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Mercruiser 496 crank no start

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Old 06-01-2021, 10:58 AM
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I have not but when I get off of work I will try. Do you know what they are used for.
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Old 06-01-2021, 11:39 AM
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GRAb a free loaner fuel psi tester from Autozone on your way home too.
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Old 06-02-2021, 08:06 PM
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Ok so I tested the fuel pressure and it was 40 psi while cranking and I swapped the relays on the top of the engine and it still won't start. I call a local service center near me to get it scanned but the soonest they can get me in is in two months. Any other suggestions?
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Old 06-02-2021, 08:09 PM
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Rinda Technologies Inc. Marine and Industrial Engine Diagnostic Tools

good investment
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Old 06-02-2021, 08:33 PM
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Where are you located?
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Old 06-02-2021, 09:12 PM
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Albuquerque New Mexico
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Old 06-02-2021, 09:12 PM
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Originally Posted by Jasbro1968
No spark and when cranking tack is slightly lower than 1000 and ill have to get a fuel pressure gauge
Originally Posted by Jasbro1968
Ok so I tested the fuel pressure and it was 40 psi while cranking and I swapped the relays on the top of the engine and it still won't start. I call a local service center near me to get it scanned but the soonest they can get me in is in two months. Any other suggestions?
Okay, so this is where we stand. Fuel psi okay. Tach shows cranking dpeed (should actually be closer to 4-500 rpm) , therefore crank sensor should be okay.
No spark though. So, lets look into this. Sorry for basic question but have to ssk - how did you check ?
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Old 06-02-2021, 09:46 PM
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I used a inline tester that lights up when there is voltage
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Old 06-02-2021, 10:21 PM
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I don't know the ins and outs of the 496 ECM but I know there's a crankshaft sensor and a camshaft sensor. Wouldn't surprise me to find out crank sensor measures RPM and cam sensor controls ignition.

On a side note, there are a few different types of both sensors so make sure you get the one for your eng serial number if replacing.
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Old 06-02-2021, 11:35 PM
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Some good tests/look see’s/info:
https://forums.iboats.com/threads/me...diacom.570913/
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