Blown ignition module?: 1998 XJ

[jpnjim]

Even though I've heard it a million times

"don't crank your engine with the coil disconnected, or you'll fry your ignition module"

 

That's exactly what I do every time I change my oil

(to pump some new oil up before starting it)

 

Fastforward 24 years of doing this (dozens of times with OBDII Jeeps)....

 

and guess what,

 

 

I pulled the plug wire like always,

and when I put the coil wire back on...

no love :( :doh:

 

It cranks forever, but doesn't start.

 

 

Before I dig out my FSM & multi meter to test the thing,

as anyone killed the ignition module on an HO or OBDII Jeep doing what I did?

[64 Cheyenne]

If you didn't blow it with 24 years of doing it, why now?

 

Myself, I'd always go to the CPS first, seems like the weakest link in the chain to me.

 

Most instances of trouble spot and needing replacement, so what are the odds :dunno:

 

When I have to crank with "no start" I disconnect the coil wire and ground it. I believe the problem comes when you don't

 

ground the coil wire, mega secondary voltage with nowhere to go is bad, or you could just unplug the coil from the harness at the plug

 

rendering the coil inoperative.

[JeffN]

just pull fuel pump relay next time

[Geonovast]

I unplug the CPS when priming oil pressure after an oil change. Shuts off spark and fuel without damaging anything.

[HOrnbrod]

or you could just unplug the coil from the harness at the plug rendering the coil inoperative.

 

:agree: To me that's the easiest way - remove the coil 12V supply.

[jpnjim]

Alright,

I get it.

Everyone here is smarter than me :doh: ;)

 

I haven't had time to play with this today,

I'll let everyone know how bad I screwed it up as soon as I know. :cheers:

 

(thanks for the suggestions so far :idea: )

[flint54]

Interesting topic. After more than 45 years of changing oil, on a great

many vehicles, I have never been concerned about this, assuming

the vehicle was running right before the oil change. I have always

felt that there is enough residual oil on the surfaces to accommodate

the couple seconds without oil pressure. On a fresh motor, or a

dubious motor, absolutely build pressure first, but on a good motor it

just doesn't register on my "worry" meter.

[jpnjim]

Yeah,

It's probably a holdover from my AMC V8 days:

 

external oil pump = loooong time between "put-put-broooomm brooommm", and oil pressure coming back.

 

If it ends up being a smoked module,

my days of doing it to 4.0L's will be over

(or I will atleast take one of the above suggestions)

 

Thanks to all so far :cheers:

 

sooooo,

who else cranks their engine after an oil change, before starting?

:popcorn:

[jmderyke]

I do when I change my oil and when i don't start any my vehicles for a while. Mostly all fuel injection systems will not start when at wide open throttle it won't send spark. fyi

[comanche12]

I never prime the oil on engine that already primed. only do on rebuilt/new engine. :dunno: But hope that your able find the issue.

[jpnjim]

It was the ignition coil.

 

D*mn thing tested out fine too. :rant:

 

Finally got around to fixing it today,

right after I bolted in the $33 BWD coil from Advance Auto,

I found the spare factory coil I had. :doh:

 

Oh well, it's good to have a spare (just have to try not to lose it again).

 

 

 

 

Either way,

I am REALLY glad I smoked my coil, and NOT the ignition module embedded inside the engine computer. :eek: :eek: :eek:

[HOrnbrod]

Yep, the ohm check of the primary and secondary windings is really only good if one of the windings is open. It does nothing to check if the internal dielectric material is shorted under load. You need a good old coil tester machine for that. Especially with the modern coils with higher step-up voltage ratings. If you carry any spare parts, always carry a spare coil. :cheers:

[Eagle]

Interesting topic. After more than 45 years of changing oil, on a great

many vehicles, I have never been concerned about this, assuming

the vehicle was running right before the oil change. I have always

felt that there is enough residual oil on the surfaces to accommodate

the couple seconds without oil pressure. On a fresh motor, or a

dubious motor, absolutely build pressure first, but on a good motor it

just doesn't register on my "worry" meter.

Agreed.

 

My '88 XJ is sneaking up on 300,000 miles on the original engine. Bearings are all original and there's no unusual noise, and the oil pressure is the same as it has always been as far back as I can remember.

 

In fact, until I saw this thread I had never heard of unplugging anything to "prime" the engine when changing the oil. And I beat flint's 45 years by a decade.

[jpnjim]

Yeah,

I've been known to overthink a problem or two now and then ;)

 

I still like the idea of pushing some oil into the empty filter with the starter after a change.

If it wasn't angled so much I could fill it first.

 

Next oil change I will either try the WOT trick, pull my fuel relay, or the cps.

Jeep cps's seems to like to be disconnected & reconnected now and again,

so I'll probably do that.

I don't think I'll unplug the primary side of the coil,

it was a PITA getting my paws in there to swap it.

 

Well thanks for all the replies,

for better, or worse,

I'm glad I'm not the only one who spins their starter after an oil change. :nuts:

:cheers:

[Exgrayxj]

You are not alone, I either pull the coil lead or otherwise kill the ign, when I can I fill the filter. Knock on wood, never a problem, but I don't currently own anything newer than 1990, except the bike, and that is '02.

The filter fill thing is from being weaned on BB mopars, with the flat filter and external pump, start a few of them with a dry filter and listen to the rattle, it will scare ya! I even do it on my Harley.