[SwoleJeep88]

I have a 95 yj with the 2.5 and it won't fire I have changed the pickup coil in distributor the ignition coil. Cap wires rotar and plugs also changed.. I have the computer out ready to send off but I've seen people say on here that if the ECU is bad the check engine light won't come on when you turn the key on..mine does come on could it still be ECU? I figured it had to be I've changed everything else.. Thanks for the input.. Oh and also changed the crank sensor..

 

[Pmryall]

Is it throwing any codes? You sound convinced it's a spark issue. So you've checked and have no spark at the plugs? And you hear the fuel pump and you have fuel pressure? Did you check your sensors. Crankshaft position sensor etc?

 

[SwoleJeep88]

When I turn the key the fuel pump kicks on and was just getting the 55 end of codes.. I'm getting power to coil checked with test light but no fire at plug.. Yes I checked

 

[Pmryall]

Sometimes you can get a bad coil. If you know how I'd check the spark coming out of the coil it should be a bright blue. Not orange. If that's good I'd visually inspect that the distributor is turning properly. Im sure you were careful but double check that all wires are going to the correct cylinder while your at it.

 

[SwoleJeep88]

No spark coming from coil how would I check if distributor turning properly I've never taken it out?

 

[SwoleJeep88]

It started where it wouldn't crank sometimes then it got more and more often and now not at all if that helps any

 

[Pmryall]

Well if you got power to the coil. And no spark coming out of the coil I'd return the coil and get a new one. To see if the distributor is turning you don't have to take it out, just remove the cap and I usually get a wrench on the crankshaft pulley and turn the engine by hand. But you could have a friend turn the key while you watch. Just a couple of clicks to make sure the rotor is turning. But since you don't have power coming from the coil I'd focus my attention there. I would also check the crankshaft position sensor. Since that can stop you from getting spark. I'm actually not sure where it stops the spark, could be at the coil. So your coil could be good but the sensor could be preventing it from firing. I sold my YJ so I can't run out and look to see if there is a sensor wire coming out of it. If there is. I'd suspect that's your problem.

 

[SwoleJeep88]

The crank sensor is brand new unless it's just a faulty one.. Idk I been fooling with it for a while I think I've just about replaced everything except the ECU and distributor so idk

 

[Pmryall]

Sounds like it. It could be the ecu. It's starting to sound like you've eliminated everything else.

 

[MudMagnetYJ]

Disconnect the battery and reconnect it. This will shoot another code for memory loss (I can't recall which one,). There is another code for the AC that Wranglers without air conditioning will get. If don't get any of these codes, I think you were correct in your first post, it's probably the ECU.

 

[SwoleJeep88]

Well replaced the ECU still no fire.

 

[SwoleJeep88]

Have no idea what it could be

 

[WICruiser]

Back to the basic diagnosis - does the new to you ECU show any codes?

 

[MudMagnetYJ]

Is the CPS a good brand? Things like that are best to go Mopar, or maybe AC Delco.

DREDnot went through his manual and made a list of what signals the Jeep needs to start. I saved it. Here it is below:

On:
Barometric pressure (from the MAP sensor)
Engine temperature (from the coolant temperature sensor)
Throttle position (from the throttle position sensor)
Intake air temperature (from the Intake Air Temperature sensor)

Start:
The crank position sensor (bellhousing)
The cam position sensor (distributor)

Running:
ASD and fuel pump relays
Injector timing and ignition timing signals


So now you should be looking at the cam position sensor, MAP sensor, coolant temp sensor, TPS, and air intake temperature sensor. Cam position sensor is the more likely option. If you don't even have spark at the coil, don't worry about the distributor yet.

 

[MudMagnetYJ]

In the fuse box under the hood, check the auto shutdown (ASD) relay. It should click when the key is turned.

The ASD is powered by a circuit from the PCM that also powers the fuel pump relay. If the fuel pump works, then the ASD is getting power. Now you need to make sure that it clicks. You can just replace it, or replace it with a relay you know is good, like the fuel pump relay, and check for spark.

After the ASD relay closes, it powers the ignition coil. The PCM then controls the ground of the coil. Here is a wiring diagram. It shows the wire going to the ignition coil from the ASD relay and the ground from the PCM. Check continuity for each wire between the ASD relay (where the 86 pin goes into the box) and coil, and the PCM and coil. Your test leads for your multimeter should be long enough. Read closely.

PS...
When checking spark, ground it to the engine, then ground it to the chassis. Spark on the chassis but not engine means bad engine ground.