1995 Merc 350 EFI; runs rich, fouled plugs and gas in oil- pls help troubleshoot

Mtnnate

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1995 Malibu Response with 350 Tournament Ski EFI had SUDDEN trouble on the lake last summer. Went from running perfectly to running rich in an instant. Then plugs fouled and I got a tow. Luckily it was the last day of summer!
Here's what I've done so far:
-replace fuel filter
-tested and replaced most all electrical engine sensors with proper marine sensors
-replaced plugs, wires, cap and rotor
-check for even spray and leakage of injectors
-check timing marks at TDC (perfectly aligned)
-changed engine oil now several times, and haven't run engine for more than a few minutes total since.
What's next? I am thinking maybe fuel pump...
Anyone have this problem before that can lend a hand? Thank you!
 

Tail_Gunner

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What type of engine.merc??? what type of fuel injection..tbi...multiport and what type of ecm there are number on the module. Do you have a scan tool?

check for even spray and leakage of injectors: Did you use a neon light to watch the spray pattern?...I am assuming tbi.
 
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thumpar

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Check the sight tube for fuel. The diaphragm in my VST was shot and loading up the throttle body with extra fuel.
 

Mtnnate

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Hi there,
@ tail gunner; Merc 350 Mag TBI, I don't have the number right now but can get it later- no can tool, I called the local boat shop and they said they cannot test the ECM.

@Thumpar, I'm checking the sight tube tonight and I'll get back to you. That makes a lot of sense.

So many little things and I really didn't trust the boat shop I went to. They just wanted to sell me their motor for $5k.
 

keith2k455

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When you say fouled plugs....more specific please. Can you post pictures of the fouled plugs? Do all the plugs look the same or are some worse than others? Different causes of plug failure can be determined by how the plugs look pretty easily.
 

Fun Times

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Do you also have a heavy amount of smoke?

With your engine model you're finding that much fuel in the engine oil and fouling out the spark plugs almost instantly than the four most common issues to look at first would be, high fuel pressure, Mercruisers fuel Vapor Separator Tank diaphragm problem, heavy leakage of the fuel injectors or a slightly rarer problem could be a bad MAP (Manifold Absolute Pressure sensor) causing the engine to run "supper" rich.

Chances are you're going to find a VST problem like Thumpar did seen here, http://forums.iboats.com/forum/engi...efi-with-cool-fuel-and-fuel-in-the-sight-tube

Good luck.:)
 

alldodge

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:welcome: to iboats

Are you sure this is a TBI and not a carb. Being a 1995 :noidea:
 

gm280

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I have to watch this thread because I can't see how a 350 engine with TBI can get fuel in the oil pan. So I will be watching for the answer... Never too old to learn something...
 

alldodge

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Not sure how you looked it up other then selecting Merc, then select 1995, then 5.7 TBI. You can also select the same thing and 1994 and it will show the VST. The Merc site is just not that good, they leave to many things to chance and it does not stay up to date. Fun Times pointed that out to me a ways back when I assumed similar issue.
 

thumpar

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Not sure how you looked it up other then selecting Merc, then select 1995, then 5.7 TBI. You can also select the same thing and 1994 and it will show the VST. The Merc site is just not that good, they leave to many things to chance and it does not stay up to date. Fun Times pointed that out to me a ways back when I assumed similar issue.
Yea, I think you are right. I did some looking and 1996 was the first year for EFI. Mine is probably a rare item. It could be a 1996+ engine in a 1995 hull but usually it is the other way around.
 

Fun Times

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1995 Malibu Response with 350 Tournament Ski
Keep in mind that he has a 350 Tournament Ski EFI engine model so it'll be in a different look up area parts wise. For the Ski engines, merc had out a 350 ski EFI with TBI starting in 1994 up to 96. http://www.mercruiserparts.com/selec...D8+1994%2D1996

Also see bottom of page 5, http://www.boatfix.com/merc/Bullet/95/95_05.pdf

For the look up on the Brunswick parts catalog, the engine models & years you select on the first page will always be correct.... it's the "part numbers" found inside they don't update...They keep them original in there/on that site. So if you're starting from scratch to find the correct parts, check the Brunswick site then search the number for the latest up date either online or here, http://www.mercruiserparts.com/partsByNumber.asp

All them early to mid models EFI's used the VST. 1997 was when they started switching over to the cool fuel systems.
 

alldodge

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Keep in mind that he has a 350 Tournament Ski EFI engine model so it'll be in a different look up area parts wise. For the Ski engines, merc had out a 350 ski EFI with TBI starting in 1994 up to 96. http://www.mercruiserparts.com/selec...D8+1994%2D1996
.

Took me a bit of going back and forth to find your link. So for anyone else wondering how you fond it, look at this link and it is the 10th line down just below Inboards. http://www.mercruiserparts.com/SelectModelType3.asp?class_id=1
Ski Engines (Including Scorpion)

I always just looked in "Inboards" for ski boats, never gave the one below it a second thought
 
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