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post #1 of 17 Old 05-25-2020, 05:18 AM Thread Starter
jbravata2
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No start

I have a '94 YJ that won't start. The fuel pressure gauge reads about 32psi and I verified spark. The Jeep will start with starting fluid but dies quickly. I have replaced the PCM, CPS and the ignition switch. I have pulled and checked all of my fuses. What else could it be?

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post #2 of 17 Old 05-25-2020, 05:58 AM
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You verified spark how?

Also... have you verified the spark in terms of numbers...voltage readings?

Have you verified it maintains the 32psi while running? It seems like it dies quickly so how would you? Does your gauge hold highest pressure reached?

I had a fuel delivery issue just two days ago...well fuel maintaining issue really. Ended up being my fuel pressure regulator... the diaphragm was leaking back to the return line. I verified by pinching off my return line with vice grips while trying to fire her up. Be care full doing this as the PSI will SPIKE.

It could be the check valve at the fuel pump or the fuel pump itself (although since you said it pumps 32 psi, doubtful).

How old is the fuel filter? Have you looked into air delivery? Any CEL codes?

Stop whining about the 'ride' - If your YJ ain't wrangling your soul free, then might I suggest you buy a stationwagon... at least you can fit all your bull**** in the back.
~YJOTM MAY '16~
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post #3 of 17 Old 05-25-2020, 06:03 AM
KARamsay
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Dumb Question - did you check the rail to make sure it was actually delivering fuel?
If you have spark, fuel then air are the only other ingredients.

If it were a carb, I'd say to look for a clogged vent in the fuel tank.
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post #4 of 17 Old 05-25-2020, 06:10 AM
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Does it only run when cranking? Sounds like you have adequate pressure at the rail and if it fires with starting fluid, the ignition sounds like it's working. If it's not a wiring issue where the Jeep only runs in start, I'd start looking at the IAC to make sure it's opening the throttle valve enough. Maybe a vacuum leak.

Have you done anything to the Jeep recently? Also, 4 or 6 cyl engine?


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post #5 of 17 Old 05-25-2020, 06:17 AM Thread Starter
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I verified spark with a simple test light that plugs into the wire boot.

It holds pressure (jumps to 40 psi) while running on starting fluid. How would I check fuel delivery from the rail?
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post #6 of 17 Old 05-25-2020, 06:46 AM Thread Starter
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I pulled each of the spark plugs and they are completely dry. What would prevent the fuel injectors from operating?
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post #7 of 17 Old 05-25-2020, 06:47 AM Thread Starter
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No recent modifications. I was backing out of the drive when it quit and hasn't ran since.
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post #8 of 17 Old 05-25-2020, 06:52 AM
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Quote:
Originally Posted by jbravata2 View Post
No recent modifications. I was backing out of the drive when it quit and hasn't ran since.
And it was regularly driven? Not sitting?

Stop whining about the 'ride' - If your YJ ain't wrangling your soul free, then might I suggest you buy a stationwagon... at least you can fit all your bull**** in the back.
~YJOTM MAY '16~
~YJOTM JULY '19~
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post #9 of 17 Old 05-25-2020, 09:03 AM Thread Starter
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Yes, it was regularly driven. One day it just died. New fuel pump, fuel filter, tune up, CPS, ignition switch, checked all fuses and swapped relays around. Is my next step to pull the fuel rail?
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post #10 of 17 Old 05-25-2020, 09:05 AM Thread Starter
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Is the fuel pressure regulator a possible culprit?
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post #11 of 17 Old 05-25-2020, 10:19 AM
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Quote:
Originally Posted by jbravata2 View Post
Is the fuel pressure regulator a possible culprit?
I just had this issue two days ago. Hence why my first post addresses it.

Stop whining about the 'ride' - If your YJ ain't wrangling your soul free, then might I suggest you buy a stationwagon... at least you can fit all your bull**** in the back.
~YJOTM MAY '16~
~YJOTM JULY '19~
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post #12 of 17 Old 05-29-2020, 10:03 AM Thread Starter
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Finally got a hold of a FPR and no change. Any other suggestions? I'm lost and grasping at straws. I'm open to try anything.
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post #13 of 17 Old 05-29-2020, 10:20 AM
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Originally Posted by jbravata2 View Post
Finally got a hold of a FPR and no change. Any other suggestions? I'm lost and grasping at straws. I'm open to try anything.



Try the opposite of what I instructed and pinch off the feed line after getting it started, see if it stays running longer. The pump may be pumping, but perhaps the check valve at the pump is now a dud.

Although I dont think this is the issue. It's a free quick check.

I'd look at the injectors and the voltage going to them. If one were down... you would still get something, but it would run like crap. But run, at least for a little.

After that... ECM.

Stop whining about the 'ride' - If your YJ ain't wrangling your soul free, then might I suggest you buy a stationwagon... at least you can fit all your bull**** in the back.
~YJOTM MAY '16~
~YJOTM JULY '19~
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post #14 of 17 Old 05-29-2020, 12:12 PM
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Have you checked for voltage at the fuel injectors? There could be a problem with your ASD circuit, which supplies the voltage to the injectors. You can see in the diagram the ASD relay in the power distribution center gets voltage, and relays it when powered up to the injectors, it should have constant voltage with the key on. The PCM has low-side drivers that ground the injectors when it "fires" them. I'd see if the injectors are getting voltage. If not, then check the relay, see if it is working.

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post #15 of 17 Old 05-30-2020, 01:21 PM Thread Starter
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Thank you everyone for your help and input! I finally figured out it was bad gas. It's an old Jeep so everything I changed was probably weak anyway but draining the old gas and cleaning the system did it!
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