Odd fuel issue? (i think)

[Workin' Rig]

Ok....

On the way to the campground friday my truck just quit. Acted like it was either flooding or starving...im thinking starving because it was not smoking....

On the way home it did the same thing but when i pulled it over i heard a hiss coming from the fuel cap,..i undid cap and a rush of air went in.

Would it cause fuel starvation if the cap was bot venting correctly? It ran fine after i popped the cap and left it loose....

Just wondering if it really was that easy or if its in my head?

The engine acts like it runs out of fuel....just kinda loses power and wont acclerate. It only seems to do it with the camper and it runs fine untill that point (usually after 20 mins or so).

Suggestions?

 

[Fellro]

If you can not get air into the tank to displace the fuel removed, it most certainly will starve for fuel. The action of drawing fuel will then create a vacuum. Once that vacuum is larger than the vacuum the fuel pump create, you will not get any fuel.

 

[Workin' Rig]

Ok...im hopeing i got the problem nailed then...i replaced the cap and il, take the camper out for a stroll one day this week to see if i fixed the problem

 

[m78]

Did you get a "vented cap " ?

 

[G.O. Stang]

Yeah as said before, you need air to displace the fuel. Otherwise you create a vacuum in the tank and it will starve the pump and engine of fuel. My truck has the evap hole on top of the tank that runs to the can in the engine bay. And that acts as a vent so my cap can seal without an issue. But without that hole, you need a vented cap or you'll run into this issue.

 

[Workin' Rig]

I got the factory replacement cap from autozone...i guess worse case scenario ill leave the cap loose when towing the camper

 

[dustybumpers]

Check the cross braces under the bed floor . Mine rusted through on my 82, and when I put the camper in, the weight would smash the floor down on the vent line. I would run out of gas with a full tank. I ran a piece of plate above the fuel tank, and cured the problem until I got a new bed

 

[Workin' Rig]

Im towing a travel trailer....my 77 is pre emission (3/4ton over 6000gvw) so i think it just vents thru the cap

 

[dustybumpers]

I misunderstood, and thought you were hauling a slide in.

Looking at rock auto, you are correct, there is no gas tank vent on your tank, it is all vented through the cap

 

[m78]

If you needed, you could vent the tank by attaching a hose to one of the ports on the tank. Run it up somewhere high and put an inline gas filter on the end of the hose.

 

[Workin' Rig]

Ok now im really stumped....

Truck was acting a little funny after a 15 min drive....went back to see if it was hissing (have new cap on mind you) didnt hear anything so i yanked the cap off and got soaked by a gas geyzer.....wtf?????

 

[m78]

Your trucks acting up because you were thinking of replacing it.

 

[Workin' Rig]

Your trucks acting up because you were thinking of replacing it.

Well it better stop or it wont take to much thinking

 

[G.O. Stang]

That sounds like the tank was pressurised. That's not a vented cap. Think of a gas can. You fill it up with gas and set it in the sun for a couple seconds. Open the cap and a bunch of vapor comes out. The gas vapor expands and needs somewhere to go. The reason for the gas geyser was because the vapor rushing out so fast, it creates a vacuum temporarily and can pull some of the liquid gas with it.

 

[Workin' Rig]

Ok...it looks like theres vent holes in the bottom....ill just leave it loose

 

[G.O. Stang]

It'd be pretty simple to swap in an emission's tank and just have a vent hose. Then you'd never have to worry about it again.

 

[smokey]

I'd just drill a small hole in the cap to act as a vent.

 

[m78]

New gas caps aren't supposed to let vapors out like the oem caps for these trucks. Thank the epa for that.
Try what Randy said, also look to see if you can connect a vent hose to the tank anywhere.

 

[Workin' Rig]

I'd just drill a small hole in the cap to act as a vent.

I didnt know i could do that without screwing the cap up....and i just put this tank in so i dont wana swap tanks again

 

[smokey]

Used to drill a small hole or two in many of the caps on the older older 60's and early 70's cars all the time.