Fuel delivery

[JanMast]

Jeep gods,

I think i am having an issue with getting fuel to the carbuerator. Its an 85 CJ7 with an inline 6.

I just recently replaced all the fuel hoses in the engine bay and dropped the gas tank and replaces those fuel hoses too, and the fuel filter.

Now the Jeep wont start. I pulled the fuel hose off the input side of the fuel filter (from the gas pump). Its an electric pump that is mounted in the engine bay. When i turn the ignition so that the electrical system kicks on, i get fuel flowing out. When i turn the ignition all the way and try to start the Jeep, the fuel stops. I know that the hoses are connected correctly to the sending unit in the gas tank because its pumping some fuel. Should i suspect a bad fuel pump at this point? Or could it be a fuse or something like that? Thanks!

 

[Torxhead]

The way I see it, a carbed engine does not need an electric fuel pump, especially in the engine compartment which is too far away from the tank. Also the fuel tank has a vent system and should be working as that can create fuel delivery problems for whatever fuel pump you use. By now all the rubber in your fuel system should have been replaced as they can crack in time. You could also have other problems not allowing the vehicle to start. I have a electric pump in my CJ with a fuel injection system and it is mounted near the Transfer Case . This allows fuel that has been siphoned to it to be pumped forward.

 

[007]

It would seem to me that based on the description that it's possibly (but perhaps not completely) a wiring issue.

You're getting fuel out the line with ignition on but not with ignition in start?

What happens when you shoot some starting fluid in the carb? Does it fire?

It seems you're getting fuel up to the engine bay. Now we need to see if it's stopping or not being lit...or both.


Sent from my iPhone using Tapatalk

 

[Fastatv]

Jeep gods,

I think i am having an issue with getting fuel to the carbuerator. Its an 85 CJ7 with an inline 6.

I just recently replaced all the fuel hoses in the engine bay and dropped the gas tank and replaces those fuel hoses too, and the fuel filter.

Now the Jeep wont start. I pulled the fuel hose off the input side of the fuel filter (from the gas pump). Its an electric pump that is mounted in the engine bay. When i turn the ignition so that the electrical system kicks on, i get fuel flowing out. When i turn the ignition all the way and try to start the Jeep, the fuel stops. I know that the hoses are connected correctly to the sending unit in the gas tank because its pumping some fuel. Should i suspect a bad fuel pump at this point? Or could it be a fuse or something like that? Thanks!

Prime the carb with a little fuel, then try to start it. Could be that while turning the engine over, the starter has such a voltage drop that the pump is not getting enough voltage to run correctly. Again, turn key to "run" position for thirty seconds, manually prime carb, then try to start it.

 

[Lumpy Grits]

Get that ele. pump back close to the tank.
E/pumps are 'pushers' not 'suckers' like the engine mounted mechanical pumps are.
Why are you run'n an ele. pump instead of the proven OEM pump set-up?
Can you hear the pump run'n at all?
LG

 

[jammer1]

Lg is correct, you need the pump as close to the tank and if possible below the center line of the tank (siphon gas to pump, pump pushes to engine). Also check the power. Sounds like it might be connected to run circuit. It needs to be connected to the start/run circuit. If the power is not run through a oil pressure switch you could turn it to run long enough for the pump to prime the carb fuel bowl then try to start.

 

[Bent]

I also just replaced my sending unit to hardline hoses. I also had a fuel starvation issue with the mechanical pump. Turns out I didn't route the new hoses through the hold down loop and it was pinched. I had to pull the tank again. Full.

 

[caveman]

I had to pull the tank again. Full.

That sucks.

 

[JanMast]

I had a great idea on how to test the electric fuel pump. I made a jumper and connected the pump to the positive side. Of the battery and no fuel was pumped.

I also started the jeep by priming the carb with some starting spray and the jeep started.

So I went ahead and changed out the pump with the mechanical pump I had on hand. I was fairly certain that I had the supply, return, and vent hoses hooked up correctly. I had just replaced all that hoses, dropped the full tank and all that. So after I verified that the new pump was in fact pumping fuel, I hooked the hose back up to the carb and she started right up. Took her for a nice long test drive.

Thanks everyone.

 

[Torxhead]

Thanks for the update. Glad to hear you got it running. Part of getting fuel to the pump is a working vent system. This allows fuel to be siphoned to the pump inlet and Lumpy states the best point.