Cool Fuel Module Gen 3 failure symptoms

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dolemite_1

Seaman
Joined
May 7, 2008
Messages
71
Hey guys,

I have 2006 twin 350 Mag Horizon closed cooled (OW360139). I recently had a no start issue that I believe I may have solved by replacement of the fuel water separator. The engine would not start 5 minutes after it was already running but has started both times since.

My question is what are the symptoms of the notorious cool fuel module failure. I know my boat had them replaced 6 years ago by the dealer right before I bought it due to failure. My fear is that in my troubleshooting I have realized that my spark plugs are quite blackened and I have a decent smell of fuel in the engine bay when the engines are running at the slip.

As I understand it, smell of fuel (due to high fuel pressure) and blackened spark plugs are a ky sign. Is this accurate? and is there anything else I can look for. I don't own a fuel pressure gauge but am not opposed to buying one if it would greatly help. Through a friend I do have access to that diacom / Rinda / mercruiser computer program where you can hook up to your engines ECM.

Any thoughts? I would like to avoid the cool fuel failure and its further result of getting to the fuel injectors.

Thx

Brian
 
alldodge

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,701
Blackened plugs is a over rich fuel mixture which can not be caused by the pump. The pump can output 60 psi pressure but only happens if something else fails like the fuel pressure regulator or a clog in the return system.

Other causes of black plugs is the MAP sensor, clogged flame arrestor, TPS or vacuum leak

What does it idle at and can you achieve WOT rpm of 4600 to 5000 rpm?
 
D

dolemite_1

Seaman
Joined
May 7, 2008
Messages
71
Seems to idle fine but I have only run it at idle in the slip. My predicament is that the first day I will be able to take it out is the first day I will have guests on board - Thursday. Not ideal.

My thought was due to the delamination of the paint inside the cool fuel module that the paint flakes off then clogs up the fuel pump, fuel regulator, fuel rail and fuel injectors- thus leading to the higher fuel pressure and in-turn causing the blackened plugs and maybe smell of fuel?

When I had the cool fuel module off the fuel regulator looked simple to take off and check but I'm sure that's deceiving.

Brian
 
alldodge

alldodge

Moderator
Staff member
Joined
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Messages
40,701
If you have paint coming off the inside of the fuel module then it needs fixed, but if you think you might have paint come off from reading the topic, no. The paint in the fuel module happed long ago, and most would have been fixed by now. The regulator is on the fuel rail (item 13)

http://www.mercruiserparts.com/bam/subassembly/31760/7585/90

When you said it would not start the one time, did it crank over and not start or not crack over?
 
D

dolemite_1

Seaman
Joined
May 7, 2008
Messages
71
I was under the impression that the paint peeling off is still an ongoing issue; no?

The fuel regulator you have there is different from mine. According to my serial number listed above and the mercury website; it is located on top of the fuel pump cap on the cool fuel module. (mercruiser 892681). Does anyone know if my fuel pump cap and regulator come off easy and can it be done while still attached to the engine?

Previously, the engine was started for 2 minutes then shut off and hooked up to a fresh water flush and then it wouldn't start.

What are the symptoms of the notorious cool fuel module failure?
 
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