Hatsuwr

Well, I decided the engine needed a good cleaning (don't think that had been done in about 20 years) so I took out most of the components in the engine bay, except for the engine itself, AC system, parts of the cooling system, and a few other small things. Put it all back together and it cranks, but won't start.

I waited a few days and dried everything thoroughly. Only things I replaced were the exhaust header, intake/exhaust manifold gasket, and brake/power steering fluid. Nothing I would expect to cause starting issues.

No codes. I had a P1492 because I hadn't put the battery tray in yet. Put it in, plugged in the sensor, and that went away.

Tested spark - have it on at least plug #2 - will test the others when someone is here to help, or if someone has an easy way to check with one person.

Used a test bulb for the connector to injector #2. It was good. Have yet to test other injector connectors, but will do the same as with spark plugs... or just get some longer cables and put the bulb near the driver's seat.

Air cleaner and hose to the throttle body are off.

Tested fuel pressure on the rail - it is there. Haven't gotten a psi reading yet, but it seemed normal.

Tried spraying starting fluid in the throttle body while cranking. No luck.


Any thoughts?

Hatsuwr

Sorry, thought my details would show up on the side.

It's a mostly-stock '96 ZJ with a 4.0.

Hatsuwr

All 6 injector connectors are firing normally.

Fuel pressure when pump primes before cranking engine is about 47 psi. Gauge fluctuates while cranking - it looks like that is in response to the injectors injecting, but I suppose it could just be vibration. The needle seems to drop ~10 psi and then return to 47ish with a frequency that seems roughly in line with the frequency of injections.

Also, didn't notice this before, but a small amount of white smoke came out of the crankcase vent tube.

*edit*

All fuses are good. Haven't checked relays yet.

I hear a small clicking or sparking noise from around the distributor area. This may be normal, I wouldn't have noticed it if I hadn't been looking for something.


Running theory is that I somehow damaged/dirtied most/all of the injector ports when I cleaned up the intake manifold. Will post back when I find more.

Hatsuwr

All injectors shoot fuel ~16 feet when manually activated while haphazardly sitting on the engine. I think that's right about spec.
So, it's not the injectors, although their shots were more 'stream' than 'spray' like. Might have to get some of those fancy four-hole injectors.

Next steps: test relays, test compression, hit it with a large hammer.

Running theory... I have angered the Jeep gods.

Hatsuwr

Compression was 120 psi.

Ok, thinking out loud...

Air - Throttle body is directly exposed. Have starting with the throttle open to various degrees. Route from throttle body to cylinders is clear.
Possible air issues:
None.

Fuel - Have tested each injector connector with a test bulb. All work. Have tested function of each injector. All work.
Possible fuel issues:
Injector connectors attached to the wrong injectors. Very unlikely.
Injectors not atomizing fuel enough. They look fine to me though.

Ignition - Have spark plug #2 - it works. Will test others when I have help.
Possible ignition issues:
Most/all other spark plugs are bad. Unlikely.
Spark plug wires connected incorrectly. Extremely unlikely.
Spark not strong enough. Don't know how to tell.
Distributor out of sync. Shouldn't be, I didn't remove it.


I can't think of anything else besides all of these things. I'll start going through them and try to be a little more sure. Any other suggestions?



Video of it not (but almost at one point) starting.

dave1123

Okay, I had to put on my tinfoil hat for this one. No firing on starting fluid shows no spark during cranking. That stuff is ether based and should light just by looking at it!

It sounds like you may have weak spark, but not enough voltage to fire the plugs under compression pressure. I'd investigate that "snapping" you heard around the distributor, like cap, rotor, or wires shorting to ground. Check the cap for a crack caused by overtightening the screws. Check the coil for resistance or swap with a spare. Also check your GROUNDS!

That white smoke you see is probably unburnt fuel washing down the cylinder walls. Keep sparks away from it. I had an explosion in a Chevy that blew both valve cover gaskets when it fired. We found the dipstick about 30 feet away and the oil pan gasket leaked after that. Too much ether!

I hope this helped.

Hatsuwr

I think you are right - found some water in the distributor cap. Didn't even consider that since I covered it and was at least getting some spark. Cleaning it out and putting some of this in to make sure it seals:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I'll update with results once my battery is charged up enough to start! Jumper chose today of all days to fail.

Hatsuwr

It works! Thanks for the advice!

Idle air control motor also threw a code shortly after starting it up... might have been contributing. Cleaned it and the port up a bit and it was good to go.



Rope caulk for the distributor.