03 496 ho rough idle loading up
06-18-2014, 09:50 PM
#11
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I understand that you do not understand because you do not work on boats for a living. Does that make me the number 1 expert - no way not even close but I have been well OEM trained and see boats daily. No offense I am not dogging U.
the cool fuel cooler keeps the fuel cool from vapor lock. Under that 43 psi fuel pressure regulator is a o-ring seal and a very small screen for the fuel excess return that is returned back to the fuel water filter area. This is what a fuel pressure regulator does regulate fuel so the fuel injectors have enough fuel supply and not too much fuel supplied. The excess fuel has to go somewhere.
When that excess fuel is blocked or hugely restricted by the clogged screen it will disrupt the fuel pressure regulator fuel pressure with possible high readings and rich running conditions. Also a bad MAP sensor can cause really rich running conditions and or poor running conditions as well like I mentioned before. Anyways that's the jist - short story of the explanation of it not to make into a book.
I wore this thread out and I do this for a living who C's this stuff day in and day out, even while sleeping. Good luck with your boat Also it is very hard to throw proper fixes really without your own eyes, hands, ears and diagnostic tools testing for showing the results plus a lot of posts up here do not give out enough info or an engine serial # in which both are so important so thanks for posting other info and engine serial #.. And yes your motor app has the gen II cool fuel system as I mentioned a couple of times now. Serial # dictates how your engine is setup and what parts are installed.
the cool fuel cooler keeps the fuel cool from vapor lock. Under that 43 psi fuel pressure regulator is a o-ring seal and a very small screen for the fuel excess return that is returned back to the fuel water filter area. This is what a fuel pressure regulator does regulate fuel so the fuel injectors have enough fuel supply and not too much fuel supplied. The excess fuel has to go somewhere.
When that excess fuel is blocked or hugely restricted by the clogged screen it will disrupt the fuel pressure regulator fuel pressure with possible high readings and rich running conditions. Also a bad MAP sensor can cause really rich running conditions and or poor running conditions as well like I mentioned before. Anyways that's the jist - short story of the explanation of it not to make into a book.
I wore this thread out and I do this for a living who C's this stuff day in and day out, even while sleeping. Good luck with your boat Also it is very hard to throw proper fixes really without your own eyes, hands, ears and diagnostic tools testing for showing the results plus a lot of posts up here do not give out enough info or an engine serial # in which both are so important so thanks for posting other info and engine serial #.. And yes your motor app has the gen II cool fuel system as I mentioned a couple of times now. Serial # dictates how your engine is setup and what parts are installed.
Last edited by BUP; 06-18-2014 at 10:18 PM.
06-21-2014, 10:07 PM
#12
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Just a quick update took the boat to local mec he scanned it no codes while not running or running said he thought I had list a cylinder then did a compression test on a couple that was fine all the while I'm tellin him how high my fuel press. Was finally he checked it and we came to the same conclusion that we had come up withe here fuel press reg so I just changed if tonight idles a lot better rented x gauge from azone 42 psi so tomorrow when I take it out hopefully she'll run good again thanks for all the help I really do appreciate it
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06-22-2014, 06:31 PM
#14
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Boat ran grrrrreat!! I real pleased with the new plugs filters and reg I lost the. Soot and the slight hesitation that I had getting up on plane so thanks all for the help !!!!!
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05-29-2018, 08:58 AM
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Off memory it should be 42 PSI running and about 45 key on not running.
You are getting into a bad place. Something weird is going on. First, you need to hook a computer to it to see if there is something else alarming. Then, assuming you are hooking it up to the schrader valve on the rail, go rent a different fuel pressure gauge from an auto parts store to confirm your numbers. I dont see how a 496 would run at 100PSI. Mine smoked like crazy at 55 psi.
The fuel pressure regulator is on the rail... it is a piece of junk. Yes, you can buy a new one. But I would assume you have another problem. Maybe even a clogged return? Just seems like you have something else going on like water in the gas and the rust messed up your regulator somehow. (maybe)
FWIW - I converted mine to a full Aeromotive system with Aeromotove pump and regulator. I didnt get along with the #10 star allen adjuster on the regulator after I made upgrades it wouldnt stay consistent.
You have several things to check:
-Fuel Pressure (again)
-Computer
-Pull the regulator apart (I dont recommend this, I doubt you will get any consistency out of it unless you install all new guts and o-rings and I still doubt that)
-Possibly pull the return line off the rail to see if there is debris in it?
-Change the fuel/water separator
You are getting into a bad place. Something weird is going on. First, you need to hook a computer to it to see if there is something else alarming. Then, assuming you are hooking it up to the schrader valve on the rail, go rent a different fuel pressure gauge from an auto parts store to confirm your numbers. I dont see how a 496 would run at 100PSI. Mine smoked like crazy at 55 psi.
The fuel pressure regulator is on the rail... it is a piece of junk. Yes, you can buy a new one. But I would assume you have another problem. Maybe even a clogged return? Just seems like you have something else going on like water in the gas and the rust messed up your regulator somehow. (maybe)
FWIW - I converted mine to a full Aeromotive system with Aeromotove pump and regulator. I didnt get along with the #10 star allen adjuster on the regulator after I made upgrades it wouldnt stay consistent.
You have several things to check:
-Fuel Pressure (again)
-Computer
-Pull the regulator apart (I dont recommend this, I doubt you will get any consistency out of it unless you install all new guts and o-rings and I still doubt that)
-Possibly pull the return line off the rail to see if there is debris in it?
-Change the fuel/water separator
Keith, I noticed you said you changed over to an Aeromotive setup. Mine currently has that setup. I bought it that way and it’s drving me crazy.
1. The idle surges up and down
2. When it surges, the A1000 pump turns on and off
3. Runs really rich, no fouled plugs, just smells
4. Regulator is NOT and Aeromotive
5. Fuel pump wires directly to Mercuriser relay
In hunting this gremlin down, I have narrowed it down to a couple things. I am not sure which direction to take. In reading the A1000 instructions, it reads like the pumpmshould always stay running. I’m not sure if wiring the pump into the stock Mercruiser Relay was the correct choice or if it should have been wired differently. Does the Mercruiser computer from the factory “cycle” the pump on and off? Or should I switch over to The Aeromotive regulator? The idle surges when I can hear the pump turn on and off. I can provide a video if that would help. Thanks for any advice.
05-29-2018, 10:58 AM
#17
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Upon your complete fuel system change did this ever run 100 percent correctly. ?
Stock cal in the pcm and possible fuel pulsations can become running issues.from the fuel system change.
fuel pressure is with key on only and while running
scan results are ?
Stock cal in the pcm and possible fuel pulsations can become running issues.from the fuel system change.
fuel pressure is with key on only and while running
scan results are ?
Last edited by BUP; 05-29-2018 at 11:12 AM.
08-25-2018, 05:39 PM
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I figured since this thread popped up first on my search for 496 running rich, I would add to it.
Last time out was 5 weeks ago and was getting a little loaded up at idle. Had it scanned while we took vacation for the week and all checked out. This morning went to FINALLY head out and it died on my wife before I could get the truck parked. Short bursts of quick starts but sounded like it was missing on all cylinders and running pig rich... couldn't get it to clear out. Came home and started to check everything. Rail pressure good, cleaned MAP sensor, checked wires and connections, took fuel sample and pulled 4 random plugs. Plugs were not terrible looking by any stretch besides a little fuel from loading up. Decided to replace all the plugs. Fired it up and bingo... idles like a champ and revs great! I have to say I've read plenty of plugs over the years and these were not terrible looking at all. I won't be judging these Delco plugs by their cover again. Hope this helps someone out one day. Pissed I missed a day on the water (after a long wait) but glad it was an easy fix.
Last time out was 5 weeks ago and was getting a little loaded up at idle. Had it scanned while we took vacation for the week and all checked out. This morning went to FINALLY head out and it died on my wife before I could get the truck parked. Short bursts of quick starts but sounded like it was missing on all cylinders and running pig rich... couldn't get it to clear out. Came home and started to check everything. Rail pressure good, cleaned MAP sensor, checked wires and connections, took fuel sample and pulled 4 random plugs. Plugs were not terrible looking by any stretch besides a little fuel from loading up. Decided to replace all the plugs. Fired it up and bingo... idles like a champ and revs great! I have to say I've read plenty of plugs over the years and these were not terrible looking at all. I won't be judging these Delco plugs by their cover again. Hope this helps someone out one day. Pissed I missed a day on the water (after a long wait) but glad it was an easy fix.
08-25-2018, 10:50 PM
#19
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the delco s do not like long periods of idle in 496 s. They will load up. Another reason I install the NGKs. A better plug and a better idle using them.
Also the delco s hate the winterization soup mix that merc recommends at 10 to 1 fuel to 2 stroke oil.
Also the delco s hate the winterization soup mix that merc recommends at 10 to 1 fuel to 2 stroke oil.
08-26-2018, 06:59 AM
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BUP, First and foremost, the information you post on the 496's is invaluable... Thank You!
I did try to use the NGK plugs you referenced but they weren't available to me yesterday. I was floored that they went from problematic to shot after the boat sat dormant for 5 weeks. It was the 3rd season on those plugs (that I know of anyway) and I do regular plug inspections throughout the season.
Lucky for me no winterizing needed here in FL... I don't miss that Pennsylvania requirement!
I did try to use the NGK plugs you referenced but they weren't available to me yesterday. I was floored that they went from problematic to shot after the boat sat dormant for 5 weeks. It was the 3rd season on those plugs (that I know of anyway) and I do regular plug inspections throughout the season.
Lucky for me no winterizing needed here in FL... I don't miss that Pennsylvania requirement!
