1994 7.4L Leaks fuel

[TBarCYa]

Since you're probably the same people that would reply if I started a new thread...

I got the engine running but need it to idle on it's own so I can set the timing. What I noticed is that there's fuel dripping down the outside of the carb that I believe is coming from the inside of the flame arrestor. Having learned the hard way, I don't want to start it without the fa but I suspect that I need to rebuild the carb. Does this sound like the right direction or should I focus on the timing first? She sounds good and will run if I give it throttle but won't stay running on it's own.

 

[GA_Boater]

TBarCYa Ya got a new thread anyway. Cables aren't leaky carbs. :smile:

 

[Bt Doctur]

either that or the fuel pump has failed and is pumping into the fa

 

[Bondo]

or should I focus on the timing first?

Nope,...... Gas leak 1st,......

 

[Scott Danforth]

Fix the gas leak, or watche it all blow up.

Either the pump failed and your pump is pushing fuel up the clear hose or your needle and seat is sticking

 

[TBarCYa]

Fix the gas leak, or watche it all blow up.

I'm wondering if that's what happened with the fire the previous owner had.

Either the pump failed and your pump is pushing fuel up the clear hose or your needle and seat is sticking

Ok, so I have a question about the fuel pump.... How would a failed pump push fuel up the clear hose? Are you talking about a clear hose from the pump to the carb? I didn't take a good look at the pump because I assumed a leaky needle or a stuck float.

 

[TBarCYa]

One more question... If the pump failed and is sending fuel up the clear hose, would it also be sending fuel into the carb because the accelerator pump is definitely sending fuel when I operate the throttle so there is fuel in the carb.

 

[Maclin]

Assuming there is a Marine fuel pump installed, that clear hose is connected to a fitting on the pump that is in between the dual diaphragms (marine requires two diaphragms) inside the pump. Once the first diaphragm fails the hose gets pressurized with fuel, and the fuel leaks up the hose so to speak. That is the warning shot that the pump needs to be replaced before it fails completely and fuel goes into the block and collects in the oil. This may or may not be happening with yours.

 

[Scott Danforth]

I'm wondering if that's what happened with the fire the previous owner had.



Ok, so I have a question about the fuel pump.... How would a failed pump push fuel up the clear hose? Are you talking about a clear hose from the pump to the carb? I didn't take a good look at the pump because I assumed a leaky needle or a stuck float.

Maclin is coving you on a brief description.

the clear hose from the pump to the carb is a safety on boats. cars dont need it because they could leak fuel all day long and the chance of a fire is slim since fuel vapors are heavier than air, they go down to the road and disperse. in a boat they sit in the bilge.....any spark and boom

this is why it is not smart to use automotive parts on marine motors.

usually when the fuel pump fails, the motor just runs like crap due to the extra fuel. then the owner take a look and sees the fuel in the tube and goes to his mechanic.

 

[TBarCYa]

Yeah, I probably should have done some research before asking about the tube... The good news is that since this is the wife's project, her response was "just buy both" so I'll be replacing the pump and rebuilding the carb this week.


Here's some backstory on the boat... It may or may not be relevant so feel free to skip this part but I have to type it out so it makes sense in my head...

The previous owner had a fire which did more damage than I had thought when I bought it. By his description, the boat was still on the lift with the drive in the water and the engine running while they loaded people and stuff. After a few minutes idling, there was a BOOM which popped the doghouse open and burned his daughter. The fire ran up under the deck to the cabin where the majority of the visible damage was. I was told that a faulty fuel sender was to blame for fumes in the bilge but I cannot find any issues with the sender.

The thing that bothers me about this description is that, as i understand it, most boat fires are ignited by the starter or an electrical spark when starting the engine and this engine was running when the fire started. What also bothers me is that there is very little damage in the engine bay. The belts, blower hoses and some water hoses (not engine related water hoses) are melted but none of the wiring is melted and the foam insulation on the inside of the doghouse has soot but isn't melted.

Knowing now that there is an abundance of fuel at the carb and that a failed fuel pump could be causing this (I'm at work and can't check the clear tube yet) it would make sense that the failed pump sent fuel up the clear hose which, from what I can see, causes fuel to drip out from under the flame arrestor and onto the intake manifold. This to me sounds like a more accurate cause of the fire as it better matches the description of events.

This doesn't change anything really, but being closer to knowing what caused the fire makes me that much closer to preventing it from happening again.

 

[Robert Conway]

My bet would be on the float/needle seat, but don't rule out the pump... I went nuts with a constant idle flooding of the carb last year. Come to find out it was my fuel pump. Old school mechanical pump had increased pressure over time. When tested, I was getting 8-9 PSI at idle. The needles are only good to 5-6 PSI before fuel gets blasted past them.

 

[TBarCYa]

I was able to verify that I don't have fuel coming up the clear tube from the pump.... So I haven't ordered the pump yet. I'll be rebuilding the carb tomorrow and will see what happens after that.

I don't know if attaching the pic will work, but the arrows are pointing to where the fuel is coming from.

 

[TBarCYa]

Oh man... This was the worst carb I've ever seen. The float bowls contained what looked like sand but was very very fine.... I'm wondering if the fire suppression system actually discharged and it's the extinguisher powder that's in the carb. One float was completely stuck down (open) which explains the flooding, one metering rod was stuck and had to be removed with pliers while the other came out easily and there's what looks like calcium build up on the metering rods and under the secondary jets (where the fuel enters the venturi not the actual jet). What a mess!

The good news is that if it started with that crap it should run awesome once the carb is clean. Everything is soaking in carb dip and with some luck, I'll get it put back together after work tonight. Fingers crossed.