Hard cold start.

[Lester]

Hey yall, im getting ready to put my 96 malibu sunsetter back together, but before i do theres a kink i want to work out with the motor. Every cold start is hard, it will start and die repeatedly unless i give it throttle, i theottle up to about 1k until it warms up and then it idles fine. If i blip the throttle it does seem like its going to die but comes right back. Once warm shes good to go. Ive replaced entire fuel system cap and rotor theres good fuel. Tps and iac are new. Has anyone run into this issue? I want to get the motor 100% before putting her back together. Also the boat idles at about 600rpm. I feel thats normal but also not sure. Motor is the black scorpion. Thanks!

Edited December 19, 2021 by Lester
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[csleaver]

If the engine coolant temperature (ECT) sensor is not sending the correct reading to the ECM it can cause either hard cold starting or hard warm starting.  Incorrect fuel pressure can also cause hard starting.

There are many other things that can cause hard starting issues, but I would check those first.

[electricjohn]

ECT sensor should read around 500 ohms cold and 5000 ohms warm, or visa versa. Don't remember which way. The only other sensor the ECM looks at during cranking is the MAP for baro.

Edited December 20, 2021 by electricjohn

[csleaver]

The easiest way to see the ECT value is with Diacom, but here is a resistance chart to check it with an ohm meter.

https://www.dropbox.com/s/5etljmegm8uw6ul/Coolant Sensor Resistance Values.pdf?dl=0

[csleaver]

The Mercruiser Black Scorpion fuel pressure specification is 30 PSI @ 850 RPM.  Because the fuel pressure regulator is vacuum biased, the vacuum hose should be removed from the fuel pump pressure regulator during the test.

The Mercruiser 350 Mag and 5.7 Tournament Ski fuel pressure specification is 43 PSI.

[electricjohn]

6 hours ago, electricjohn said:

ECT sensor should read around 500 ohms cold and 5000 ohms warm, or visa versa. Don't remember which way. The only other sensor the ECM looks at during cranking is the MAP for baro.

So it's visa versa. Thanks csleaver.

Edited December 20, 2021 by electricjohn

[Yorkgr75]

On 12/19/2021 at 3:30 PM, Lester said:

Hey yall, im getting ready to put my 96 malibu sunsetter back together, but before i do theres a kink i want to work out with the motor. Every cold start is hard, it will start and die repeatedly unless i give it throttle, i theottle up to about 1k until it warms up and then it idles fine. If i blip the throttle it does seem like it’s going to die but comes right back. Once warm shes good to go. Ive replaced entire fuel system cap and rotor theres good fuel. Tps and iac are new. Has anyone run into this issue? I want to get the motor 100% before putting her back together. Also the boat idles at about 600rpm. I feel thats normal but also not sure. Motor is the black scorpion. Thanks!

I know this is an old post but curious if you solved the problem and what the issue was?  I have the exact problem with my Black Scorpion.  Doesn’t like starting cold but once going, she’s solid.   I also throttle to about 1000 RPM’s to warm up the motor.  Typically idols around 600.  New fuel pump, plugs, cap, fuel filter, regular service, etc… can’t figure it out.  Thanks!