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Old 04-04-2017, 12:55 PM
jsteele jsteele is offline
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Join Date: Apr 2017
Boat: 94 190 PS
Location: South
Posts: 2
94' 190 PS No Tach/RPM signal to ECM????

Please HELP!

I'll give you all the cliff notes version of the issue. Boat is in great shape, has approx 1200 hours, 350 TBI. Last summer the engine hydro locked and we believe it blew a head gasket. We took the exhaust manifolds and risers off and didn't see any evidence of leaking. We decided to replace the starboard side head gasket as we saw rust and water in the front starboard cylinder. The boat would run prior to taking the head off. We cleaned up the block deck and head and installed new gasket, put everything back together and the boat wouldn't crank. We weren't getting any pulse from the injectors. Verified gas at carburetor and verified spark. Decided to send ECM off to www.obd2allinone.com. They verified that the ECM was good and had no issues. They also did some updates on the ECM.

Took the boat to our mechanic in Colorado and he installed the ECM and still had no injector pulse. Our mechanic said there is no tach/RPM signal coming from the engine into the ECM and he also replaced every sensor on the boat along with a known/running distributor off another 350 TBI. Our mechanic even installed another ECM off a running boat into ours and still nothing. He said he could pour gas down the carb and get it to run but no injector pulse.

Mechanic said he's getting RPM reading on analog gauge on dash.

Very strange and we can't figure it out? Any help would be appreciated.

Jarrus Steele
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Old 04-05-2017, 06:00 PM
jsteele jsteele is offline
TT Newbie
Join Date: Apr 2017
Boat: 94 190 PS
Location: South
Posts: 2
Anyone have any input or suggestions?
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Old 04-05-2017, 08:53 PM
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AUProStar AUProStar is offline
TT Regular
Join Date: Aug 2016
Boat: 1995 Pro Star 350
Location: Southeast
Posts: 46
Sounds like a wiring issue to me. ECM needs input signal from pickup coil and then sends output signal. I would focus on wiring integrity/signals power and ground. Google How To Test General Motors distributor mounted ignition control module. Good series by easy auto diagnostics. com. Make sure your distributor reference high signal is making it to the ECM

Start with the basics and see what you are missing. If it will run on carb cleaner focus on fuel delivery

Also go to scannerdanner.com or you tube and search for a video entitled How to test an ignition coil/module with a test light

All of this is not feasible to explain in a forum. Spend some time on references about and start troubleshooting. Don't throw parts at it as you can build in a problem. New parts can also be bad, terminals spread out when testing etc etc
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