Fuel Problem

I've been haveing an intermitting fuel problem with my CJ that you guys may be able to help me solve. When driveing on pavement as fast as I dare drive (around 55mph 3k rpm) my CJ sometimes sputters and then dies. I can prime the carb with a little gas and it run till it burns that fuel off. I have found that if I disconect the fuel line (it seems to release some pressure) reconect it then pump the accellerator about 15 times it fires right up and usually runs fine the rest of the day. I have rebuilt the Rochester 1 barrel replaced all the fuel lines and replaced the filter and no change. Never happens off road. The only thing I can figure is on smooth pavement trash in the tank floats up and blocks the line. I plan to remove and clean the tank if I can ever get home from work with enough daylight to do so. In the meantime I figured it wouldnt hurt to run this by you guys to see if you may have any other ideas.

 

lots of checking to be done, I'll try and keep it simple

is the gas cap vented or non-vented ? non-vented and the tank can't "breathe"; remember the pump is pulling/sucking fuel, and if the tank can't breathe, it will choke of fuel to the pump.

take a flashlight; turn it on AWAY from the tank opening (no spark), remove the cap when the fuel level is lower, peer inside and rock the Jeep; you might be able to see debris/foreign matter moving around inside the tank.

fuel filter: is yours inside the top of the carb, or do you know if you have one there ? if so, pull it out and blow thru it. In line filter, is it before or after the pump ? Ideally, you want it before the pump so junk doesn't go thru the pump; if you have one, and you suspect junk in the tank, cut it open to see if any is captured inside the filter.

fuel pump testing: remove the line at the carb; place inside 1 quart container; start the Jeep and let it IDLE on the gas inside the carb; it should fill this container within 45 seconds, a strong and steady pulsating stream of fuel. Be careful of sparks and moving engine parts; and NO SMOKING.

heat soak/vapor lock: is the carb mounted on top of a thin paper gasket, or a thicker insulator type gasket? the carb could be boiling the fuel in the bowl and/or vapor locking on you by absorbing engine heat while driving like you indicated. If thin paper gasket, you might see if you can find an insulator that will work with your carb and get it up a little higher away from the manifold. Same with the fuel lines; are they routed away from exhaust/heat sources ?

lots of typing, but these simple checks can be made in a very short amount of time.

 

I had a car with these symptoms.
it was a sock filter on the pickup tube in the tank would work fine till at speed then it would plugup. if you open the line you could hear the suction.
Whatever it is I bet its in the tank.

 

Not sure about the gas cap but looks oem. Next time I have this prob I'll try removeing the cap and strarting the jeep.
Filter in carb is clean.
Inline fuel filter is before pump. Fuel pump is working fine.
It doesn't look like there is much debris in the tank when looking in with flash light but I'll prob still remove and clean it.
Is there a sock filter in the tank? I thought that was only on in-tank fuel pumps.
Thanks for the ideas guys.

 

no sock
yours should be just a threaded outlet in the bottom of the tank.
sock was primarily used when the sending unit included a pickup tube; your outlet hose would have to hook up to a tube on the sender.

 

Jim, My 69 with the twist on locking ring type pick up sending unit under the seat tank has a sock on the pickup in the tank. Not sure about other types.