1991 v-6 carb. went kaboom!!!

X

xltier

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took my buddys boat to the ramp today to get it going for the weekend.backed it in the water and lowered the drive.got in and pulled the cover back to watch.started up fine and ran about ten minutes.shut it off and went to get screwdriver out of truck.he shows up and we hit the key again and kaboom,it blows its cookies.lifted the vale coversw up so as to bend them upward and blew the gaskets out from under.carb. doesnt seen to be flooding cause it ran great at first.anybody have any ideas.i dont think it turned twice when it let go.it woke the neighbors baby up from a nap.just like a shot gun blast. scared the crap out of us.sorry for the long winded post.thanks
 
B

Bry21317

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Re: 1991 v-6 carb. went kaboom!!!

Man,
From what it sounds like you are lucky to be here posting. That would scare me to death for sure.

I am sure that someone will be along to post something on as why this could happen. I am not sure, but I sure would like to know so that I know what to check for sure.

Also did you run the Blower or was that off? I always leave my blower on when I am about to start for at least 5 mins with the cover up to get the fumes out. Was the blower running when you shut it down to get the Screw driver? If not, there could have been fumes that ignited from something, but there still would have had to be a spark that caused this.

Is it a Marine starter or did he put in an Auto starter? I would think that since the fumes would be in the bottom of the boat and thats where the starter is that if the starter had a spark maybe it could have ignited them. Other than that, I have no idea.

Bryan
 
X

xltier

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Re: 1991 v-6 carb. went kaboom!!!

the cover was rite off.this came from within the engine.
 
tommays

tommays

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Re: 1991 v-6 carb. went kaboom!!!

For and as yet unkown reason you had a LOT of fuel in your OIL as that would be the ONLY way to pop the valve covers


If you have a mechanical fuel pump i would think it was leaking into the motor and the sight tube would be showing gas
 
180shabah

180shabah

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Re: 1991 v-6 carb. went kaboom!!!

Ditto what Tom said - 1991 still had the mechanical fuel pumps. They started switching in '92.
 
X

xltier

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Re: 1991 v-6 carb. went kaboom!!!

thanks alot guys.i ordered a pump for tomorrow.if you hear a SONIC BOOM around 11 a.m.not to worry, its only me.lol
 
erikgreen

erikgreen

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Re: 1991 v-6 carb. went kaboom!!!

Did you verify that was the problem?
 
Don S

Don S

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Re: 1991 v-6 carb. went kaboom!!!

Did you change the oil and filter? Have you guys ever checked the oil? If fuel in the oil is the problem (which it sure sounds like) the oil would be over full and thin. Plus would smell of gas.

I doubt just changing the fuel pump is going to fix all the problems you will now have from the oil explosion.
 
X

xltier

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Re: 1991 v-6 carb. went kaboom!!!

Don S said:
Did you change the oil and filter? Have you guys ever checked the oil? If fuel in the oil is the problem (which it sure sounds like) the oil would be over full and thin. Plus would smell of gas.

I doubt just changing the fuel pump is going to fix all the problems you will now have from the oil explosion.
Click to expand...

we are changing the oil and filter.to be honest the oil looks and smells normal.when i took the hose off the fuel pump[vent] it dripped very thin oil and gas mix- alot.need to find some valve covers now too.thees a good 3/4 inch gap between the covers and the heads.wow,what a bang.huge cloud of smoke also.anybody have any other ideas there thinking.i got the rest of the week off.thanks
 
Don S

Don S

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Re: 1991 v-6 carb. went kaboom!!!

we are changing the oil and filter.to be honest the oil looks and smells normal
Click to expand...
No doubt it does now, the gas has burned off.
Might want to check around the oil pan, oil filter, timing cover. Who knows what the front and main seals look like.
A compression test would be a good idea. Carb might have some problems as backfires takes out powervalves, and I couldn't imagine a full blown explosion doing less.
 
180shabah

180shabah

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Re: 1991 v-6 carb. went kaboom!!!

OK, just came back to check for updates and I always find it interesting how one little part(fuel pump) can be the cause for so much work and expense(valve covers, and possibly everything else mentioned above) if not caught early.

Then two things really hit me:

- Although, this may end up costing quite a bit in repairs, you are incredibly lucky to still be here to ask questions, and spend that money.

- I have to assume that this engine is using all marine parts(where required) or this could have been ALOT worse, and possibly taking human life.
 
C

Coors

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Re: 1991 v-6 carb. went kaboom!!!

Not to hijack, but the answer might help us all.
Back in the '60s, in auto mech days, I replaced several mech pumps, ruptured diaphrams, oil needed changing.
Why didn't they internally boom?
Is it the closed enviroment of the doghouse?
 
X

xltier

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Re: 1991 v-6 carb. went kaboom!!!

180shabah said:
OK, just came back to check for updates and I always find it interesting how one little part(fuel pump) can be the cause for so much work and expense(valve covers, and possibly everything else mentioned above) if not caught early.

Then two things really hit me:

- Although, this may end up costing quite a bit in repairs, you are incredibly lucky to still be here to ask questions, and spend that money.

- I have to assume that this engine is using all marine parts(where required) or this could have been ALOT worse, and possibly taking human life.
Click to expand...

yes on the marine electrical.another 30 seconds and i would have been leaning over it checking the shift switch.wow.
 
Don S

Don S

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Re: 1991 v-6 carb. went kaboom!!!

Most don't explode. But all it would take is one mistuned engine, one backfire, one little bit of fire and the fuel/air ratio just right and BOOM!!!!!!
 
Don S

Don S

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Re: 1991 v-6 carb. went kaboom!!!

yes on the marine electrical.another 30 seconds and i would have been leaning over it checking the shift switch.wow.
Click to expand...

My guess is that you will now check the oil a little closer and smell it before you ever start it. Am I wrong in that assumption?
 
X

xltier

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Re: 1991 v-6 carb. went kaboom!!!

i have been a auto mech all my life and i have seen some bad oil and this isnt even close.the confusing part is that it was running just before no pobs.just never know.thanks for all the tips.ill check them all out.
 
R

rodbolt

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Re: 1991 v-6 carb. went kaboom!!!

Coors,
years ago I saw a 350 in a camero do just that due to a bad pump.
I warned the fools and they kept trying to start it, took the drivers side valvecover clean off and pushed the front crank seal out of the timing cover.
not much other than checking the oil and the pump vent for fuel before starting can be done to prevent it.
luckily no one was hurt this time.
 
X

xltier

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Re: 1991 v-6 carb. went kaboom!!!

rodbolt said:
Coors,
years ago I saw a 350 in a camero do just that due to a bad pump.
I warned the fools and they kept trying to start it, took the drivers side valvecover clean off and pushed the front crank seal out of the timing cover.
not much other than checking the oil and the pump vent for fuel before starting can be done to prevent it.
luckily no one was hurt this time.
Click to expand...

wondering if i should wire up a electric fuel pump.block off the hole in block.but im not sure how to wire it so it turns off when motor quits.some cars go to oil pressure switch for ground.i know automotive is a NO-NO here.this is goona be a ski-tube boat and i want it safe.rite now we dont trust it.
 
Don S

Don S

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Re: 1991 v-6 carb. went kaboom!!!

Here is how Mercruiser wires an electric fuel pump.

FuelPumpWiring.jpg
 
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