1972 Carburetor Advice

[rfitzpatrick]

I recently started up my engine after rebuilding the carburetor and I'm having some issues. When starting up the engine, I started to have a lot of white smoke come from the tai pipe. This normally indicates a head gasket, but I never had this issue prior to rebuilding the carb so I'm hoping it has something to do with the carb before I start doing anything else.

Someone indicated that the carb might be overfilling with fuel, so I referenced the manual as I did when I rebuilt it. I have a 1972 FJ40 and the engine manual shows a few different carburetors. Mine was the FJ, FA one in the manual as indicated by the discharge weight. The other thing to note here is that the manual says to adjust the float to be 4.1mm in the open position, so that's what I did. Another thing to note is that both of my venturies look identical, whereas the manual shows different venturies for the primary and secondary.

If the carb is overfilling and causing this issue, then I assume I need to address the float. Seeing as how I have it set to the spec in the manual, any advice on where to go from here would be appreciated. Also, what about the venturies?

 

[bhsdriller]

Where's the fuel level in the sight glass window, should be about half

 

[charliemeyer007]

My 72 came with a 2 bbl Rochester so I can't really with your oem. The needle valve could be leaking because of crud in the seat or it isn't adjusted correctly, bad/damaged valve. Too high a fuel pressure might cause a good one to leak.

 

[rfitzpatrick]

Where's the fuel level in the sight glass window, should be about half

Oops, I thought I attached that image. I'll have to find the right one in all my pictures or get a new one, but if memory serves it was more than half full

 

[rfitzpatrick]

Also of note is that I installed a new OEM fuel pump. Could it be pumping too much fuel into the carb?

 

[Skreddy]

I think you’re getting float measurements mixed. Float should be 4.1mm from carb top in closed position. Should be a gap between float tab and needle of 1mm in open position.
@rfitzpatrick

 

[charliemeyer007]

+1 for the issue is likely float adjustment 1/2 way up should be the max on flat ground.

 

[65swb45]

Put your hand over the tailpipe for a second, then put it to your nose. Does it smell like gas, antifreeze, or burning oil?

 

[rfitzpatrick]

Put your hand over the tailpipe for a second, then put it to your nose. Does it smell like gas, antifreeze, or burning oil?

We held a rag by it and it smelled like gas

 

[rfitzpatrick]

I think you’re getting float measurements mixed. Float should be 4.1mm from carb top in closed position. Should be a gap between float tab and needle of 1mm in open position.
@rfitzpatrick

Maybe I mixed up my explanation but I set it to 4.1mm as in the image in my first post

 

[Skreddy]

The pic in lower left of the FSM image? So for that, you had the top of the carb off and flipped it upside down for the measurement?
Something to try if you pull the top again: when I set the float height I’ll blow into the fuel inlet hole while I move the float up and down to ensure it’s cutting air flow (fuel) when it seems like it should. Then you know the valve is working. Side benefit is you may get a taste of some carb cleaner on your lips and that’s a great excuse for another beer to wash it out.

 

[liko]

Following marks train of thought....
1. Smell exhaust
2. Smells like gas
3. Check your oil, might smell like gas also...fuel pump leak?
4. You say it's new? It can still happen. check the diaphragm.
5. Maybe just need an oil change. Smell your oil.

 

[rfitzpatrick]

The pic in lower left of the FSM image? So for that, you had the top of the carb off and flipped it upside down for the measurement?
Something to try if you pull the top again: when I set the float height I’ll blow into the fuel inlet hole while I move the float up and down to ensure it’s cutting air flow (fuel) when it seems like it should. Then you know the valve is working. Side benefit is you may get a taste of some carb cleaner on your lips and that’s a great excuse for another beer to wash it out.

Yes. I had the entire carb apart for a rebuild. When looking at the FSM, I saw this measurement and took note of it because my float was set much differently when I took it apart. I wish I would have measured what it used to be before making the adjustment to 4.1mm.

I'll pry take the top off again to double check the float measurement and make adjustments. I appreciate the tip of blowing into the inlet hole. I'll give that a try also.

 

[rfitzpatrick]

Following marks train of thought....
1. Smell exhaust
2. Smells like gas
3. Check your oil, might smell like gas also...fuel pump leak?
4. You say it's new? It can still happen. check the diaphragm.
5. Maybe just need an oil change. Smell your oil.

I held a rag over/near the exhaust. It spits out some black liquid that smelled like gas

I checked the oil and it looked good, but I'll smell it to see if I can smell any hint of gas

 

[rfitzpatrick]

@65swb45 I'm curious if you have any more thoughts about this issue. I left you a message about a possible rebuild or if you had any carbs for my 72.

I tried running the engine last weekend again, but this time I couldn't even get it to start. Fuel was about 2/3 of the way up the sight glass after cranking it a few times.