Lessons learned on the EFI GT-40

[jjgag60]

Lesson learned on the EFI Gt-40. I just bought a boat this spring with a freeze damaged block. The new motor turned had to be .40 over and according to all the experts, the EEC will not handle .40 over. When I got the new motor installed it wouldn’t idle. It hunted back and forth and then stalled and flooded the engine. The boat ran so rich, it “fuel washed” the cylinders and took out one of my rod bearing after 25 hours. The motor had to be rebuilt again. This time I did some research and learned all about our EEC –iv computers. One of the best books on the subject is “Ford Fuel Injection by Charles Probst. He goes into a lot of detail about our sensors. You will need the downloaded PCM manual to locate which sensors we have. Between the two publications you will learn a lot about our systems. If you can’t afford a STAR Tester (I found one on Ebay) Charles tells you how to use a volt meter and count the needle swings to check your EEC out. No one would look at the computer off the boat because it was a marine product. I replaced my ECT and ACT sensors after I found out the ECT is a very important sensor, it is third in command, and for around $20.00 each at NAPA there were cheap. After the motor was rebuilt, and the new sensors were installed, it runs great. It idles at the right RPM now and my spark plugs are starting to turn paper bag brown and not black. Some basic checks I have learned to find out the status of your engine are the following:

1. Check the spark plugs. They should be “paper bag brown, not white (lean) or black (rich). Both cause early engine failure.

2. The next time you change the oil cut open the oil filter. Pull the filter product out and look inside the paper folds. If you see bronze or copper colored flecks you have problems with your bearing going out.

3. For $18.00 you can have your oil examined and they will tell you if there is any water, gas, or metals in your oil. A very good indicator on how your engine is doing.

4. Purchase a Star Tester or use the volt meter to check out your EEC-IV, our computers are very good at storing codes and doing checks on the sensor with the Key off or Key on Running. It is amazing what you can check and trouble shoot.

[TravisFling]

RE: Lessons learned on the EFI GT-40

Great information. Thanks! Glad you're up and running.

[jeclarke]

jjgag60,

Thanks for the recommended book on EEC IV. I think I'll put it on my Christmas list.

You mentionded that .040" overbore was a problem and that the engine had to be rebuilt again. What was different about the 2nd rebuild? Or was it a case of because of the larger cylinders, some adjustments needed to be made to the computer settings to handle it.

John Clarke

[jjgag60]

Lesson learned

When I rebuilt my motor, we had to go 40 over on the pistons. When we started it and could not get it to idle, I contacted PCM and asked for assistance. They said they had not had any luck with any Gt-40 being bored more than 20 over. They couldn’t help me. The bad idle was caused by a bad sensor and subsequently I spun a rod bearing because the motor ran to rich and caused a fuel wash in the cylinders. The motor was rebuilt again and this time I replaced the ACT and ECT sensors, and that helped the motor idle and not run so rich. If I was to do it all over again, I think I would have bought the Chevy replacement engine for the GT-40 from SKIDIM and bolted it in. I would have been cheaper in the long run.

[peteSki]

I've got a 97 SN with GT-40 and I want to get one of these star testers. There is one on eBay right now, but the model is 007-0004, but in the service manual the recommended model is 007-0041-B. They look similar, even the connector. Am hoping someone can help out and tell me if this is the correct one, as I can't seem to find too much info on the web regarding these testers from Rotunda.

Have read up on how to get codes using an analogue multimeter... has anyone done this? Is it easy to read the codes or is it worth spending $200 on a star tester?

Pic below of the one from eBay.

Thanks in advance.

Pete

[2gofaster]

I've been working on and building EEC EFI equipped ford engines for 20 years and the EEC definitely has no issues running engines with small overbores like that. Glad you got it figured out.

[AirTool]

Can anyone explain why INCREASING the displacement/cfm of the engine causes it to run RICH?

Doesn't intuitively make sense to me.

[bobchris]

you hve a larger cyl bore so you'll have a larger volume of fuel/air mixture entering the combustion chamber, with an O2 sensor like cars have the EEC can change the pulse width of the injector to compensate but the marine version doesn't have that option so it runs rich.

[AirTool]

you hve a larger cyl bore so you'll have a larger volume of fuel/air mixture entering the combustion chamber, with an O2 sensor like cars have the EEC can change the pulse width of the injector to compensate but the marine version doesn't have that option so it runs rich.

You make no sense nor answer the question.

[2gofaster]

you hve a larger cyl bore so you'll have a larger volume of fuel/air mixture entering the combustion chamber, with an O2 sensor like cars have the EEC can change the pulse width of the injector to compensate but the marine version doesn't have that option so it runs rich.

Care to think about that a bit? lol More air volume without increased volume of fuel results in a lean condition.

That said, the air delta between a 4" bore and a 4.04" bore is well within the EEC's ability to run as that results in only about 1/10 of 1 air fuel ratio point difference in practice.

[tadelfio]

huh?? lol

[compskier]

Lesson learned

When I rebuilt my motor, we had to go 40 over on the pistons. When we started it and could not get it to idle, I contacted PCM and asked for assistance. They said they had not had any luck with any Gt-40 being bored more than 20 over. They couldn’t help me. The bad idle was caused by a bad sensor and subsequently I spun a rod bearing because the motor ran to rich and caused a fuel wash in the cylinders. The motor was rebuilt again and this time I replaced the ACT and ECT sensors, and that helped the motor idle and not run so rich. If I was to do it all over again, I think I would have bought the Chevy replacement engine for the GT-40 from SKIDIM and bolted it in. I would have been cheaper in the long run.

I know you posted this quite a while ago, but I'm exploring options to put a long block in my 2002 Ski Nautique GT40 engine. So if I understand correctly, replacing the ACT and ECT sensors corrected the 40 over bore on your GT40. Did you just replace with new sensors the same as what came with the engine or did you get different sensors that accommodated the 40 over?

[Fgroce]

He had a bad engine coolant temperature sensor, the engine was running with the choke on all the time and diluted his oil. This caused his spun bearing. There is no problem with boring a 351 .040 over it will be just fine. I replace all sensors with Ford OEM if possible.

[wakejunky]

What are the ACT and ECT sensors? What do they do that is so critical to having a smooth running motor?

[Blamey]

Air change temperature sensor and eninge coolant temprature sensor.

The EEC monitors these sensors to determine the air/fuel mix of the engine and to get optimal perfromance.

My guess is if the sensor was bad the engine would read as cold and the EEC would keep the engine choked like you would with an older Card engine when starting it cold.