Not getting fuel

Okay, so it is a 1974 Chevy 3/4 ton, 4x4. It has a 454 with the dual tanks. Fuel filters are all clean.

So anyways, I will be driving along (usually happens on the freeway) and it will start to hesitate like it was running out of gas, then it would be fine. The other day, I was getting off the freeway (60 miles from home) and sitting at a traffic light and it starts hesitaing, and trying to cut out. I get about a block and it dies. I check the lines and no fuel is going into the carburator, and everything is dry. So I change the fuel pump right there (luckily another Chevy was driving by :evillol: and helped me go get one). After that, it runs great driving around town for the weekend. I then head back home on the freeway (60 mile drive) and when I get about 10 miles from home, it starts hesitating again and I have to pull over, and it starts running great again.

Got any ideas???

there is a inline filter in the carbuerator, right where the fuel line flare nut screws in. You have the symtoms of something constricting fuel flow. Unlike today's fuel pump's that produce 60-70 psi. yours is mechanical and puts out a whole 12 psi. So just check out that inline filter, if that isn't problem go ahead and trash can the truck. J/K

You have a dual tank system with a switch located next to the ashtray, correct?

If this is the case, the dual selector valve is at fault and is located on the passenger side on a cross member, if memory serves me correctly. Years ago there was a kit to rebuild these. I had the same problem on my '78 dually and I know the frustrations involved. The valve ends up sticking and drawing from both tanks. When one gets empty, or close, the pump will suck air. I lived with the problem for awhile by keeping both tanks at least half full. You can try that for awhile to see if the problem goes away, if it does, then check the selector valve.

Skipr, I unhooked the line from the carburator and there was still no fuel coming out, no matter where I unhooked it at. The fuel is not even getting to the carborator.

Mikado14, I had that selector thing replaced about a month ago, along with all the fuel lines. I also had both tanks almost completly full (one full and the other down about 2-4 gallons.

There is a fuel filter (with a clear surround so you can see in) about 4 inches down the line from the carb. When it quit running all together, there wasn't a drop of fuel in there (while turning the engine over).

Thanks for the Replies!!!!

Damm , you got an odd problem then . just for the hell of it, disconnect line at the double input, single output valve. And hook up a straight through line (bypass valve) and see what happens. I'm curious to find out what the cause is , keep us informed

Where is this double input valve at?

I'm sorry thats a fancy way of saying the tank selector valve. Under passenger side bolted to frame. Probally just just behind cab.Two tank lines that can alternate to a single out going line, which goes to engine.

oh ya. I've always just called it a tank selector valve/selanoid. I've already replaced that...Is it possible it went bad already?

I would bypass it with a tee and let it suck off both tanks and see if that is the problem.

Okay, well I think it was just vapor lock, or whatever it is called. At least that is what others are telling me from there experiences with these same circumstances.

Okay, well I think it was just vapor lock, or whatever it is called. At least that is what others are telling me from there experiences with these same circumstances.


That actually happens? I thought it was just a word, but doesn't really exist...like "the riot act" has anybody ever seen this at all? Or "it was just a weather ballon".

Do you happen to know exactly what it means? What exactly is going on inside those tanks?

Theoreticaly it is vapors from petro disstalate rise in pressure due to heat, occurs in fuel lines when too close to heat source. I just hav never seen or known anyone to acutally have this happen. Now I can say I do. What did u do to cure problem? Do you live in high altitude?

Do you happen to know exactly what it means? What exactly is going on inside those tanks?

vapor lock is usually from running your fuel lines where there's alot of heat. the heat causes the fuel to, well vaporize, inside the line. to cure this you could wrap the lines in that heat resistant tape they use to wrap the headers with. most autozones and pepboys carry this stuff.

Okay, My fuel lines run up throught the frame, and the headers are pretty close--which must be what's causeing it.

Nope, don't live at high altitudes or anything.

Guess I'll have to go wrap them up then.

You have never said, is there a fuel tank selector?
Have you tried removing the line at the pump and blowing air back into the tank? Select the other tank on the switch and repeat? At least this will verify that the selector is working.

One other thing, on the year truck you have, I believe that the fuel caps are vented. Have you changed your fuel caps? When it does this, have you tried removing the cap and seeing if it will then run?

yes I do have a fuel tank selector. I'm pretty sure it does work, even though my guage does not work. It is working fine right now, but I have not gone on any long drives since this incident.

How would blowing in the lines show which tank it is switched to. Would I have to have someone listen for the air going into the tank?

Ya, someone did mention the fuel caps. The ones that are on there are not vented. They simply scew on until they are tight (not the kind that you have to line up and then only turn a 1/4 turn or whatever; or the kind that click and don't tighten anymore at a certain point; They just screw down until they are completely sealed.)

Thanks for the help so far everyone!!!!

Hey, another thing. Like I said, my gauge jumps around, no matter which tank I am running off of. Now, what are the chances that both fuel sending units have gone bad?? Could it be in the wireing or something else? If so, which wires should I take a look at?

the gauge in this is totally seperate from the pump and I don't Think there is any corrilation with this problem. The pump is mechanical on the passenger side of the block as you know. This leads me to think that there is probably not any relationship between the two problems, although I have seen stranger.

yes I do have a fuel tank selector. I'm pretty sure it does work, even though my guage does not work. It is working fine right now, but I have not gone on any long drives since this incident.

How would blowing in the lines show which tank it is switched to. Would I have to have someone listen for the air going into the tank?

Ya, someone did mention the fuel caps. The ones that are on there are not vented. They simply scew on until they are tight (not the kind that you have to line up and then only turn a 1/4 turn or whatever; or the kind that click and don't tighten anymore at a certain point; They just screw down until they are completely sealed.)

Thanks for the help so far everyone!!!!

Yes, you would have to have someone listen at the fuel filler on each tank, and listen to both to be sure that it is not bleeding into the other tank when it is not selected.

On a mechanical fuel pump, the tank needs to be vented. Either through the cap or a charcoal canister on a '73. I think, and this is pulling it from my feeble memory, that a '73 was vented caps only. And at the time was Regular fuel only, you remember, the leaded kind.