GT40 engine loping

slmskrs wrote: Just a quick thought. If the idle speed solenoid is failing to open upon hot start and therefore little air is getting mixed with the fuel, if you cracked the throttle slightly to let air in, then it should start rather than just dumping fuel into the cylinders with no start (it would just immediately start racing). Just wanted to check to see that it is not starting when you crack the throttle (at the start, not when it is already "flooded"). If it start when the throttle is cracked open, then it is the solenoid (or something in the line (low voltage, etc.)). If it doesn't start if you crack the throttle at the beginning, then I don't think it is the idle valve solenoid. Just a thought....

Yep that would be a valid test. I will try that next time it happens as a fault finding option.

Chris that is the one of the benefits with fuel injection perfect idle hot or cold. Normally best if you leave the throttle alone and let the computer do all the adjusting of mixture and timing. Until something goes wrong.

I have a pretty good ignition system, I think that maybe the needle doesn't seat right & lets extra gas flow into the bowl.

I wonder if the FI loping could be a leaky injector?

I don't understand what you mean by loping???
Is it idling high than low/up and down like surging.

gun-driver wrote: I don't understand what you mean by loping??? Is it idling high than low/up and down like surging.

Surging. Up and down, up and down, about a about a 3 second cycle. It will get worse and worse, and half the time it will finally drop low enough that it stalls. The manual apparently refers to it as a rolling idle.

We've had rain the past two weekends and it's supposed to rain on Saturday. I need a few warm days to have the correct environment for the engine to lope when hot. I have my fuel pressure gauge and a vacuum gauge already connected so I can see what they are doing when it happens. I'll post again when I have some results or move further along in the diagnostics.

Guys went out the weekend and after 2hrs of hard running turned the boat off and sure enough no restart. Tried to restart with some throttle and then removed ISC assy. Still no start the only way to get a restart was max throttle it would restart and run rough until it cleared. I have now ruled out the ISC-BPA. With max throttle the throttle position sensor would probably have been signalling the computer to apply max duty cycle to the injectors making it harder to clear the rich condition.

Plugged the code reader in and found a continuous stored code 15 (Power interruption to EEC computer). Removed 60 pin plug from computer and found some oxidised pins. Cleaned them roughly but a proper clean would need to wait till boat was back on dry land with correct cleaning agents. It restarted but it had probably a 30-45 mins to cool down with the engine cover raised.

It is looking like a heat soak problem with a bad high resistance connection some where. Although this is the first time it has had a stored error code. Maybe the problem is getting worse though.

After some research and investigating found that the EEC has it's own power wire run directly from the battery. It has a 50 amp inline fuse also in the battery enclosure. Always wondered where that extra power wire from the battery terminal went. This power wire runs back to the 12.5 amp cct breaker on the EEC computer bracket then to the EEC relay also mounted on the EEC bracket. The RHS relay when viewing from the rear is the EEC power relay the LHS relay is the fuel pump relay. The EEC power relay supplies power to pins 37 and 57 of the EEC connector. Interestingly it also supplies power to the fuel pump relay activation circuit. The EEC then supplies the ground to complete this circuit and start the fuel pumps. The 15 amp cct breaker on the EEC bracket is the power source for the fuel pumps.

I cleaned up all the contacts but did not find any real bad connections that may have been causing the problem. The 60 pin connector had a couple of pins with white deposits but nothing really substantial. I had a spare relay so I have replaced the EEC relay with it as the HR joint may have been inside the relay. Will see how this goes on next trip out. Will take my voltmeter along with the code reader.

I'd love to see a picture of the wiring, Joel. Mine still has the fuse. My understanding is that you do a couple of jumpers on the breaker panels. Do you lose the wire to the battery altogether?

I haven't had problems with the fuse. But by removing it, I would never have problems with it.

Here you go. You can see the wire tied to the fused side of the 60A breaker (with yellow eyelet crimped on). Now, in my boat's case since I have the electronic dash this wire goes forward to the On/Off/Bilge toggle switch that the electronic dash boats have.

Joel where is the on/off/bilge toogle switch located in the engine bay or up at the dash?

If I was to rewire mine I would run a 6-8 gauge wire from the main battery cable terminal on the power assist relay to the 12.5 amp breaker. This small run of wire less than 1 foot would replace the current wire from the battery box to the 12.5 amp breaker.

My understanding of it is that the wire from the battery is eliminated entirely (not just replacing the wire with a fuse with another wire without one).

You didn't. But I saw a reference to replacing the current wire with an unfused wire above and figured I'd chime in.

This is the Code Reader Gordon the book that comes with the code reader has a lot better run down of the fault codes than the GT40 manual in reference section.

Joel my wiring looks factory all the liquid insulation is still on all the breakers. Would be nice to see the PCM Bulletin that was issued it would clear up what was done.
There must be more to it than just that wire. Seems weird to run that wire back to the dash when the wire on that breaker already goes there via the 10 way harness connector. The wire from the inline fuse probably appears at the dash harness connector and they have done something under the dash with this circuit. I am leaving my inline fuse EEC wire standard at the moment to see if the fault has been rectified.

It plugs straight in the the EEC tester connector above the relays.

Update had the boat out for four days over the Easter break. Put almost 20 hrs on the meter without the problem reoccurring. Looks like it was the EEC relay.