gt40 running rough |
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Mike9812121298
Senior Member Joined: March-24-2017 Location: Seattle Status: Offline Points: 139 |
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Posted: August-16-2017 at 10:34am |
i started with a cracked block, so i swapped over a f150 block and roller cam. Now that i got the engine back up and running i cant figure out why when i gas it, it just wants to bog down.
The idle sounds good. i checked the timming set it at 12, changed plugs, replaced the high pressure fuel pump, Anyone have any ideas what might be going on? |
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Dreaming
Platinum Member Joined: May-21-2010 Location: Tacoma, WA Status: Offline Points: 1870 |
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hi Mike, I got caught thinking that 10° was the timing number for all 351's, but apparently that is not the case for gt-40's, because of the timing advance being ECU controlled some how.. I believe the static number is 5°, so I would guess your timing is 7° too far advanced. I would check that first. there is a GT-40 manual in the reference section.
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10662 |
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Here's a link to a thread with some timing discussion and a link to the GT-40 manual in the thread which should help you figure out your issue(s)
link |
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Blamey
Gold Member Joined: August-18-2015 Location: White Plains,NY Status: Offline Points: 631 |
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I don't know much about these things but can the GT40 handle that roller cam?
My understanding is the GT40 ECU is very sensitive to engine changes and doesn't adapt well to modifications. Tthe original GT40s where Rockers. |
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96 Super Sport
Previously: 95 Sport Nautique, 1980 Ski Supreme |
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21113 |
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You're confusing roller cam with roller rockers but the concern over whether the ecu can compensate for the different cam is valid. Some folks are running Gt40p's (with a point more compression and a little better flow) without issue, others have reported a change as benign as a .030 overbore caused issues. So who knows.
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fgroce
Senior Member Joined: July-05-2016 Location: Georgia Status: Offline Points: 350 |
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One thing to look for is didn't the firing order change on the ford engines in the mid 90s. May not notice it at idle but may show up at speed. Also make sure you have the correct Thick Film Module for the distributor. Question when you replace a cam do you set timing for the ECM or set ignition timing with regards to the cam shaft specs. Just a thought.
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FGroce
88 Ski Nautique For 28 years Now 2002 Ski Nautique |
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Mike9812121298
Senior Member Joined: March-24-2017 Location: Seattle Status: Offline Points: 139 |
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It's the same thick film module that was came on the gt40. Would this need to be off the f150 because it's going to put out a different signal? I looked up the firing order and it looks to be the same.
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Mike9812121298
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Also right after I replaced the fuel pump, the engine would rev in the drive way and sounded good. It took about 3-4 days to get the new prop on then I took it to the lake. Once I got it in the water it started to stumble again in gear and out of gear.
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Dreaming
Platinum Member Joined: May-21-2010 Location: Tacoma, WA Status: Offline Points: 1870 |
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There was another thread similar to yours that was looking at bad plugs, might be worth a shot, check to see if you have a cold cylinder or 2?
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10662 |
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351's have always had the same firing order. Actually 2...............one normal and the backwards version for the RR engines. So cross that off your problem list. |
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Mike9812121298
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https://youtu.be/dV-GdmME4Sw
I think I got it. Now time for a water test |
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fgroce
Senior Member Joined: July-05-2016 Location: Georgia Status: Offline Points: 350 |
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I wasn't sure about the 351's firing order I know the 302 had 2 different firing orders. The thick film module should be the black one Motorcraft part number 5U2Z12A297D this is the latest number as of now. There is another thread about the difference between the black and grey modules. Hope this helps.
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FGroce
88 Ski Nautique For 28 years Now 2002 Ski Nautique |
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KENO
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So...............are you gonna keep it a secret? |
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Mike9812121298
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Haven't got it in the water yet. Just finishing dinner, I'll post something in about 2 hours
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Mike9812121298
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https://youtu.be/d5kWbnia32E
So it started off running good. Good power, smooth then after the video after about 2 2.5k rpm it started to run bad again. I'm gonna check the timing tomorrow and make sure nothing moved. I'm thinking I need to check the LP fuel pump maybe it's not getting enough fuel and bogging down after it got warm |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10662 |
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So you're still keeping secrets What did you do to it to get it somewhat running right? You're looking for help but you don't seem to want to say what you did.or describe the problem very well. Running bad can be interpreted a lot of different ways. |
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4945 |
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To Ken's point, if it takes a while to start running bad it could be something as simple as an obstructed anti-siphon valve.
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gun-driver
Grand Poobah Joined: July-18-2008 Location: Pittsburgh, Pa Status: Offline Points: 4112 |
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Sounds like either a sensor problem or fuel delivery to me.
What was your temp when it started to run poorly. Need more information, of what got changed from when it did run. Really doubt the cam is the issue as long as it's not a big change, biggest issue when changing things is the ECM's ability to deliver the proper fuel air ratio needed which just switching to a roller cam shouldn't effect. |
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Mike9812121298
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So I've messing around with it this morning. I moved the timing down to 5 ran sluggish. Tried 10 a little better, tried 15 a little better, I kept moving it up until 35 and now it revs up and doesn't bog down. It sounds like it's running good. I've been reading that it shouldn't even run at 35. I must of installed something wrong when I put it back together? I checked for tdc and it lined up with the balancer marks
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gun-driver
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This was done while the spout was disconnected? |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10662 |
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If you have 35 degrees at idle with the spout connected which is what I'd guess is the case, then you need to do some learnin" about how EEC-4 controls timing.
No load at idle, that would be pretty much an expected number. Rev it up with no load and it'll drop Rev it up with load and it'll drop too. The computer looks at all the inputs and varies timing accordingly. It's easy enough to have Google find you a typical timing table and you'll find that 35 degrees How many times do different people have to mention the spout before you give an answer about your timing setting and checking method? |
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Mike9812121298
Senior Member Joined: March-24-2017 Location: Seattle Status: Offline Points: 139 |
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Yea spout disconnected
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10662 |
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Sounds like you have 35 with it disconnected
So what's your timing with the spout hooked back up like normal? |
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Mike9812121298
Senior Member Joined: March-24-2017 Location: Seattle Status: Offline Points: 139 |
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https://youtu.be/fSR3-0YPDAE
So that's with the timing set at 35 with the spout disconnected. The spout was plugged back in before water test. That would make the overall timing over 60. I'm guessing I installed something wrong because it should run with that much timing. But it ran great with no bogging down and idle was good. How do u explains this? |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10662 |
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When the spout is plugged back in, is the timing changing or is it stuck at 35 degrees?
If it doesn't change and stays fixed at 35 then it would seem like your signal from the computer isn't getting to the distributor. If it is going up to 50 to 60 degrees...............that's a head scratcher and scary timing numbers. Like you said, it shouldn't run or at least run without engine damage. Strictly a guess here, but I'll say it's fixed at 35 and a bad sensor or the ignition module is the culprit. Key word is Guess |
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Mike9812121298
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with the spout plugged back in it will stay at 35. When i had the timing set at 10 with the spout in, rev' up it would advance to 30 or so. that's why im thinking i must of installed something wrong to where its showing 35 but means 5. i checked for tdc on cylinder 1 and that was correct.
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JoeinNY
Grand Poobah Joined: October-19-2005 Location: United States Status: Offline Points: 5693 |
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Are you sure you know which cylinder is number 1?
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8122pbrainard
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10662 |
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Since I claim to know nothing about GT-40's, I'm probably at the end of my helpfulness if you want to call it that but I think you should check your MAP sensor.as a starting point.
Plenty of info in the manual but special equipment is needed for most of the testing, I'd try and dig up some local Ford guy with the right equipment. Maybe Dreaming knows or can recommend somebody since he's from your area |
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Mike9812121298
Senior Member Joined: March-24-2017 Location: Seattle Status: Offline Points: 139 |
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I timed it standing by the plyon looking toward the back of the boat. left front would be cyl 1
i know the rotor is facing cylinder number 2 more than number 1 but i put the number 1 wire on the post its starting at i printed out a manual let me take a look at the map sensor this afternoon |
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