Back fire on start stock 496HO
08-17-2018, 09:31 PM
#1
Registered
Thread Starter
Back fire on start stock 496HO
Ok guys, BUP should have the answer. Every time now when I start my starboard engine it back fires before start. Like a shotgun. 2004 496 HO little Or no maintenance on EFI. 300 hrs new plugs, wires. Runs fine once started. A little tough to restart. Should I just send my injectors to BUP for reconditioning and testing, or could it be a head issue?
08-18-2018, 07:40 AM
#3
VIP Member
VIP Member
Do the above tests, pull the codes, check IAC, water separator filter. Having injectors tested, flowed, and rebuilt can never hurt and they are very suspect. And for what it costs from Bup, not expensive to do.
08-18-2018, 09:02 AM
#5
Registered
Thread Starter
Compression checked 130-140 6 months ago. Will repeat and leak down. Will Do Rhinda injector test. Water separater check...I’m worried about a possible valve seat failure...any chance ? I’m also thinking maybe pulling one plug wire at a time to isolate possible offender...
Last edited by 38fountained; 08-18-2018 at 10:48 AM.
08-18-2018, 11:39 AM
#6
Banned
iTrader: (9)
scan and knowing the parameters. fuel pressure testing is the first 2 steps for pin pointing issues or not. Then move on to comp and leak down. Easier testing first to rule out then move on. When was the last time you changed fuel filters and did fuel samples ? How many hours on the engine(s) ?
Have to jump in on this --- Pulling spark plug wires on DIS set ups is asking for huge trouble - whom told you to do that? thats 50 year old carb testing methods. And if you have gas fumes in the engine compartment - we will say good bye to you now. 4 years ago people working on a 496 in my area burned down a complete section of the docks and boats in the marina from pulling plug wires off and the spark / gas fumes caused a huge fire. I am posting this as a huge safety issue for everyone AND NOT TO DO THAT FORM of backyard testing plus possible ignition / ecm / pcm inflicted issues.
And for the record --- NOT A SALES promotion but injector testing and flow testing / cleaning IS PART OF MAINTENANCE along with fuel samples. I have never had a used set of all 8 injectors come in that were completely balance across the board. NEVER. And on a 496 regardless MERC - Volvo - Indmar - PCM - Marine Power - it needs to be done. NO way around it. Its really not the injectors themselves but the contamination issues are the factor here especially from improper fuel maintenance and storage.
Added info on top of --- Keep in mind internal fuel pump wear happens on all electric fuel pumps. Guess where that wear ends up ? Then you have the rubber fuel lines that no one ever changes. Currently the range for those are 4 to 7 years max for change out .
2 contamination issues right there that happen in every marine engine even carb engines, the same happens.
Have to jump in on this --- Pulling spark plug wires on DIS set ups is asking for huge trouble - whom told you to do that? thats 50 year old carb testing methods. And if you have gas fumes in the engine compartment - we will say good bye to you now. 4 years ago people working on a 496 in my area burned down a complete section of the docks and boats in the marina from pulling plug wires off and the spark / gas fumes caused a huge fire. I am posting this as a huge safety issue for everyone AND NOT TO DO THAT FORM of backyard testing plus possible ignition / ecm / pcm inflicted issues.
And for the record --- NOT A SALES promotion but injector testing and flow testing / cleaning IS PART OF MAINTENANCE along with fuel samples. I have never had a used set of all 8 injectors come in that were completely balance across the board. NEVER. And on a 496 regardless MERC - Volvo - Indmar - PCM - Marine Power - it needs to be done. NO way around it. Its really not the injectors themselves but the contamination issues are the factor here especially from improper fuel maintenance and storage.
Added info on top of --- Keep in mind internal fuel pump wear happens on all electric fuel pumps. Guess where that wear ends up ? Then you have the rubber fuel lines that no one ever changes. Currently the range for those are 4 to 7 years max for change out .
2 contamination issues right there that happen in every marine engine even carb engines, the same happens.
Last edited by BUP; 08-18-2018 at 11:50 AM.
08-18-2018, 12:04 PM
#8
Banned
iTrader: (9)
<div style="text-align:left;">describe runs fine after start up ? can you reach full rpms at WOT ? 5000 rpms HO mag and 4800 for mag 496 is WOT</div><div style="text-align:left;"></div><div style="text-align:left;"> I would not rule out CRANK SENSOR here either for starting issues. That signal and cam sensor have to sync for start up among other things</div>
Last edited by BUP; 08-18-2018 at 12:12 PM.
08-18-2018, 12:46 PM
#9
Registered
Thread Starter
Thanks BUP, you’re a life saver. 300 hrs total. New plugs the ones you recommend and wires about a year...crank sensor and cam sensor come up as code on the Rhinda. Will do more testing. Bleed down on fuel pressure?
08-18-2018, 01:26 PM
#10
Banned
iTrader: (9)
<div style="text-align:left;">describe runs fine after start up ? can you reach full rpms at WOT ? 5000 rpms HO mag and 4800 for mag 496 is WOT</div><div style="text-align:left;"></div><div style="text-align:left;"> I would not rule out CRANK SENSOR here either for starting issues. That signal and cam sensor have to sync for start up among other things</div>
will fix in the next post
