how to check for spark on a 00 xj

never used/seen a dizzyless engine, how do you check for spark on these crazy things?

You can disconnect the coil rail from the spark plugs, and connect an in-line spark tester between one of the coil rail spark plug boots and one of the spark plugs.

thanks, like a noid light?

Like this: http://www.amazon.com/Lisle-20610-I..._1?ie=UTF8&s=automotive&qid=1287467486&sr=8-1

Generic DIS info: http://www.aa1car.com/library/dis.htm

un plug the coil if the motor shakes more its good .. if no change its bad .. it has a coil on each cylinder right .. so it has a plug on each coil unplug each of them AND SEE THE CHANGES

Doesn't work that way. Our "coil" is a big, long slab of plastic and resin with the coils molded in and one hard-to-reach plug in the back. And I'm not sure but there may just be 3 coils.

I believe it is three coils firing two cylinders each-- I've never had the "luck" to play with one of them, but if you can access the "wires" (just rubber boots), you can clip an inductive timing light around each boot and see if it will cause the timing light to flash-- indicating spark on that plug.

Right. The rail is made of 3 coils. each firing two spark plugs at the same time. Its a waste spark system. An inductive timing light may work, if you can get it to go around the boot as the boot is nearly right up against the head.

My machinist has a tool that would work for this. I don't know what it is called or where you can but it. It has 16 leads (meant for an 8 cylinder). One goes to the boot, one to the plug. There is a gap between the wires that shows the spark.

do you know if the coil rail HAS to ground anywhere on the head?

It would always be possible to replace the booties with wires to each plug and give you a little room if it doesn't HAVE to be directly on the plugs.

what about taking the rail off and putting a plug back in and grounding the plug to something while cranking?

The rail should be grounded to the head, but its not necessary for testing purposes.

Careful, if you run the coils with no plugs on them, it can damage them. An unloaded coil produces an awful lot more voltage and can arc internally as a result.

I'd go with inductive probes, or remove coil rail, unscrew the plug in question, screw a shorter plug with the same thread into the hole to keep the engine from blowing fuel everywhere, then connect a wire from the empty spot on the coil rail to a spare spark plug held against the block as usual.

kastein said:

Careful, if you run the coils with no plugs on them, it can damage them. An unloaded coil produces an awful lot more voltage and can arc internally as a result.

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What's interesting is that if you go through the 2000 FSM for the ignition system (section 8D), it doesn't outline a test procedure for spark plug firing on the 4.0; the closest it gets is telling you to check the plug conditions and replace as necessary. One thing it does mention on page 8D-3: "the PCM opens and closes the ignition coil ground circuit for ignition coil operation". So, basically, if a coil isn't being grounded by the PCM, the appropriate plug won't fire.

I went through this last year with a periodic misfire; it was a real PITA to track down due to the all-in-one design of the coil packs on the rail. Eventually I figured out that responsibility for diagnosis and testing of the coil rail had been moved more or less completely into the PCM and a 'no user-serviceable parts' approach taken to the coil rail. Assuming that the wiring from the PCM is good, this essentially creates a situation whereby replacing the coil rail and seeing if the problem goes away is the test procedure; after that, it's time to start suspecting the PCM and/or wiring to and from it.

connect a wire from the empty spot on the coil rail to a spare spark plug held against the block as usual.

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One thing I'll add to this: it is a wasted-spark system, so be sure that you're ready for the fact that both plugs on a given coil will fire when the engine's cranked over. It would really suck to only jumper the suspect one then find out that you fried someone or something because the other plug on that coil wasn't jumpered as well. My gut feeling is that to be safe you'd have to jumper all six plugs since you can't really just pull one lead.

it's not "which" plug isn't firing, it's if any of them are put new engine in and it's turning over but not catching and it has fuel (albeit old, old fuel)

Is it throwing any codes? Did you index the cam sensor correctly?

no codes, but after it's cranking 2-3 seconds the check engine symbol pops on, then goes off a few seconds after I stop cranking. thinking it might be the cam sensor, have a new CKPS to throw in since I beat the old one like a mule during the install. can't remember if we removed the cam sensor though in the first place. Might have to break out the old straw and watch for TDC :doh:

Or the CPS. But when my CPS went out when I did an engine swap it would throw codes during cranking. Something about max dwell not reached on the coil. Can't remember the exact code number.

talked to my buddy helping with the project, he said the chain and cam were never touched during the swap and it came out of a running wj so that hopefully solves those two possibilities, might pick up a cps on my way out to his place tomorrow, couldn't hurt