61 Cj5 Replacement Fuel Pump Question.

Stock F134, runs like a top when getting fuel. I have installed a replacement Solex carb. Purchased all new fuel lines and a new fuel replacement fuel pump, one of those with the bowl built in. Had a devil of a time installing it and the glass bowl is on the top of the fuel pump, which seems weird. Questions: Is the glass bowl supposed to get full of fuel? Mine certainly doesn't. Looking down at the fuel pump from the top when installed, is the suction side on the right?

Anyway, it start right up after sitting for a few minutes and will run beautifully, in an undetermined time it will die, repeat. Sit a while and start right back up.

Help!

 

I suspect you have an air leak, probably before the pump. The pump bowl goes dry, then when it sits gravity causes it to refill. The pump is working or it would not start back up. You say "all new fuel lines" so I presume that includes the line from the tank, the flex line to the pump, and the line from pump to carburetor. Check the flex line going into the pump.

Another possible cause for this sort of behavior is the incorrect fuel cap on the tank. You need a vented cap, and a lot of suppliers sell caps for these Jeeps which are not vented. You can test this easily by loosening the cap and running the Jeep.

I have a "replacement" pump on my CJ2A which is probably the same as what you have. These have a vertical divider, possibly a screen, in the glass bowl between the two check valves at the bottom. Mine would fill about half way when running. After a year of intermittent use the pump began to leak even though everything is tight. I suspect the material of the gaskets and diaphragm are deteriorating. I have rebuilt the original AC pump to replace the reproduction pump with.

 

Thanks for the reply.....just curious, does the fuel line from the tank go on the right side of the fuel pump....when you're looking down at it installed. In other words is the fitting on the fuel pump correct when it's installed the port closest to the the tank.

 

I believe so, but regardless if your Jeep will run at all with that pump you have it connected correctly else no fuel at all would reach the carburetor.

 

Ok, good to hear, I've got the tank connected to the left side. I see gas going into the bulb but it no where near tries to fill it.

 

I do have the Solex replacement Carb. Any chance this could be the problem? This is the second one and relatively new.

 

I suppose the float could be out of adjustment and not letting the bowl fill all the way, but I am more inclined to think it is one of the two possibilities I mentioned above.

Have you checked the connections on the flex line? Is it a new one? Have you tried running it with the gas cap loose?

When you start swapping parts based on guesses you can complicate the diagnosis.

 

I'm afraid to admit that I've been fighting this for a long time, starting with an electric fuel pump, and swapping parts. I finally just replaced all of the fuel lines with new, including the flexible hose. I'm going to try driving it without the gas cap loose, and I looked at it and it doesn't look vented, so I'll let you know. Thanks for the interest and advice. I'll report back.

 

The connections to the fuel pump were right. I took the gas cap off that's been on there since I bought it 20 years ago and the thing never died once. I would never have even imagined that could have been the problem and I've been fighting this for a couple of years. So big Cudo's to Old Pappy for suggesting the gas cap. I guess the venting part must have corroded up and stopped up somehow. Time will tell but it sure seems to have fixed the problem....

 

What is the fuel pressure? Solex can only take 1.5 to 2psi.

 

I'm not sure what the fuel pressure is but it's one of those replacement, bolt on, mechanical fuel pumps from one of the Old Jeep parts suppliers. It can't be too high because I only get about 1/4 inch of fuel in the glass bowl, which is located on top of the fuel pump. I'm really beginning to think it was the gas cap.

 

A quarter inch fuel line will put more pressure into the carburetor then will a 5/16 inch line. This is simply due to fluid dynamics.

 

I had it connected correctly, I was just looking at some diagrams of the fuel lines and it looked like the line from the tank connected to the right side of the pump. I looked more carefully at the pump and there were arrows pointing towards the flow.

 

My solex has a fuel pressure regulator set up the PO installed. Due to what scout pilot mentioned above.