not getting fuel.....i think

[allabs5150]

Ok not to wish any misfortune on anyone, but i hope someone here has encountered this problem cause I am puling my hair out trying to figure it out.

Jeep in question is 87 yj 4.2 manual transmission.
Problem:
I have not ruled out the possibility the problem could be the Weber carb set up which although I was never 100% happy with was much better than the stock junk the jeep came with.
When driving the jeep once I get out of first gear the problem occurs once I get close to 2,000 rpm the jeep acts as though its not getting any fuel and sputters till I shift into the next gear, again once I hit aroung 2K rpms in 3rd 4th & 5th gears the problem arises. Now I can still drive the jeep with not much of a problem as long as I dont throttle the thing up, which is sometimes a problem when driving busy roads.
Now thinking it is a carb issue I just picked up a newley rebuilt MotorCraft 2100 which I have not installed yet, only because I notice the problem seems to almost totally go away when the Jeep has a 1/4 tank or less of fuel in it, and once I fill the tank anywhere over 1/2 to full the sputtering gets so bad the Jeep is not driveable.
Now I am wondering if there is some kind of fuel pick up issue????, or the fuel tank is not venting right?????? or if there is a float in the tank that goes haywire once the tank is full of fuel???????.
Now like I said it's not like the problem never happens when the Jeep is almost run dry on fuel, but it ALWAYS happens when it has a 1/2 tank or more of fuel which is kind of making me think its NOT a carb problem.

Any help is greatly appriciated as I am running out of hair to pull out

 

[BaconYJ]

Start small by replacing the fuel filter and the gas cap.

 

[RLBJeep]

What type of fuel filter are you running? It should be a 1 in, 2 out type with the bypass connected to a fuel tank return line that runs to the gas tank. Do you have a charcoal canister? Fuel pressure regulator? Vapor lock could be an issue without the proper venting.

What tpye of Weber are you running.. a progressive (32/36) or synchronous (38)? The second barrel on the progressive carb only gets gas when you are on the throttle. If you have a progressive, look down the secondary barrel and have somebody hit the gas, fuel should be flowing into this barrel in the same manner as the primary barrel. If not, it might be time for a cleaning.

 

[allabs5150]

Yes I am running the 1 in 2 out type fuel filter, no fuel pressure regulator, and the charcoal cannister well that something I have to look at

The Weber is the 32/36 so i will look into the possibility of the secondary barrel not flowing fuel......just seems to me with the problem being much more frequent when the fuel tank is 1/2 tank or more filled the problem lies there somplace

 

[RLBJeep]

If the symptoms were reversed I would say you have a fuel pick up issue, but your problems don't surface until you have over a 1/2 tank of gas. I would look down the barrels of that carb, first at idle, then at over 2,000 RPM and see what the fuel delivery looks like, you may have an accelerator pump problem. If everything is ok I would check the condition of the vac line that runs from the carb to the distributor. If that is ok check the dist. vac advance. You have a Weber, has the Nutter bypass been done?

 

[allabs5150]

RLBJeep I see what your saying, if the systems were reversed & the proble occured more often with a 1/2 tank or LESS of fuel I would be almost sure it was a fuel pick up problem.

As I was pulling more hair out today I was thinking accelerator pump too, but tommorow I will take your advice look down the carb at idle and a 2,000 rpm and see whats going on, along with checking the vaccum lines

No the Nutter bypass has not been done

I'll keep ya posted.....thansk for the advice

 

[RLBJeep]

Let us know what happens. Do a search on the Nutter Bypass for the YJ. I think it should be done if you are running a weber on a 4.2 in place of the bbd w/ stepper. I remember reading that the YJ wiring is the same but the color of some of the wires is different. I am far from an electrical wiz and I did mine in 30 minutes.

 

[allabs5150]

Let us know what happens. Do a search on the Nutter Bypass for the YJ. I think it should be done if you are running a weber on a 4.2 in place of the bbd w/ stepper. I remember reading that the YJ wiring is the same but the color of some of the wires is different. I am far from an electrical wiz and I did mine in 30 minutes.

Ok RLBJeep......thanks for all your help, I am still working on the issues, but as far as the nutter bypass goes dop you think I should still do it even after I switch over to the MotorCraft 2100 carb?

 

[RLBJeep]

Yes, I am pretty sure you have to do the Nutter anytime you disconnect a computer controlled stepper motor from the BBD. If not the computer will continue to make adjustments to the timing. I have attached a good link that is very helpful in completing this mod. Good luck.

http://home.sprynet.com/%7Edale02/wiretrik.htm

 

[YJoffroad]

Hi guys, i'm new here. Just joined yesterday. I recently just bought an '89 YJ w/ the 2.5L which is fuel injected, and i'm having a similar problem as allabs5150 only it doesn't matter how much fuel is in the tank. It's very consistantly kind of sputtering a little right when I hit 2700 rpm, but once i get past that it's fine. I don't know if you guys are still looking this far back in the forum, but hopefully someone can help me out. Thanks