a carburetor shouldn't spill fuel like this, right?

[ShoalSurvivor]

recently purchased and installed a Carter AFB-4.3L-Marine-Electric Remanufactured 4 Barrel 4.3L Marine Carburetor - Electric Choke. Same model, installed easy.

I have been diagnosing fuel supply and bypassed the oil pressure sensor to test the fuel pump.
This is what I'm seeing at the carburetor with the ignition on, without starting:
View attachment IMG_6399.MOV
I would expect the float and valve to stop that flow and suspect a problem with this carb.
Is this expected?

thank you!

 

[Scott06]

No you either have too much fuel
Pressure or needle seat and or float is hung up

 

[ShoalSurvivor]

No you either have too much fuel

Will a failed pump pump too much pressure?, or just not enough?
Can I rule out a fuel pump issue?

thanks!

 

[alldodge]

Unable to see the vid, but if the carb is flooding then float level is to high of needle and seat are not closing off fuel

 

[Scott Danforth]

Will a failed pump pump too much pressure?, or just not enough?
Can I rule out a fuel pump issue?

thanks!

usually failed pump means not enough pressure or no pressure

 

[Scott06]

Will a failed pump pump too much pressure?, or just not enough?
Can I rule out a fuel pump issue?

thanks!

Seen them both ways. i would suspect taking the top off carb and looking through the needles and seats and floats will find your issue, but on the offhand you have to much fuel pressure it can also over come he float . Did u have yhe same issue with old carb?

 

[nola mike]

Also, you're miswired somewhere. Your fuel pump shouldn't run with the engine off. This is exactly why...

 

[ShoalSurvivor]

Also, you're miswired somewhere. Your fuel pump shouldn't run with the engine off. This is exactly why...

I bypassed the oil pressure switch and the fuel pump runs with the ignition on, before starting

 

[nola mike]

I bypassed the oil pressure switch and the fuel pump runs with the ignition on, before starting

Hopefully only for testing, and hopefully you can see why it's a bad idea to do that.

 

[ShoalSurvivor]

Seen them both ways. i would suspect taking the top off carb and looking through the needles and seats and floats will find your issue, but on the offhand you have to much fuel pressure it can also over come he float . Did u have yhe same issue with old carb?

Come to think of it, I may have had the same issue. This is where the problem started. I will check the fuel pressure tomorrow.

I just bought the carb, and don't want to break into it if it is not working - I'd rather return it. I did remove the inlet covers on top to expose the metering rod. the good side moved freely, the leaking side metering rod was stiff and stuck in. I tried to free it, them replaced the covers and it still leaked fuel.

thanks.

 

[Scott06]

Come to think of it, I may have had the same issue. This is where the problem started. I will check the fuel pressure tomorrow.

I just bought the carb, and don't want to break into it if it is not working - I'd rather return it. I did remove the inlet covers on top to expose the metering rod. the good side moved freely, the leaking side metering rod was stiff and stuck in. I tried to free it, them replaced the covers and it still leaked fuel.

thanks.

You can use a simple fuel pressure gauge, oftentimes places like autozone will rent them to you .

Biggest issue you will have to rig up a T to test it. Merc makes a test fitting but it is a little salty for one time use ...

Fuel line is 3/8" double flare fitting, probably rig up a fitting to go to hose and T the fuel pressure tester in. Need 6 psi max, typically 4-6 psi is good.

Also worth checking that the fuel is not contaminated. Take your fuel filter off dump the contents in a clear container. If there is crud in there could keep needle and seat from sealing on both carbs.

Bottom line spend a little time diagnosing what's going on with fuel quality and supply pressure. If those two are good send the carb back.

 

[ShoalSurvivor]

Fuel pressure gauge was on order and just arrived.

I connected it directly to the fuel pump output (in place of the fuel tube that connects to the carb, without a Tee.
It reads over 9 when operating, and a little over 1 when disconnected. I don't know if it should zero out or if it's reading atmospheric pressure, but either way, it seems to be way too high.

I will replace the pump and try again.

My fuel is old. I don't see crud, but the color is off. There is microscopic particulate but nothing that would block a passage. I will dump this fuel and start over. Side note - can I burn this 38 gallons off in the Expedition or is that just asking for trouble?


I can't rule the carb as bad until I replace the pump and fuel.
Next....

 

[ShoalSurvivor]

Now i'm really confused!
I have an original mercruiser fuel pump. It's operating at 9-10 psi.
The aftermarket versions list 9-10 psi operating range - and are $55.
An original fuel pump is now $630.
How is it that my original is operating at the same as aftermarket specs? I cannot find there specs of the OEM pump, but a new Edelbrock 1409 carb says limit pressure to 6.5 psi.

I also just found a fuel pressure regulator - anyone have experience with one of these?

 

[jimmbo]

Deleted

 

[Scott06]

Fuel pressure gauge was on order and just arrived.

I connected it directly to the fuel pump output (in place of the fuel tube that connects to the carb, without a Tee.
It reads over 9 when operating, and a little over 1 when disconnected. I don't know if it should zero out or if it's reading atmospheric pressure, but either way, it seems to be way too high.
View attachment 382139View attachment 382140
I will replace the pump and try again.

My fuel is old. I don't see crud, but the color is off. There is microscopic particulate but nothing that would block a passage. I will dump this fuel and start over. Side note - can I burn this 38 gallons off in the Expedition or is that just asking for trouble?
View attachment 382144

I can't rule the carb as bad until I replace the pump and fuel.
Next....

That fuel looks phase separated would not use it
Attached screen shot from merc V8 manual 24 says carbed engines 3-7 psi.
airtex makes the fuel pump for merc can find them under that name , must be sure to get low pressure one…9-10 psi is too high

 

[ShoalSurvivor]

That fuel looks phase separated would not use it

that was caused by the angle and the glass jar. the fuel is consistently one color/layer, no sediment.

 

[alldodge]

Don't know which V6 other then one with a 4 bbl
Find the original fuel pump was 805656A5, is this the pump your have?

Put a couple gal of old stuff in a full tank and the truck should not have much issue, or run it in the lawn mower, but even the mower can have issues

 

[dubs283]

Is there a correct water separator filter and anti siphon valve in place?

 

[Lou C]

Other than the fact that the fuel pressure is too high for a carbed engine, it is possible that on the Edelbrock carb one of the floats can hang up against the inside of the float bowl. I recall a post on this forum about this very problem.
The Edelbrock has 2 floats one on each side. Is this happening on both sides or only 1? If only 1 I’d remove the air horn & inspect the floats.

 

[ScottinAZ]

as stated, at 9-10 psi you are likely overcoming the floats. Either different pump with less pressure, or an inline regulator to get that down to 4-7 psi would be where I would start.