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Discussion Starter #1
Hello all,I need help in getting my 1990 Jeep YJ running again.I purchased this six years ago and has been trouble free since then.It currently has 100,000 miles on the clock and has never been driven in winter salty conditions.When I try to start it,it turns over fine but that is all.When I turn the key to run position I can hear the hum of the fuel pump and I do have spark.Any help to point me in the right direction would be greatly appreciated.
Here are the specs:
1990 Wrangler YJ 2.5L
TBI with 5 speed manual transmission
 

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Welcome to the Forum opperman,

Check out the post above by IRQ. Click on "show full signature". Click on the red + sign. That will take you to several Factory Service manuals. Find the FSM for your Jeep and search the index for 2.5 motor. There should be a diagnostic flowchart for no start. Either in the general engine section or the specific 2.5 section.

Good Luck, L.M.
 

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I'm not certain about the throttle body injection model you have but on the later models
It should blink momentarily prior to starting, if it does not it is one of the signs of a faulty PCM.

Here is a write up:

Here you can learn about capacitors:
 

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Discussion Starter #7
I do not see a CEL appear when I turn the key and don't ever recall seeing one when the Jeep was running properly.
I have looked under the dash and cannot find a PCM.The only device I see that resembles a PCM is an Emissions Maintenance Time(that is what is printed on it) Also no matter what I do with the ignition switch I can't get a CEL to light on the dash,any thoughts? Thanks in advance
 

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PCM (computer) is on top of the heater box. Just a bit right of center.

The first thing to do is make sure the bulb is good. Previous owners have been known to remove the bulb prior to sale if there's a fault. The fact you have spark makes me think the issue is in your fuel system.
Did you follow the no-start flowchart? Do you have a fuel pressure gauge or at least access to one.

Good Luck, L.M.
 

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You have either a engine control module (ECM), or a powertrain control module (PCM).

Typically it is located in your engine bay, as Lucky has stated the FSM is full of troubleshooting instructions.
 

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Discussion Starter #10
Hi folks i'm back after trying a few things on the YJ.I disconnected the fuel supply line at the throttle body turned key to run position and got fuel to this point so I'm assuming the fuel pump and filter are good.The next thing i tried was to pour a little gas into the throttle body and I did get the engine to fire.Any suggestions where to look next??
Thanks in advance
 

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You need a fuel pressure gauge. Your FI system needs a certain amount of pressure in order for the injectors to operate. I have a carbed 4.2, so I don't know exactly what that pressure needs to be. The info is in the FSM.

Good Luck, L.M.
 

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Discussion Starter #12
Hi guys,I'm back to report what I have done with the fuel pressure gauge.Since I was working alone and wanted to keep an eye on the gauge I put a three foot piece of hose on it so I could observe the readings.I read the fuel pressure before and after the fuel filter and the reading was 5psi.If I turn the key on and off several times I can get the pressure to build up to 15psi and hold that pressure either before or after the filter.I don't know if adding the extra three feet of hose to the gauge has messed with my readings.Any suggestions? Thank you again, Opperman
 

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What does the FSM state the fuel pressure should be? I kinda-sorta remember it should be around 30PSI. I may be way off.

Good Luck, L.M.
 

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Discussion Starter #16
Hi guys, heres what I did today with the no start YJ. Since I had the fuel filter out I put my fuel pressure gauge in line with the fuel line and had wife turn over the engine.I saw 19 psi. on the gauge and went back to 0 psi. when key was turned off.I was originally thinking it was a fuel pump issue or dirty pickup now I'm at a stand still again.Anyone have any ideas where to check next? Thank you, Opperman
 

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Do you only have fuel pressure when you crank it or do you maintain 19 psi with the key on? Also you could have a bad injector. Rent a noid light and check your injector.
 

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Discussion Starter #18
I have the 19 psi while cranking only.I will have to read up on a noid light. thank you
 
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