stardust22

Hey y'all, thanks for looking.

I have a 4cyl 1986 jeep cherokee 2.5l. I went outside one morning to go to class and it wouldn't start. It has a very healthy crank and almost catches but not quite...

I checked fuel, spark, and compression and all those are good. My brother just replaced the CPS (less than 20,000 miles ago) and I am clueless as to why it won't start.

I replaced the coolant temperature sensor because I read online that it could be the culprit, and I tried to find the IAC but found out my model does not have an IAC and instead has an ISC (Idle Speed Control). So, replaced that and nothing.

I have tried spraying starter fluid into the throttle body while cranking, which does nothing.. It is definitely getting sufficient fuel and spark, and compression is good.

At this point it is possible that it could be the TPS or MAP sensors, but before I throw more money into it I wanted to get y'alls opinions.

Thanks.

jordan96xj

How did you confirm spark was good?

stardust22

Unplugged all four spark plugs separately and reattached their wire to it. Had a buddy crank the engine while I held the spark plug against a solid ground.

tjwalker

How about "quality of spark". Sometimes missed. You need a strong, blue, snapping spark to fire the engine. Yellow/orange/white is spark to be sure, but weak spark, which is often caused by a faulty ignition coil.

Your coil can be tested for both primary and secondary resistances with a meter and a manual.

stardust22

Tj,

The spark on all four spark plugs are strong and blue.

BlueRidgeMark

Okay, good diagnostic work so far.

Next question: Is that spark happening when it should? Pop your distributor cap and take a look at the rotor.

stardust22

Yes it is. I checked that as well while I was running tests on it.

cruiser54

How do you know the fuel pressure is correct?

stardust22

I never actually checked the fuel pressure, but it is definetly getting fuel from the injector.