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PCM GT40 5.8L EFI abrubtly barely runs.

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phkemp View Drop Down
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    Posted: August-08-2012 at 3:39am
290 hours on this 1996 engine. Was running this weekend perfectly fine. Tied up for about three hours, when I started it up to head to the ramp...engine is basically not operable. The idle is very erratic, and when throttled up, there is a delay in revving up, it starts to rev, then threatens to quit unless I throttle back; I have to throttle up and down to get the revs up at all, but they don't stay. There is also an erratic, (not regular) knock every 5 or 10 seconds, sounds like the port valve cover area, but I can't feel anything if I put my hand on it. If I try to work it up to higher revs, it stalls out, and also when I return back to idle it'll stall, unless I give it little pokes above idle speed. And it knocks like I said. Kind of a metallic knock, like something hitting the valve cover (not saying that's what it is, that's just what it sounds like. Sort of a hollow sound if that makes any sense)

Today I replaced the plugs (first time, but others were fine despite their age due to low hours;) drained the fuel and replaced with fresh; removed and cleaned the flame arrestor, which was pretty dirty (and then promptly lost it when I put it on the bumper of my tahoe and went to run an errand...trying to find, but need a new one). I also drained the fuel cell, removed it. The filter didn't stay on the high pressure pump, it was stuck pretty good in the bottom of the fuel cell. There also was some corrosion around the bottom of the high pressure pump, I'm guessing from water settling in their when the boat is idle all winter, but the bottom/inside looked clean. The filter did not stay on the high pressure pump like they say it should, I had to work it out of the bottom of the fuel cell. Thinking that maybe the filter was really clogged and causing my problem, I replaced the fuel cell without the filter and tried running the engine briefly...problem didn't improve any.

So...that's about as far as I can go, unless anyone can give me some ideas based on my vague description:

1. Not a gradual decline...it was running great, then on start up three hours later, was a dog.
2. Idle is erratic
3. Quickly throttling up stalls it out
4. Working the throttle up from idle back and forth can increase the revs, but it's not smooth at all, and won't maintain high revs.
5. When I was returning to the dock on Sunday, working in and out of idle speed to keep moving slowly, when engaged with the prop the engine shook quite a bit as well. Not as much when in the driveway in neutral, but still a shaky.

Any ideas before I tow down to a shop and hope they can make a quick diagnosis? Also, I believe that a properly equipped shop can run some diagnostics and get error codes to figure things out quickly? If that's the case I hope to find a shop that can do that, rather than have a mechanic try to diagnose manually?

Thanks in advance.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Dreaming Quote  Post ReplyReply Direct Link To This Post Posted: August-08-2012 at 3:55am
look for the Poor mans GT40 diagnostic chart in the engine repair section.   sounds like a fuel issue to me, but I am not really familiar with the newer GT40's
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Post Options Post Options   Thanks (0) Thanks(0)   Quote phkemp Quote  Post ReplyReply Direct Link To This Post Posted: August-08-2012 at 4:54am
Thanks, I'll search that up. The low pressure pump is definitely putting plenty of fuel in the FCC Bowl. If the high pressure pump was failing/bad (or a relay for it) that would, I imagine, allow the engine to start, but run poorly, and certainly not rev high...which it won't. Would a bad high pressure pump result in pinging/knocking/backfiring or whatever the noise is I am hearing? Any idea? I'm kind of tempted to replace the relay, which is cheap, and then maybe the high pressure pump, which is about $140...but if that nails it, well worth it before I throw the dollars at the repair shop.

The high pressure pump did have some corrosion on the bottom and sides, I imagine from water sitting in the bottom of the bowl...and I wonder if there is corrosion/blockage inside as well. Looking up into it from the bottom it looks ok. I think I saw a thread somewhere on testing the high pressure pump, I need to give that a try.

Thanks again
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lewy2001 Quote  Post ReplyReply Direct Link To This Post Posted: August-08-2012 at 5:07am
Have you checked your fuel pressure??? That will tell you if your HP pump is the cause.
If you're going through hell, keep going

89 Ski

<a href="http://www.correctcraftfan.com/diaries/details.asp?ID=5685" ta
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Post Options Post Options   Thanks (0) Thanks(0)   Quote phkemp Quote  Post ReplyReply Direct Link To This Post Posted: August-08-2012 at 5:38am
Researching how to check pressure on HP pump...I know I saw it somewhere around here!
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Post Options Post Options   Thanks (1) Thanks(1)   Quote lewy2001 Quote  Post ReplyReply Direct Link To This Post Posted: August-08-2012 at 11:43am
You connect a fuel pressure gauge to the Schrader valve on the fuel rail.

You should have 39 +- 3psi with key on engine off and 31 +- 3psi at idle.

If you're going through hell, keep going

89 Ski

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Post Options Post Options   Thanks (1) Thanks(1)   Quote gun-driver Quote  Post ReplyReply Direct Link To This Post Posted: August-08-2012 at 11:47am
Originally posted by phkemp phkemp wrote:

Researching how to check pressure on HP pump...I know I saw it somewhere around here!


There's a shrader valve at the end of the fuel rail. Bottom right corner
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Bri892001 Quote  Post ReplyReply Direct Link To This Post Posted: August-08-2012 at 1:42pm
This is the thread, inside that, there is a link to a google doc spreadsheet with different options.

http://www.correctcraftfan.com/forum/forum_posts.asp?TID=25584&title=poor-mans-gt40-diagnosis

I'd be looking at ignition as well. Especially with the knocking, it could be a spark arcing. Things like cap and rotor, and spark plug wires. See if you can see any visible arching with the motor running (or trying to run) in the dark.

Sorry to hear on your Spark Arrestor. I'd try giving Jody at Florida Inboards a call. He might have something like that laying around.

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Post Options Post Options   Thanks (1) Thanks(1)   Quote Kevin's '79 Quote  Post ReplyReply Direct Link To This Post Posted: August-08-2012 at 3:06pm
I have a '97 Ski Nautique and I had a similar problem. Mine ran fine and then after turning it off for a while and then when I went to start it back up it would not run past idle speed and backfired when you gave it throttle. What it turned out to be was a crack in the clear fuel line that is inside the FCC. When you take the FCC back off you will see the clear fuel line that goes to the high pressure pump and I would say that you may find it has a crack in it which is not allowing it to pump at the right pressure. This line was later changed to a more durable one and it can be purchased from Discount Inboard Marine. Vince at Discount Inboard Marine diagnosed my problem and it turned out to be exactly what I have described above. Hope this helps. Kevin
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Post Options Post Options   Thanks (0) Thanks(0)   Quote phkemp Quote  Post ReplyReply Direct Link To This Post Posted: August-08-2012 at 5:01pm
Thanks guys. Kevin, the sound I'm getting is more of a 'knock' inside the engine, as opposed to a backfire, though maybe it could be.

I will next test the fuel pressure on the rail, hoping I can borrow a gauge but if not, probably worth 40 or 50 $ to buy one.

Based on my reading of all these threads and spreadsheet, I've also ordered new ignition wires, new ECC and Fuel relays, and the hose to the pump inside the FCC, as well as a new FCC filter and O ring. Sounds like after 15 years it's worth replacing that stuff anyway, even if not a fix.

Any other things to look for at this point appreciated.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote phkemp Quote  Post ReplyReply Direct Link To This Post Posted: August-08-2012 at 11:25pm
Kevin! After seeing your same suggestion on another thread and seeing it fixed someone else's problem that mirrored my symptoms, I just went outside to pull the FCC again, before heading out to buy a pressure gauge kit. Took off the pump and hose. It looked fine at first...but then I found it...a tiny crack on the hose. Barely visible, but then when I squeezed the hose, it opened up visibly. I had already ordered new spark plug wires (after 15 years, probably not a bad idea anyway), fuel and ECC relays (also pretty cheap and they're 15 too) as well as a new FCC filter. I called skidim back after reading your reply earlier, and had them add one of those hoses...all of one dollar!

I can't wait till Saturday when it gets here so I can see if it's the fix, it's the first thing I'll do. I'm very optimistic, based on your symptoms, my symptoms, and the symptoms of the guy on the other thread who you gave the same advice to, and it fixed the issue for you both.

I'll post up how I make out. I have to say, it's hard to believe that a little $1 piece of hose, with such a tiny little hole in it, could essentially render the engine inoperable. Assuming that is my cause. We'll see this weekend!

Peter
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kevin's '79 Quote  Post ReplyReply Direct Link To This Post Posted: August-09-2012 at 11:34am
Peter,

Mine was the same way. I could barely find the crack in it and I too was surprised that the fix was so inexpensive. I also purchased new plugs, o ring, and fuel filter when I did mine since they were also original. The fix took no time and mine ran flawlessly afterward and has ever since.

I hope your problem is fixed.

Just imagine what it would have cost to take it somewhere and have a mechanic figure it out.

Thanks again to Keith for providing a forum where all Correct Craft Fans can exchange ideas and work together to solve problems.

Kevin
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bri892001 Quote  Post ReplyReply Direct Link To This Post Posted: August-09-2012 at 12:45pm
Peter,

Hope that hose is the fix with you. Sounds like a strong possibility. Be sure to post back with your results.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote phkemp Quote  Post ReplyReply Direct Link To This Post Posted: August-15-2012 at 4:14am
Well, Kevin was right, thankfully. The short hose from the high pressure fuel pump in the FCC had the tiniest of cracks:



Skidim sent a new one (a proper piece of fuel hose, not this clear plastic junk (along with clamps and a new FCC o-ring. It costs all of one dollar. It's hard to believe a tiny little crack like that could basically shut the engine down.

Had I gone to a repair shop, unless they had a savvy mechanic (like Vince at Skidim) who has seen this before, I would probably have a new fuel pump by now and who knows what else. This fix was a piece of cake (even getting the FCC unscrewed was easy with just an oil filter wrench...from what I've been reading, I'm lucky with that). The symptoms were so bad I was pretty worried, with the poor idle, inability to rev up, and backfiring.

This little piece of hose put me back on the water with a perfectly running engine. THANKS to all of you for your input and suggestions.

Peter

1997 Hydrodyne Grand Sport Elite
PCM GT40 5.8L EFI, 310 HP
Hybridized with Big Air Wake Tower and Bimini
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bri892001 Quote  Post ReplyReply Direct Link To This Post Posted: August-15-2012 at 1:34pm
   Glad you got it fixed.

I added this thread to the diagnosis thread.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote NCH20SKIER Quote  Post ReplyReply Direct Link To This Post Posted: August-18-2012 at 12:21pm
Common problem - I suffered the same issue after towing for 6+ hours for a weekend in Virginia. Skidim diagnosed the issue over the phone and I was back up and running in 2 days
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Post Options Post Options   Thanks (0) Thanks(0)   Quote seacamper Quote  Post ReplyReply Direct Link To This Post Posted: June-29-2014 at 9:54pm
Hey Guys,
Did the 99' FCC have this same problem?
Thanks,
Tom
1980 Ski Nautique Boat Bar
1988 Mastercraft Tristar Open Bow
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gun-driver Quote  Post ReplyReply Direct Link To This Post Posted: June-29-2014 at 11:27pm
I believe so.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: June-30-2014 at 4:53am
My 95 GT 40 acted up briefly, I do not have this type fuel pump, mine uses the older style feed pump and pressure pump system.
1. on acceleration it would feel like the engine shut off then would come back.
2. at low speed it sounded like I was running on 4 cylinders.
3. it always started but was running rough, at the worst I really feared I would not make it the last mile to the dock, it did make it but was rough.
I changed the oil, changed the fuel filter, cleaned the safety shut off lanyard connection and went with a new thermostat, impeller and checked all the cold water feed connections. I added a qt of ATF in the full fuel tank to clean the fuel system and injectors.

I suspect the GT40 has sensors that look for variations in temperature, oil flow etc and it kicks you into a fail safe limp home mode when the engine goes out of the normal parameters. My temp had been going up above 180 at idle and 160 running but now is constant 160 with no fluctuation.
Glad your fix was so simple to.
I really do not know exactly what the fix was for sure but it runs like a top now.
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