Hi, all. first off, i wanted to say that i have been a long time lurker of this forum and have found it extremely helpful. that aside, its come to the point where i finally have not found what i was looking for and thought that id ask. i have a 1978 f100 with 300 i6, one fuel tank. aft axle 19 gallon with r/o valve. i dropped the tank over the weekend to clean the sending unit and install a new float, and while unhooking lines, i broke the valve stem for the roll over valve. i was told to just cap the line going to the valve off and id be just fine, so that's what i did. after i got the tank back up and a few gallons in her, i drove her around the yard for a bit and she ran great. went in, took a shower, and went out to get some gas, and when i switched the truck off at the pump, it almost acted like it was running off of compression. what was actually going on, was the carb was gushing fuel and smoke, and i believe that the engine was running off of that. knocked off all vacuum lines and had white smoke from the tailpipe for around five minutes after engine finally stopped running. uncapped the line at the back of the truck, and after repriming the fuel lines she ran great. would having that line capped likely be the cause of my problem? if so is there something i can do until i can find a new rollover valve? thanks in advance to anybody who can help.

 

First off, welcome to FTE, the best Forum on the Web! You will collect TONS of information here, and learn even more! Don't be afraid to ask questions...also look up your local Chapter for guys in your area that may be near by...

As for your question...


You can buy one from LMC...www.lmctruck.com


Question 1: Was it hooked up to the charcoal filter canisters in the engine bay?
Question 2: What type of Fuel Cap do you have on your filler tube? Vented or Non-vented

You can either put a vented cap on your truck, or (not the best option) run it without the cap...what the valve does is vents the vapors out of the tank, it used to be hooked into the charcoal canister in the engine bay, which vented into the breather (if I am not mistaken), to help in the venting and dispersion of gas fumes...

Hope that helps some, and I'm sure others will chime in to help as well...

 

roll over valve? No roll over valve that I know of in our years. If you are meaning item 32 in the pic that is the fuel selector valve.

Which nipple did you beak?

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It's Item #4...usually called a rollover valve, but in LMC it is called the vent valve...

 

I thought that was a vent line.... go figure! It has a check valve iirc. Aren't rollover valves to shut off electric fuel pumps?

 

Yup. It was part number four. That tells me my vacuum routing is waaaaay off. I think the canister was hooked up to the carburetor. Perhaps the fuel gushing was an internal problem with the Carb?

 

Excuse my ignorance, but what is irrc?

 

If I remember correctly. spelled wrong....

 

Yeah. It hit me about 45 seconds after I posted. Total derp moment

 

From a similar post (line routing):

https://www.ford-trucks.com/forums/1...-say-what.html

Here's some pics that member 76f350spercamprspeal posted:

Ford Truck Enthusiasts Forums - View Single Post - Buying New Gas Tank - Evaporative Emissions Control... say what?

That might help with checking your routing. With that vent nipple broken I would avoid filling the tank full till you replace it.

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thanks for the links! for now, i think as soon as soon as i get time, i will look up the vacuum routing and fix that removing the evaporative emission control. and pick up a vented cap.