1986 Merc 470 - New fuel pump - Now flooding carburetor...

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generator12

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Hey guys, I just replaced my original Carter fuel pump with a Sierra 18-7282, and I'm overflowing the carb. I used the gasket that came with the pump, and it looked to me to be the same thickness as the original, which came off in one piece.

The original pump was operating okay, but I had to prime the carb when starting after a shut-down of a week or more. Once started, she ran fine and would restart easily later the same day.

Has anyone any suggestions? Gasket thickness? Carb float rebuild?

Thanks!
 
X

xltier

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Re: 1986 Merc 470 - New fuel pump - Now flooding carburetor...

generator12 said:
Hey guys, I just replaced my original Carter fuel pump with a Sierra 18-7282, and I'm overflowing the carb. I used the gasket that came with the pump, and it looked to me to be the same thickness as the original, which came off in one piece.

The original pump was operating okay, but I had to prime the carb when starting after a shut-down of a week or more. Once started, she ran fine and would restart easily later the same day.

Has anyone any suggestions? Gasket thickness? Carb float rebuild?

Thanks!
Click to expand...

if your sure the pump isnt putting to much pressure out than you got a piece of crud in the needle valve.sometimes tapping the top of the carb while running will send it free.did you check the ball and spring on the gas tank outlet for drainback.right where the fuel hose cannects to the tank.
 
Don S

Don S

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Re: 1986 Merc 470 - New fuel pump - Now flooding carburetor...

Check the fuel pump pressure, if it's within specs. you have carb problems.
 
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generator12

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Re: 1986 Merc 470 - New fuel pump - Now flooding carburetor...

X, thanks for the quick reply. No I didn't check the pump output as it's the specific pump named as the OEM replacement. In fact, looking at the actuator arm on it, I worried putting it in that the cam wouldn't move it enough to pump. As to the carb, I ran the engine with the original pump (after manually priming it) and it started very quickly (first time this season) and ran perfectly for ten minutes on the muffs. Then replaced the pump and have this problem.

In any case, I'll try tapping on the carb as you suggest.

Thanks again.
 
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generator12

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Re: 1986 Merc 470 - New fuel pump - Now flooding carburetor...

Stony, thanks for responding. Yeah, I seem to remember such a thread as well and looked for it before I wrote this one. But no luck.

If you locate it, I'll be much obliged.
 
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generator12

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Re: 1986 Merc 470 - New fuel pump - Now flooding carburetor...

Thanks Don. That seems reasonable.
 
Eric 3.7LX Alpha 1

Eric 3.7LX Alpha 1

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Re: 1986 Merc 470 - New fuel pump - Now flooding carburetor...

generator12 said:
Hey guys, I just replaced my original Carter fuel pump with a Sierra 18-7282, and I'm overflowing the carb. I used the gasket that came with the pump, and it looked to me to be the same thickness as the original, which came off in one piece.

The original pump was operating okay, but I had to prime the carb when starting after a shut-down of a week or more. Once started, she ran fine and would restart easily later the same day.
Has anyone any suggestions? Gasket thickness? Carb float rebuild?

Thanks!
Click to expand...

That problem is within the carb itself not the pump. The fuel bowl is slowly draining into the intake after a long period of being off. When you try and start it, the carb is empty.

See if you can install a pressure gauge inline between the pump and carb inlet to see what it's putting out. Should be between 3 and 6 psi

Here is a link to a series of carb rebuilding videos posted by Alpheus, another member:
http://forums.iboats.com/showthread.php?t=362542
 
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generator12

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Re: 1986 Merc 470 - New fuel pump - Now flooding carburetor...

Eric 3.7LX Alpha 1 said:
That problem is within the carb itself not the pump. The fuel bowl is slowly draining into the intake after a long period of being off. When you try and start it, the carb is empty.

See if you can install a pressure gauge inline between the pump and carb inlet to see what it's putting out. Should be between 3 and 6 psi

Here is a link to a series of carb rebuilding videos posted by Alpheus, another member:
http://forums.iboats.com/showthread.php?t=362542
Click to expand...

Thanks Eric, and everyone else.

I'll post the solution when I find it.
 
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generator12

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Re: 1986 Merc 470 - New fuel pump - Now flooding carburetor...

Epilogue...

I checked the pump output pressure and found it at 17 PSI - three times what it should be. No replacements in stock at Sierra - on backorder. So I'm in the ever-decreasing concentric circle of trying to get Sierra to authorize a return credit and refund from the supplier, MarineEngine.com. Hope I don't disappear up my own a__hole.

Meanwhile I guess I'll go to my "friendly" local marine dealer and offer them my first-born for an OEM.

Thanks for all the help and guidance everybody.
 
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a1nowell

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Re: 1986 Merc 470 - New fuel pump - Now flooding carburetor...

Generator,
Have you considered switching to an electric pump? I believe it may be cheaper.

Larry
 
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stonyloam

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Don S

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Re: 1986 Merc 470 - New fuel pump - Now flooding carburetor...

I guess I don't really see where another Sierra pump would make much difference.
Click to expand...

It would make a difference if it was a manufacturing defect in that one pump. Wouldn't be the first fuel pump to be bad right out of the box.
 
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a1nowell

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Re: 1986 Merc 470 - New fuel pump - Now flooding carburetor...

Generator,

If you have to replace the FP, there is a used one at www.breezeworks.net I do not know if it has been rebuilt.

Larry
 
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stonyloam

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Re: 1986 Merc 470 - New fuel pump - Now flooding carburetor...

Found this on a hot rod site :

"I haven't kept up to speed with this thread but noticed your last thread. I've got oodles of experience with these engines in boats, and thought you might want to know that if you use a "regular" thin fuel pump gasket instead of the Mercruiser approximately 1/4" - 5/16" thick gasket, the pump pressure becomes way too high and causes the float valve to blow off it's seat and essentially flood and dump gas. I've had customers change multiple carburetors only to be humbled by this info."
post# 591 here: http://www.jalopyjournal.com/forum/showthread.php?t=256713&page=30

I think it might be time to contact my local Mercruiser dealer.
 
Don S

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Re: 1986 Merc 470 - New fuel pump - Now flooding carburetor...

I think it might be time to contact my local Mercruiser dealer.
Click to expand...
Good point Terry

I just went digging for service bulletins about the fuel pumps and gaskets.
Here is one about long blocks and fuel pumps and which pump goes on which block with which gasket.
Would think it may help figure out the problem and be a way to get the correct OEM gasket.

View attachment pumps.pdf
 
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generator12

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Re: 1986 Merc 470 - New fuel pump - Now flooding carburetor...

Fuel pump...flooding carburetor....epilogue:

Tried to locate an OEM (Carter) but all I heard from everyone was, "on back-order", estimating July 5th. So I relented and ordered a Mallory replacement. Three days later I open the box and find.......A CARTER! What a world!

Installed with the original spacer gasket and now she's giving me 5 PSI up to 3k rpm, as fast as I want to go on the muffs. The original was putting out 6 - 6.5, so I'm confident I'm now okay.

Again, thanks for the thoughts and ideas, guys. These discussions are more helpful than is sometimes realized by the contributors, as -even if no specific suggestion provides a solution - they tend to settle the OP into the proper train of thought. You've helped me several times and it's appreciated.
 
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