Jeep Wrangler Forum banner
  • Hey everyone! Enter your ride HERE to be a part of JUNE's Ride of the Month Challenge!

1 - 16 of 16 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter · #1 ·
I just got a 94 bone stock YJ that stopped running a few years back and I'm trying to diagnose why. I have already tested for spark with an inline tester and got spark, I checked pressure at the rail at 45psi, and I got an injector noid tester from the parts store that lights up when the injectors get a signal to fire and it lights up when turning the engine over.

I also checked for codes and got no codes.

After all this I sprayed some Carb cleaner in the throttle body and was able to get the engine to sputter for a second.

Does anyone have an idea of what is causing the problem?

Thanks!
 

·
Registered
Joined
·
15,660 Posts
Couple possibilities but first verify good spark with plug wire hooked to loose grounded spark plug

The likely issue is bad gas

The zebra is jumped timing chain




Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #3 ·
Couple possibilities but first verify good spark with plug wire hooked to loose grounded spark plug

The likely issue is bad gas

The zebra is jumped timing chain




Sent from my iPhone using Tapatalk
What do you think would have been the cause of bad gas? The previous owner said it just wouldn’t start one day. He gave up trying to figure out why and now I’m trying to figure it out a few years later. Maybe the gas has gone bad over the couple years, but why would that have been the issue in the first place. And what is the zebra you refer to?

Thanks!
 

·
Premium Member
Joined
·
655 Posts
I think he meant by zebra was the not likely scenario.

If it sputtered when you put carb cleaner, it sure sounds like fuel. Maybe pull the injector rail out with the injectors and see if they can actually spray fuel and aren't all gummed up.

One thing to check. I know I said fuel, but is the engine not getting enough air? Is the idle air motor not letting enough air in. Maybe hold the throttle open and attempt to start at a few different spots.

I do agree that some new fuel would be good. You want to rule that out. Especially given the age of it. Also, you can't always trust what previous owners say. Probably not complete story.
 

·
Registered
Joined
·
15,660 Posts
When you hear hoof beats around here it is unlikely to be a zebra but it still could be

Horses high probability when hear hoof beats zebra low probability which is why they refer to unlikely rare diagnosis as a zebra


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
15,660 Posts
Not unheard of for someone to fill up with diesel fuel or have even beef rare occasions when gas station had diesel in the regular tank and many people had an engine that stopped running soon after a fill up


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #7 ·
I got some fuel on my fingers while installing the fuel pressure gauge on the rail and it smelled like gas to me. Not sure what diesel smells like though. Maybe it’s similar. Is there an easy way to drain the tank on these? Or do I need to drop it? Thanks!
 

·
Super Moderator
Joined
·
12,676 Posts
Google "Occam's Razor" for an explanation of the zebra/horse analogy.

"When you hear hoof beats around here it is unlikely to be a zebra but it still could be.

Horses high probability when hear hoof beats, zebra low probability which is why they refer to unlikely rare diagnosis as a zebra".
What Digger84 is saying is, look for the simplest solution first.

OP, get a fuel transfer pump at Harbor freight (about $10.00) and use it to pump the old gas out of the tank. It beats a mouthful of gasoline. Use the old gasoline to start your BBQ (JK) or discard it properly.
Only put a couple gallons of fresh gasoline in the tank. You may need to drop the tank if the old fuel pump is bad.

Good Luck, L.M.
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #9 ·
I have a shaker siphon I just wasn’t sure if it would just go down the filler neck into the tank or not. I’ll give it a try tonight. The fuel gauge is not currently working. It says full tank but I know it’s not. I doubt that’s related but I guess one more thing I have to figure out.

I’ve read elsewhere of people with similar issues saying it was caused by a faulty crank position sensor. Is that a possibility or does everyone agree here bad gas is the cause?
 

·
Super Moderator
Joined
·
12,676 Posts
Find a post by Got it at last. In his signature there's a free link to several Factory Service manuals and a couple Factory Parts Manuals.
Open that link and click on the manual that you need.

There should be a troubleshooting matrix for you to follow in the "engine" section. The matrix could be in the general engine section or in the section for your specific engine.

Good Luck, L.M.
 

·
Registered
Joined
·
261 Posts
I had exactly the same issue and it was the crank position sensor. It’s not expensive and it’s a really easy install. The fact that you’re getting it to sputter with fuel in the intake may point to gas, though. Fresh gas can’t hurt. I would try that first and then go straight to the CPS.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #12 ·
Worked on the Jeep again tonight. Tried to suck gas out of the tank but no luck. I think the fuel is so low I can’t get the syphon hose to stay under the fuel level. I decided to remove the fuel rail bolts and pull it out an inch to be able to visually see if the injectors are firing. They did not fire. I still have 45psi at the rail. And the noid light indicates the injectors are getting the pulse. Very confused why they aren’t firing. Any ideas? Tried to post a video of the noid light pulsing but it only will let me post a photo.
 

·
Super Moderator
Joined
·
12,676 Posts
Worked on the Jeep again tonight. Tried to suck gas out of the tank but no luck. I think the fuel is so low I can’t get the syphon hose to stay under the fuel level. .
You might try to put a couple gallons of gas in the tank to see what happens. It seems too simple to think the Jeep might just be out of gas. The gas gauges on these old heaps are known to be inaccurate.

In a quiet environment you should be able to hear the fuel pump turn on for a couple seconds when you turn the key to "on" position.

Have you changed the fuel filter? You might be getting enough fuel through a partly clogged filter to get fuel pressure to get it to read pressure at the fuel rail and sputter, but not enough fuel to actually run.
Another "zebra" is a partly clogged sock on the fuel pump pickup tube.

Keep us posted on your progress.

Good Luck, L.M.
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #16 ·
Worked on the Jeep again tonight. Tried to suck gas out of the tank but no luck. I think the fuel is so low I can’t get the syphon hose to stay under the fuel level. .
You might try to put a couple gallons of gas in the tank to see what happens. It seems too simple to think the Jeep might just be out of gas. The gas gauges on these old heaps are known to be inaccurate.

In a quiet environment you should be able to hear the fuel pump turn on for a couple seconds when you turn the key to "on" position.

Have you changed the fuel filter? You might be getting enough fuel through a partly clogged filter to get fuel pressure to get it to read pressure at the fuel rail and sputter, but not enough fuel to actually run.
Another "zebra" is a partly clogged sock on the fuel pump pickup tube.

Keep us posted on your progress.

Good Luck, L.M.
Planning on swapping out the fuel filter this weekend. When I have it removed if I turned on the ignition would the pump empty the tank? Trying to figure out the best way to get as much gas out of the tank as possible. Then I could put in some fresh gas.
The fuel pressure gauge I have attached at the rail has a bleeder and I’ve tried bleeding the pressure off and then turn the car over again and it goes right back up to 45psi. So I’m assuming the pump is functional.

The fuel gauge on the dash does not work. It shows full even when the ignition is off.
 
1 - 16 of 16 Posts
Top