Need help!runs out of fuel at hiwy speeds.

[PAPA KENT]

Need some input guys,My 76 with stock 400 and carb. runs great going any where from 20-40 miles into town in the mornings when it's cool and on the way back home in the middle of the day when it's warmer while traveling around 65 it starts cutting in and out and when i slow down to around 45 it gets fuel again and i can make my way back up to 65 for 3 - 10 then back again.Today it was worse where it died several times and then i had to prime the carb again to get it to run at all. I have replaced the fuel pump 100 miles ago,replaced rubber lines from pump to carb and hav'nt replaced from sending unit to rear steel fuel line yet.Backing up a little on the history about a month ago i was pulling from the drivers tank and the return line was filling the pass. tank and over filling it so i by passed crossover switch and stayed pulling from the drivers side but it ended up where i had volume but not enough pressure to run so i "assume" the cross over switch was also pulling from the pass. side so i ran my fuel line from the pass. side which was a dead tank for who knows how long and this problem started.I have 2 inline filters and the mini in the carb so i don't think dirt is the problem.a good friend of mine said that his father has had this problem and it was the sock breaking down and cutting off fuel,or i think maybe the old hard fuel line from the sending unit.Lack of time has been a major factor here from pulling the tanks to replace the lines. and where can a guy purchase a new sock?

Any ideas would be appreciated.

Kent.

[Ziegelsteinfaust]

I would pull the tank, and clean + inspect the sending unit.

There is a filter sock that could be your problem.

[PAPA KENT]

Thanks for your input.Do you know where you can purchase a sock without buying the entire sending unit?Since the rubber lines from the sending unit are hard as a rock i figure part of my problem might be there also so replacing the sock would be mandatory.

[Ziegelsteinfaust]

I have run them with out the sock, but the car I did it too was a 69.

Either way you have to drop the tank, and inspect.

Unless you have a tear in your fuel line to the tank, and your sucking air .

[PAPA KENT]

That's what i'm wondering if i'm not sucking air,and your right it has to come down to inspect it.I've never had this problem with my 50's or 60's cars or trucks but again i've never had fuel lines this hard on anything before.I was told that the socks in these square bodies when they get old they can beak down and close enough fuel for a stall and i suppose running without a sock would'nt hurt either since i'm running 2 fuel filters.

Thanks!

[Ziegelsteinfaust]

I have seen new socks but all they would stop is a big piece of something, and not dirt.

[INSIDIOUS '86]

Originally Posted by PAPA KENT

Thanks for your input.Do you know where you can purchase a sock without buying the entire sending unit?Since the rubber lines from the sending unit are hard as a rock i figure part of my problem might be there also so replacing the sock would be mandatory.

If they crack it will suck air instead if fuel. Idk if you can get the tank socks seperate but they keep large debris from clogging the lines. Check the filter at the carb too. Essentially the whole fuel delivery system would be back to new condition at that point. If the issue persists then the problem has to be elsewhere
Posted via Mobile Device

[RPOZ11]

Fuel Pump.
My 73 C/20 did that until I got fed up with it and started going part by part thru the fuel system.
I can get 90mph now.

Make sure your mufflers havent collapsed internally.
Otherwise, eveyone elses suggestions above are good pointes to follow.

[PAPA KENT]

Originally Posted by INSIDIOUS '86

If they crack it will suck air instead if fuel. Idk if you can get the tank socks seperate but they keep large debris from clogging the lines. Check the filter at the carb too. Essentially the whole fuel delivery system would be back to new condition at that point. If the issue persists then the problem has to be elsewhere
Posted via Mobile Device

Good morning,Thanks for your input.I dropped the drivers tank yesterday,I could see where the sock had been kinked directly in front of the pick up tube so i removed the sock,and replaced both rubber fuel lines.The only thing i forgot to do was blow out the sending unit in case of blockage there.It did idle fine for about 5 minutes then i drove a mile down the hill,put it 5 gallons of gas and made it about 2 blocks and again no fuel to the carb so my wife picked me up and went down about a hour later reconnected the pass. tank to the feed line and made it home.So i guess it's time to see if by chance the return line on my new pump is actually sucking instead of returning fuel.

The pass. tank works great untill it gets warm then it acts like it vapor locks so i guess i will have to pull that tank next.

[PAPA KENT]

Originally Posted by RPOZ11

Fuel Pump.
My 73 C/20 did that until I got fed up with it and started going part by part thru the fuel system.
I can get 90mph now.

Make sure your mufflers havent collapsed internally.
Otherwise, eveyone elses suggestions above are good pointes to follow.

Hey thanks. Well it has a new fuel lines,pump and 2 filters so back to the pump i guess. The mystery here is it would feed from the drivers tank and return to the pass tank then of course overfill that tank before i bypassed the cross over switch and after that it won't run off the drivers side like some of the fuel from the pass. tank was feeding the inlet also. And like described in a earlier post the pass. side works great untill it gets hot so i'll play with it some more, and both mufflers have about 3000 miles on them and the flow "seems even" hot or cold.

[motornut]

kinda sounds like what happened on the 79
it was the back flow valve in the fram gas filter,blowing in/out

http://67-72chevytrucks.com/vboard/s...d.php?t=579621

[PAPA KENT]

I want to thank everyone for their input. Since the drivers tank had good volume and i assume low pressure it would'nt even run on that tank since i bypassed the cross over switch so i assume i must have a crack and a air leak in the sending unit. and it would run on the pass. side tank untill you put 20-50 miles on it with the temps getting hotter during the day you would lose fuel pressure.

Jon from Jonscustomshop on the 60-66 board and his father were telling me at one of my visits to his fathers home that the 73-87 fuel tank socks were well known for breaking down and folding in half and the pick up tube well long and behold this looks to be the problem on the pass. side.The drivers side was'nt as bad so i though i better list a picture of this one.

Thanks a bunch everyone for your feedback!

Kent.

[Jabes1]

As long as you run a pre filter you can remove the sock. I removed mine for my EFI conversion to eliminate the chance of this happening and leaving me stranded.

[mexlokote]

i bought my truck brand new fuel tank and sending unit very cheap at this site

rockauto.com

safe place to shop i bought many parts for my truck,
now i have no issues with my fuel