Topic: bad spark plugs? No. Bad timing chain? Maybe...

[GBJeep]

Alright, if you guys remember I was the one that asked if my spark plugs looked bad a week or two ago.  Well The reason I was changing them was that my Jeep would "stumble" at times, mostly on the hwy.  So I changed the plugs, 02 sensor, and had some exhaust welding done.

Today, on the hwy, it did it again and this time backfired and the engine shut off.  Going 65 I put it in 5th and released the clutch to start it again.  Of course it backfired and died again.  So I pulled off the road and called a tow truck.

I have nothing against mechanics, I just prefer to save the money and do it myself.  The Jeep is being towed to a mechanic my family uses.  I just dont know where to start with it, as far as diagnosing goes. 

PO said engine was rebuilt at 120k.  Currently has 175k.

My initial thought is timing chain.  I would prefer it to be an easier problem to fix. 

What do you think it could be?  Also, if it is the timing chain has anyone done that?  I know in the forum Jeffy looked up what it takes to get it done for someone once, but that posted never responded with what happened.

[sharpxmen]

check spark and fuel (if you hear the pump when you switch the key on and then if you have pressure) and then report back - based on that can be multiple reasons.

[GBJeep]

So I have been reading up more on the timing chain in these jeeps, and from the sounds of it they are pretty tough to break and won't ruin the engine if they do break like the Hondas.

I did not hear anything other than the backfire.  So I did not hear the timing chain "slapping" or anything like that.

I did try to start it once on the side of the road.  It would turn over just fine, but it wouldn't start.

***I was writing this as you replied***
I did hear the pump when I tried to start it.  I have not checked for spark yet.

[GBJeep]

Yeah, the fuel pump was replaced about 30k ago.  When the exhaust was done, at the same time as the fuel pump, they said the cat looked fine. 

I should have mentioned that.

[sharpxmen]

although the chain can break it is very unlikely - the hondas have a cogged timing belt, more common occurrence in that case (as with all the other vehicles using a timing belt).

after you check spark and if it turns out ok, check if you actually get fuel at the rail, easiest way would be with a pressure gauge but if you don't have one you can remove the return line and use a hose on the return fitting on the rail and put the other end in a plastic water bottle (or coke bottle) - put the contact on or crank it and check is it has fuel coming out - should be significant so if it only drips then there's not enough fuel flow.

with the cat unless is completely clogged/plugged you'd still be able to start it but will lack power

[sharpxmen]

a few things you can also check:

ASD relay - will give you 12v at the coil and injectors but only when you crank it, if you have spark it means is fine but if you don't check this relay

CPS (crankshaft position sensor) - responsible for your spark and timing, if you don't have spark but the ASD relay is fine (12v at the coil) this would be the next thing to check

Camshaft position sensor - gives the signal for the injectors opening - you can check if the injectors get signal by removing one of the injector connectors and connect a small 12v light bulb to the connector pins, should blink while you crank it

you said that you already hear the fuel pump so the fuel pump relay should be fine.

also, is your CEL on when you put the key in the on position? - it can tell you if the PCM receives the 12v power (but since you hear the fuel pump would be fine).

[GBJeep]

sharpxmen - thanks for the help!

So after finally getting it home and checking it out.  I first checked the fuel pressure, which was good, and then checked spark, which was none.  Started taking apart all of the plugs wires cap rotor and finally get to the coil.  As I was taking it off I noticed that two of the wires to the coil seemed to have been "fixed", as in e-tape over them.  So i pulled that off and somone once soldered the wires there.  That was coming loose so I spliced in some new wires, put it all back together and voilia (sp?). 

All better.  I think I need to do a better job of not fearing the worst when this thing breaks. 

[sharpxmen]

yey