Full Size Jeep Network

Hopefully you guys can help me, if not I have to find a baby jeep forum.

I just bought a 73 CJ5 with the 4.0 and AX15 from a 1998 TJ. I bought it 3 hours from home. About 80 miles from where I bought it, I ran out of gas. Had my wife bring me a gas can with a couple gallons, then I started it right up and drove to a gas station to fill it all the way. After filling it, it wouldn't start.

The next day I towed it home and have been tinkering with it since. So far I replaced the CPS and the coil. I know it's getting fuel, but for some reason it's not getting spark. Anyone have any ideas on what it could be?
I have 0 ideas at this point as I checked all of the connectors, relays, fuses, and I changed the CPS and Coil which are the 2 normal culprits on a 4.0.

Check all your grounds. Then check them again. The big culprits for 4.0 issues are crank sensor, cam sensor(on last gen versions), and poor grounds. You can verify your 5v reference stuff is functioning as well but I would start with all the grounds.


Sent from my iPhone using Tapatalk

I should add. It cranks forever and won't start. At first I ordered a coil and CPS from rock auto, and the jeep started up right away, I drove it around the block and everything was ok. A few hours later I needed to go to the store and it wouldn't start again.
So now I got a decent coil and CPS (as opposed to the cheap crap Chinese rock auto stuff) and it still won't start, just endless cranking.

Test the new CPS. Test the coil. Verify they both work. Lots of CPS come out of the box as junk. But I'd guess you have a ground issue. Poor grounds will make it difficult for the 5v sensors (such as the CPS) to function. Check the passenger side of the block for the two sets of grounds as well as the one on the back of the head. Clean them and make sure they are making good contact.


Sent from my iPhone using Tapatalk

Wait, how can it crank but not turn over? Unless this was a typo?

Have you checked for spark? And when you say CPS, do you mean crank position or cam position? Either can cause it to not run.

Stuka wrote:Wait, how can it crank but not turn over? Unless this was a typo?

Have you checked for spark? And when you say CPS, do you mean crank position or cam position? Either can cause it to not run.

Sorry typo, between working 50+ hours and a 3 month old my brain doesn't work to great.

It is the Crank sensor I've changed out. I hanvent checked the cam sensor yet.

I'm assuming it's not getting spark, since it's getting fuel.

Stuka wrote:Wait, how can it crank but not turn over? Unless this was a typo?

Have you checked for spark? And when you say CPS, do you mean crank position or cam position? Either can cause it to not run.

I think he meant it turns over but no fire. A 98 4.0 wouldn't have a cam sensor as it still runs a dizzy. It wasn't until jeep went to the coil on plug that they put in the cam sensor. The crank sensor is mounted on the bell housing and are frequent issue makers.
I'd suggest he starts simple and moves forward from there. Grounds. Test the coil for signal in. Test the cps or put one of the original ones that worked back in (it may work just fine).
Check for fuel at the rail. Check for fire at the plug.


Sent from my iPhone using Tapatalk

All of the grounds are in place, there is fuel to the rail, the small bit of exhaust that comes out of the pipe reeks of gas. I've tried it with both could the one I bought it with and the replacement. If it was the CPS it wouldn't have fuel as it cuts the spark and the fuel.

Where is the computer mounted?


Sent from my iPhone using Tapatalk

On the firewall behind the battery

I wish I had an easy answer for ya. Since things look a bit dirty it may be worthwhile to pull the grounds and clean any paint/corrosion off them. The one from the back of the head into the firewall looks kinda shady. Also, you may want to pull the connectors apart and clean them well and add some dielectric grease.
Does your computer have a few wires coming off it that go to a ground? Kinda like these??


I played hell with my XJ and had to spend a good while fixing grounds and checking wires/connectors. If your getting fuel then you can probably take aim at ignition. Are you getting voltage to the coil?


Sent from my iPhone using Tapatalk

I found a couple of broken wires and another ground, but they don't look they they broke off recently. I did not realize when I bought it how messy of a swap the PO did. Lots of messy wires, sensor ends that are no longer needed, wires that went to the old engine etc.

I did try starting it again after messing with the grounds a bit. It didn't fire but the fuse box started vibrating when I turned the key to the on position. I'll upload a video of it when I can.

I do not have wires coming off of the computer like that.

tedlovesjeeps71 wrote:

Stuka wrote:Wait, how can it crank but not turn over? Unless this was a typo?

Have you checked for spark? And when you say CPS, do you mean crank position or cam position? Either can cause it to not run.

I think he meant it turns over but no fire. A 98 4.0 wouldn't have a cam sensor as it still runs a dizzy. It wasn't until jeep went to the coil on plug that they put in the cam sensor. The crank sensor is mounted on the bell housing and are frequent issue makers.
I'd suggest he starts simple and moves forward from there. Grounds. Test the coil for signal in. Test the cps or put one of the original ones that worked back in (it may work just fine).
Check for fuel at the rail. Check for fire at the plug.


Sent from my iPhone using Tapatalk

They don't have a distributer. They have a cam position sensor in the location of what looks kind of like a distributer. But has no distributer guts in it.

EDIT: I may be confusing the year now that i think about it. I recall working on a friends 4.0 Wrangler, and the distributer was basically gutless with just a pickup. Feel free to correct me though.

Stuka wrote:

tedlovesjeeps71 wrote:

Stuka wrote:Wait, how can it crank but not turn over? Unless this was a typo?

Have you checked for spark? And when you say CPS, do you mean crank position or cam position? Either can cause it to not run.

I think he meant it turns over but no fire. A 98 4.0 wouldn't have a cam sensor as it still runs a dizzy. It wasn't until jeep went to the coil on plug that they put in the cam sensor. The crank sensor is mounted on the bell housing and are frequent issue makers.
I'd suggest he starts simple and moves forward from there. Grounds. Test the coil for signal in. Test the cps or put one of the original ones that worked back in (it may work just fine).
Check for fuel at the rail. Check for fire at the plug.


Sent from my iPhone using Tapatalk

They don't have a distributer. They have a cam position sensor in the location of what looks kind of like a distributer. But has no distributer guts in it.

EDIT: I may be confusing the year now that i think about it. I recall working on a friends 4.0 Wrangler, and the distributer was basically gutless with just a pickup. Feel free to correct me though.

Not to be argumentative brotha but if his motor came from a 98 TJ it will have a distributor. The cam position sensor your thinking of didn't enter into the 4.0 until 2000. Same time the went to a coil rail/coil on plug.

91-1999


2000^



Sent from my iPhone using Tapatalk

Which is why I said I may be off on the year. But still, he needs to check for spark. No point in doing anything else till he checks that. Could easily be a magnetic pickup.

I agree. Test for spark.


Sent from my iPhone using Tapatalk

98 DOES have a cam sensor. It is in the distributor housing. It will also cause a no start. I have a 97 TJ, same set up.

I give up... Sorry to the OP for the sidebar.