Mercruiser 140 Fuel Issue...NEED HELP...!

N

NGO

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Jun 24, 2011
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I have a 1973 Crestliner with a 140 HP Mercruiser...
At the begining of this year i gave it a full tune up: plugs, wires, points, condenser, rotor, dist. cap, carb rebuild, fuel filter (x3), and replaced the coil...

First time out the boat ran good for about 15 miles...on and off not straight through, then died and would not start again...after 10-15 minutes of struggling I was able to get it going and got back to shore, although it wasn't running right.

Though it might be old fuel, water, or debris in the tank so I pulled the tank (18 gal tempo) emptied rinsed, let dry and vacuumed it out. Also replaced all the fuel lines.

Second time out, did the same thing, ran great for awhile, died and would not start...took the line going into the carb off and no fuel, so after being towed off, I replaced the fuel pump (took the old one apart and the interior was rusty and the lower diaphram was cracked up).

Third time out, same thing died after about 15 miles and wouldn't restart, again no fuel being deliverd to the carb. The entire fuel system is clean and/or new...

Vapor lock maybe, I know very little about that...

Any help would be greatly appreciated.
Thanks,
-Nate
 
N

NGO

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Re: Mercruiser 140 Fuel Issue...NEED HELP...!

Should note that I have not replaced the anti-siphon valve...which until researching tonight I thought was a normal barbed fittting...so that might be the problem.
Thoughts? - Vapor Lock, Anti-siphon, or something else.
 
jimbo_jwc

jimbo_jwc

Ship Happens
Joined
Dec 19, 2010
Messages
633
Re: Mercruiser 140 Fuel Issue...NEED HELP...!

Check valve built in hosebib fitting on gas pickup line . Mine would barely open with air pressure then would run motor for awhile . Removed cleaned as the spring against the ball has close tolerance to fitting and it was not opening enough with fuel pump pulses
 
N

NGO

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Re: Mercruiser 140 Fuel Issue...NEED HELP...!

I took a look at this today...I have no anti-siphon/check valve in the fuel system...
So what is causing me to loose fuel pressure after running for awhile?
The only thing I can think of is vapor lock, unless the brand new pump also failed, which doesn't seem to be the case as I had it off and it seems to have plent of suction.

Any help would be greatly appreciated.
Thanks again,
-Nate
 
D

dingdongs

Chief Petty Officer
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May 29, 2009
Messages
649
Re: Mercruiser 140 Fuel Issue...NEED HELP...!

the lift pump on the side of the block may need a new diaphragm as it may have a hole.you say it has full pressure so is there a carb problem.filter blocked.maybe refit the old coil if this ones getting hot.did it do this b4 your complete tune up?????
 
N

NGO

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Re: Mercruiser 140 Fuel Issue...NEED HELP...!

The pump is brand new, filters and fuel lines are also all new, and the tank is spotless, but not getting fuel to the carb...I was doing it prior to the full tune up...
Funny though as it runs fine until shut down when warm, then it'll start back up and when I give it throttle it dies and will not restart until completely cool.
Thanks again for all the help, I just don't know what to do next to prevent/fix the problem.
-Nate
 
N

NGO

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Re: Mercruiser 140 Fuel Issue...NEED HELP...!

Bump...still need help on this one...
Any ideas would be awesome...
Thanks,
 
CobiaXL

CobiaXL

Banned
Joined
Mar 8, 2010
Messages
353
Re: Mercruiser 140 Fuel Issue...NEED HELP...!

Vent tube for fuel tank clear of all debris?Remove gas cap soon as it sputters and quits running.Did it release a lot of pressure?Does it start right back up?Let us know
 
N

NGO

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Messages
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Re: Mercruiser 140 Fuel Issue...NEED HELP...!

Vent tube is free...opening the gas cap doesn't seem to help...
Doesn't start until completely cooled off.
Again, when i take the fuel line off at the carb and turn it over i get no fuel, once cool get fuel again.
Thanks...
 
D

dingdongs

Chief Petty Officer
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Messages
649
Re: Mercruiser 140 Fuel Issue...NEED HELP...!

try running on an outboard tank as it sounds as there is a block somewhere.trying this will hopefully find if its your tank and related lines.just because there new doesn't mean they're correct!!!!!!! may need the carb stripping and cleaning too.
 
N

NGO

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Jun 24, 2011
Messages
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Re: Mercruiser 140 Fuel Issue...NEED HELP...!

Thanks, i'll give it a try...
Also thinking about rigging up an electric pump that i can connect to my carb in case this continues to happen, at least that should allow me to get off the lake.
 
N

NGO

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Jun 24, 2011
Messages
14
Re: Mercruiser 140 Fuel Issue...NEED HELP...!

bump...still haven't figured this out...
 
F

fmalott

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Jun 28, 2010
Messages
561
Re: Mercruiser 140 Fuel Issue...NEED HELP...!

i'm kind of puzzeled on the antisyphon thing i'm not sure if this will help when i tried to start my baot at the begginning of the year i could not get any fuel to the carb so i poured fuel right in the carb started right away but stalled because no fuel so i kept pouring fuel down the carb kept running until i stopped pouring so i pulled the line off the carb started motor fuel pump was working great so i pulled the fuel tank out vent was clean line was a liitle cracked i replace it but still did not make a difference. so what i did was i got a primer ball hooked it up right at the tank it only had about two inches of line i did this to rule out bad fuel line. so i pumped the primer ball until my hand fell of still no fuel. so i took out the anti syphon valve made sure the little ball was not seized it looked good the fuel line inside tank was good put back together pumped primer ball still no fuel what the #@*& i said i removed the valve again and did not replace i just put a normal fitting on so now i hooked everything back together pumped the primer ball and the fuel shot out three feet that was my problem the valve was faulty in some way so what i did in stead off putting a valve back in i installed a shutoff valve on the line i kept the primer ball on it acts like a anti syphon valve and the boat runs great now
P.S. try a primer ball to see if that will draw fuel if it doesn't than it's a tank problem if it does draw good fuel than it's motor problem one way or the other it will eliminate one problem look through the forum i seen many threads where motor won't start until cooled off
 
E

EClass20

Seaman Apprentice
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Sep 1, 2010
Messages
32
Re: Mercruiser 140 Fuel Issue...NEED HELP...!

3.0 Merc, 140

I have been having the exact same problem for 7-8 months now. Everything fuel related is brand new. 5psi to carb. Carb cleaned and rebuilt. Everything ignition related is brand new. Good compression. Frustrated, I finally took it to a Marina.

They tinkered with carb settings and my timing and Dewell. I had it spec @ 6* they put it @ 8* I had my points spec @ .022 per and they set them @ .018 Dwell I had @ 34 they have it 28.

Went out and it ran great finally. Scooted around for about 2 hours. Stopping and re-starting a few times. Got to 40 mph WOT a few times. Then my problems started up again. It starts as a sputter of a misfire, bogs and then catches and runs strong. Over and over worsening until it dies. Won't restart for 30-45 minutes and barely well enough to limp it back to my trailer. I don't think it is vapor lock as I had my blower on the whole time and my engine cover was cracked open. I let idle 5 mins before shutting down each stop. I supposedly had my tank drained and cleaned last fall but the guys at the Marina said they found particles in my carb filter. I was very low on gas and thought debris or maybe my gauge was off and I ran out. I removed the sender and I had gas left. Looked pretty clean. My tank air vent looks clear but I didn't open my cap. I am trying an external tank this weekend and will update you on my findings.
 
N

NGO

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Messages
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Re: Mercruiser 140 Fuel Issue...NEED HELP...!

fmalott and EClass20...sounds like all three of us have the exact same problem...I don't have an anti-siphon, but i'm going to try the primer bulb idea and also rig up an electric back up...
I'm at a loss as to what to do after that though...
 
F

fmalott

Chief Petty Officer
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Jun 28, 2010
Messages
561
Re: Mercruiser 140 Fuel Issue...NEED HELP...!

i asked the same question on the electric pump i was told not to use one for some reason
 
N

NGO

Cadet
Joined
Jun 24, 2011
Messages
14
Re: Mercruiser 140 Fuel Issue...NEED HELP...!

I think they say not to have an electric beacause of safety reasons and that it's not coast gaurd approved, or you need to know how to hook it up so it is CG approved...
Either way, to me it better than getting stuck out in a storm or something.
Let me know if you learn anymore.
 
F

fmalott

Chief Petty Officer
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Jun 28, 2010
Messages
561
Re: Mercruiser 140 Fuel Issue...NEED HELP...!

yes listen to Don S he gave me the same link but i could not find it no more to give to you THANKS Don S i got it saved now
 
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