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MPI 350 (1998) ECM no power

Your IAT sensor is a two-wire type.

IAT of 0 deg F when it is 80 deg F will cause a rich condition which should be easy to smell.

How do you think the IAC is suppose to respond to a meter? Unlikely the IAC will keep the engine from starting.

If you would follow a standard troubleshooting procedure instead of shooting from the hip, you would probably be reinstalling the engine now...
 
Docksidemarineservices said:
Besides all of the above. Shoot some starting fluid into the intake and crank her over. If she fires for a few seconds or even back fires, or does nothing you will know what direction to look.
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100% agreed, You need to see if it's going to fire at all. If not it may be the injectors not working correctly or internal engine problems.

stringer_bell said:
Checked with tech mate and was getting 0 F as manifold air temp, is that the 4-wire sender right next to the TPS on the throttle body?

My engine is MEFI-2
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This engine model does not utilize the manifold air temp sensor, if it did, it would be mounted on the flame arrestor or in later years incorporated into the MAP sensor, and you would be getting a diagnostic code.

The 4 wire is the IAC valve. (Idle Air Control)

The IAC wiring can be tested with a test light hooked to ground. The test light should blink on wire at a time.

Opening the throttle helps bypass the IAC.

Makomark is correct, you would be better off using the troubleshooting procedures in the service manual #24,
http://www.maxumownersclub.com/forum/site_files/manuals/mercruiser/24.pdf
 
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Thanks guys for help and patience.

I followed the troubleshooting procedure and everything checkled out.
I get coil to fire #1 few degrees before TDC, all injectors ohm out, all harnesses in ECM check out.
all sensors ohm out as per procedure.

Techmate reports no codes

engine will not fire even with ether sprayed in the TB?
 
Fire " at the correct moment ".

Compression.

Fuel .

You firing at the " correct moment " ?

Dead mans switch is the only thing comes to mind at this " moment ".
 
It fired up when I gave it 12v directly to the fuel pump! I think it might be fuel pressure related, or FPR is bad?

it ran without ECM connected I think it was the leftover fuel in the cylinders?? I forgot to plug in ECM after testing pins....
 
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While I was testing OBD and then following the flow chart to a-3

83D8087D-1108-4D7D-9D8F-B30D99B7E0AC-6052-000003B6489DBCC4_zpsc2d0031b.jpg


i unplugged the connector from ECM to ring out some terminals and forgot to plug it back in

then I wanted to try powering the fuel pump directly off 12v relay to eliminate pump not getting power while cranking and engine fired up and ran for 10 seconds then I shut it off. I think it only ran because of the fuel that was already in the cylinders? ECM was unplugged, so I don't know how it would have fired the injectors like that?

I am going to try and use my ECM on friends engine and see if it starts, if not are there any ECM diagnostic/repair choices?
 
Ohm test the fuel injector fuse and related circuits, Also check them for 12v power as well.

Try this,The test light should blink while hooked to CKT 467 & 468.

DISCONNECT ALL INJECTORS.​
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•​
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CONNECT TEST LIGHT J-34730-2 OR EQUIVALENT TO INJECTOR HARNESS CONNECTOR. (TEST ONE INJECTOR HARNESS FROM EACH GROUPING OF INJECTORS.) CHECK FOR BLINKING LIGHT WHILE CRANKING.
​
 
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Had some surgery and was out for a week. Back at it again

following test procedure to see if ecm gets power

j1 connector pins 11-16-32 all have power with key on (test light to ground)

manual says if that's the case, check grounds to ECM

ground wires j1 14-30 both are grounded with key on (test light to power)

manual says bad ecm

Makes sense?

What are my options to fix this ecm? 16210729 mefi2 861265r6
 
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Slim to none...you can carefully check where the harnesses connect for corrosion, cracks etc. Take a good look at the harness pins for the slightest corrosion. Clean the circuit board connectors w/an ink eraser...it will polish the contacts and try it again. Check w/a a marine salvage yard for a used one.
 
Update/solution: I got it started!

It turns out ECM is fine. Most things pointed to ignition issue. I ohmed out resistance in the ignition coil, and it was out of spec. I replaced it with new. Also replaced spark plug wires, ignition module in the distributor, and distributor gear. Cap was new already. Installed AC MR43LTS plugs, gapped to .45"

Starts right up, and runs good

I have slight intermittent miss somewhere, its not related to one specific cylinder (does not seem), but its noticeable at idle, and throughout RPMs. It is random, not rhythmic? I am trying to upload video of the motor running so you guys can get an idea.

Thanks for all the help and suggestions!!!!!!
 
Docksidemarineservices said:
555 on a mercruiser is a four pin flat connector. If you have depth finder through a smart craft gauge it may be plugged into this connector. Unplug it and hook up your scan tool.
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I don’t have a depth sounder on it I have found the plug by the oil filter it just doesn’t want to connect mercruiser scanner loads select inboard gets to determine ecm type and says error
 
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