5.7 GXI tbi - No beep and no start

[tmkilburn]

Ran fine last weekend. Now it cranks but won’t start. The engine typically deliver 2 loud beeps when turning to the on position, it no longer does that. I also do not hear the fuel pump prime. 50 amp breaker is good and I have continuity across it. Kill switch is good at the helm, have continuity across it as well. Pulled the plugs and harnesses at the back of the engine to check for corrosion, seeing no problems. Ground block at the back appears good. Loosened and tightened the grounds back down. Any help is appreciated.

 

[alldodge]

Check for 12V across the kill switch when the key is ON
Check your fuses on the motor
You have 3 relays, start, fuel pump and main power. Swap the fuel pump relay with the main power

 

[tmkilburn]

Thanks for the reply. Checked the fuses behind the 50 amp breaker. There was a 12.5, a 20, and a 40 amp fuse. The 40 was actually blown which I believe is for the trim relay? No change after replacement. I swapped the relays in front of the throttle body, no change. I didn’t check for 12v across the kill switch but I can feel on of those relays click when the switch is moved back and forth...

 

[tmkilburn]

Additionally I pulled the ecu harnesses and found the pin for the fuel pump. When I ground out that pin the fuel pump runs.... I’m thinking possible ECU problems. I also tested the pin for 12v on the pin labeled “ECM bat pos” and have 12v there.

 

[alldodge]

Looks like your in the right area in trouble shooting. Number 6 in pic is the 40 amp which shows two 20 amp and is for instrument harness. For it to blow (red/purple) that one look behind the helm. Did it blow again when replaced?

 

[tmkilburn]

Fuse hasn’t blown after replacement. I’m going to go hook my meter up to the test port and get the error codes written down.

 

[tmkilburn]

Tested 12v good across the kill switch. I tried doing a diagnostic scan using a paper clip and my test meter. The test was supposed to give me continuity tones through my test meter in the form of beeps corresponding to error codes but instead I only got one continuous beep.....

 

[alldodge]

Not sounding good Does your beeper on the boat still work? If so, may be time to send it off to get tested. Be nice if there was someone with similar boat you could install your ECM on their motor

 

[tmkilburn]

Found a guy that test, repairs, and sells replacement ecms. Going to ship it to him and hope for the best. If it needs a replacement it will be $1800...

 

[Lubak572]

Mefi Bob in California

 

[alldodge]

Agree Bob is a good source

If you do need another, look around or ask at places like Offshore Only. They have a wanted section and stuff comes in all the time. I bought a spare mife3 last year for 350 I think, just in case mine ever has an issue.

 

[QBhoy]

Hi.
Triple check the lanyard kill switch. It’s doing exactly what it would do if it was pulled. Defo making a contact across the switch ? Not just testing 12v on one side of it ? Try linking it out with a wire to make sure. Test for continuity through the length of the wire maybe. All the best.

 

[tmkilburn]

I tested continuity across the switch. Was good. I also held my screwdriver across the leads on the back and no change. I could also hear one of the relays clicking in the engine compartment when I would connect and undo the harness under the dash.

 

[tmkilburn]

Update:

Got a call from Ken over at ODB Diagnostics. They connected the ECM up and are showing that is is completely fried/dead. It is beyond repair so I am in the market for a replacement MEFI 3....

 

[alldodge]

Bummer, go ask for one on OSO wanted section. There is a guy over there yesterday wanting a 3 and had several come up with one

Edit: Oh that's you over their already, should have noticed the name, just not paying enough attention.

 

[tmkilburn]

That’s me! I’ve got a few leads and an also scouring eBay.

 

[QBhoy]

Excellent stuff. Glad you found a lead on the issue. Probably know already but make sure you get the righ part. It’s probably not a tbi engine you have, if it’s a gxi. Just checking. Haha.

 

[tmkilburn]

Excellent stuff. Glad you found a lead on the issue. Probably know already but make sure you get the righ part. It’s probably not a tbi engine you have, if it’s a gxi. Just checking. Haha.

Yes. Relieving to have it figured out. I hate chasing electrical gremlins. My GXI is definitely a throttle body. Just like my old 93 GMC 1500 pickup. Full model is 5.7 GXI-A

 

[QBhoy]

Yes. Relieving to have it figured out. I hate chasing electrical gremlins. My GXI is definitely a throttle body. Just like my old 93 GMC 1500 pickup. Full model is 5.7 GXI-A

Ah. That’s weird. The GXi and MPI VP and Merc versions are almost certainly all common rail direct injection. As in the have a fuel rail and 8 injectors. Tbi usually means the injection is at the intake throttle body. That’s what the gsi and gli have I’m sure.

 

[tmkilburn]

Ah. That’s weird. The GXi and MPI VP and Merc versions are almost certainly all common rail direct injection. As in the have a fuel rail and 8 injectors. Tbi usually means the injection is at the intake throttle body. That’s what the gsi and gli have I’m sure.

I don’t know the differences between years and models but if you look up the intake for a GXI-A it’s a throttle body but a GXI-F, for example,is port injection. Looks like at some point in time there was a transition between tbi and port injection during the life of the GXI series engines.