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91 YJ still wont start

7K views 30 replies 7 participants last post by  bubbadah 
#1 ·
Ok I replaced the CKS and no improvement. Intermittent starting followed by bad running and stalling. I do have spark at the plugs and the coil. I poured fuel in the manifold and tries it and it seems the same. I also ran a screwdriver across the large bolts on the starter and the starter turned. I am missing something. This is on a Dix cylinder with auto transmission.
 
#2 ·
you replaced the throttle position sensor (tps) right? My motor would start sometimes ... run for a few seconds .. run rough then die and would not start.

That was after i replaced the cks. When the cks went out it would not start at all.

If I remember right you said you put on a new tps right?
 
#7 ·
confirm you have fuel, you know you have spark ... it would seem to be timing if you have both and she won't fire. Does the motor backfire or sputter? I actually smelled fuel.

Did you run a fuel system cleaner through? Those almost always plug fuel filters unless it is done on a regular basis.
 
#8 ·
Do you think resetting the computer will help? I was told to do a factory reset after every sensor change. pull the pos + and neg - cables and touch them together for 15 seconds.

Also give a brief history of what you have done so far, maybe some one will think of something we missed.
 
#11 ·
I guess good spark vs a bad spark Is the question. I pulled the boot off plug and put it next to the plug and could see nothing's. I inserted an insulated screwdriver in the spark plug boot and held the screwdriver next to the block and got spark. I can't say for sure I am getting excellent spark and it may be intermittent. There are times when the engine wants to fire and then times when it's completely dead. I could have spark at that time. When a coil fails, does it fail 100 percent? Or cod it cause an intermittent deal like this?
 
#13 ·
Ok tried the coil and I am still stuck. It cranks and nothing. Occasionally it tries to crank and once in a while it starts and runs. At one point I got it to idle for ten minutes and then it died. I am at $120.00 in parts and I am nowhere. I think I may be towing it to mechanic.
 
#14 ·
Mine had the same issue, I finally got it going. The thread is named 91 yj won't start...help!!! Or something close. Turned out to be a faulty fuel pressure regulator. Mine started working again after some work on it, but the diaphragm was good.

First thing to check would be the vacuum line to the regulator. If it's dry then the diaphragm is ok.

Next would be to carefully pull the return fuel line from the fuel rail. Have a piece of hose to slide onto the nipple (to route the fuel away from the engine compartment and into a gas can). The return line is the one closest to the radiator. With the hose in place turn the key on so the fuel pump runs. See if fuel is going through the hose you put on. If there is the regulator could be stuck like mine was. Make sure you have no leaks and try to start it this way. If no go, use a vice grip and pinch the hose tight and try to start it. (When I did this it forced the diaphragm to move and also flooded the engine. Now pull the fuel pump relay ( it's located in the engine. compartment in front of the battery. Second one from the engine side of the box. Now the fuel pump won't run. To clear the flood situation you can try to start it while holding the accelerator to the floor. Keep turning it over until it starts to run. It will die when the fuel is burned out. If you are severely flooded like I was, you may need to have someone help by turning the motor over with the gas pedal held down. And when it begins to run be at the ready to put the relay in to start the fuel pump. It will run rough for about a minute or so, may need to pump the gas slightly to help it run. But it should come out of it.

I hope this helps.
 
#17 ·
Yes I did the tps, I am stuck again. I hate to keep throwing money at it. I am thinking cap, rotor. Wires and plugs. I am planning that anyway but it was running fine and the plugs, cap and rotor look ok. I will spend the week tracing all the wiring but I might end up towing it to a mechanic.
 
#18 ·
Just a note on SPARK...... you should be able to HEAR a good spark.......and it should be BLUE-WHITE...... not yellowish.....
 
#20 ·
Grab ahold of the plug wire, if it knocks you on your ass, its a good spark. If it just gives a little jolt, its weak...:)
 
#23 ·
You mentioned that it had been running fine. What happened? Did you change something or do some work? Can't remember what was done.
 
#25 ·
I had a buddy come over and we are thinking fuel pump. We can't here it priming. When I press the pressure release on the fuel rail I get vey little fuel . I was going to go borrow a pressure gauge but wonder If I'd be wasting my time. If no fuel shoots out of that valve and we can't hear the pump it seems a slam dunk. Any thoughts?
 
#26 ·
Not to be a smart A$$ but is there fuel in the tank. Remember the movie Sling Blade.
It happens!!!!!!!
 
#27 ·
That would be really funny but yes, a full tank of gas. That will make dropping the tank fun if I need to go that route. I hear absolutely nothing from the pump so hopes are high. As soon as I get a bit of time my plan is to inspect all wiring leading from that fuel pump and then check the pressure at the rail. I will also disconnect the fuel line and see how much pressure is in the line just to be sure it's not the fuel pressure deal on the fuel rail.
 
#28 ·
Ok now I am perplexed. Zero pressure at the rail so I did the fuel pump. Same symptoms plus my fuel gauge is pegged on full. I must have messed up putting it back in the tank. Will need to drop the tank again. Starting to feel I am throwing good money after bad at this point.
 
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