496HO Down on power
08-09-2022 | 09:19 AM
#171
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Joined: Nov 2004
Posts: 14,095
Likes: 3,685
From: On A Dirt Floor
I vaguely remembered some others having rust issues on their injector rail.
Here’s one thread of several:
8.1 fuel rails
and here’s a quote from raylar on one other:
Here’s one thread of several:
8.1 fuel rails
and here’s a quote from raylar on one other:
Paddles:
I've seen a few such fuel situations in quite a few early model Merc 496's. In those cases it was caused by the inside of the injector fuel rail rusting inside from moisture in the fuel system especially from sitting in winter to summer temperature variations. You have a 2002 engine with only about 100 hours use and that means it has sat way to much unused!
First put a fuel pressure guage on the Schraeder valve on the fuel rail and check the fuel pressure at , key on engine not running, engine on idling, vacuum line disconnected from fuel pressure regulator on Cool fuel regulator under the black plastic cover and then at speed when the engine sputters, and stalls.
The key on fuel pressure should be about 43-45 psi and about the same when engine on a idling with vacuum to the regulator pinched off or disconnected and should stay up between 40-43 psi when running at 3000 rpms. If there are issues with the fuel pressure from these readings then the problem could be in the fuel filter, fuel pump side of the system.
If however these readings all seem to be good then it could be the dreaded rust in the fuel rail problem! The check for this involves removing the fuel rail and injectors and carefully removing the injectors, giving a good look up inside the fuel rail for signs of rusting and debris. When take the injectors out of the rail, turn them upside down over a nice white paper towel and spray some good carb cleaner up into the inlet side of the injector where the fine screen is and then tapping the injector down onto the towel and see what comes out. If you get any real debris out of the injector this way you should have the injectors cleaned and re-flowed by an injector service shop or replace all the injectors. You will also have to replace the fuel rail itself with the newer ones which were finally plated by GM in later models to stop this problem.
I am not saying this is definitly what is wrong here, but with early 2000 Merc 496's that sat alot it has been a big problem.
A sitting unused for long periods marine engine is a problem waiting to happen.
Hope this helps and let us know what you find or figure out on the engine and its problem.
Best Regards,
Ray @ Raylar
I've seen a few such fuel situations in quite a few early model Merc 496's. In those cases it was caused by the inside of the injector fuel rail rusting inside from moisture in the fuel system especially from sitting in winter to summer temperature variations. You have a 2002 engine with only about 100 hours use and that means it has sat way to much unused!
First put a fuel pressure guage on the Schraeder valve on the fuel rail and check the fuel pressure at , key on engine not running, engine on idling, vacuum line disconnected from fuel pressure regulator on Cool fuel regulator under the black plastic cover and then at speed when the engine sputters, and stalls.
The key on fuel pressure should be about 43-45 psi and about the same when engine on a idling with vacuum to the regulator pinched off or disconnected and should stay up between 40-43 psi when running at 3000 rpms. If there are issues with the fuel pressure from these readings then the problem could be in the fuel filter, fuel pump side of the system.
If however these readings all seem to be good then it could be the dreaded rust in the fuel rail problem! The check for this involves removing the fuel rail and injectors and carefully removing the injectors, giving a good look up inside the fuel rail for signs of rusting and debris. When take the injectors out of the rail, turn them upside down over a nice white paper towel and spray some good carb cleaner up into the inlet side of the injector where the fine screen is and then tapping the injector down onto the towel and see what comes out. If you get any real debris out of the injector this way you should have the injectors cleaned and re-flowed by an injector service shop or replace all the injectors. You will also have to replace the fuel rail itself with the newer ones which were finally plated by GM in later models to stop this problem.
I am not saying this is definitly what is wrong here, but with early 2000 Merc 496's that sat alot it has been a big problem.
A sitting unused for long periods marine engine is a problem waiting to happen.
Hope this helps and let us know what you find or figure out on the engine and its problem.
Best Regards,
Ray @ Raylar
08-09-2022 | 09:20 AM
#173
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Joined: Aug 2010
Posts: 1,384
Likes: 565
08-09-2022 | 09:50 AM
#174
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Joined: Jun 2004
Posts: 7,317
Likes: 1,037
From: frankenmuth michigan
Smitty,
Thanks for the quick turnaround. I can't wait to get it all back together.
I wondered about using anything "petroleum" on O-rings. I know things like motor oil and WD-40 will attack standard Buna-N O-rings, causing them to swell and soften up. Didn't know if Vaseline did this as well.
I got a small packet of what appears to be white, semi-translucent grease from Mosetti with the new plug wires, presumably to lubricate the boots. Would this be the silicone grease we are all referring to?
Thanks. Brad.
(937)545-8991
Thanks for the quick turnaround. I can't wait to get it all back together.
I wondered about using anything "petroleum" on O-rings. I know things like motor oil and WD-40 will attack standard Buna-N O-rings, causing them to swell and soften up. Didn't know if Vaseline did this as well.
I got a small packet of what appears to be white, semi-translucent grease from Mosetti with the new plug wires, presumably to lubricate the boots. Would this be the silicone grease we are all referring to?
Thanks. Brad.
(937)545-8991
08-09-2022 | 09:57 AM
#175
Platinum Member
Joined: Jun 2004
Posts: 7,317
Likes: 1,037
From: frankenmuth michigan
So, another reason to do the following winterization strp i learned from member sutphen30 very long time ago.
Remove water separator (add new or dump out) snd fill with fresh fuel 2 stroke oil mix. Many 2 stroke oils have fuel stabilizer mixed in. If not, add a splash of stabil. Run engine, when you see slight blue smoke from exhaust , the mix is in and being burnt. I do this for all fuel injected snd carbed engines.
Some people remove inlet line at separator and hook small gas filled of this mix to inlet and then run engine.
Not a good typer. Hope that makes sense.
Edit in: I just did that to this sea doo boat other day. You can see the fuel line i added to inlet so i could run on a small 2 gal gas can (not pictured) premix of fuel/oil.
Remove water separator (add new or dump out) snd fill with fresh fuel 2 stroke oil mix. Many 2 stroke oils have fuel stabilizer mixed in. If not, add a splash of stabil. Run engine, when you see slight blue smoke from exhaust , the mix is in and being burnt. I do this for all fuel injected snd carbed engines.
Some people remove inlet line at separator and hook small gas filled of this mix to inlet and then run engine.
Not a good typer. Hope that makes sense.
Edit in: I just did that to this sea doo boat other day. You can see the fuel line i added to inlet so i could run on a small 2 gal gas can (not pictured) premix of fuel/oil.
I used to dump a quart of synthetic 2 stroke or atf and a whole can of seafoam in 30 or 40 gallons of fuel in my supercharged baja on last ride too, same results
08-09-2022 | 11:07 AM
#177
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Joined: Oct 2012
Posts: 2,230
Likes: 536
I have always used dielectric grease on the o-rings with no issues.
BUP used to post that mercury called for a 25:1 "soup mix" (2 stroke oil). BUP said that was was to much, do a 50:1 mix when winterizing. I did that for the 9-10 winters I owned my 496. Never had a rust or fuel injector problem. When BUP cleaned my injectors, he did find some metal shavings in the screens. The high pressure pump was changed on the engine sometime before I owned it. The shavings could have come from the bad pump??
BUP used to post that mercury called for a 25:1 "soup mix" (2 stroke oil). BUP said that was was to much, do a 50:1 mix when winterizing. I did that for the 9-10 winters I owned my 496. Never had a rust or fuel injector problem. When BUP cleaned my injectors, he did find some metal shavings in the screens. The high pressure pump was changed on the engine sometime before I owned it. The shavings could have come from the bad pump??
