Check your grounds I know it sounds stupid I just did a rebuild myself and the timing ended up being off like 3 teeth but check that and use dielectric grease on all electrical connectors it will be your best friend workin on a jeep

 

Some of the diagrams are confusing. My #1 is at the 5:00 position viewing from the side.

My ballast resistor gets battery current to the front and put's about 9 to the rear/wire to the pump. I gather it's OK to bypass/eliminate it, just noisy!

Checking cam timing and verifying that your timing mark on the pulley is correct have been suggested because you situation is so....imposable! There is some stuff on that in post #20.

Edit. I see now in your photo you have #1 at 5:00. If course that's where you started the firing order. Regarding Rich's idea with the timing light in #42...if it's popping and kicking out. Maybe unplug all but #1 and see if you can verify spark at tdc on compression that way.

Aftermarket performance cam? Like Slick said, I'd want to be sure there's not something off there. (Slick's pretty sharp)

Like you wrote, you need to be able to crank it over. If you can't just crank it with the coil wire off, might as well address that!

 

You said you replaced the cps before you rebuilt the engine, when you pulled the engine did you happen to leave the cps attached to the transmission? If so when you put the engine back in it might have damaged the cps. I made this mistake when i reinstalled my engine I chased this problem for about a week until i decided to check it

 

It's back to basics - fuel, air, spark, compression -- and a way for the gasses to get out again.

To dispel wild *** guesses by the clueless -

Doubtful it the cam is ground wrong or even the timing gears installed wrong. - it stopped running BEFORE you rebuilt it. It's something external, not related to the rebuild. How did it know you were gojng to put in the wrong cam or screw up the timing gears.

CPS - without a cps working - you get NO SPARK AND NO FUEL. rule that out. You cannot expect to check a CPS with an Ohm meter.

O2 sensors don't affect initial starting. You could remove them entirely and it will still start.

Even things like temp sensors, TPS etc don't come into play if it won't start. They affect how it RUNS after it starts.

If you have fuel pressure it's not the resistor - the resistor is to run the fuel pump. If the pump didn't run, then you'd have 0 fuel pressure.

If the Noid light flashes, it's getting a signal from the ECM fuel is getting into the cylinders if it has pressure. Your fuel fouled plugs indicate it's getting fuel. If the plugs are fouled, that alone can prevent starting. Try the tow-truck driver's trick - hold the coil wire out from the distributor 1/4" to increase the secondary voltage - often that starts fouled plugs.

If the spark is even close to 0-10 degrees during cranking - that's close enough to start.

What's left? You said it has started briefly for a few seconds, if the exhaust is plugged it cannot exit the gasses, therefore it cannot take in more air - it dies.

Loosen the exhaust manifold at the headpipe - or loosen the connection at the cat. Give it a chance to breathe.

Also - connect a vacuum gauge to manifold vacuum - cranking it should have AT LEAST 10" of vacuum - if the exhaust is plugged tight - it'll be close to 0.

Let us know!

 

Just to help inform you, upon rebuilding my current engine I found that I could not install the distributor in the correct position with the alignment pin installed in the cam sensor. I talked to a tech at Melling who then contacted an engineer at the shop that made the master program to grind all of their cams and they addmitted that they do not index the distributor drive gear when making any of the Jeep cams. They assumed that you would be able to turn the distributor to compensate. Since no one ever complained to the company they've been milling them out that way ever since the new design. Also should be noted that "old" timing gear sets (no one can confirm how old yet) will have fewer teeth. The FSM says there should be 15 teeth between the timing marks on the gears when they are properly installed, even the guy at Melling said this, until he noticed that there are more teeth on the newer gear sets. He said he couldn't be sure how many teeth there were suppose to be since no one re-wrote the information he had. Kind of wish I could get a Mopar engineer to give me the straight story behind this. I've confirmed there should be 20 teeth with newer timing sets that have 24 teeth on the crank gear and 48 on the cam gear.

I will admit however that would not cause his initial starting problem but certainly could be a new problem causing the same symptom. I tend to agree that the problem is somewhere else. And for a cat to stall an engine it would have to be completely melted shut. I've never seen one so bad it wouldn't let an engine start though. I've never heard of anyone who has witnessed such a thing, but I would not rule it out if someone could provide evidence that it will.

It bugs me that we still don't know why it won't start and make me fearful that mine wont when I finally attempt to start it...

 

Problems from rebuilding may be complicating things, but remember IT QUIT BEFORE THE ENGINE WAS REBUILT. If would have been better/easier if WHY was determined before rebuilding.

It started a few times briefly - a very plugged exhaust certainly CAN keep it from running longer, - it tries, then dies. Then the plugs get fouled, stopping even from trying more.

A baffle inside the cat can come loose and block off the inlet or outlet, completely plugging it off. It's not real common, but it does happen. I saw it several times when i had my shops.

Just recently a friend called - her Toyota was running fine, she parked it in her driveway, wouldn't start the next morning. Everything seemed normal, but I didn't have tools with me. I did try holding my finger over a vacuum hose while cranking - very little vacuum while cranking. I found a block of wood and whacked the bottom of the converter a few times (it rattled when I did that) - it started an ran fine! I suppose it moved the broken baffle out of the way enough. She replaced the converter a few days later - but it was still running fine then.

Taking loose the exhaust so there's a big crack won't be hard, especially since he had it loose for the rebuild. Even if that's not it, it eliminates that as a possibility.
He He - seems like most everything has been tried already!

BTW - the cam sensor determines WHEN the spark should fire for each individual cylinder AND it determines the time for the injectors to fire. (As opposed to the Crank Sensor - it determines WHICH cylinder is #1.)
If the injectors fire at the wrong time, too early or too late it will still run, fuel gets in there anyway, just not atomized as well as it should be.
But if the spark fires at the wrong time it will not even try to start - too soon it'll buck and kick, too late not much happens - sometimes you can hear late in the exhaust - a low grumbling sound.
That's why the suggestion to use a timing light during cranking (checks spark timing.) If it's firing even close to what it should be, then it's not the cam sensor.

But - he said he had trouble seeing it because it was unstable - "bucking?" Remove the coil wire - see if it still has cranking troubles. If so, it's not because of the spark being off, it's a starting circuit problem.
If the cam was indexed wrong, there should be a "sweet spot" where it runs, just the index marks won't be right. Seems like I remember he said he twisted the distributor around to no avail. -- no "sweet spot."

 

thanks guys I appreciate all the support and especially the " not assuming I am an idiot" I am as frustrated as you can imagine because I have tried so many different things. and rrich I will try loosening the exhaust later today. btw I pulled the starter off this morning and found that the starter drive was ground off but the starter ring on the flexplate looked ok. so my new 300.00 high torque starter is the problem but at least I won't have to put in a new flexplate. I put a rebuilt starter back in and it cranks fine now. it also fired and ran for a few seconds by feathering the throttle quite a bit. when my dad gets back from nebraska, if loosening the exhaust doesn't do it, I will try putting the timing light on it and see what we can see.

thanks again guys and again I really appreciate all your suggestions. eventually I am going to get this stupid thing running.

and yeah I know I should have fixed it before I rebuilt it (here's me looking sheepish and scuffing my shoe) but I was mad at it and I was sick of getting covered in grease everytime I tried anything so I did it and yes my Dad told me I ought to fix it before I rebuilt it too. but what's done is done. live and learn.

 

Not quite: the Crank sensor determines the spark timing. The distributor points the spark at the correct sparkplug. The cam sensor is used to determine which fuel injector to fire.
Evidence:
1. The flywheel has 3 identical groups of 4 notches, the groups are spaced 120 degrees around the flywheel. Each group corresponds to one pair of cylinders (1&6, 2&5, or 3&4) approaching TDC. The Crank Position Sensor doesn't know which pair is which.
2. Firsthand experience: I installed a new flywheel, that turned out to be made wrong - the groups were 60 degrees away from where they should have been. The timing was 60 degrees advanced. Swapping back to the original flywheel brought the timing back to normal. (Distributor and wires were not touched in either swap).
3. Hearsay: I've read that it will run without the camshaft position sensor (but I don't know this for a fact, so take it with a grain of salt) - the computer will revert to batch firing the injectors.

None of this relates to the problem of this thread, but I hate to see misinformation floating around.

 

"it also fired and ran for a few seconds" Fantastic! While you're checking the exhaust, check the tale-pipe and make sure there is not a potato in it!

 

What you have probably heard was it will run without the CPS once it's already running. It will, until something causes the computer to lose track of which is which. ie: A sudden change in RPM.
Upon initial starting BOTH signals have to be there.

The distributor rotor only guides - directs - the spark to the right cylinder, it does not determine WHEN anything. The cam sensor underneath tells the computer when to fire each individual cylinder - it also tells the computer WHICH injector to fire and when.

 

What you have probably heard was it will run without the CPS once it's already running. It will, until something causes the computer to lose track of which is which. ie: A sudden change in RPM.
Upon initial starting BOTH signals have to be there.

The distributor rotor only guides - directs - the spark to the right cylinder, it does not determine WHEN anything. The cam sensor underneath tells the computer when to fire each individual cylinder - it also tells the computer WHICH injector to fire and when.
Use a good scanner where you can see the relationship between the 2 and what they do.


At least that's for the OBDII systems, the old RAMBLER type may be different.

 

Ok not to hijack the thread but I am having the same issue.87 4.0. New plugs fuel filter pump map sensor. Please let us know what you find!
I am replacing cps this weekend.

 

lol, well I disconnected the exhaust and I did not find a potato in it. anyway after I disconnected the exhaust I decided to video it so you can see what I am up against. I am sure it is out of time I just don't know why. I am thinking that one of the new components I bought is bad but I just feel like I am chasing my tail.

click the picture and it will take you to the video.

 

Guess you are beyond this but just in case. (some diagrams are just plain wrong).

There's the screw. That's #1 with the yellow connector sitting on it.

 

Did it run like that before you disconnected the exhaust? Or worse?

Did disconnecting it help even a little?

I see you are in a shop with a hoist - do they have a scope? If so, hook it up. It will tell you what's going on. Take a picture of the pattern when it's doing that and post it here.

The plugs - fouled now after that? Did you put in new or clean ones before the video?

Next step, I'd try adding some propane, it could be super lean for some reason - take a propane torch, remove or drill out the tiny orifice so you get more propane. Remove the tip - run a hose from there to the TB. Give it a shot of propane. See if it'll start - with new plugs of course.

It does not sound to me like a timing issue from the video - just lots of misfiring.

It sounds like it's starving for fuel - like low fuel pressure or something is limiting the flow.

Any real backfiring? Out the top or bottom?

Did you check fuel pressure? What happens to the pressure when it tries to start like that. You can have normal pressure but low flow. If something's restricting the flow, the pressure will drop radically when it tries to flow.

Did you ever put a manifold vacuum gauge on it and try to crank it?

It's bound to be something simple - but finding "what" is the hard part.

I wish I was there!