GT-40 bogs/lacks top end speed |
Post Reply | Page <123> |
Author | ||
scooter t
Groupie Joined: September-19-2010 Location: Moncks Corner Status: Offline Points: 49 |
Post Options
Thanks(0)
|
|
Yea I didn't realize the pic was going to be so big. I will try an post a few more later and see if someone can help me get a handle on it. I have learned a few things thanks to those who have shown interest.
|
||
I Love to ski, but what I Love more is watching my children learn to Love it too.
|
||
Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
Post Options
Thanks(0)
|
|
I'm always interested. Whether or not I'm helpful, that's another question
|
||
scooter t
Groupie Joined: September-19-2010 Location: Moncks Corner Status: Offline Points: 49 |
Post Options
Thanks(0)
|
|
In pursuit of solving my boat issue, I would ask that someone help me identify a few parts on my motor. This is my second summer owning the boat and I am as far from being a mechanic as one could get... but I'm learning thanks to ya'll. What are these?
|
||
I Love to ski, but what I Love more is watching my children learn to Love it too.
|
||
scooter t
Groupie Joined: September-19-2010 Location: Moncks Corner Status: Offline Points: 49 |
Post Options
Thanks(0)
|
|
I just realized in the bottom picture, that's the LP fuel pump.
|
||
I Love to ski, but what I Love more is watching my children learn to Love it too.
|
||
scooter t
Groupie Joined: September-19-2010 Location: Moncks Corner Status: Offline Points: 49 |
Post Options
Thanks(0)
|
|
I skied this afternoon and right off the rip the boat was surging. Normally it will run ok at first and then escalate from there. Still got the hole shot, but my top end is around 38. Any where from 15-20 is rough.This is my question... the "bicycle" valve at the front end of the left fuel rail, what type of gauge do I use, does the ignition need to be on or off and what is ideal pressure? Also, is there another valve to test or is that the only one?
|
||
I Love to ski, but what I Love more is watching my children learn to Love it too.
|
||
gun-driver
Grand Poobah Joined: July-18-2008 Location: Pittsburgh, Pa Status: Offline Points: 4127 |
Post Options
Thanks(0)
|
|
The top picture is your pressure regulator. The other pictures are your LP fuel pump. The "bicycle" is the schrader valve to test the fuel pressure it should be 39 +/- 3.
A fuel pressure gauge is what you want. When you turn the key to the first position you should hear your pump pressurize the line, it should have the 39+/- 3 as stated above. Then check that it stays at 39+/- as you throttle up if it doesn't it may be that your pressure regulator is stuck in an open position. Top end on that boat should be closer to 48mph @ 5200rpm thats what I get out of mine with a 1442 prop. Also check your vaccuum pressure the fuel regulator works off vaccuum pressure. |
||
scooter t
Groupie Joined: September-19-2010 Location: Moncks Corner Status: Offline Points: 49 |
Post Options
Thanks(0)
|
|
I tested the pressure today and this is what I'm looking at: 40 psi with the key on and it fades. I checked this maybe 10 times and the fuel pump came on every time with the same result. With the boat cranked and in neutral I have a steady 33. With it in gear at 1500 rpm I still have a steady 33. I let it run for 10 minutes and it didn't change.
Gun-Driver or anyone willing.... the vacuum test, give me some instructions please. |
||
I Love to ski, but what I Love more is watching my children learn to Love it too.
|
||
gun-driver
Grand Poobah Joined: July-18-2008 Location: Pittsburgh, Pa Status: Offline Points: 4127 |
Post Options
Thanks(0)
|
|
I'm thinking you have a fuel pressure problem. The pressure should stay constant from idle to WOT.
I think it could be two things 1) HP pump going bad. (not maintaining pressure) 2) Fuel regulator stuck/gummed up, not fully closing. (Allows too much fuel to return to tank when accelerating. ) The fuel regulator opens with vacuum to allow the extra fuel not needed at idle and low rpm to return to the tank. As you throttle up the vacuum decreases and the regulator valve closes more, routing more fuel to the rails to maintain the 39+/- 3 psi Since the fuel pressure starts at 40 then is fading with out the engine running I don't think its a vacuum problem. |
||
Luchog
Grand Poobah Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
Post Options
Thanks(0)
|
|
what about leaking injectors?
|
||
gun-driver
Grand Poobah Joined: July-18-2008 Location: Pittsburgh, Pa Status: Offline Points: 4127 |
Post Options
Thanks(0)
|
|
Luch, I would think that would make it run rich at idle and hard to start. He said the hole shot is good but stumbles at 15 - 20 (assuming mph not RPM)and he's only getting 38mph at WOT. He should be getting more like 48mph with that boat. By the way scooter do you know what prop is on your boat. Not that it has anything to do with the engine problem just curious. |
||
Luchog
Grand Poobah Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
Post Options
Thanks(0)
|
|
do we know if it's running rich? does he know? have he checked the plugs?
It could be an air leak on a line coupling, a filter, a faulty regulator or an injector. a sensor, many options. Usually when a regulator is bad fuel gets sucked on the vacuum hose. that indicates a ruptured valve, at least on the GMs. If not you need a vacuum pistol, and you test fuel pressure while giving it different vacuums. (full vacuum being idle and low being wot) speed is irrelevant as long as we dont know what prop is on the boat and overall engine condition. when did this problem start? what was the last thing changed on the boat before it begun? |
||
scooter t
Groupie Joined: September-19-2010 Location: Moncks Corner Status: Offline Points: 49 |
Post Options
Thanks(0)
|
|
I checked with the PO about the prop.... he said as far as he knew, it's the original 3 blade prop from factory. Nothing in the manuel tells me what the standard prop size is. I was reading the manuel and it shed some light on why the pressure on the gauge was dropping with just the key in the on position. The FP will only run for 2 sec and then turn off. I will say.... it would go from 40 to 20 in less than 60 sec. I would have thought it would hold the pressure. May not indicate anything?
I haven't checked the plugs only because the PO said he replaced them summer before last. When I got her there were 311 hours, now there are 351. But, I will eyeball them asap. When I drove to Alabama to see/get her, while on a ride, the PO mentioned it surging but it was so minimal I didn't notice it. Plus I tripping out on the idea of owning her, I was numb. So the problem has been there from day one..... but it's getting worse. Thank you guys for attempting to help. So what's next? |
||
I Love to ski, but what I Love more is watching my children learn to Love it too.
|
||
scooter t
Groupie Joined: September-19-2010 Location: Moncks Corner Status: Offline Points: 49 |
Post Options
Thanks(0)
|
|
The last thing done: checked anti siphon valve, ok. Checked screen on the dip tube, ok. Looked at the screen on the LP pump, ok. And I replaced the in line fuel filter. I pulled all 8 plugs today, the gaps looked the same. I noticed a little oil on all the plugs around the threads. Here are 2 pics.
|
||
I Love to ski, but what I Love more is watching my children learn to Love it too.
|
||
scooter t
Groupie Joined: September-19-2010 Location: Moncks Corner Status: Offline Points: 49 |
Post Options
Thanks(0)
|
|
Hello,
No one responded from my last reply, so what I realize are the plugs are good and it's not running rich. I bought a fuel pressure gauge and was checking the pressure last night at the schrader valve and this is my update: I was not getting 39 psi while just turning the key on even though the FP was pressurizing. I would have to switch it on and off 2-3 times before it reached 39 psi. Cranked and in neutral I have 34, in gear up to 2000 rpm I have 34. I pulled the vacuum hose from the FPR and I got 40 psi and the rpm increased. Gun-Driver mentioned earlier that maybe it was the HPFP or the FPR. Any suggestions? I'm finding out that EFI makes pinpointing an issue much harder. |
||
I Love to ski, but what I Love more is watching my children learn to Love it too.
|
||
wakeboardin2k4
Platinum Member Joined: December-14-2006 Location: Hopatcong, NJ Status: Offline Points: 1117 |
Post Options
Thanks(0)
|
|
I drove a customers 02 196 and according to the speedo it did 92mph. Ill see if I can get him to help you with your top end issue cause clearly his boat is something special
|
||
"I'm planning to bring my girl that rides on a trailer with me and leave my girl that complains about camping at home"
|
||
lewy2001
Grand Poobah Joined: March-19-2008 Location: NSW Australia Status: Offline Points: 2234 |
Post Options
Thanks(0)
|
|
Shawn hard to tell from those pictures of the plugs if it is running rich or lean.
It sounds as though the early GT40 engines did not have the FCC. It is not often that we send people over to PN for troubleshooting. GT40 Fuel Pressure Check You apply a jumper to fuel pump relay to test. Fuel Pump Relay Detailed description of fuel pump relay. |
||
If you're going through hell, keep going
89 Ski <a href="http://www.correctcraftfan.com/diaries/details.asp?ID=5685" ta |
||
scooter t
Groupie Joined: September-19-2010 Location: Moncks Corner Status: Offline Points: 49 |
Post Options
Thanks(0)
|
|
Thank you sir for the info. I have checked out CCF and PN just seeking some friendly advice. One thing I notice on many topics... a lot of views and not so many replies. But those that have, its much appreciated by all needing guidance. We all have to start somewhere.
My boat does not have the FCC . So right now I am being steered towards the HPFP or the FPR. I'm still reading and waiting for the right lead before I make a move. As for the plugs, my neighbor who is a die hard ford man said the plugs looked normal to him. He rebuilds mustangs, so I trust his opinion. Nothing like a good challenge!! |
||
I Love to ski, but what I Love more is watching my children learn to Love it too.
|
||
gun-driver
Grand Poobah Joined: July-18-2008 Location: Pittsburgh, Pa Status: Offline Points: 4127 |
Post Options
Thanks(0)
|
|
The problem with these GT-40 EFI/MPI is that even though they're strong and efficient running motors they are hard to trouble shoot on descriptions. The computer monitors and controls everything from spark advance,fuel/air mixture,temperature,oil pressure to a self preserving knock sensor.
So lets say you get some bad gas its hard to pin point the problem because if the motor starts to detonate due to the poor quality fuel the motor protects itself with the knock sensor. So to diagnose a simple fuel problem it's harder with out putting the motor on the computer box to check codes and so forth. This was a rough explanation but I hope you get the point I was trying to make. |
||
Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
Post Options
Thanks(0)
|
|
Just connected the dots here, it looks like it could be related to your fuel regulator. Think about it, by removing the vacuum line, you are removing all vacuum. This mimics a throttle full opened condition and therefore puts more throttle to the rails and sends less to the tank. |
||
scooter t
Groupie Joined: September-19-2010 Location: Moncks Corner Status: Offline Points: 49 |
Post Options
Thanks(0)
|
|
Gun-Driver I know exactly what your saying. Down here in the south they would tell you.... "sho you right" (sure your right).
Bri892001.... that has been my gut feeling all along. That's the direction I am going. I have to order it, so maybe in a week I will have some good news. |
||
I Love to ski, but what I Love more is watching my children learn to Love it too.
|
||
scooter t
Groupie Joined: September-19-2010 Location: Moncks Corner Status: Offline Points: 49 |
Post Options
Thanks(0)
|
|
Hello Guys,
Want to update on my surging issues. I spoke with Vince from Ski Dim on Thursday and told him my situation. He called PCM and talked with a tech there. At that time I was ready to order a new FPR... but PCM said based on what I had told them that it was probably my HPFP. So I ordered one, but before I installed it I did test the fuel volume from the LPFP to rule it out. It was good to go, so I put the new pump on this afternoon and went for a quick splash. I am happy to say she ran like a top!! My top end went from from 38 to 45 and I didn't notice any surging. I only had 30 min of daylight, so I can't say for certain it's a done deal. But I'm felling pretty good about it Thanks a million those who shared their knowledge!! If the surging haunts me I will let you know. |
||
I Love to ski, but what I Love more is watching my children learn to Love it too.
|
||
Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
Post Options
Thanks(0)
|
|
That's good to hear. Glad you found it
|
||
kapla
Grand Poobah Joined: March-27-2008 Location: BA, Argentina Status: Offline Points: 6148 |
Post Options
Thanks(0)
|
|
45 is in the low side though....
|
||
<a href="">1992 ski nautique
|
||
scooter t
Groupie Joined: September-19-2010 Location: Moncks Corner Status: Offline Points: 49 |
Post Options
Thanks(0)
|
|
So what should my speed be at WOT with a 95 GT 40 that has 350 hours and a 3 blade prop? How much does weight matter because I had 280+ pounds in the boat plus my 170?
|
||
I Love to ski, but what I Love more is watching my children learn to Love it too.
|
||
waltmagfire
Newbie Joined: May-09-2011 Location: texas Status: Offline Points: 2 |
Post Options
Thanks(0)
|
|
on which fuel pump?
I'm having similar problems. |
||
Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
Post Options
Thanks(0)
|
|
Do you know what your RPMS are at WOT? Are they close to spec for that engine?
45mph doesn't sound bad to me. The Sport Nautique is a little bigger/heavier than a Ski Nautique, so I would think it wouldn't go quite as fast with the same motor. That doesn't sound like a lot of weight but it is some weight and if they were in the front, that could matter too. Do you have the stock 3 blade or an ACME? |
||
scooter t
Groupie Joined: September-19-2010 Location: Moncks Corner Status: Offline Points: 49 |
Post Options
Thanks(0)
|
|
I think she was turning about 44-4500 RPM.... Some where close. If I'm not mistaken spec's are 4600 at WOT. Bri you mentioned the Sport, I have a 95 Ski Nautique Signature Edition. Some where earlier Gun-Driver said he is running 48 at WOT and we have the same boat, but he has a different prop. I have the factory 3 blade prop for now.
|
||
I Love to ski, but what I Love more is watching my children learn to Love it too.
|
||
Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
Post Options
Thanks(0)
|
|
Oh, I think it was the angle of your avatar picture that made me think it was a sport. It kind of makes the front look longer.
Sounds like you're in the right range for RPMs. Yeah, I'd bed the difference has something to do with the prop then. |
||
TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21169 |
Post Options
Thanks(0)
|
|
That does seem to be a little on the low side, at least for an early GT40 in a fast No Wake Zone hull. You should be pulling all of 4800 RPM, if not closer to 5000. Speed will vary depending on how fast or slow your particular hull is, but I would say that 46-48mph would be more typical.
|
||
kapla
Grand Poobah Joined: March-27-2008 Location: BA, Argentina Status: Offline Points: 6148 |
Post Options
Thanks(0)
|
|
prop can be a determinant factor on wot speed...
anyway I was just kidding! lol... Oh I´m getting 47-48mph(gps) wot @4700rpm (not sure if my tach is accurate) with the acme 1442. I have a fresh carbed 351w with gt40p heads, perfomer intake, CR cam, 310 hp... |
||
<a href="">1992 ski nautique
|
||
Post Reply | Page <123> |
Tweet
|
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |