7.4mpi just started running rough and with gas coming out exhaust

O

Ozshadow

Member
Jul 14, 2013
166
Lake St. Clair
Boat Info
99 Sundancer 270 wide
Engines
7.4 mpi B3
1999 7.4mpi 0L854***
270 Sundancer single engine B3
Just before I was about to pull into the marina on plane my boat started sputtering and missing like it had water in the gas. I dropped it down to about 1k. It idled in running but a little rough. It smelled rich. It wasn’t until I got to the dock that I noticed a fuel sheen from the exhaust. You could smell it.

inside the bilge is fine. The plugs were new. I have yet to pull them but they are still all connected. The water was cold. The oil is new and clear with no fuel smell.

Thoughts on what would cause this? Particularly the gas in the exhaust?

Could this be a bad cool fuel module? Is that something that can be replaced in the water at the dock? It’s a single but still difficult to reach. Gen 2 type.
 
Only way I can think of gas getting into exhaust is it wasn't burning in the cylinder. You might want to do a compression test if all the plugs looked good like you said.
 
^^^^ A+
My bet would go to a stuck injector. Been there more than once as a mechanic working on other's cars / trucks..

Usually only flooded carb (stuck float), stuck closed choke or a stuck open injector will cause an engine hyper rich condition (and strong fuel smell and a sheen)
 
Last edited:
Bill Curtis said:
^^^^ A+
My bet would go to a stuck injector. Been there more than once as a mechanic working on other's cars / trucks..

Usually only flooded carb (stuck float), stuck closed choke or a stuck open injector will cause an engine hyper rich condition (and strong fuel smell and a sheen)
Click to expand...

His engine is fuel injected though.
 
Could be as simple as a faulty engine temp sensor tell the engine it is cold even after reaching operating temp. The fuel injection will then feed extra fuel thing the engine is still cold.
 
UPDATE
I’m not sure it’s JUST an injector. It runs rough and weak. The entire starboard side plugs are fouled. I’m sure they were wet. The ceramics are black. The 4 on the other side are white. Each cylinder has its own injector in this MPI setup. Can one bad injector foul every single plug? Would this mean a bad ECM? It believe it is a MEFI2 system.
 
Last edited:
@Ozshadow did you compression test your block? I found on mine the rocker arms had come off one cylinder and it wasn’t opening the valve. This caused all the fuel from that one injector to begin to fill the plenum and eventually flood the other cylinders.
 
Is it possible you have separate fuel pressure regulators for each rail?

(and, btw, what's the "passenger side" of a boat??)
 
No, only the regulator on the cool fuel system. I copied my post from sharing it on a car forum too = passenger side.

I have not tested the compression. I’m now focused on what could impact all 4 banks even if it is confirmed one cylinder or injector could do it.
 
@Ozshadow have you checked for spark on the side of the engine you’re saying is not burning the fuel. You mentioned in a previous post I just saw that the ceramic parts of your plugs were black. Only thing I can think of that would cause that is either overspray from paint which could cause a bad connection there or oil has been leaking down on them and they have grounded out and aren’t sparking anymore or are very weak.
 
You must log in or register to reply here.

Forum statistics

Threads
113,172
Messages
1,427,833
Members
61,084
Latest member
AntonioJamm
Back
Top