Need Advice on Next Steps – 1989 YJ 2.5L Cranks but Won’t Start

89JeepYJ

89JeepYJ

New Member
Joined
Feb 22, 2026
Messages
10
Location
Gloucester, Virginia
Looking for some guidance on how to proceed with a project Jeep Wrangler YJ.

It’s a 2.5L 4-cylinder with about 107,000 miles. The first thing I checked was whether the engine would turn over, and it does crank normally.

Next I went through the fuel system. I ended up replacing:
  • Fuel tank
  • Fuel pump
  • Fuel filter
I also replaced the spark plugs and verified that I’m getting spark at each plug.

When I try to start the Jeep, it cranks but won’t fire. If I spray starting fluid into the intake, it occasionally sounds like it wants to catch for a second, but then it goes right back to just cranking.

I decided to run a compression test and got the following results:
  • Cylinder 1: 90 PSI
  • Cylinder 2: 90 PSI
  • Cylinder 3: 80 PSI
  • Cylinder 4: 130 PSI
Obviously those numbers aren’t within the recommended range, which makes me think the compression issue could be why it won’t start. Would these compression numbers alone prevent it from starting, or should I continue diagnosing fuel/ignition before tearing into the engine?

At this point I’m trying to figure out what my next steps should be. Should I be looking at valves, head gasket, rings, or something else first?

Any advice from those of you with experience on these engines would be greatly appreciated.
 
First off is this new to you? Been sitting a long time? Past history, head gaskets, over heating kinda thing. If your getting spark and you introduce fire water (gas) and it tires to start but wont, Id try some more cause it should fire for a little bit. If it never does Id be thinking valve timing/timing set installed wrong, it skipped a tooth, or the dist is off a tooth. That last one caught me on my 91. It would run then not start but it sounded weird and didnt run real good obviously. The compression isnt great but it should still run in light of that. The ECM will time it within reason but off a tooth on the dist is to much off. have you checked fuel pressure? can you hear the fuel pump buzz for a couple seconds when you turn the key to run? There is so many crappy parts to be had these days its sad. I'll add Ive had 15 jeeps and have avoided 87 thru 90 because of smog crap or the TBI injection. That being said Im not even sure if yours is FI or carbed. Regardless, the same applies pretty much.
 
It’s new to me. I bought it about a month ago and from what I can tell it had been sitting for roughly 25 years before I got it. First thing I checked was that the engine would turn over, which it does.

I went through the fuel system and replaced the fuel tank, fuel pump, and fuel filter. I can hear the pump prime for a couple seconds when I turn the key to the run position. Right now it cranks strong but won’t fire. I do have spark, and if I spray a little gas into the throttle body it will try to start but won’t stay running.

I’m not sure if it overheated. I changed the oil and didn’t see any signs of coolant contamination or anything that would suggest a blown head gasket.

I don’t have any real history on it since it sat for so long. Since it tries to fire with fuel added, I’m leaning toward either a fuel delivery issue or possibly timing. From what I read in my Chilton manual- the timing is controlled automatically and cannot be manually adjusted.
 
25 years is a long time to sit for sure. It do sound like a fuel delivery issue for sure. Are you getting fuel to the fuel injector? It itself might be completely corroded and/or gummed up and plugged off. Rockauto has parts for the TBI systems which can be tricky.
 
It is delivering fuel. I removed the supply line at the throttle body and when we turned the key, fuel was coming out.

I also noticed I do not have a check engine light. In fact, none of the dash lights come on when the key is turned on. I ordered new bulbs from Amazon, but it seems unlikely that all of them would be bad.

I then turned my attention to the ECU once I finally found it under the passenger-side dash. It appears to back right up to the ignition coil on the firewall. While looking at that area, I noticed there is a plug missing at the top of the ignition coil.

Is that intentional, or am I missing a critical connector that could be causing my no-start issue?

IMG_3757.jpeg
 
Top Bottom
Back