the SLOW system that puts you into limp mode In the second link Basler the guy who started the thread had a bad oil pressure switch, couldn't go over 2800 rpm, eventually disconnected both wires for oil and water and the boat ran normally. Don't know if he ever replaced and reconnected them link another link |
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96SNEFI
Senior Member Joined: March-23-2009 Location: Canada Status: Offline Points: 138 |
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Thank you KENO. Those were threads that I found. There's a story on the other site as well with an Apex engine..
I think I am closer to MrMcD's general cut-out problem than the magic 2700 problem. But I'll have a go with pulling the wires today and see what happens. Even a couple few years ago now I had what I thought was an overheat but maybe it was this sensor limp mode thing. I was confused earlier with the wire removal. I wondered what would happen removing them and 8122pbrainard quoted it would go into limp mode. But then I read here and elsewhere that the system will work without those sensors connected and that they're just a defense mechanism. Any thoughts on whether the sensors are standard automotive or do I need to get the PCM ones? |
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MrMcD
Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3734 |
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When mine failed, I was on the lake in the winter setting the prop shaft packing.
I had just purchased the boat damaged and installed a new shaft. This was supposed to be a shake down cruise. I was afraid I had a major problem. There were no other boats out there to tow us in. When it started acting up I kept the power on trying to get back to the dock. Oil Pressure and temp were OK by the gauges. I can't say I tried to run below 2,700. I tried to keep it going and it was sputtering, surging. Sounded like it was running on 4 cylinders and the power available seemed like 4 cylinders I reported the issue on this forum and was directed to checking the coolant and oil pressure senders. I bought those and installed them, also installed a new thermostat and fuel filter. I also changed the engine oil and tranny oil. One of these items fixed the problem. I believe it was either the coolant or oil pressure sensor. The problem was solved. In actual overheat the red light on the dash popped on and it was like the key was turned off, then back on, then off and back on. Engine sputtering. I was cruising at 3,200 RPM when this happened. In this case I knew at the first sputter what was happening and turned the key off right away, looking at the temp gauge it was at or near 200. I did not try to run below 2,700 RPM as the priority was to shut down and cool it off for repair. |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11045 |
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I'd get the PCM sensors if you have a problem They may have a Ford part number associated with them, but they're only for the marine/industrial division and weren't used on cars and trucks since they didn't have a limp mode |
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96SNEFI
Senior Member Joined: March-23-2009 Location: Canada Status: Offline Points: 138 |
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Thank you. Wouldn't the limp mode be up to the computer with these as just dumb binary sensors? |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11045 |
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Something has to tell the computer that it needs to go into limp mode and that's what these 2 sensors do. At 5 psi decreasing the oil sensor completes a circuit to ground and at 200ish the same happens with the coolant sensor. When that happens the smart computer limits speed to 2700ish rpm at which point it stutters and runs like crap but under 2700ish it'll run OK again. |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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The water temp is an Index 8039014 210 degree. The oil pressure switch has no manufacture name just the numbers 15 and 10098
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11045 |
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One other thing about those two switches.
When either switch activates it'll cause that red warning light right in the upper middle of your dash to light up telling you that you have high coolant temperature or low oil pressure.................if the light isn't burnt out |
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96SNEFI
Senior Member Joined: March-23-2009 Location: Canada Status: Offline Points: 138 |
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If that's a part of the test then no I don't get that. I've just done these on-water tests. Disconnected oil pressure switch as shown by Gary S, Ran - miss/stumble. Disconnected water temperature switch on top forward starboard with the two wires. Ran - miss/stumble. The light lights up on start but not with these tests. Rats. So back to an earlier idea of starving for fuel. Why does this problem show itself after getting warm and not just always once up into higher revs? Once it decides that that's how it'll behave then it's reproducible. It seems to take a bit to get there as I had run it a bit just on the lift and it didn't do it (with no load of course). I think I'll get a fuel pressure gauge doodad and see what I get from that. What am I supposed to see for pressure at idle and then running at revs? I also have a fuel pump on hand but not yet installed. Thanks always folks. Still frustrated as heck. Shouldn't I be able to cruise uninterrupted without a care in the world until the gas runs out. :) |
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MrMcD
Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3734 |
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I connect one of my AC hoses from my freon gauges, these hoses connect to the fuel pressure test gauge and to most fuel pump test ports on the fuel rail top of your engine.
The long 5" hose allows you to route it forward and observe pressure while you drive the boat. You need to know pressure as you idle, accelerate and durring your failure mode. Edit, I worked on a Ford 5.4L recently and I needed an adapter to connect to my AC hose to the fuel rail. I will have to look at my GT40 and verify what connector it has. Did you check the anti siphon valve at the gas tank, it can choke out fuel flow when it fails. I think the 96 GT40 uses the fuel pump module, there is a short fuel hose inside the module that can split and cause pressure issues also. Once you know if you have a good fuel supply it will at least rule out many things. Running all the time in an efi engine without a thermostat could leave your engine in cold start mode all the time. This would leave you over rich and waste fuel. Not a good idea. |
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96SNEFI
Senior Member Joined: March-23-2009 Location: Canada Status: Offline Points: 138 |
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Thanks I have run without the thermostat due to being concerned that I'm overheating what with these shenanigans. I'll need to investigate how to check the anti-siphon valve. Sounds like surgery. A long time ago I wanted to get at the plumbing in and around the tank and found it rather onerous not wanting to break things so gave up. It does have the FCC canister with a little pump and filter inside. I remember that little hose. I guess I could have a look but I'm just about ready to say screw it and put the thing away for the winter. I have other things the spouse needs me to do than fartin' around with a stupid boat and throwing money and time at it looking for the quicker fix. Like I said earlier, I'm not concerned about wasting fuel right now as I just want the thing to be bl@@dy reliable. My one and only ski this year and it died on me shortly before the dock and I had to swim the rest of the way in. Sucks. The season is running out. If I wasn't 4 hours from a dealer it would long since have been in the shop. |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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This has me wondering. Do you have any pictures? The water temp sensor your looking for only has 1 wire....... This is what it should look like |
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96SNEFI
Senior Member Joined: March-23-2009 Location: Canada Status: Offline Points: 138 |
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Thanks for asking for clarification. The GT40 book indicated it's the one up top, not the one on the top of the water pump. I read somewhere here that it's the 2-wire one. The 2-wires attach to the same post. The water pump one had one light tan wire. Or I completely misunderstood something. Not the first time. |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11045 |
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I agree with Gary, if it had 2 wires, it's the wrong one
There's been some misleading stuff posted over the years Look at the second post in the link below with the picture from the manual, Each sensor has a tan/black wire. The link was posted earlier in this thread but here it is again. But, like you're thinking, it's probably not your issue since the red light doesn't come on when you have the issue and the engine speed is lower than 2700 ish. As far as the light , it comes on when the switch thinks there's a problem, and with the wires disconnected, it'll never come on. At startup it lights up because you have no oil pressure when you first turn the key to the RUN position on the way to the START position link |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11045 |
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I think I'd put the thermostat back in and get a fuel pressure gauge for a fuel injected engine. It'll have the right fittings supplied with it.
Also check the anti siphon valve like mentioned. It's pretty easy to find right where the fuel line connects to the tank. Don't stop there though, pull out the suction line from the tank and see if it's plugged up with junk. You'll read various different things about whether there's a screen at the bottom of the line in the tank. The only way to know what you have is to pull it and look at it and ensure the line and the anti siphon valve are both clear. If there's no screen junk just gets sucked up the line and plugs the anti siphon valve It's given plenty of people fits because they didn't check the line and valve and instead they replaced one or both fuel pumps and didn't resolve their problem till they eventually got to looking at the valve and suction line. So in big capital letters .....CHECK THE VALVE AND THE SUCTION LINE IN THE TANK The pumps aren't gonna have good discharge pressure if the suction side is restricted You can find specs for fuel pressure in the manual on page 4-1 |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11045 |
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The link below has some pictures of a clogged/restricted suction line. His anti siphon valve was clear but the suction was a mess, so look at both.
There's a link in there to his thread on Planet Nautique too with more info link |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11045 |
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And here's another link with some info
link And if you follow the links in the linked thread above you'll find a thread started by you in 2014 asking about accessing the valve and screen. It doesn't say if you ever checked them though |
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Aengenend
Newbie Joined: March-04-2013 Location: Netherlands Status: Offline Points: 25 |
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We had something similar on a friends 1995 GT-40..
Once some 20 years ago the low pressure pump had a bolt missing and was sucking in air, therefore not filling the fuel control cell fast enough to maintain high speeds for prolonged times. When the issue came up and rpms were lowered for a while all was good until some longer high rpm runs. This season the low pressure pumps vanes were not smooth enough anymore to suck fuel from the tank through the anti siphon valve, we turned all the vanes around so the running surface was new again, primed the pump by sucking the air out trough a clear plastic hose by mouth and all is good for a couple of years ( hopefully another 24 since it's the oem pump from 1995...) |
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SN 93, Pro Boss HO, GT-40P, ACME 422
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96SNEFI
Senior Member Joined: March-23-2009 Location: Canada Status: Offline Points: 138 |
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I went about wanting to check all that but with the age and the plastic tank and the hose that didn't want to reasonably come off...I didn't want to break things and make the job bigger so I gave up. At least I have a better idea of what it looks like as a reminder after all this time. Drooping shoulders and head, shuffling off with defeat...ok fine...I'll have at it again :) If it breaks stuff then the season is over anyway. It seems then that the GT40 book is wrong if the SWITCH is the one at the pump and not whatever that is up top that it says. Or again...I misinterpreted. Not the first time. Aengenend: I think I would prefer just replacing the pump. But I'll be looking at the tank parts before then. I don't really want to have gas everywhere but there it is. Thanks again KENO and your input Aengenend. I won't be doing this until next week sometime. Not even testing the other water sensor switch unplugged. But no, I don't think I'm getting limp mode from all this. |
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