Setting the Timing....

I did a search found that alot of the threads didnt answer my question.....
I dont have a manual and i just need some basics on setting the timing on the 92 Xj 4.0 AW4 for better starting up and running.
Can you help?

The timing is set by the computer.

Sweet! Thank you!!

Talyn said:

The timing is set by the computer.

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Is that true for the renix also? So.. basically all you have to do is time the distributor correctly when you put it into the block?

The rotor just has to be close enough in the cap for the spark to go to the right wire.

Within reason, that's true. Schooled in the old days, it took a timing light and tach/dwell meter to get it right. As emissions grew under the hood, there were some wierd vac lines that had to be plugged to get the advance turned off.

Part of the procedure is sticking the distributor back at Top Dead Center precisely. You can drill out the #1 spark plug lead on an old cap and get it really trued up from there. A used cam chain will be too loose to help, tho. Street motors tolerate an amazing amount of slop.

stephenspann27 said:

Is that true for the renix also? So.. basically all you have to do is time the distributor correctly when you put it into the block?

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I'm not very familiar with Renix as the oldest Jeep I had was a 91 XJ, but I believe it to be the same. Maybe someone else can chime in on this.

On the newer models, however (not sure when it changed, maybe with OBIT), the CPS (cam position sensor) in the "distributor" body , has to be synched closer with the "toothpick" method. If the timing chain stretches enough to throw this off, engine can miss. (until readjusted).

I havent had any "missing" yet. My desire was to find out whether I can advance the timing just enough so that when I hit the ignition, it can fire quicker for a speedier start up. i know that you can do this on old school rigs, but I didnt know if you could do it on the XJ.
It seems that when i hit the ignition, it will crank for a 1-4 seconds and then go. I have replaced the starter twice.
I know this sounds crazy, but it is desired mainly inpart to being a fireman. Those few second do make a difference when we get called out, mixed with the drive can mean the difference in being at the scene quicker.
You would be amazed how just a few seconds can really make a big difference.
The other thing is Oil Lubrication at start up. What Viscosity is best for those nights when i do get called out and it gets started and has just a few blocks to go and then gets shut off? any ideas?
I have been running "Rotella" 15-40 with a quart of MMO, and using a Mopar Filter,
I dont like the cheap stuff.

sprngfldxj said:

It seems that when i hit the ignition, it will crank for a 1-4 seconds and then go

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I've read on other threads here that the xj is designed that way, to ensure the oil pressure is up a little before actual ignition.

if all the electronics, fuel system and engine are in good working order, start up time is determined by how fast the flexplate/flywheel spins so the cps can send a signal to the ignition coil and fuel injectors.

what dramatically increased start up time on my 89 were; larger gauge battery cables, additional ground strap and ground wire cleaning, larger battery to starter relay wire, and battery upgrade. i also prime the fuel pump by turning the ignition key to the "on" position until i hear the radio play(accessories turn on) before i turn the key to the "start" position.

Your fuel pressure is dropping off when sitting. Either a leaking injector of the drain back valve/pressure regulator is leaking allowing gas to flow back to the tank. Sometimes if you put the key on the on position to allow the system to build pressure for a few seconds before starting helps.

It isn't a design feature, although it could be a good idea.

Some good info here, not all 100% correct.

On the Renix, it isn't going to fire until the CKP (aka CPS) has sensed and sent to the ECU the information that the engine is cranking at 300+ RPM.

For what reason, I don't know, but that is how it was meant to be. You could, if money is of less concern than the time, install a high performance starter and a monster CCA battery to spin the engine to 300+ RPM faster. I'm not sure if anyone make a gear-reduction starter, like Mean Green, but should be easy to search.

Fuel pressure dissipitating? Sure. You can check if that is your problem on some (maybe all?) XJs by turning the key to the RUN position and allowing the system to prime for 3 seconds. Do this maybe two, three times and the fuel system should be fully primed and if that was your problem you should see an improvement. If that is your problem then somewhere (search is your friend) there is one or more threads on the "BMW Mod" which is simply using a BMW fuel check valve in addition to whatever is in the pump. You can also go to Jegs or Summit and order an external fuel check valve.

You could also just need a tuneup.

Or, it is just the nature of the beast.

I'd run a 5W-30 or 5W-40 (synthetic) for better flow at startup. Maybe you have to start up you motor and run it hard while it is cold to save lives. If so thank you for your sacrifice. You are sacrificing by placing heavy wear on your rings, pistons, and cylinders. Motors I abused like that (when I was young) became heavy oil burners quickly. Since then, I only run a motor hard when it is fully warmed up. BTW - even if you could advance the timing more, it would not make it start quicker. With timing advanced, motors become harder to start.