1990 Merc 4.3 fuel pours in carb after killing motor

[jeepin]

I have a 1990 4.3L that developed a fuel problem over the winter. It ran fine for 5 years, then last year upon startup fuel continued to pour into the top of the carb after turning the motor off. I replaced the float and adjusted in the carb with no results. In an unrelated story the motor had to be replaced and the same problem was present with the new motor. There is no fuel visible in the clear tube coming from the fuel pump. Any ideas? I was thinking possibly excessive fuel pressure.

 

[wca_tim]

Re: 1990 Merc 4.3 fuel pours in carb after killing motor

electrical of mechanical fuel pump?

which carb?

buy a cheap fuel pressure gauge and mount it in the line right before the carb so you know...

If the fuel pressure is in spec, replace the needle valve(s) in the carb...

I would bet you'll be trying another fuel pump...

oh, and change the oil...

Hopefully this is helpful.

 

[Bondo]

Re: 1990 Merc 4.3 fuel pours in carb after killing motor

I replaced the float and adjusted in the carb with no results.

Ayuh,.....

Totally Rebuilding the Carb would be Better.....
Did you replace the needle,+ seat,..??

 

[wca_tim]

Re: 1990 Merc 4.3 fuel pours in carb after killing motor

duh on which fuel pump... clear tube... sorry...

 

[jeepin]

Re: 1990 Merc 4.3 fuel pours in carb after killing motor

Thanks for the ideas, I replaced the needle and seat a few years ago. The oil is new in the motor. I am leaning towards the fuel pump as it is 18 years old. I was told if the fuel pump failed you would notice it in the clear tube, but nothing as of yet.

 

[Bondo]

Re: 1990 Merc 4.3 fuel pours in carb after killing motor

Ayuh,...

It sounds like you have a Carb Issue,.....

The Mechanical Fuelpump stops when the motor stops,...
There's No Way it can keep pumping with the motor Off....

Once Again,......
Did you Rebuild the Carb,..?? Or, Just replace a couple of parts, a Couple Years ago,..??

 

[CharlieB]

Re: 1990 Merc 4.3 fuel pours in carb after killing motor

Either it is time to replace the needle and seat again or there is something in there holding the needle OFF the seat causing the flooding. Either way that carb comes off and apart.

The recommendation to change the oil is valid as often flooding will result in oil dilution with fuel, not only reducing lubrication properties but creating an EXPLOSION HAZARD.

Pull the dipstick and SMELL it, wipe it with a clean rag, place it in a zip lock bag, take it away and smell it again when you are certain that your nose is long clear of all gasoline vapor. We get 'accustomed' to slight odor too rapidly and become unable to detect trace amount of an odor.

 

[jeepin]

Re: 1990 Merc 4.3 fuel pours in carb after killing motor

I will replace the needle and seat again, and check the float level. The boat has only been run once since the new motor was installed. I have not been motivated to fix it as it is paid for and with the price of gas... Thanks all!

 

[Maclin]

Re: 1990 Merc 4.3 fuel pours in carb after killing motor

A bad mechanical fuel pump will not cause a carb overflow.

With the way it is now, every time you turn the engine over it will waste gasoline. And letting it sit like that can do harm to the engine, you must change the oil right away anyway, so while you are in there just pull the carb after and have a look-see.

Seems like gasoline being wasted by dumping it into the engine thru a carb that needs work is MORE motivation with the price per gallon what it is, I'm just sayin'....

 

[jeepin]

Re: 1990 Merc 4.3 fuel pours in carb after killing motor

Ok, this is a really old post, but the solution was to readjust the float in the carb. I resolved the problem.