Help My Please ! 500 EFI Mercruiser Backfire !
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Help My Please ! 500 EFI Mercruiser Backfire !
After running after 15 min one of my motors is backfiring out the stainless marine risers , I changed the main harness , new coil , new cap and rotor , new spark plug and wires , 42 pounds fuel pressure off the rail at start up , cruise , and wide open ! Even when it's backfiring ! Checked the tank no anti Syfin ball ! Line clear ! Now taking the injectors out to be cleaned !!!!! Even tried disconnecting the tach !!!!! Help me !!!! 305,496 , 9006 text me or email at [email protected]
#3
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Will agree with above to ^^^^^
Ignition related - pick up coil and or module in the distributor.
will add but your engine reaches WOT ??? If not then - Possible a exhaust valve problem and or valve train problem - valve springs as well. I would pull the valve covers at the very least here to check for a sucked valve and or valve spring(s) Again, I see where you said WOT so you can hit max recommended RPM's or NO -
could be fuel injectors never rule them out.
Testing ideas as well
Compression test and Leak down test ?
fresh gas and gas samples - anything - crud lifting off the gas tank ?
Scan the engine ? Fault codes / sensor parameters ? Timing ?
You are able to hit WOT meaning that your engine acts like ITS NOT down on power ? If so then that would rule out broken valve spring(s) and or sucked valve(s). Just want to be clear on this.
Ignition related - pick up coil and or module in the distributor.
will add but your engine reaches WOT ??? If not then - Possible a exhaust valve problem and or valve train problem - valve springs as well. I would pull the valve covers at the very least here to check for a sucked valve and or valve spring(s) Again, I see where you said WOT so you can hit max recommended RPM's or NO -
could be fuel injectors never rule them out.
Testing ideas as well
Compression test and Leak down test ?
fresh gas and gas samples - anything - crud lifting off the gas tank ?
Scan the engine ? Fault codes / sensor parameters ? Timing ?
You are able to hit WOT meaning that your engine acts like ITS NOT down on power ? If so then that would rule out broken valve spring(s) and or sucked valve(s). Just want to be clear on this.
Last edited by BUP; 07-30-2015 at 11:44 PM.
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Thank you guys ! Now I will change the pick up , under the rotor , and sent the injectors out , oil looks new and perfect , spark plugs look great . When you say headers do you mean the stainlessarine risers ?
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how many hours on the engine?
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Wide open throttle no problem ! Only happens after 15 to 20 min running , just had all the injectors done will install tomorrow . If my stainless marine riser is leaking will that cause a back fire ? And if so why doesn't it do it when I start the motor ?