Mercruiser 3.0 hard cold start

[EvQdeadhed]

Mercruiser 3.0 hard cold starting getting worse now won't start, when it DOES start it will re start super easy but if sits for 15 min it hard starts again. Adjusted choke, no change. Noticed milky oil but not a big change in oil level. Oil slightly smells of gasoline but not positive it's not water. Would a leaking intake hold water in cylinder making for hard start or is this maybe a carb issue?

 

[Eric 3.7LX Alpha 1]

A faulty mechanical fuel pump can leak gas into the oil. Pull the clear hose that runs from the fuel pump to the carb and see if any gas is in it. Should be dry, if the diaphragm in the pump fails it's suppose to divert the fuel that would have leaked in the bilge into the carb instead.

 

[Bondo]

Mercruiser 3.0 hard cold starting getting worse now won't start, when it DOES start it will re start super easy but if sits for 15 min it hard starts again. Adjusted choke, no change. Noticed milky oil but not a big change in oil level. Oil slightly smells of gasoline but not positive it's not water. Would a leaking intake hold water in cylinder making for hard start or is this maybe a carb issue?

Ayuh,..... Welcome Aboard,..... Does it crank over on the starter, 'n not start,..??
Or not crank at all,..??

 

[EvQdeadhed]

Ayuh,..... Welcome Aboard,..... Does it crank over on the starter, 'n not start,..??
Or not crank at all,..??

It cranks

 

[EvQdeadhed]

A faulty mechanical fuel pump can leak gas into the oil. Pull the clear hose that runs from the fuel pump to the carb and see if any gas is in it. Should be dry, if the diaphragm in the pump fails it's suppose to divert the fuel that would have leaked in the bilge into the carb instead.

I will check this. But I have another question. Will fuel cause the oil to be milky? Or just water? Is it possible I have multiple issues? A carb issue and a water intrusion?

 

[EvQdeadhed]

It cranks, it SORT OF seems like a fairly slow crank but not terrible

 

[EvQdeadhed]

It cranks

?

 

[alldodge]

Slow crank can be: weak battery, corroded Bat cables, starter or motor bearings are seizing after water intrusion

Gas in the oil will not make it milky, only water will do that

 

[EvQdeadhed]

I will check this. But I have another question. Will fuel cause the oil to be milky? Or just water? Is it possible I have multiple issues? A carb issue and a water intrusion?

So you're saying the fuel can make its way up to the carb through clear hose then drip down through intake into cylinder therefore into oil? Can a faulty fuel pump cause hard cold starts, and almost perfect running engine when it is running? Because when it starts, it idles fine around 850 and runs fine. The water in oil is a whole other issue but I'm wondering if something happened during a starting attempt that could have blown the head gasket. I do see a very tiny bit of what looks like air bubbling out where manifold meets head. In one spot

 

[alldodge]

We don't know which 3.0 you have do to no serial number, or even a year.

 

[EvQdeadhed]

Slow crank can be: weak battery, corroded Bat cables, starter or motor bearings are seizing after water intrusion

Gas in the oil will not make it milky, only water will do that

Slow crank can be: weak battery, corroded Bat cables, starter or motor bearings are seizing after water intrusion

Gas in the oil will not make it milky, only water will do that

Any thoughts on my very hard cold starts? If I got her running it would idle fine and run good at high rpm. If I shut it off and re started in within 10 minutes it would start right up but if It sat just a bit longer like 20 or 30 minutes, it would hard start. I take this as either fuel or water dripping back down maybe? Remember I also have water in oil

 

[EvQdeadhed]

We don't know which 3.0 you have do to no serial number, or even a year.

2000 merc 3.0 ser. OF371405

 

[Bondo]

Any thoughts on my very hard cold starts? If I got her running it would idle fine and run good at high rpm. If I shut it off and re started in within 10 minutes it would start right up but if It sat just a bit longer like 20 or 30 minutes, it would hard start. I take this as either fuel or water dripping back down maybe? Remember I also have water in oil

Ayuh,.... What color are the spark plugs,..??

 

[EvQdeadhed]

Ayuh,.... What color are the spark plugs,..??

Plugs are very light black they don't look horrible

 

[Bondo]

Plugs are very light black they don't look horrible

If the fuel pump was dumpin' gas down the intake, I'd think they'd be blacker, 'n 'ell,.....

Are you advancin' the throttle when yer tryin' to start it,..??
It's carbed, not Efi,.....

 

[alldodge]

The serial number doesn't add up with a 2000 motor, shows 90 to 95

So far as hard starts, you say it cranks slow, so see above comments
Might also have incorrect timing

 

[EvQdeadhed]

Plugs are very light black they don't look horrible .. th

If the fuel pump was dumpin' gas down the intake, I'd think they'd be blacker, 'n 'ell,.....

Are you advancin' the throttle when yer tryin' to start it,..??
It's carbed, not Efi,.....

Yes . And choke is adjusted and working properly. The hard cold starting got progressively worse over last 30 days but again. It runs tip top when running.and idles fine. 20 minutes after shutting it down it hard starts again. I'm concerned about the milky oil for obvious reasons but also I always checked oil BEFORE cranking and it looked clean.i believe because the water settle to bottom and therefore showing me a clean stick. It wasn't until this week when I checked oil AFTER cranking and noticed milky. So I worry I have been running it that way all season. It also smells like gasoline.

 

[EvQdeadhed]

The serial number doesn't add up with a 2000 motor, shows 90 to 95

So far as hard starts, you say it cranks slow, so see above comments
Might also have incorrect timing

That's interesting ok . But regarding timing, it runs great and idles fine when running

 

[EvQdeadhed]

So after looking today, it does appear that the clear hose from fuel pump to carb was wet. I'm currently unable to start it Because I'm charging battery. But this could be why fuel in oil. Also after pulling the manifold riser the gasket looked bad there was some rust where it shouldn't be and the manifold had good amount water in it. I think the manifold is cause of water in oil and my hard cold starts. Any input is appreciated

 

[Eric 3.7LX Alpha 1]

So after looking today, it does appear that the clear hose from fuel pump to carb was wet. I'm currently unable to start it Because I'm charging battery. But this could be why fuel in oil. Also after pulling the manifold riser the gasket looked bad there was some rust where it shouldn't be and the manifold had good amount water in it. I think the manifold is cause of water in oil and my hard cold starts. Any input is appreciated

The back side of the fuel pump has an arm that is operated by a lobe on the camshaft. If the diaphragm fails gas can enter the oil from the back side of the fuel pump. That clear hose is on the back side(engine side) of the diaphragm. As a test, pull the hose off the fuel pump and fire it up, if gas leaks out that nipple, the diaphragm is shot. A leaking welch plug in the carb draining the fuel bowl after sitting for a while and bad fuel pump could cause your problems. The old rubber components in a fuel system weren't designed for ethanol.