running out off fuel.

[70challengerrt]

After about 6 miles the car runs out of fuel. If I pull over and wait a couple of minutes its good for about a 1/2 mile and is like this till I shut the car down for a while . I have a new mechanical fuel pump from carquest, the fuel lines were blown though with compressed air, the tank was cleaned, the carb was swapped to make sure it was not a bad carb, and this only happens a 2000 rpms or above. It will sit and idle all day long. All I can figure is the fuel pump is junk and the bowls run empty or the cam lobe that runs the pump is rounded off. Do you guys think I should switch to a electric fuel pump? I did not check fuel pressure.

[Bullitt-]

any chance you have the vapor lines plugged off? if there is no vent to the tank you create a vacuum & "run out of gas"

[70challengerrt]

Its the same with the gas cap off.

[Bullitt-]

Then thats  not the problem. how about clogged filter or pickup screen, I would think you would not bet 6 miles if pump was the issue. Does this jus thappen when the engine is HOT?

[70challengerrt]

new fuel filter with clear lense. Yeah only when its warm, Thats the only reason I go 6 miles is the car was cold starting out. I was just thinking that the pump couldn't keep up but thats a good point that I wouldn't make it that far in the first place. By the was 6 miles is a long ride home pulling over every 1/2 mile to let the fuel system build up. I did pull the fuel line further away from the block to see if thats the problem. The fuel line is metal up to valve cover hieght then I switched to rubber hose.

[Bullitt-]

I was thinking of vapor lock as a possability but 6 miles probably would not build up enough heat for that. Are you absolutely sure it's not electical. I've seen lot's of posts running down grimlins in the ignition systems that are very temp. sensitive.   

[70challengerrt]

Im pretty sure it not electrical because after it sputters I let off the gas and it back fires a like its running lean. I was just outside looking at it and and I was wondering if the vented gas cap is junk? When I ran it with out the gas cap was for another problem which was electrical and I never thought of pulling it off when I pulled over. I will have to give it a try tomarro.

[Bullitt-]

Good luck & let me know what you find. 

[ShelbyDogg]

To check for vapor lock, when it happens, pull over right away and shut everything off.  Are you running a Holley 4BBL? Have a paint can plastic top with you and remove the air cleaner.   Pull off one of the front-lower bowl screws while holding the paint cap under it to catch any fuel spilling out. See if anything comes out. 
If you have vapor lock, not much will come out. 
Change your needle and seat and check your float level before continuing. (VITON RUBBER NEEDLES STICK CLOSED)

If it's vapor lock. Install Fuel lines and vapor separator that the 440-6 and Hemis used.
 Run a new 3/8" fuel line and a 1/4" return line, get a new 3/8 pickup and sock (has the return line fitting), Install the fuel filter that has the 3 connections on it.  1 for fuel in, 1 for fuel to the carbs,1 tiny one for the return line.  Install the HIPO fuel pump that 440 and Hemis use. It'll have screws showing all the way around the base. (Carter, Holley, etc.) That'll fix it.  Whe you order your fuel lines, get the set of clamps to hold them to the car. This way, fuel always circulates through the lines and doesn't "sit" next to the exhaust.

This is the same thing you can do if you run out of fuel while jumping on it.
I've had both problems.
Rob

[ShelbyDogg]

I was thinking about Bullitt99's post too.  He could be right about the electrical problems.  Do the check fuel thing that I suggested but then check for a good strong 8 cylinder spark at the coil wire. If that pickup in your distro is heat sensitive, the pickup coil could be breaking down after it gets really hot during your 6 mile trip. Has your ECU been changed?   Your comment about the backfire, grabbed my attention.

Rob

[fishn4cuda]

I've had a similiar problem and it turned out to be someone reversed the wires on the coil. Once the coil got hot the engine would stumble and die as if it was running out of gas. If you let it cool down 15 - 20 min it would start right up and I could barely make it home before it would start to stumble again.

[rallyechall]

You did not mention if you have a fuel regulator in your system. If so, it may e too small for the demand of your motor. i have run into this, but it really only happened at speed as opposed to mileage. How fast is the car running when you have this issue? Mine was about 65-70 mph. I removed the regulator and all was well.

[MEK-Dangerfield]

I've had more fuel related problems than any of you care to hear about.    Let me give you two possibilities. #1 is the pushrod for your fuel pump could be worn. I would be fine at start up, fuel pressure-wise, but if I got on it after it was warm, my pressure would drop like a rock. My pushrod was worn 1/4 inch, so apparently, most of the gas is pumped in the last little movement of the pushrod. #2 could be that the previous owner was an idiot. Check out your complete fuel lines. Someone apparently had a tough time installing mine, so they cut the line in half and used a rubber hose to splice it together. Needless to say, after a few decades, a nice little crack developed on top of said rubber hose, so my fuel pump was sucking in air too.  Are your rubber hoses fine up front? How about the one connecting the sending unit to the solid fuel line? All clamps tight on them?

  Mike

[70challengerrt]

Ok here we go. I took apart the fuel filter (its the clear one that you can replace the element) and there is a tube with holes crossed drilled in it. In the holes were some debris blocking more than half the holes. So I cleaned them out and it ran better but still runs out of fuel when running it hard. So I started looking closer at the metal lines and took of all the support brakets that hold it up. Under one of the brakets the line was smashed almost flat. I spliced in a new line and now it runs good. The previous owner must of had problems fitting the line under the bracket and gave it a little help with a 2# hammer . Thanks for all the ideas and the advice once again its nice to have guys to bounce ideas and problems off of.
Thanks
Todd
           

[Bullitt-]

Glad to hear you have found the solution. Who would have guessed?
Thanks for letting us know the results.
Amaizing how often the solution to these problems are so simple.