Back fire on start stock 496HO
01-25-2019, 08:34 AM
#31
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Wait till you try an aftermarket ignition module (on a engine that calls for one not a 496) you’ll be pulling your hair trying to figure out all the bonus drivability issues you will have, but hey you save a couple bucks LOL
Last edited by boatnt; 01-25-2019 at 09:26 AM.
01-25-2019, 09:55 AM
#32
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Thread Starter
So, if my problem persists, bouncing TAC, engine stall, no high power performance at all with my latest automotive IAC, it’s probably the IAC and time for a Merc IAC?????
01-25-2019, 02:50 PM
#33
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Don't see an IAC causing a bouncing tach or no high performance. Bouncing tach, maybe loose connection and/or misfire, and performance would be misfire, loose connection, fuel, bunch of other things
Stalling, maybe IAC but could be other things and may still be loose connection
Stalling, maybe IAC but could be other things and may still be loose connection
01-25-2019, 05:31 PM
#34
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I am not talking about the IAC, The IAC is a 2 wire(PWM) pulse width modulated valve ,They might look the same but yes the resistance values are different,
I was just answering his question of a replacement Crank sensor,Those as you know work differently what matters is the air gap between the reluctor and the sensor, the reluctor is the same in the Marine and auto applications because it’s the same crankshaft the sensor is a three wire sensor ,a sensor signal, a 12 V and a low reference wire, so as long as the gap between the reluctor and the sensor are the same it’s the same sensor and yes GMs Crank sensors are also a NON ribbed single O ring design to help eliminate them from sticking in the block.
And not really interested in taking a bet if you were referring to me, just trying to help out
Also for the OP I was pretty sure has a auto store bought aftermarket IAC because all the forums recommend the $ 60 to $ 70 dollar aftermarket IAC. Not the way to go. And my point is alot of times the aftermarket IACs do not work how they should for the MERC set up.
The same goes for aftermarket fuel injectors they never flow like the OEMs and ignition parts are the worst from the cheap aftermarketers.
Last edited by BUP; 01-25-2019 at 06:24 PM.
01-25-2019, 05:49 PM
#36
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Its not a big deal paying an extra 30 bucks per what I have and install compared to the aftermarkets. I always op for an exact replacement regardless of the 30 to 40 bucks more without the headaches is priceless and less down time. Also the advice about the IAC what should be installed is priceless. Also there is alot more to just changing out the IAC for all that to work correctly...
Last edited by BUP; 01-25-2019 at 09:41 PM.
01-26-2019, 09:14 AM
#37
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Thread Starter
BUP, list the web site again, the previous one not working. Plus could the IAC cause a cam and crank code thrown. Both are inactive when scanned. Should I swap PMC and see what happens. I have to include the fact that the boat was exposed to Irma, uncovered and bilge pump tried to keep up. Not sure how much water got into engine compartment...
01-26-2019, 11:41 AM
#38
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I am sure Bup will reply ,but the answer to your question is NO!,
a couple of mechanical issues that can cause it would be ,missfire,streched timing chain,(cam and crank sensors not correlating) a crank reluctor that has moved,etc but these issues would be there most/all the time,
as for a intermitten issue I would inspect the connectors for a tight fit, drag test the terminals and if loose replace,I would inspected at sensors as well as the ecu,apply a little dialectic grease on the terminals,NOT a lot!some people thing the more the better but that causes the female terminal to expand,
do a voltage drop test and dont underestimate a GOOD ground,make sure the engine is grounded correctly and your ecu is receiving a good ground and 12v,,check them while cranking,a lot of times a voltage drop will show good but under load (cranking) it will fail,,
01-26-2019, 12:05 PM
#39
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if the engine stalls on its own a crank and cam sensor can be set BUT ITS NOT AN ACTUAL FAULT. The IAC itself will not cause a cam / crank sensor codes (real actual cam / crank codes). Many times the IAC does not even show a fault code when its bad but there is reason for that - there has to be certain events seen taking place within the PCM for the IAC fault code to show. Sometimes they take place and show a bad IAC fault code and sometimes they do not.
Added info -- the 1 st very early gen Merc 496 s do not even show the cam or crank sensor faults period. Just saying. If I recall its was the 2001 models only.
I do not know if he ( the OP ) has a stalling issue or a jumping tach or poor running engine or whatever at this point.
Possible corroded and or wet connections / connectors being the main issues - is this a storm boat per mentioned or I am miss reading that info ?
The TACH signal comes the crank sensor - a bad crank sensor can produce a NO ENGINE START and NO TACH signal at the very worst case. Lessor issues from a bad crank sensor can cause loss in engine running rpms, back firing, poor running conditions, poor tach signals among other things.
Prob best to have your boat look at by someone who is well trained on this stuff. The forums are a huge dart board for getting things properly fixed . - its all guesses without hands / eyes / ears and the array of diagnostic tools needed to fix boats correctly. And IMO I believe you have more than one issue going on.
Added info -- the 1 st very early gen Merc 496 s do not even show the cam or crank sensor faults period. Just saying. If I recall its was the 2001 models only.
I do not know if he ( the OP ) has a stalling issue or a jumping tach or poor running engine or whatever at this point.
Possible corroded and or wet connections / connectors being the main issues - is this a storm boat per mentioned or I am miss reading that info ?
The TACH signal comes the crank sensor - a bad crank sensor can produce a NO ENGINE START and NO TACH signal at the very worst case. Lessor issues from a bad crank sensor can cause loss in engine running rpms, back firing, poor running conditions, poor tach signals among other things.
Prob best to have your boat look at by someone who is well trained on this stuff. The forums are a huge dart board for getting things properly fixed . - its all guesses without hands / eyes / ears and the array of diagnostic tools needed to fix boats correctly. And IMO I believe you have more than one issue going on.
Last edited by BUP; 01-26-2019 at 12:24 PM.
01-26-2019, 12:49 PM
#40
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The ecu does not realize the engine has died because all the other sensors are providing a input to the ecu,except the crank and cam sensor (because the engine is not turning ) so it will trigger a false code.
another way to trigger a false crank sensor code as well as a knock sensor code(which I know we are not dealing with) is EMI ,depending on how the wiring harness is routed especially if its close to any ignition wiring you can be picking up Electromagnetic interference,
