1992 2.5 YJ seems to have fuel issues


Jeepster92

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Feb 23, 2021
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I have a 92 YJ with the 2.5 litre. Here is the problem that I am having : I only drive it a couple times a week until I fix it up some. When I fill it up with gas it runs fine. I drive it a couple times and it will die like it's out of gas. So I put a gallon in it and it's fine, but when I finish filling it at the station the pump shuts off at say 6 or 7 gallons. The is a leak in the filler hose, but I can't find any leaks around the lines or tank. But I still can't figure out why it's not filling all the way.
 

Flyer58

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Apr 12, 2020
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Magnolia, Texas
I also have a '92 YJ with the 2.4L and 5 speed and have rebuilt the engine and currently have the fuel tank out to fix a sending unit issue.

Lots of questions. Does your gas gauge work? Have you figured out what you MPG's are? How many miles on the 6 or 7 gallons of gas? 15 MPG or so is normal depending on the driving it could be a little higher or much lower if you go off road. Do you smell gas fumes which may indicate a steady leak?

It could be a fuel filter problem or the screen on the fuel pump inlet. Could be a venting problem. Could be a leak on the fuel supply or return lines between the tank and the engine. Could be a fuel pressure controller problem or a pump problem.

I'd start with checking the fuel pressure at the test port on the injector rail. You can probably borrow a fuel test gauge at a local auto parts store and is pretty simple. When safe and after idling for several minutes crawl under and looks for any gas drips or leaks You can also test the fuel flow from the pump but be careful. It involves a length of hose going from the engine fuel supply line to an empty gas can and then there's a way to use a jumper wire at the relay to get the pump to run. This can be done safely or cause problems for you and a the local fire department if your not careful.

Your gas tank from the factory is probably limited to 15 gallons BUT it's actually a 20 gallon tank with a long internal vent tube which kicks off the gas pump handle early leaving 5 gallons of air in it. There was a 20 gallon option and the only difference was a shorter vent tube. Go figure, pay more and get a shorter tube.

Lots of common knowledge here to help but need a few more answers first. You'll find the Factory Service Manuals in the Y Resources section of this forum.

Let us know.
 
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Jeepster92

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I have replaced the fuel filter and the fuel pressure regulator. When I went to replace the filter, I discovered that there was none. There was just a rubber line between the the ones. I had to cut throught the rubber line to fit a filter on it. When I first start it and drive it acts like it is choking out. Or when idling after a start I can push the ecelorator quick while it's in neutral and it wants to choke out. When I bought it I drove it 70 miles home with no problem. I am beginning to think that someone may have put something in the tank.
 

Flyer58

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It may be a pressure issue with the pump or inlet screen on the pump. Sounds like it may be starving for gas. No telling what's in the tank after 30 years. Someone may have been tired of changing filters or had the same pressure problem and just bypassed it.

I can't recall the pressure test numbers but it's all in the FSM. Pretty easy to check.
 
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Jeepster92

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Feb 23, 2021
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I used a fuel pressure tester from auto zone but part of it was missing so I had to jerry rig it. It was showing around 30.
 

ddross

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Mar 20, 2021
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Mesa, Colorado
I have a 91 2.5L and I believe the pressure ratings for a YJ 2.5l should be 31 to 39 psi. I am curious if you did a leak down test when you had the fuel pressure gauge on it since you replaced the fuel pressure regulator? I think it should hold 30 psi after 30 minutes after the engine has been turned off.

I have one question since you mention the gas pump clicks off after 6 or 7 gallons at fill up. When you do fill up what does your gas gauge read? Also, the vent tube Flyer58 mentioned can be removed to allow the tank to be filled to the full 20 gallons or very close to it. Power Addicts on Youtube has a video on how to do it, and there are other write ups on how to convert a 15 gallon tank to 20 gallons. I did it to mine years ago and it registers full for quite a while until the gas level drops to the point where the float can measure it. Since you mention how you can add a gallon of gas and the jeep will run it sounds like it is picking up gas without issue. I think Flyer58 has a good suggestion to check the miles you get out of tank of gas after a fill up.
 

Flyer58

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Apr 12, 2020
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Magnolia, Texas
I was just thinking about the two fuel vent check valves on top of the tank. I wonder if those may be getting blocked and causing a vacuum in the tank. Can you hear air rushing in when you remove the filler cap?
 

jeepjoe43

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Dec 4, 2020
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Location
Black Canyon City, AZ 85324
Had an issue with mine with 6 gallon fill-up, though mine wasn't dying for that reason.
Could drive 1/4 mile to the station, put 6 gallons of gas in it, go home and let it sit stinking of gas all week and put more 6 gallons of gas in it again.
Broken tank, 10" crack about half tank level.
My dying problem was at at a plug, broken wire to the plug for the coil.

Agree with Fyer58, yours sounds pressure related.
Replaced my pump and it ran 35PSI, as it should be.
Shut it down after it warmed up, and about 30 minutes later it actually went up to 41PSI.
Probably engine heat getting to the fuel rail, started dropping after that.

There is the off chance it could be a fuel pick-up rotted off, ethanol is not kind to older fuel systems, but I doubt it.
Could still be a rot issue on the pressure side of the pump where enough weight of gas against the leak will let it run.
Not enough and it won't.
I know it's a bitch, but I'd start with the pump And the sending unit.
And a thorough inspection of the tank while it's out, check the vents and remove the skid pan.