FrossB

So I bought my 1996 Cherokee Country about one month ago. It has a 4.0 with 170k on it. Haven't had an issue with it till a few nights ago.

Went to start it for work and it just cranks and cranks but doesn't fire. Checked the CPS sensor and it tested fine via an Ohm tester but that isn't always conclusive. But I took a chance in assuming it was good. I then checked what kind of fuel pressure I'm getting by using the Schrader valve on the fuel rail. Checked out fine. Pulled a few plugs to check spark and was getting orange spark (not a powerful spark). So I replaced the plugs and the ignition coil and still won't fire.

Not sure if its a possible cause but my first O2 sensor is broke. I wouldn't think that's an issue since it ran perfect for a month in that same state.

Do I just buy a new CPS anyway? I don't want to blindly throw parts at it if I don't have to. Any other ideas? By reading all the other threads with this problem, they are solved with what I've already tried

Thanks

freegdr

Have you checked all fuse for power on both side with key on ,?

FrossB

What specific fuses? I visibly checked the smaller fuses and they all looked good

PocketsEmpty

Try putting it in neutral, and then cranking it. Does it start up in neutral? If so, then your Neutral Safety Switch (NSS) is probably to blame

freegdr

Check all under hood and under dash for power if theres no power even a good fuse is useless

FrossB

Nothing when in neutral either. I humored myself with buying a new CPS just now and it didn't help

FrossB

Is there a specific fuse tho? Obviously I wouldn't need to check a headlight fuse for a starting problem. Could this be an o2 sensor/exhaust issue?

x91evo

You say your fuel pressure is fine, what was it while cranking?

Check #11 fuse inside the car by the passenger footwell,
also check all the mini fuses under the hood. I think #8 is the one youre looking for, but check them all anyway.

But to me sounds like a bad ignition coil, or bad (maybe out of sync) cam position sensor.

x91evo

Also I hope you bought that CrankPS from the dealer. If its not return it and go to the dealer. Thats the only sensor that is rumored to fail alot if it is not a dealer part.

FrossB

I'm not sure what my specific fuel pressure is. I turned the key on and it sprayed fuel pretty good out the Schrader valve so I (again) assumed it was fine.

And I changed the ignition coil and plugs and that didn't help.

I've heard the stories about the aftermarket CPS. I had to order it from my jeep dealer cuz they didn't stock it. But my local autozone had their ****ty version of a CPS so I humored myself by trying it anyway. I know the manager at autozone really well and he said he would let me return it even if I had installed it and it didn't work.

Radi

If it cranks your NSS isn't the problem. If you have consistent spark, the CPS is likely fine.
O2 sensor isn't used for starting, it'll be read later once the motor is running.
I'd grab a fuel pressure gauge and see what you have. 5 psi is enough to create a good spray out the schraeder valve, but you need much more than that for the motor to run.
Can you hear/feel the injectors clicking while you crank the motor?
Will it pop over with starting fluid?

FrossB

I haven't paid attention to the clicking of the injectors but I know that when I pulled the plugs to change them they had gas on them. So fuel is getting sprayed into the cylinder. And I tried spraying starting fluid into the intake tube too and it didn't even pop once

FrossB

Guess I'll check some fuses again today. Fingers crossed!

Radi

Still have a weak spark with the new coil or has it improved from orange to crisp blue?

FrossB

Being that it's real sunny out I can't tell for sure but it looks more white than orange now.