Fuel delivery issue

[farm1810]

How could a system that is this simple be making me pull the little hair I have left totally out?  Anyway, after 2 different electric pumps, replacing the feed hose twice.  Blocking off the tank outlet (the one with the flared fitting) and changing to the drain port (NPT), and reinstalling the mechanical pump...  I have having the same problem.  Jeep runs for maybe 20 minutes and then quits.  Prior to this I could see in the fuel filter that I had no fuel.  This up by the carburetor.   Now that I have the mechanical pump I also have the glass top on it.  This time when it quit I have no fuel in that bowl at the fuel pump either.  So, I pulled the hose off that comes from the gas tank to the fuel pump.  Initially it had nothing.  Then I pointed it down toward the ground by a couple of inches and quickly got fuel flow.  I plugged the hose back on the fuel pump.  I could turn the key and look directly at the pump.  I cranked for about 15 seconds, nothing.  I stopped for a moment.  Cranked for another 15 seconds and suddenly I started to have fuel in the fuel pump bowl.  Stopped for a couple more seconds.  Cranked and got fuel into the fuel filter.  Stopped for a moment.  Then lowered the hood, jumped in.  A couple pumps on the gas pedal and Vroom!  Fortunately I was only about 100 yards from my barn.  That is where she is sitting for the moment.  Any ideas at all?  I ran the hose inside the frame rail and added a couple of brackets to keep it away from the exhaust pipe.  All ideas welcome!  Thanks.

[Rus Curtis]

These vehicles are simple, but they are all roughly 70 years old!!

Any system (doesn't matter, pick your favorite) that has multiple sub-systems, must have all the parts working together. 

You could take your jeep, rebuild the engine, carb, charging system to perfect specs.  Replace the radiator and tires.  But if you've got a hand-full of rust in the fuel line clogging the pump or the carb from getting a steady flow, the jeep won't run.

Each component can have a bunch of issues.  Each can be resolved.

I read that you have a gas filter before the carb.  Have you ever had one before the pump?  Have you flushed the fuel tank out?  Have you hooked up gas similar to a boat:  A spare gas can with a hose directly to the fuel pump?

Changing connection from pickup to drain for your fuel could add trash into your line.  I once lost my ability to crank and used the drain port to sample and got 1/2 & 1/2 gas and water in my glass collection jar.  Anything floating or swishing around in your gas can be a problem.  Here's an image, from the CJ3A Information Page, of what the pickup should look like inside the tank:



That depression just under the pickup opening is the drain.  That's where all the debris/crud/water will collect (to more easily drain it out).

Take the time to check the entire circuit.  Disconnect the tank line and blow it out (maybe wrap a towel or cloth around the other end to observe what comes out).  Drain the pump.  Disconnect the next line up to the carb and blow it out too.  Maybe even open the carb bowl to see if you have sediment in there.  Drain the tank (if possible, strain into another container), send a puff of air back through the pickup (checking for blockage) and see if there's any more debris - or water that drains out.  Consider cleaning or replacing the tank.

Are you using ethanol blend?  How full to you keep the gas tank?

BTW, if it eases your frustration, fuel delivery was one of my toughest challenges after first getting my jeep back in the late 70's.  I didn't understand where it was coming from and wasn't getting a lot of help either.  I replaced the tank, added a filter and used a lot of gas treatment to get by. 

[Dasvis]

Is the tank venting?
  Try it with the gas cap off.

[scoutpilot]

Possibilities:

Air is being sucked in at a fuel line connection. Any rubber to straight-cut metal tube connection will leak air into the system when only one clamp is used.
Loose fittings on the pump will suck air.

Very low fuel level in the tank. Park facing uphill and guess what? No gas in the line.

Tank cap not venting p-roperly.

[farm1810]

Thanks so much.  I thought I had a gas cap issue so I drilled a .032 hole through it.  I have a new aftermarket gas tank, that isn't to say it doesn't have issues.  My next move is to run a metal gas line to be sure the rubber line isn't collapsing (which happened during this journey!).  My next move is to run a 1/4" copper line inside the 5/16 rubber line to the fuel pump.  I also ordered a new fuel pump, just in case.  I want to run the copper inside the rubber to insulated it and use the copper to be sure the line doesn't collapse!  Good grief!  More to come.  Thanks for the feedback all.  R.

[Rus Curtis]

All good suggestions!  Forgot all about the cap.....
Thanks for adding the additional info.  Helps with the picture.

A word of caution on the copper.  It may split from engine vibration.  It's best to stick with steel vs. copper.  I would not add a hard line inside a rubber hose.  With that issue, I'm thinking swapping out the hose for a hard line.  If you've got a portion of rubber hose running as a part of the fuel delivery, a quality "fuel" hose will not collapse.  The pump isn't drawing that much pressure to begin with (I think 4-5 lbs).  If a fuel hose is collapsing, that's a good indication that it needs replacing (or that it might not be "fuel" line to begin with.

[farm1810]

I had originally gotten a piece of fuel hose from the local NAPA store.  This problem arose and at some point I removed the hose and tried to blow through it.  I could barely flow through the hose.  I took a piece of solid core wire and started to see where a problem might be inside the hose.  Sure enough, the hose was collapsed about 2 feet from the fuel tank and continued to be collapsed for about 16".  So I went to Advanced Auto Parts and got a piece from them.  I have not checked that hose as yet.  As far as a the fuel tank.  I purchased that tank new about 20 years ago and it sat in my shop in a box all this time.  Before finally using it, I did blow it out with air.  I first put non-alcohol fuel in the tank as I wanted to run the engine but I had not fully wired the Jeep, put in the gauges, etc and I thought it might sit for a bit between running.  So time goes by and I have the gauges hooked up.  I knew that I had about a gallon in the tank, so I added another gallon and looked at the gauge, then 2 more, and looked at the gauge.  Since I had to cut the arm for the float to length I wanted to see how close the gauge was to accurate.  So then this problem with it shutting off after about 20 minutes running came up.  So I drained the tank and I put that fuel into my car and have since used all of it.  And in the meantime, after changing the hose and whatever else, I put about 5 gallons of fresh 10% ethanol fuel back into the Jeep.  So long story, but wanted to point out - tank never used before and still looked like new steel when I looked into it with a flashlight before installing, has new fuel in the tank, has hole drilled in the gas cap (and I have tried taking the gas cap off when this happens and it changes nothing).  Oh well, today is a new day.  Off I go for the next experiment.  Oh, and I am taking your advice about the steel line and using the tank pick up instead off the drain opening.  Thanks again.  If nothing else just communicating with someone who can relate is quite therapeutic.

[SteveKfl]

I found "bio-fuel" grade hose at NAPA has a PVC type liner.  It is stiffer and handles Ethanol fuel.  Very expensive, but so is all of the double-work or a towing.  Happy motoring is with "confidence" you'll make it home again.

[Rus Curtis]

This IS troubleshooting; Eliminating bits and pieces so you can zero in.   It certainly sounds like that first rubber fuel line was causing problems.  I wonder if it didn't slough off pieces of rubber to get lodged down-stream.  Have you seen any black bits in the filter or pump bowl or fuel samples?

[farm1810]

Haven't seen any black bits in the filter, but todays update.  I started over.  I drained the tank.  I took the feed I had from the drain and plugged that.  I put a double flared 1/4' fitting into the outlet of the tank.  I routed the steel line away from the exhaust and up through the frame beyond the motor mount.  I installed a new mechanical fuel pump.  I used new 1/4" fuel hose where needed.  I installed a new in line fuel filter.  Ran the Jeep at idle for about 30 minutes then drove around the yard for 10 or so, then let sit at idle, then drove around the neighborhood.  Tomorrow, a longer drive on back roads.  We'll see.  I am not upset about the extra work as i enjoy that probably more than driving.  I am upset because I don't really know what was wrong!  Grrrr.  Oh, an interesting observation.  The prior mechanical fuel pump was typically filled with fuel (in the glass bowl) about 1/2 - 3/4.  This one might be 1/4 full, but you can see movement, splashing, etc.  Gracious. 

[scoutpilot]

The pump bowl is not supposed to be filled to the top. There should always be some air in the top. It helps maintain the pressure.