Weird gt40 miss/stumbling - please help!

MrMcD wrote: I had a BMW once that had water in the gas tank We finally cleaned it out using alcohol.   I don't remember what kind we used but I was told the alcohol would disperse the water off the bottom of the tank and help it burn as it traveled through your fuel system..

Mark,
Heet in California?

Ran the boat for 40 minutes today. on 4 or 5 occasions during this time I had an engine stumble while on plane and the engine either died or almost died. I went to neutral, the rpm either stabilized or I restarted the engine. I was thinking in my head that my fuel pumps were probably going bad so I headed back to the dock. On a whim I went to town and picked up some contact cleaner, and the returned and disconnected the battery and ecm in order to clean the contacts. I Sprayed contact cleaner on the ecm pins and the harness connector, let them dry and then assembled. I also unbolted the ground connections from the bell housing and doused them in contact cleaner, and re-assembled. After that we ran the boat for about 1.2 hours. Right away the boat stumbled once and caught itself at 1krpm but after that it didn’t miss a beat, I’m back on to thinking the stumble/die issue has been due to a bout of bad gas or water in The gas that worked its way through the system.

I’ve been having similar low power/ stalling issues on a jet ski that I have which I filled up with a Jerry can that was in my garage for 2 weeks during the hot and humid part of summer. I think I put 12 gallons of this same gas in my boat at the time as well.

Hopefully tomorrow is another good day.

Kyle

What tune is the new ECM ? 290 or 300? Just curious

Kyle, I am curious if you made sure the multipin connector is in good shape. I think you saw a lot of corrosion in there. What’s your confidence that connector is doing it’s job?

The SS sure is going to be good for the long haul once you get this settled. I spent a lot of time chasing my ignition switch a few years back. It almost made no sense to replace it, but when I decided to do so, the issues went away.

kylem428 wrote: Hey Ken, it is the black module CBE40 and crosses to the Napa TP29 module and the oem ford part number. Kyle

That's a number and color I came up with too.

Just a thought or maybe a question

You mentioned that you replaced the TFI module

What is the part number of the replacement and what color is the casing gray or black?

Good to know Mark.

My suspicion was confirmed this afternoon. Coming back from work I ran the boat for another 15 minutes on the boat lift without issue then randomly the erratic behavior came back. The engine quit, I removed the sprout plug and the boat ran fine. I believe the ECM is definitely sending a strange signal to the TFI causing the boat to run poorly. I’ve been studying the GT 40 manual, and I can’t think of a different explanation. That being said, I also bought a code reader off of Amazon so we will see if the ecm has thrown any codes once I receive it sometime today or tomorrow.

Kyle

Yeh Gary I noticed that too while looking. I’ll have to look at the PN thread but if I recall the D1L1 ecm May also be a usable replacement. I’ll have to double check on that.

Thanks,

Kyle

So I got the boat to run today and had it running for about a half hour on my lift after replacing the distributor with a spectra fd14 from O’Reillys. The interesting thing is that I still expect that maybe I have a bad ecm. I set the initial timing of the new distributor by unplugging the sprout connector and timing it to 5 btdc. As soon as I did this, I turned off the engine, plugged in the sprout, and it would crank, fire once and die. I then disconnected the sprout, and ran the boat. It ran fine. As it was running, I reconnected the sprout and it would immediately die. Disconnect sprout, and it would run fine timed at 5btdc. After this, I disconnected the battery on a whim while I took a phone call. After my 30 min call, I reconnected the battery and started the boat without the sprout connector. After running for 5 minutes or so I reconnected the sprout connector and it stayed running! Not sure if the computer was reset by the disconnect and had to “re learn” something By running the boat without the sprout for a short period, or if this is a fluke thing that it is now only working for a little while, with my fear being that it will go back to doing as it had. Good to know that at least for now I can disconnect the sprout if it starts running poorly in order to limp my way home at 1000 rpm or less. The downside is I have no way of testing the sprout circuit of the ecm when engine is running poorly without a breakout box. I can only check continuity with ground for a short.

Think I need to find an ecm??

Kyle

I have not taken one apart yet but in reading it looks like you do have to pull it to change that. Seems crazy. I did find this though- sensor troubles   Kind of sounds like your trouble with the erratic tach and all, interesting reading anyway

Here are some Ford part numbers which might be some help,you can click on the image to make it larger

Kyle, a new distributor is pretty cheap, and it sounds like there’s something going on there, and if it were me, I’d do it just to get my boat back up and running. I don’t think you have to worry about timing if you get it close enough (mark position of old distributor and especially rotor). ECM controls timing on the GT40. Others may argue against swapping parts for good reason, but that’s what I would do.

I hate it when Carnac gets it wrong

Have you checked the ground connection from the ECM to be clean and tight?

Also maybe unplug and check the cleanliness of the connections in the big connector to the ECM.

I figure they're both easy and cost nothing.