'97 GT-40 miss or sputter.

[aupatking]

If you saw fuel coming through that pass-through connection on the FCC, it’s worth the $37.50 to know you’re not pumping fuel into your bilge.

 

[Wish]

@aupatking I already replaced that in the hunt for the cause. It was not the cause. Actually it is hard to believe that CC allowed such a thing as part of the fuel delivery system. Especially when you compare it to the replacement part. Mine looked exactly the same when I pulled it. If you have what he has pictured above on your GT40..REPLACE IT!! It will fail, it will leak and it is dangerous in my opinion. Had I known it was that cheap of a part, I would have replaced it yrs and yrs ago just for peace of mind.

[Wish]

Pretty sure we fixed it unless this evening testing was a one off. Hope not as we have been able to consistently reproduce the miss fire. We took it out 3 times this evening. Skied a set. Left it sit for 15mn, ran the course several kore times without a skier and then let it sit again for 15 and took it back out for a 3rd outing. Ran great all 3 times. Trying to decide if I should have you guess what it was or just spill the beans. Have to read back though the thread but don't think anyone named it.

[FLeboeuf]

Plug wires?

[Wish]

Nope

[whitecaps]

spill the beans please! Fellow Gt40 owner must know this information.

[TEL]

loose coil wire

[Wish]

@TEL very warm.

[Orlando76]

Bad damper valves on the ventilation regulator?

[Wish]

@Orlando76 have no idea what that is so no LOL.

[skihacker]

Bad ignition coil

[Orlando76]

It’s in between the flux capacitor and the diesel rated spark plugs ;)

[FLeboeuf]

Corroded fuse

[Wish]

@skihaker got it. So this is something we did visually inspect along with wire. Both "looked" ok. But it came down to it being the

probable cause perhaps with internal issues. When I took it off and flipped it over (pic 1) it was obvious it had problems. Installed and without a mirror or standing on your head, you couldn't see the pitting (pic 2). The wire seemed ok but replaced. I bet if I take the wire apart will see burns and pitting. 1400hrs on a coil. What's the life span on them? Thinkn I got a lot more use out of one then I was supposed to. ?.

 

 

 

[Hockdog]

Stale unicorn farts.

[Wish]

Pics out of order and can't edit. Pic 1 is how it looks installed. Pic 2 is removed and flipped over. Pic 3 zoomed in.

[DanE]

@Wish That pitting won't affect anything.

We're talking 50 000 volts, the spark will find it's way regardless.

Coil can still be faulty though with internal issues.

[Wish]

@DanE the parts guy disagrees with you. Pitting may not be a cause of the boat miss firing but it's an indication the coil was not working properly and the arching that would continue along with the pitting and melting would only get worse. Course he's trying to sell me a new coil haha.

[Rednucleus]

I'll bet it's fixed. Coils and other electric components love to fail as they get hot. When I 1st started skiing 40 yrs ago my buddy bought a runabout with an ancient Evinrude ("The Green Hemorrhoid"). Once warmed up, it would die till it cooled. So we would ski up the Snohomish River till it quit, then drift back to the launch and start all over till we could afford to get the coil changed. Good times!

[vtmecheng]

Pitting means too much resistance or current draw somewhere. Happy you got the thing fixed. Now go for a set and have a few beers knowing your boat is back.

[Orlando76]

@vtmecheng too much current draw would likely lead to melting. What we’re seeing there is arcing. Probably bad coil, possibly loose/bad coil wire.

[Zman]

@Wish Happy to see you solved your issue, and made a few other improvements along the way.

[Wish]

@Zman thanks. Will see how it goes over the next week or so....knock on wood. Appreciate all the input and I know for a fact that reading other threads regarding the GT40 has helped me trouble shoot my boat on this and other things. Hopefully this thread will do the same. I would have "liked" the advice given on this thread but for some reason I can't do that anymore or edit my posts. So again thanks for the input and consider your comments "liked" ?

[gapullin]

As I've already mentioned, your next step is to put a timing light on each plug wire sequentially, 1-8. Almost for certain, you will lose spark during a miss. What you need to know is whether you are losing spark to all cylinders during a miss, or just a portion. If you are losing spark to all, your problem is almost certainly ahead of the distributor. If less than 8, your problem is at or behind the distributor.

 

[gapullin]

My bad, page 4+5 didn't come up on my phone immediately. Glad you got it solved!

[vtmecheng]

@Orlando76 so a poor connection with high current draw wouldn't cause arcing at the connection?

[BraceMaker]

Can't have high current draw on a coil output.

12V step up to 50k V = high voltage low amps note the input wires are tiny.

Essentially you give up current to get voltage.

[vtmecheng]

Sorry, by high current I am referring to current that is too high for the poor connection. I should really be more specific, was trying to respond quickly. Also, I really don't like the electrical side of things. Give me structural failure and impact shock.

[Wish]

It's baaack! :s . Well, the new ignition cool did solve the problem 100%, but only for a while (2 months or so). About a week ago It started doing almost the same thing in that we can get away with one then on the second set after it sits for 10mn, hood up between skiers, it is unusable do to the periodic miss. But now with much warmer water and air temps the problem is coming on after 4-6 passes. Start up, and 4 maybe 5 passes are all good. Then it misses. I did put another new ignition coil in today (older new one looked fine) to see if maybe the one I had went bad or something in the electrical system made it bad. Unfortunately the 2nd new coil made no difference at all. Again, seems to be heat related?? I'm stumped. Any help welcome.

[Killer]

could it be the ECM acting up? they are prone to age (and heat).

[Wish]

That was suggested to me. Is there a way to isolate the ECM off its plate? The plate it's mounted to gets very hot. Maybe hard foam insulation between plate and ECM?? Or would the heat damage already be done? Anyway do test an ECM?? No fault codes on reader even when it misses. 1400hrs on boat sooo. Maybe ECM. But doesn't explain why the new coil fixed issue for many sets (2ish months). Engine runs soooooo good..for a while.

[Wish]

For fun I swapped out the MAP sensor with a new one since its mounted to the same bracket as the coil. Bracket has heat exchange fins so made to keep cool-ish I guess. But no change with the swap so any thoughts welcome. Shout out to @Jody_Seal.

[Killer]

@wish I've read about Mustang owners moving the ECM on their vehicles due to heat. would need some kind of a cable made up to do this, but I like your idea.

 

another option could be to remove the dog house to see if anything changes?

 

OR swap the ecm from another boat that has no issues to rule it out.

 

 

[Wish]

Peter, I did think of that. What's odd is the previous new coil solved the problem for a month or so. So that was my thought. Something else made it go bad over time. First thought was distributer since that's the direct connection to it. So put a new coil in thinking it would last as long as the first new one. Not the case. It had no affect on the problem. Nothing changed. I did change out plugs from manual suggestion OEM (replace iridiums).

[Kevin89MC]

I read this thread with interest, as I like wrenching on my own stuff as well. Electrical issues can be a real bear to track. I am just a shadetree mechanic, no formal training.

Because of your 2 month fix it appears that it is an electrical issue. I know at the beginning you said the plugs & wires were fairly new, but I'd suggest either replacing the wires or swapping them with a known good set. I've had several auto engines over the years act up and new plug & coil wires often will solve the issues. They handle very high voltages and it doesn't take much to make them act up, especially when they get hot. You might have gotten a set with one or 2 marginal wires from the start, and over time they have failed. The new distributor may have masked the marginal wire for a bit. Good luck.

Kevin

'89 Prostar

[ToddF]

does it have a tfi?

didn't you say you put a new distributor? I just bought a new one and it was bad, took quite a while to figure that out

Also if you did replace dist and not TFI I would look at that for sure.

[Wish]

@ToddL I'll look. If it has one, a quick read on a mustang web site suggests not the cause as the boat runs well for one set.

 

....your car will not function without a working TFI. Furthermore, TFI’s fail without warning. They either work, or they don’t. There isn’t an in-between. You can do a visual inspection for cracks in the housing, around the mounting holes or film seepage. If any of these are present, it is time to replace the TFI (in fact, you’d be lucky to find any of those symptoms and still have your Mustang running!).

 

Anyone experience issues with these items? Could they cause this?

 

Stator sensor

Poor wire connection on an injector

Bad tachometer

 

[ToddL]

@ToddF - see @Wish 's response above.

[Wish]

What's the usable life of plug wires. 250hrs? 500hrs? 750? 1000?

[Siouxcitysmitty]

I can't directly answer the usable life question, but, I replaced my original set at 650 hours (proactive change, boat was running fine). I notice that I picked up ~2 mph of top end just with the wire change. So, although my boat wasn't missing, there had obviously been some level of degradation.

[Andre]

@Wish

I did 1700 hrs with originals Taylor 8mm on my 94 MC.

Were still working fine but found a bit of rust so no chances.

[JAS]

If you are still having problems and plan on working on GT-40 yourself, consider getting a Star code reader. Good info on Planet Nautique if you do search

[DanE]

@Wish Have you replaced the 2 relays located near the ECM yet?

[Wish]

Have a code reader and no codes thrown. I have replaced both since owning but can't remember how long ago. Maybe 10yrs ago.

[DanE]

@Wish You can't rely on a code reader.

If the check engine light don't go off, there is no codes stored.

I had one relay go so bad it only fed the fuel pumps with 4 or 5 volts and no check emgine light.

Those relays feeds your engines entire fuel and ignition system including the ECM and they are prone to get bad with time. There is no set threshold in voltage where things stops to work, system voltage is supposed to be around 14 volts and when the points in the relays get burned/ corroded enough the voltage they put out drops- can only be measured during workload.

When the voltage drops to a certain point things stop working, at what voltage? Who knows but don't expect fault codes for every imaginable fault that may occur.

[ToddF]

@wish I have had a few intermittent TFI issues.That once replaced, problem solved

Not saying that is the issue but they are cheap and easy to swap out

They can cut out based on heat and then come back on when cooled down. That is what mine have done in the past

And the Tfi can be relocated from the dist. Not the ecm that is in the kick panel on mustangs so no need to relocate

[Wish]

DanE so there's no way to test them??. And do you think either one would allow a full ski set with 0 running issues, then 15 later it starts missing?? I'm only guessing but if it was volts as the prob wouldn't it be bad from the start?

[DanE]

Yes you can test them, just pointed out that engine harness needs to be connected in full and engine running while you measure.

Measure volts against an open loop will not reveal bad contacts.

Obviously what triggers your symtome is heat, whatever cause it is probably there when you start up in the morning on the verge of making a symptome.

Like I said there is no set voltage where things go bad but if it gets low enough it will cause problems. I'm not claiming the relays are the culprit but they will eventually need a replacement anyway.

And yes heat affects resistance and therefore voltage in electric circuits.

[Wish]

@Toddf where is the TFI located? Is this it (yellow arrow)

?

[ToddF]

That picture with the yellow arrow is the tfi module, typically it is placed on the distributor but it looks like they placed in a different location already, which could be good or bad depending on heat soak.

It also looks like the housing with the cooling fins was designed because of heat soak.

 

I would try the wire wiggle test on the tfi too, doubtful that is the cause.

But it should unbolt pretty easy,

one tip: the tfi is like a 4 or 5 mm bolt and most sockets don't fit in the plastic opening very well, so I have had to tap the socket in or have a thin wall socket to be able to get the bolts loose.

 

I know you replaced the MAP sensor, not sure if that is a BAP or MAP, the map will have a vacuum line going to the manifold the bap will just read the barometric pressure not manifold pressure, either way the boat would still run just crappy.

 

I used to keep a TFI module in my car just in case.

Now I keep a tps in my boat