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GT40 EFI starting issue |
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Canuck-Surfer 
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 Topic: GT40 EFI starting issuePosted: July-08-2022 at 11:21am |
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I know this is the 2nd GT40 staring issue, but mine is unrelated to TigerDyne's issue so I'm staring a new thread.
Background: Newly rebuilt GT40 with 18 hours. Ran fine until last Friday (except for hard starts when engine was hot after sitting). Saturday morning I went to crank it, it started immediately and ran for 5 seconds then died. Would sound like it would about to start when cranking but would not. Troubleshooting steps: Drained FCC. Then turned ignition to prime. I DO hear LP pump prime and can then drain a full FCC. So the LP pump is working I believe. INTERESTING NOTE: After draining and refilling FCC, the engine cranks and runs for about 4 seconds before dying again. Subsequent attempts do not start at all. Ordered a HP pump from Skidim. Replaced this morning. Engine cranked again for 4 seconds and died. Was able to start it a second time for 4 seconds. But now it wont start at all. I have triple checked the Kill Switch and even placed a dime to ensure it is depressed. I have replaced both fuel relays. Last interesting note: If I press the schrader valve on the fuel rail immediately after starting, then a good squirt of gas comes out. But if I wait 10 mins after last cranking attempt, almost nothing comes out. Could the injectors be leaking and if so could they be suspect? Injectors were tested during rebuild and not replaced. I'm at a loss about what to do next. I do have a spare LP fuel pump on the shelf, but I don't want to start randomly replacing parts unless it makes sense. Gary, Ken, others, impart your deep wisdom on what you would do next! (Also, I have a spare ECU as well. Could this smell of an ECU issue? I find it wierd that after draining and refilling FCC, that it always starts for a few seconds.)
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1996 Sport Nautique GT40 EFI
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JayG80
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Posted: July-08-2022 at 11:46am |
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You should measure fuel pressure to help trouble shoot. How old is LP pump? It can be weak and still make noise. There is a screen inside the LP pump that you can inspect for debris. I would replace if pump is old.. LP is prone to failure at some point
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2007 Ski
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Canuck-Surfer
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Posted: July-08-2022 at 1:28pm |
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Fuel rail pressure is 40 psi.
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1996 Sport Nautique GT40 EFI
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Gary S
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Posted: July-08-2022 at 1:36pm |
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Check the lp pump like above and check the anti siphon valve for crud. If you do a search I posted like a 6 page how to service that lp pump. Like said they don't last forever and yours being a 96 and all.
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Canuck-Surfer
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Posted: July-08-2022 at 2:12pm |
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OK I will totally do this. Just quick question, where is the anti-siphon valve?
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1996 Sport Nautique GT40 EFI
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Gary S
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Posted: July-08-2022 at 2:37pm |
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It is inside the fitting that the hose connects to on the gas tank.
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MrMcD
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Posted: July-08-2022 at 4:56pm |
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40 PSI Fuel pressure confirmed??? IF 40 PSI holds while cranking the engine he has fuel. Pumps are working. The way he describes it starting and then dieing says the pumps might stop once the engine starts. Watch the FP and see what happens before tearing into other issues.
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KENO
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Posted: July-08-2022 at 8:03pm |
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I'd probably try something free and easy and unplug the lanyard/kill switch connector and jump the 2 wires together in case the switch itself is bad even though it's depressed like it should be
Then you can put the dime back in your pocket .
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Canuck-Surfer
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Posted: July-10-2022 at 1:42pm |
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Kill switch bypassed…no change.
I located the anti-siphon valve. I’m about to remove it and check it. Also the fuel screen they can get gummed up…is that on the other end of the pick up tube in the tank or is it in the low pressure fuel pump? If it’s in the tank I’m guessing I have to pull the tank out to be able to lift it out. I don’t see much clearance from where the fuel connecter goes into the top of the tank to remove it. Once I eliminate the anti-siphon valve and the low pressure fuel pump, I’m guessing my next troubleshooting would be the TFI? |
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1996 Sport Nautique GT40 EFI
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JayG80
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Posted: July-10-2022 at 1:48pm |
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There is a screen inside the LP pump.
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2007 Ski
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Canuck-Surfer
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Posted: July-10-2022 at 3:56pm |
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Ok, so I removed the ASV and there as a little bit of debris on its screen. The ball valve moved very easily both by pushing it and by sucking. I don’t think the spring is gummed up. I’ve replaced the high pressure and low pressure fuel pump now. Only thing I’ve had to buy is the high-pressure everything else I already had sitting on the shelf. I’ve also replaced the relays. I’m guessing my next step is the TFI? Could this possibly be a computer issue? I do have a spare ECM on the shelf but it doesn’t seem to be an ECM issue if it can fire up and run for a few seconds. I haven’t gotten it to actually fire and run for five seconds today which is first.
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1996 Sport Nautique GT40 EFI
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Canuck-Surfer
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Posted: July-10-2022 at 5:24pm |
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Swapped out ECM to my spare. No change. Local parts store has TFI module in stock. Will pick it up tomorrow morning and try it.
Side note: while cranking I am getting exhaust smoke out the back so I do have some form of combustion occurring. |
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1996 Sport Nautique GT40 EFI
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JayG80
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Posted: July-10-2022 at 8:18pm |
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When you put in the new HPP, did you change or at least inspect for cracks the 2.5” hose? The high pressure pump is suspended by that small fuel line.
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2007 Ski
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JayG80
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Posted: July-10-2022 at 8:32pm |
Edit, when mine split it would run up to 1500 rpm and not rev beyond that. So maybe not your issue. Also, be aware there is a retrofit for the wires on top of FCC to prevent fuel leak around wires.
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2007 Ski
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Canuck-Surfer
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Posted: July-10-2022 at 9:48pm |
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I think the tube has been changed before. Its black and looks to be in good condition. I’m going to borrow the fuel pressure metre for my buddy again tomorrow and confirm that I’m getting the correct 39 psi on the new HP pump. I’m beginning to think I have an ignition issue and not a fuel issue.
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1996 Sport Nautique GT40 EFI
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Gary S
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Posted: July-10-2022 at 10:04pm |
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Here are the part numbers for the TFI module-
As a side note though I'm leaning toward the PIP sensor inside the distributor and here's why. I had an late 80's something Mercury Topaz that was running fine. Shut it off when we had got home- the next day went to leave and it was no start. Had no spark so I went through the tests and it was the TFI. In your case it's actually starting and then shutting off right? The PIP sensor is the sensor that tells the ECM that yes the engine is running much like a crankshaft position sensor which other manufacturers used. It seems to be a usual suspect when the engine does not run. Usually people change out the whole distributor assy. I realize your in Canada but this is what you need- cast gear. http://www.rockauto.com/en/catalog/ford,1995,f-350,5.8l+v8,1126910,ignition,distributor,7108 None of these including the OEM ones are marine,the cap is vented and that vent needs to be siliconed up. 
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Canuck-Surfer
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Posted: July-10-2022 at 10:06pm |
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Yep. That’s what I used to get the TFI from my part store. I’m picking it up at 10 o’clock tomorrow morning. So you agree it could be the TFI Gary?
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1996 Sport Nautique GT40 EFI
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Gary S
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Posted: July-10-2022 at 10:29pm |
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Oops added more info while you were typing. Not sure see above.
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Gary S
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Posted: July-10-2022 at 10:32pm |
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Lets see if Ken or gundriver agrees....
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Canuck-Surfer
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Posted: July-11-2022 at 12:36am |
A few notes here, prior to today, on first start she would run for a few seconds. Subsequent start attempts would turn over but not start. Played with her for 2 hours today. Never started, just turned over and sounded like she would want to start. Lots of exhaust fumes so we are getting combustion. The disty idea is novel. However, the disty, cap and rotor were all new when the engine was rebuilt last summer (28 hours ago). It was a motorcraft with metal gear. Could it realistically fail this soon? Lastly, what should the tach/rpm’s show while cranking but not running yet? The tach is mostly pegged out or swinging wildly all over the place. Is this normal or is this possibly a clue? |
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1996 Sport Nautique GT40 EFI
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KENO
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Posted: July-11-2022 at 7:37am |
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I think a wacko tacho might be telling you something
 I'd disconnect it at the coil and see what happens. And I'd try the new TFI module too
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Canuck-Surfer
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Posted: July-11-2022 at 9:41am |
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Keno, what might the tach be telling me? I don’t follow.
I will replace the TFI this morning and disconnect the tach and reboot back. Fingers crossed. |
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1996 Sport Nautique GT40 EFI
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KENO
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Posted: July-11-2022 at 1:42pm |
It shouldn't be bouncing or pegged so if it's malfunctioning and grounding itself it'll cause problems because it's also grounding the ignition coil since the signal is from the negative post of the coil, and a grounded coil doesn't like to make a spark. Disconnecting it just takes one possibility out of the picture.
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Canuck-Surfer
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Posted: July-11-2022 at 2:39pm |
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No good news to report. New TFI didn’t change anything. :(
Keno, you say to disconnect the tachometer from the coil but it’s just a plug. Can I just disconnect it from the back of the tack? Or is there an easy way to disconnect just the tach from the coil that I’m not getting? Fuel pressure is 39 pounds through entire cranking attempt. If I had any hair left to fill out I would pull it out. I’m at a lost guys. I guess my next things are try to disconnect the tach like Ken said and then find another distributor? I hate just throwing parts of this thing. |
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1996 Sport Nautique GT40 EFI
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Canuck-Surfer
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Posted: July-11-2022 at 2:42pm |
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Also, Like yesterday she’s no longer starting and running for five seconds. The engine turns over and over but never gets going. When I release the key she does roughly rumble for two or three RPMs before dying.
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1996 Sport Nautique GT40 EFI
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JayG80
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Posted: July-11-2022 at 4:09pm |
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Here are some data points on fuel pressure from my 2002 GT 40. Started Engine in the water,
2,000 rpm while in neutral and the pressure is 35 psi. Turned
off the engine and pressure leaked down to 32 psi, at 2 minutes it was 25
psi, at 3 minutes it was 20 psi, at 4 minutes it was 15 psi. Started
boat again and and at 2,000 rpm in neutral I pulled the vacuum line and the
fuel pressure went to 39 psi. Ran boat in the lake at
around 3,500 rpm and fuel pressure was 40 psi. Edit: Notes from 2015 fuel pressures recorded when troubleshooting performance issues, turned out to be a bad muffler baffle.
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2007 Ski
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Canuck-Surfer
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Posted: July-11-2022 at 4:12pm |
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The service manual also states that pumps primed and attempting start should be 39 pounds plus or minus. So my pressure is fine. I’m moving on to something else at this point.
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1996 Sport Nautique GT40 EFI
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Canuck-Surfer
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Posted: July-11-2022 at 6:54pm |
Gary, I got the gray TFI this morning. I had also seen Keith’s original post in the Poormans thread that listed the same part number. But tonight and reading further down through the Poormans thread it looks like I should’ve gotten the black TFI. Is there any reason why you specifically posted the gray one above? |
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1996 Sport Nautique GT40 EFI
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KENO
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Posted: July-11-2022 at 7:13pm |
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Sorta sounds like you and Jay might be agreeing that your fuel pressure is good
His numbers all sound right in accordance with the manual and the way the system operates.
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Canuck-Surfer
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Posted: July-11-2022 at 7:33pm |
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Yeah, I posted while in the boat all grumpy when the TFI didn't solve anything. I appreciate the numbers.
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1996 Sport Nautique GT40 EFI
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JayG80 wrote: