Carbon fouled spark plugs

[Mugsey]

Every since I replaced my fuel pump on my 1980 Mercruiser 260 I am carbon fouling spark plugs and producing black smoke from the exhaust at idle. I had an edelbrock carburator on the boat and figured it my have been the problem so I replaced it with the original Rochester carb (newly rebuilt) but the problem persist. Is the fuel pressure to high? Could it be the wrong spark plugs? I'm currently using A C delco R 44 plugs. The ignition coil ,plug wires and distributor cap as well rotor are all new. Any advice would be much appreciated.

 

[Don S]

Re: Carbon fouled spark plugs

Is the fuel pressure to high?

Get a gauge and check it, we can't tell from here.

Have you checked in the carb to see if it's flooding over from the bowl? Perhaps there is gas going thru the clear hose indicating a bad fuel pump. Is the choke opening properly?

 

[Mugsey]

Re: Carbon fouled spark plugs

Choke is working perfect, fuel pump is good. Fuel level in the carb visually looks high,can the float level being to high cause excessive fuel output at idle?

 

[Bondo]

Re: Carbon fouled spark plugs

Of Course it Can........

 

[180shabah]

Re: Carbon fouled spark plugs

...fuel pump is good....

What is the fuel pressure?????

 

[Mugsey]

Re: Carbon fouled spark plugs

Don;t have a gauge to measure the fuel pressure but it is a brand new mercruiser fuel pump

 

[Mugsey]

Re: Carbon fouled spark plugs

Like the no brainer question I posted about the float level being to high causing excessive fuel at idle please indulge me one more. Can excessive fuel pressure from the new fuel pump force the needle valve out of the seat and push the float up raising the fuel level in the bowl causing the same condition or is like unlikely? I ask because the carburator is newly rebuilt so I would assume the float level is correct.

 

[Don S]

Re: Carbon fouled spark plugs

Being NEW or NEWLY rebuilt doesn't mean it MUST work
Yes a new pump can have too high pressure.
Yes a newly rebuilt carb can have something stuck in the needle valve and not allow it to close.
Since you didn't have this problem till you replaced the fuel pump, you REALLY need to check the fuel pump pressure. Having the tools is part of repairing your own equipment.

 

[Mugsey]

Re: Carbon fouled spark plugs

Affrimative Sir! Thanks !