Automotive Crank Position Sensor in 496 mag?

[Nick70]

I’m methodically trying to figure out why my engine has started running rough and down on power. 496 mag/375hp, 625hrs. I’ve replaced the plugs, wires, and now coils. After the coils I think it got a little better but still not 100% and still had recent rough start..I just swapped out the CPS today. Installed one for a 496 from Advanced Auto. I was hoping/expecting it to fire right up..of course not. Cranked, catch, backfired die..backfire was new. Starter would not turn it again as my battery charger wasn’t turned back on after being on hard recently. 12.2v though. I’d have expected it to still turn. I digress..anyone know if it’s OK/NOT OK to use the automotive Crank Sensor? This one was $80..the Mercury is over $300.

 

[paulswagelock]

It should have worked fine.
I bet you will find at least one very clogged injector causing your engine trouble, maybe 2 or 3. Common problem on an aging 496. Search my older posts and you will find details on how to swap them out.

 

[Spark600]

I agree with the fuel injector, On my 496 I had them check before they cleaned them. Had several 20% clogged and one 50 % clogged.
Ran great when it was back together.

 

[see ray]

Call mercruiser customer service. 1 920 929 5040 , those motors have been known to have fuel an injector cool fuel problems and they will work with you and replacements you would want to call them with your hull , and serial number for your motor so they could check to see if you were on the recall list for your 8.1 496 motor. Oh my 05 340 Sundancer, they replaced my plugs wires and fuel injectors and put new cool fuel modules. I’m had the same problem with the one motor and they did the replacement on both Coolfuel modules on both motors and injectors on both , . There is an open recall on those MOTORS it’s just a phone call, make it. Hope this helps keep us informed

 

[dvx216]

When you changed your plugs was there any sign on them or did they all look the same.

 

[Nick70]

When you changed your plugs was there any sign on them or did they all look the same.

They all looked kind of gunky..like there wasn’t sufficient burn

 

[Espos4]

You mentioned in another thread that you recently had the cool fuel module rebuilt.

Was it due to flaking paint or a pump failure?

Either of those could have sent debris down the line where they would clog the next “filter” that they come to, which is the screen inside each of the injectors.

 

[KevinC]

Last year a friend of mine was complaining about loss of power on his 320DA (twin v-drives) and was having a problem getting up on plane and maintaining it. After a lot of other work he eventually pulled his fuel rail had paint chips in the injectors and sent the injectors out for testing. Several injectors failed. After a rebuilding all of injectors he was back to normal power and performance.

-Kevin

 

[Nick70]

You mentioned in another thread that you recently had the cool fuel module rebuilt.

Was it due to flaking paint or a pump failure?

Either of those could have sent debris down the line where they would clog the next “filter” that they come to, which is the screen inside each of the injectors.

No, the reason I had it rebuilt was my own ham handedness. While doing the plugs/wires I moved the fuel line too much causing the line out of the module to leak.
I sent it out to get fixed and the tech informed me that the unit has already been updated.

 

[see ray]

When skipper buds replaced the cool fuel modules and the injectors/plugs ( due to paint peeling and bad injectors/recall) they also polished/cleaned the fuel tanks and flushed the lines this was last year

THE COOL FUEL/INJECTOR ISSUES WERE ON GENERATION 3 , II would just call Mercruiser with your engine serial numbers they will be able to look you up by the hull number , and they’ll tell you what’s cooking because there were some recalls and bulletins on some of the 8.1 motors from 03 and up so you can always check doesn’t hurt