Poor Man's GT40 Diagnosis

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

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

This sounds like something I would maybe do.

8122pbrainard wrote: 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!

'99 Nautique Super Sport, GT40

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!!

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.....

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

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.

Bri892001 wrote: 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?

A Hard Start When Warm issue solved by replacing leaky fuel injectors as described here:

Some info on gt40 SLOW/limp mode in the linked thread

We have had a starting issue for several years on and off. 1999 Sport Nautique with GT40 engine and 1023 hours (all ours!). A few things to mention:
- recent tuneup (2022) with new spark plugs and wires, points & condenser, fuel filter and timing check.
- have had the lanyard clip not fully seated in the kill switch bite us on occasion over the years.
- changed neutral switch some years back (local Nautique dealer recommended that and it did seem to help for a few years), and I’m still suspicious the issue we have is connected with the position of the throttle cable in relation to this switch contact.
- our symptoms: when ignition switch is turned I can hear the (starter solenoid?) click and hear the low pressure fuel pump run in the fuel cell. But the engine may or may not even try to turn over. What I do; and this always works, is shift the throttle cable from forward to reverse and then back to neutral. I may need to do this a few times, but it always starts. No issues with running once we’re going. And if I do shut down there’s a 75% chance it’ll start right back up.
- we changed our 6-year old Autocraft Silver size 34 out for a new Everstart Maxx size 65 today; more as a preventive measure than anything because I don’t have good reason to believe we have a battery issue. Still had to jiggle the throttle to start.
- pulled off the dash cover and checked for any loose connections; none found.

I know just enough to be dangerous and when my son (works on cars a lot) was here last week we got out the multi-meter and he was pointing me towards a bad (or just old) starter or starter solenoid.

But I am determined not to be a “parts chaser” and then I found this thread. I hope someone has dealt with this issue or can point me in the right direction. Thanks for any suggestions!

Steve

Sounds like a neutral safety switch issue. I would jump it by putting both wires on the same side and see if this fixes the issue. If so, get another switch. Also, if so, put it back and keep jiggling for the time being to be safe. If that doesn’t fix it I would look at the kill switch. Sounds like you have chased both before. Not much else that the shifter can change to go from no turnover of the engine to turning over. You can use a multimeter to test both as well. In any case (meter or jumping) needs to be before you jiggle.

If you think it is throttle position and not the neutral safety switch reset your throttle cables. There is a great write up by Alan on how to do this. Search via google. I’ll look in a bit.