My father and I started a father/son project truck last year. The truck was originally a 1979 F 100 Flareside 2wd and we placed the body on a 1977 F150 4wd frame after his truck was wrecked. We left the stock 351M engine and the trans in the rolling 4wd frame. My father passed away in January and I am trying to get the truck running and on the road again. After sitting since October, I had to replace the fuel pump and the truck started and ran fine. I moved the truck across the yard and it began to overload(?). Fuel began coming out of the two vent tubes near the choke flap. Can someone please give me some advice on what to checkto resolve this problem? Thanks in advance.




















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Sorry for your loss. As for the carburetor, if fuel comes out of the vents, that means the needle is stuck open. This happens when varnish or debris builds up in the seat, and the float can't shut it off. The inside of the fuel bowl works a lot like a toilet, except there's a needle and seat instead of a flapper.

 

Your best bet is to rebuild the carb , but a couple of lite taps may break it loose.

 

Sorry for your loss..my condolences

Put some "sea foam" cleaner in the tank...it will help it out.

 

Sorry for your loss.

I recently rebuilt my carb and it did the same thing. Make sure when you adjust your float in your carb that you pay close attention to the measurments the rebuild kit will give you. I was told by some people that because of the gas we are running now that you might have to adjust your floats to a different level. Probably the best thing you could do is call a Carb Rebuilder and ask them about proper float levels. When mine did it I just took the top off the carb and re-adjusted the floats and havent had an issue since. This is all based on if your working on a Motorcraft 2100 or equivilent.

Good Luck,
JRB65

 

Not trying to sling you guys out, but...

I should have been more clear. If there's debris in the seat, it needs to physically removed. And if the carburetor has gotten dirty enough such that debris is in the seat, I recommend the entire carburetor is rebuilt in the first place. Seafoam is not going to solve this problem.

That's not true. All the float has to do is manage the volume of fuel in the bowl. Set the float height to whatever the sheet in the rebuild kit says and be done with it.

Folks, this is an age-old, simple problem. It has nothing to do with modern fuel blends or Seafoam. No need to complicate the solution with off-the-wall hypotheses.

 

I would like to thank you guys for the condolences and the information. The 2100 series carb was rebuilt in September last year, although it has been sitting for a few months. I will check the needle for sticking and debris first. Then if I can locate the information that came with the rebuild kit I will check the float adjustment. Thank you guys. I hope to document any work I do to the truck on the forums.

 

I never said my post was the complete solution...I said it will "Help" prob does need to get the carb cleaned and floats/seats checked.

 

FMC400,
All I can do is tell what happened to mine after I rebuilt it. I adjusted the float to what was indicated in the instructions and I had Fuel pouring out the top of my Carb. I ended up taking the top off and very slightly moving the float down and it quit pouring over the top. So when I had heard that the new gas had a different Dencity causing the float to not register the same (That being the reason for adjusting the float different) it made sense. Have a great day...

JRB65

 

Thank you all for the information. The problem seemed to be the float was 1/4" to high. I bought a rebuild kit and rebuilt the carb, now my only issue is adjusting the choke properly. Does anyone have a detailed set of steps for properly adjusting the choke? The instructions that came with the kit are vague and lacking a lot of detail for a carb newbie. Thanks in advance.

 

Here's a post of mine from a while back about setting up the choke and the fast idle; let me know if this helps.

https://www.ford-trucks.com/forums/7...ml#post6422219

Also, some helpful info about the choke in general:

https://www.ford-trucks.com/forums/8...ml#post6939116

 

Nice !! Thanks for that

 

Thanks for the info fmc400. It made the whole process easy and painless. The only problem is the choke still isn't operational. The choke hasn't been operational since day one and Dad had it wired open. I removed the choke cap to ensure that the spring was locked into the fork and it was. The line from the choke stove (I am not sure if that is the appropriate term or not) runs to the back side of the carb into a fitting that appears to draw fresh air from the air cleaner. I am not sure if that is correct or not. The steel line that exits the choke stove and goes to the choke cap appears to be only halfway inserted into the stove itself. I'm not sure if that is having any effect on the choke or not. I have sprayed the steel line with WD 40 while the engine was running and I did not see any signs of bubbling but that probably will not reveal an issue being and no air or pressure is being forced through the lines.
I also have read where the EGR should be connected to a ported vacuum switch. The EGR is currently connected to a small port on the rear of the carb. I have a vacuum diagram for a 77 351M but I cannot make heads or tails of it being as most of the switches and emission related items have been removed. Can someone please point me in the right direction?
Thanks again! You guys are awesome!

 

When you say the choke is not operational, does that mean it's getting heat, but does not open? Or it's not getting heat at all?

What you've read about the EGR valve being connected to a ported vacuum switch is correct. It must not be connected directly to the carburetor because it must not come on until the engine reaches operating temperature. In the most basic setup, one side of a 2-port PVS should be connected to a ported vacuum source on the carburetor. The other side of the PVS should run to the EGR valve.

 

Thanks for the reply. I am not sure if the choke thermostat is even getting heat or not. Is there a way to test and see if heat is actually going through the choke stove? Also, Is the choke stove supposed to pull vacuum from some source or does it just receive a fresh air source? It is currently connected to a port behind the choke flap in the flat plat that just pulls fresh air through it. I know I may sound like an idiot but, what is a PVS? Could the EGR be connected to the second nipple on the PCV? Thanks again for the help fmc400.