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1998 Mercruiser 57 EFI ECM

mixed_up

New member
"Boat was running fine at crui

"Boat was running fine at cruising speed, 3200-3400 RPM and died suddenly. There was a single loud snapping noise that came from the engine compartment, could have been a backfire, but not sure. Since, the motor cranks over fine, but will not start.

- The tachometer is stuck @3000rpm
- The alarm buzzer has quit working, looks like it ties into the tachometer wiring
- The fuel pump is not coming on when the key is turned on
- Checked the fuses and all are fine
- checked the main breaker and it is fine
- checked the main wiring harness connection and it is fine
- checked the relay's and verified they function and all are good
- Grounds are all connected, tight, and clean
- verified power to the main circuit breaker and across it
- checked all the wiring to the fuel pump back to the ECM

Conclusions
it appears there is no signal from the ECM to the pump. Suspect no spark, but haven't verified with 100% certainty.

Please help...."
 
You may have broken your distr

You may have broken your distributor shaft or drive gear. Pull the distributor cap and spin it over to see if the rotor moves.

Dave
 
"Checked Distributor, moves fi

"Checked Distributor, moves fine, and all seems to be good, still need to put a plug in and check to see spark for sure or not"
 
start with the basics. Does it

start with the basics. Does it have spark as checked at the plugs and then coil...?

fuel pump won't energize unless the ecm sees oil pressure (i think)
 
"MistaHays
I stand to be corr


"MistaHays
I stand to be corrected here, but from memory a timer circute within the ECM activates when you first turn on the key for a couple of seconds to pressurise the fuel system then shuts it down until the fuel pump control circute in the ECM recieves feedback from the oil pressure sensor.
As I say though, I stand to be corrected.
Cheers
Peter C"
 
"Carbed engines use the oil pr

"Carbed engines use the oil pressure sensor, EFI engines look for a distributor reference pulse to turn the fuel pump back on after the initial key up. That's why I though distributor shaft or drive gear.

The tach being stuck at 3000 indicates it not receiving the reference signal. I would check the pick up coil and ignition module next.

Dave"
 
"The pick up coil is good, but

"The pick up coil is good, but am unsure of the ignition module. I am figuring that the computer isn't a likely thing to go bad, but you never know for sure. Is there a way to test the ignition module?"
 
"Replaced ignition module, but

"Replaced ignition module, but the problem is not solved, still same symptoms... All gauges have no power or do not work, No power signal is being sent to the electric fuel pump, and no spark. I traced out the wiring harness and verified power to the computer and across all fuses and relays... Thinking it has go to be the ECM, but would like to make sure before buying something that expensive"
 
"find your tach wire, it will

"find your tach wire, it will be grey on the coil
remove that and see if you get sparky
you have a T-bolt 5 ignition, if your take takes a dump it will ground out all the motor controls
clean your connections on the coil also
check the wires for corrosion by bending them, if it feels crunchy replace the wires

stop throwing your money into parts

do you have a factory manual, if not shoot me an e-mail, i have one for u"
 
"Did some more homework last n

"Did some more homework last night, checked out the wiring to the coil, all looks good, none of the wires are grounded or corroded and have continuity to the computer and to the ignition module and to the wiring harness. Also, checked out the fuel system loop and have continuity to and from the computer with no grounds. All ground cables and wires are all tight and in good condition with a good connection... just seems like too many things are in good condition and yet to many things are not working, and the only thing that ties it all together besides power and ground is the ECM, just hoping someone has had this problem before as well

Thanks for all the ideas so far I am going to make sure to post the solution, cause there will be somone else who runs into this!!"
 
Have you tried checking for Tr

Have you tried checking for Trouble Codes? This would tell you if the self diagnostic system is working and what (if any) codes are present and help determine if the ECM is bad.

Dave
 
Fixed the problem... someone p

Fixed the problem... someone prior to my ownership eliminated the emergency kill switch and did not do a good job of it. I was able to determine that the key switch did not have any connection to the ignition system and with a small jumper the problem was solved!! What a pain... Thank you for all your help!
 
Brandon:

Good work; thanks


Brandon:

Good work; thanks for giving us the solution! Don't you just love finding a problem like yours created by some gomer w/o any wiring knowledge who decided to alter the original wiring?
 
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