GT40 Low Pressure Fuel Pump Not Being Triggered

Hello to lewy2001. You seem quite knowledgeable about the Ford EEC IV diagnostics. I am hoping you can help me with my boat. I am new to boat ownership. Recently picked up a 1995 SN GT40 Pro Boss. The boat is incredibly clean. It was very well maintained prior to my ownership. That having been said, I noticed after getting the boat home it would have an extended crank condition. After about one minute of cranking it would fire up and run well. When trying to restart after running it a both, it would fire right up. Once it cooled back down, it would go back to an extended crank. Without getting any time to diagnose the extended crank, I took it to the lake for a quick shakedown, and once in the water, it cranked and fired immediately (faster than it ever started before cold) but would stall after 1-2 seconds of running. It kept doing this at the lake. So back on the trailer and back home. Played with ignition switch (which looked new) and it fell apart while removing it. Figured that was it. Threw a new switch in it and no change. Noticed at this point, fuel pumps don’t prime but will pump when directly jumped to 12v source (could not get the pumps to activate through the STO diag port). After reading your post, I checked my battery box for a fuse (no fuse present), battery cables clean and tight, lanyard attached and appearing to work. I tested for power at both of the plugs that power the relays next to the ECU and found power only at terminal 30. No power at the other terminals no matter if key was on or off. I’m assuming this is the issue since I’m supposed to have power to terminal 86? Seems odd that the running concern changed after simply towing it to the lake. I’m assuming the vibration on the trailer has caused the running concern to change? Let me know what you think. Thank you in advance for any help you can provide.

MBO090 wrote: Does anyone report problems with the EFI computer or is it rocksolid?! Thanks anyway!!

The EEC1V computer was used on Ford based automobile engines and they proved quite reliable. The GT40 PCM engine was released in 95. So some of these engines out there are approaching 20 years of age. The ECM in the marine application has also been reliable. There have not been many reported failures on this forum. Which would be the best indication as most owners with problems would find their way here via google.

Your problem could be a intermittent relay problem. But do not rule out a wiring/connector problem or fuel pump. Having a spare relay or two will not go astray as they seem to be the weak link in a otherwise great engine package.

MBO090 wrote: Questions: Is the box named Test ECC (?) a relay? Are there any fuses under the dashboard that can cause this problem? Any Ideas anyone...?!

No it is just a protective plastic housing over the STO and STI connectors used by a Ford OBD1 code reader. No fuses under the dash that could cause this problem. If you have a large fuse holder in the battery box that is a known source of GT40 problems and a modification was done to remove this fuse totally. Also check safety lanyard connections.

Have a look in the thread I mentioned above it will show you a code reader attached to those connectors. The engine in this thread had similar problems to yours so read complete thread.

Hey Rick, I was having the same issue a couple months ago. Turn key, sometimes pumps would activate, sometimes not. And a couple of times, boat would quit after running.

I didn't bother pinning out the connector, but simply swapped the fuel pump relay after posting a message here and looking at that thread.

Relay is 12 bucks at Autozone.

Ultra

Thanks for the info! This is VERY helpful! So I wonder if the problem could also just be an intermittent failure of the low pressure pump?

I'm going to do some tests today & HOPEFULLY get it all squared away.

2001 Super Air Nautique with GT40 engine (and perfect pass...in case that makes a difference!). I've scoured the forums for help, and have finally narrowed down the failure to terminal 86 on the relay plug for the low pressure pump. Turns out that it is not cycling to +12V when hit start on the keypad - or if I crank the engine with the keypad.

I have tested both HP and LP fuel pumps, both relays, and finally got out the multi-meter to see what is happening. Terminal 86 on the low pressure pump relay plug is getting -30mV when I crank the engine and with no relay plugged in. For the high pressure relay plug, I get about 12V at Terminal 86 when cranking.

I have hard-wired to the low pressure pump from terminal 30 - and the pump runs perfect. I've also done the obvious relay-swapping, etc... with no luck.

I have some specific questions;

1. Do the high pressure and low pressure pumps run simultaneously (i.e. is Terminal 30 essentially 'common' to both of the pumps)?

2. If I need the boat to run Friday...until next Sunday... for our 'big' summer vacation, can I simply wire Terminal 30 from the HP pump to the LP pump so they both will run simultaneously?

3. What conditions need to be met for the low pressure pump to run? Are these conditions the same as the high pressure pump?

I should note that the boat was running OK on the last 3 outings. I recently re-carpeted & surely pushed the wiring harness around a bit under the dash, etc... is there a wire down there that I should trace?

Please help - thanks in advance!