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Poor Man's GT40 Diagnosis

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Bri892001 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bri892001 Quote  Post ReplyReply Direct Link To This Post Posted: May-27-2020 at 3:39pm
Originally posted by cboland cboland wrote:

Problem: No start when hot.
Fix: Replace low pressure fuel pump.

Problem: Rolling/oscillating idle at startup when hot.
Fix: New MAP sensor.


Thanks, spreadsheet updated for both above:
Spreadsheet
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fast351 Quote  Post ReplyReply Direct Link To This Post Posted: June-09-2020 at 3:27pm
Starting engine causes dash fuse to blow (in battery box) as soon as the start button is released. Solution: Replace internally corroded battery cable clamp.

Diagnostics:
1) Battery at full charge
2) Voltage at starter solenoid will vary as much as 4V from the battery voltage.

Cause:
Starter solenoid engages high current (resistorless) wire to ignition while cranking for hotter spark, also backpowering the EEC. The high current draw from the starter caused the corroded connection in the battery clamp to arc over temporarily to allow the starter to turn over. As soon as the solenoid disengaged, all the current to run the engine was being drawn through the 20A fused lead that goes to the dash wiring (presumably this separate lead is there to fix the low voltage issues with the PP??).

This had me pulling out my hair and questioning my EE degree for about an hour and a half (and 5 20A fuses). It wasn't until I wiggled the positive battery cable that I noticed is was loose in the molded over lead battery clamp. The clamp was holding onto the insulation which is why I didn't notice it when putting the battery in in the spring. When I pulled on the wire it came right out of the clamp and it was green dust inside. It looked PERFECT from the outside.

Moral of the story: Just because it looks right doesn't mean it is.

BTW, I have always wondered about the separate power lead from the battery to the dash. Why not just pull it from the 8 pin connector at the engine? That seems to be the way it was designed. I figured it was for radio noise immunity. Must be the low PP voltage tho.
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lewy2001 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lewy2001 Quote  Post ReplyReply Direct Link To This Post Posted: June-09-2020 at 8:30pm
If it is a large fuse holder in the battery box that will be the EEC power source if it is still original wiring. Have a look at this thread.
EEC Power Fuse in Battery Box
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 gjpearce Quote  Post ReplyReply Direct Link To This Post Posted: August-16-2020 at 1:06pm
EXCELLENT WORK
I just started loosing power to the low pressure fuel pump.  This was diagnosed by just running long jumpers from the battery to the fuel pump.  Voila, boat runs.  So I ran a long wire directly from the back of the engine and then connected it via toggle switch directly to the fuel pump.  So to start boat, flip toggle, listen for pump, then hit start button.  Only need to remember to flip toggle off when done boating.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: August-17-2020 at 5:39am
This sounds like something I would maybe do.

Welcome to the "backyard hack" club  Wink


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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: August-17-2020 at 6:59am
Originally posted by KENO KENO wrote:

This sounds like something I would maybe do.
But I'd think you would have at the verry least added some fusing. That big breaker on the engine isn't going to do much to protect his jumpers!  


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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: August-17-2020 at 7:52am
Originally posted by 8122pbrainard 8122pbrainard wrote:

Originally posted by KENO KENO wrote:

This sounds like something I would maybe do.
But I'd think you would have at the verry least added some fusing. That big breaker on the engine isn't going to do much to protect his jumpers!  

I might even try to find the problem in the wiring and fix it Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gjpearce Quote  Post ReplyReply Direct Link To This Post Posted: August-18-2020 at 10:41am
Thank you for the advice and I will add a 10 amp inline marine fuse.  Appreciate your input.
Thank you
Yes, fixing the wiring harness would be ideal, but i live in the boonies in rural Central Florida and I just want an inexpensive boat that I can use several times a week for 15- 30 minutes that will not leave me stranded in the lake.  The boat has low hours but was sunk overnight in the freshwater lake after a hurricane 2 years ago when my boathouse collapsed due to poor engineering and tornado winds.  Skisafe totalled it but let me keep the title, so naturally i had everything cleaned out and checked out while it took 2 years to get the boathouse rebuilt. Boat always ran well while cold, but my mechanic has replaced most all electrical parts (except wires!!)  This fuel pump issue was so easy to solve by just running a bypass power wire and toggle switch by myself.  Wife was ready to force me to buy new boat after she was stranded in boat with impending afternoon thunderstorm while I swam to dock to get PWC to tow boat in......I am happy with a poor man's GT40 as long as it works.  A nice simple GT40 please along with all the help you guys provide.  Thanks again!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote David F Quote  Post ReplyReply Direct Link To This Post Posted: August-21-2020 at 11:42am
'99 Nautique Super Sport, GT40

Problem:  Engine sputtered and died, fuel tank 3/4 full.  Engine would not restart (cold or hot).

Diagnostics:
checked fuel pressure - 0 psi
checked for running LP pump - pump ran when ignition on cycle
relays - could be heard clicking with ignition on cycle, swapped positions - no change.
cracked outflow line at LP pump - no fuel flowing during pump run cycle so no fuel to FCC
Removed fuel tank pick-up tube and anti-siphon valve - both appeared fine, not clogged or damaged.  
Bench tested HP pump in FCC and it ran without abnormal noise.

Solution:  Replaced relays (why not, the're 20 years old), replaced LP pump with Carter (non PCM) equivalent pump, replaced fuel pick-up tube, replaced FCC fuel filter (first time since I have owned the boat - 12+ years).  Left HP pump disconnected and cycled LP pump many times to prime lines and fill FCC.  Electrically connected HP pump confirmed fuel pressure and engine fired right up.

Conclusion:  LP pump was likely faulty even though it ran (not sure how or why).  Fuel pick-up tube looked fine, but i could spin plastic tube on fitting easily (so could have been sucking air...not likely).  I did not test removed relays after engine running again.  New fuel delivery system (excluding HP pump) should be good to go for another 20 years.

I probably should have bench tested original LP pump for fluid flow (the pump runs when bench tested).  May still do that and report.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Canuck-Surfer Quote  Post ReplyReply Direct Link To This Post Posted: September-19-2020 at 11:44pm
Can someone with edit rights to the database add either this link or the part number to MAP sensor PN notes. Ford number is E7DZ-9F479-A

https://www.rockauto.com/en/partsearch/?partnum=E7DZ-9F479-A
1996 Sport Nautique GT40 EFI
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slmskrs Quote  Post ReplyReply Direct Link To This Post Posted: September-20-2020 at 10:26am
Originally posted by David F David F wrote:



I probably should have bench tested original LP pump for fluid flow (the pump runs when bench tested).  May still do that and report.




On my '96. I did the LP pump flow test and although it was pumping, it was at a little more than half the expected volume. Replaced it and problems went away. Lesson learned that it can still be pumping but be faulty. You are solid for the next 20 years!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Canuck-Surfer Quote  Post ReplyReply Direct Link To This Post Posted: September-20-2020 at 11:26am
Originally posted by Gary S Gary S wrote:

Sensor Air Charge Temperature - F2DZ-12A697-A
Sensor Engine Coolant Temperature- F2AZ-12A648-A
For example-
Link 1

Link 2

Can someone add these part numbers to the spreadsheet? I looked there first and didn't find them, then stumbled upon them earlier in the thread here. Also, I'd be willing to make changes if someone grants me edit rights.

Also, Gary, do you have the part number for the Temp Switch/sender. Here is the Rockauto link for a 95 F-250 5.8. There are 2 different senders listed from Motorcraft (SW2328 and SW925). There is also WVE 1T1116. Do any or all of these work?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary S Quote  Post ReplyReply Direct Link To This Post Posted: September-20-2020 at 12:28pm
Link not working, but I cannot find any reference to that part listing for that temp switch in the waterpump in my Ford or PCM book.....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Canuck-Surfer Quote  Post ReplyReply Direct Link To This Post Posted: September-20-2020 at 12:55pm
Originally posted by Gary S Gary S wrote:

Link not working, but I cannot find any reference to that part listing for that temp switch in the waterpump in my Ford or PCM book.....



Do you think its PCM specific?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary S Quote  Post ReplyReply Direct Link To This Post Posted: September-20-2020 at 1:31pm
The one on Nautique parts is the SLOW switch. Not near my parts book at the moment so I'm not sure if its a pcm thing or a Ford part. The rock auto one is confusing it looks like they are showing two different pictures . The one with the cone point and the plastic plug in connector is the coolant temp for the ECM
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Canuck-Surfer Quote  Post ReplyReply Direct Link To This Post Posted: September-20-2020 at 1:35pm
Originally posted by Gary S Gary S wrote:

The one on Nautique parts is the SLOW switch. Not near my parts book at the moment so I'm not sure if its a pcm thing or a Ford part. The rock auto one is confusing it looks like they are showing two different pictures . The one with the cone point and the plastic plug in connector is the coolant temp for the ECM

If I am replacing all the other ones, should I go ahead and replace the SLOW switch too considering cheap price? Also, which one sends temp signal to dash temp gauge?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary S Quote  Post ReplyReply Direct Link To This Post Posted: September-20-2020 at 2:09pm
The one mounted into the waterpump sends the water temp signal to the dash gauge through the "10" pin connector. The SLOW water sensor at around 210* sends the signal to the ECM. The low oil pressure switch is also connected through the ecm . Then obviously both trigger the limp mode and turn on the dash light through a single pin connector.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bri892001 Quote  Post ReplyReply Direct Link To This Post Posted: September-21-2020 at 12:02pm
Originally posted by Canuck-Surfer Canuck-Surfer wrote:

Can someone with edit rights to the database add either this link or the part number to MAP sensor PN notes. Ford number is E7DZ-9F479-A

https://www.rockauto.com/en/partsearch/?partnum=E7DZ-9F479-A

I added this particular Part Number.  You mentioned a couple others as well. Do you have a complete list of the ones you want?

I'm thinking it might make sense for me to add a separate tab, just for the part numbers, so I'm able to fit in a little more information.

Also, what do you guys think of the layout of the spreadsheet in general?  I'm thinking of changing it so that it's rows of data, and then people can filter results by engine issue, and see a list of the different resolutions in the links?  As the information has accumulated, I'm thinking the current layout might be a little cumbersome.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Canuck-Surfer Quote  Post ReplyReply Direct Link To This Post Posted: September-21-2020 at 1:28pm
Originally posted by Bri892001 Bri892001 wrote:


Originally posted by Canuck-Surfer Canuck-Surfer wrote:

Can someone with edit rights to the database add either this link or the part number to MAP sensor PN notes. Ford number is E7DZ-9F479-A

https://www.rockauto.com/en/partsearch/?partnum=E7DZ-9F479-A



I added this particular Part Number.  You mentioned a couple others as well. Do you have a complete list of the ones you want?

I'm thinking it might make sense for me to add a separate tab, just for the part numbers, so I'm able to fit in a little more information.

Also, what do you guys think of the layout of the spreadsheet in general?  I'm thinking of changing it so that it's rows of data, and then people can filter results by engine issue, and see a list of the different resolutions in the links?  As the information has accumulated, I'm thinking the current layout might be a little cumbersome.




What about a separate tab in the worksheet that has a comparison of PCM part numbers to Motorcraft and other Napa or rock auto part numbers?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bri892001 Quote  Post ReplyReply Direct Link To This Post Posted: September-24-2020 at 6:30pm
Originally posted by Canuck-Surfer Canuck-Surfer wrote:

 
What about a separate tab in the worksheet that has a comparison of PCM part numbers to Motorcraft and other Napa or rock auto part numbers?

Yup, I can do that. The Part Names down the left side, then a separate column for each of the major parts houses.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote workky Quote  Post ReplyReply Direct Link To This Post Posted: June-08-2021 at 12:02pm
Ignition Module Motorcraft DY-1077
Temperature Sensor (water) Motorcraft DY-681
TPS Motorcraft CX-1013-A
MAP Motorcraft DY-532
PIP sensor (Distributer) Motorcraft DU-50
IAC idle air control Motorcraft CX-1826
Low pressure Fuel pump Carter P4389

These are a few PN for sensors for the GT-40. These are Motorcraft parts, I have started disliking Aftermarket parts and will only replace with Ford stuff from now on. Please correct me if I have something wrong.

I may try this winter to find a new Management system for my boat, The factory ECM sucks and I feel with modern technology and a modern ECM the GT-40 would run much more efficient. Just have not figured out what to do yet.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote workky Quote  Post ReplyReply Direct Link To This Post Posted: June-12-2021 at 10:09pm
1995 correct craft super sport with GT40 fuel injected

Problem
Won’t start after engine is warm, will start after it cools back off

Bad ignition module

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bri892001 Quote  Post ReplyReply Direct Link To This Post Posted: June-21-2021 at 6:04pm
A Hard Start When Warm issue solved by replacing leaky fuel injectors as described here:

I logged it on the spreadsheet under fuel injectors and logged workky's hard warm start above as a thick film ignition module: 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 2001SAN Quote  Post ReplyReply Direct Link To This Post Posted: April-05-2023 at 6:30am
Recent experiences for what it's worth. Rough running caused by moisture in the dizzy cap. Then on the same day, boat would start but not run. Bad kill switch.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: August-28-2023 at 4:19pm
Some info on gt40 SLOW/limp mode in the linked thread

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 2001SAN Quote  Post ReplyReply Direct Link To This Post Posted: September-02-2023 at 6:08am
No start condition fixed by replacing the power assist solenoid. Again... Last one lasted around 4 years.
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