No sprk, but good ASD,cps,coil...

[jawalter]

98 xj 4.0, 293K miles
Also, good coil pulser stator thing... Good fuel pressure...
Crank but no start.
Stalled at highway speed. Sputtered, not a clean stall like bad cps. Sat for a minute and restarted. Drove another 2 miles then sputtered again w/ a huge backfire - i though the engine went, but all looks good.
Any thoughts before I try a new ECM?
I'm stumped...
Thanks y'all,
JW

 

[CharlesS]

Spark?
Have you checked for 12V to the coil when cranking the engine and see if the coil is providing spark to the plugs?

 

[joe_peters]

Define "good fuel pressure".

And, as CharlesS inquired--condition of the spark? Blue and snappy is good.

 

[jawalter]

Spark?
Have you checked for 12V to the coil when cranking the engine and see if the coil is providing spark to the plugs?

Checked that. No spark at the coil while cranking.
Tested the components I know would cause this as listed above. Don't know how to test the stator (coil take up) but replaced with new. No results.
Good battery...


Joe_Peters: Fuel Pressure - tested at the fuel rail. Next test will be firing of injectors. Plugs aren't wet, so not hopeful I'll see any firing.

Getting past my experience in diagnosing issues here...

Thoughts appreciated...

JW

 

[jawalter]

Started worrying I blew something internal during that backfire - oil looks fine, coolant looks fine, although I think I see a blown weld in the exhaust manifold.

O2 sensors appear to be ok, no melting or blown bungs. TPS wouldn't cause or contribute to these symptoms....

JW

 

[joe_peters]

Test the cam sensor--it provides data to the PCM for firing injectors.

 

[jawalter]

Test the cam sensor--it provides data to the PCM for firing injectors.

Thanks.
Cam Sensor = stator/coil take up. Everyone calls it something different. Flat plastic piece under the distributor - hall sensor. I bench tested it for resistance with good results. Is there a way to test it during crank?

JW

 

[CharlesS]

Yes...
Disconnect coil so vehicle doesn't attempt to start.
Feed VOM probes in thru side of wires of CPS connector on side of distributor and watch 5VDC appear and disappear the same as when points open and close.
If this doesnt happen; the CPS is bad.

 

[jawalter]

Yes...
Disconnect coil so vehicle doesn't attempt to start.
Feed VOM probes in thru side of wires of CPS connector on side of distributor and watch 5VDC appear and disappear the same as when points open and close.
If this doesnt happen; the CPS is bad.

Thanks Charles, I'll report back later this evening....

JW

 

[jawalter]

Thanks for earlier suggestion Charles.
Summarry:
98 XJ - 5spd - 293,000miles
Engine died on freeway, similar to as if the CPS failed. Restarted for another mile, sputtered, HUGE backfire, then stalled.
Have crank with no spark and no signal to injectors. Fuel rail at 49psi.
ASD - test good.
CamPS - volt/ohm check tests good.
CkPS - volt/ohm test good.
Coil - bench tests good.
AllData Dx tree suggest replacing the pcm.
Still no start.
Bought a code reader - both pcms are throwing P0351 (primary coil circuit code). Troubleshooting that circuit shows no shorts and good voltage.
Old pcm was throwing the CamPS and CkPS codes. After erasing these codes, they aren't back again. Just the P0351 coil circuit code.

Could I have jumped teeth on the timing chain during that backfire?
This then causing either the CamPS or CkPS to halt the engine?

I really, really want to hit 300K!!

Thanks,
JW

 

[joe_peters]

Short answer--yes.

Try setting things to mechanical zero--no. 1 at TDC and check the valve positions.

 

[jawalter]

Short answer--yes.

Try setting things to mechanical zero--no. 1 at TDC and check the valve positions.

Appreciate that...I like short answers! Hitting that tomorrow...
Didn't mention, but the block and mechanical inards are from a 99 donor. Shouldn't matter though...

JW

 

[jawalter]

Short answer--yes.

Try setting things to mechanical zero--no. 1 at TDC and check the valve positions.

Everything lined up fine at TDC.

However, although I tested for shorts in the primary coil circuit, I'm getting continuity b/n the two large grounds wires that ground out to the coil/block mount. I'm about to dig into the diagrams. That doesn't seem right...

Thx,
JW

 

[jawalter]

Damn!! It was all 3!!

So it turns out that the coil, the CPS, and the CamPS all went at once.

So my thinking is the CPS went, causing the shutdown on the interstate. The coil must have gone then as well, b/c the first thing I did to repair was to replace the CPS. Then I had crank - no start - no spark - and no voltage to the injectors.
Switching relays with ASD caused no change.
Coil bench tested fine, so assumed it was OK.
Tested CamPS voltage during crank, it was OK.
So must be the PCM. New PCM = no change.
Bought a scanner for $50 at AZ.
New computer was throwing a Primary coil circuit code and a failure to read TCM code (I have a manual...so couldn't figure that out)
Old computer was throwing CPS code, CamPS code, and Primary coil circuit code - still in the PCM from engine failure.
Erased codes from old computer, cranked the engine for a while and reread. Threw CamPS code and Primary Coil Circuit code again.
New CamPS took care of the former. Still tried to troubleshoot the coil circuit -other than the coil- as the original bench tested fine.
The next steps in the ALLdata testing process involved building some crazy three pronged capacitor jumper and shorting things out. I figured for that effort I might as well buy a new coil before spending that much time and money. Sure enough...it started after installing the new coil - which by the way - bench tests exactly the same as the old coil. Tried starting with the old CamPS, and it started, but threw same CamPS code with the old one installed.
So new CPS, Coil and CamPS.
Anyone ever had all three go at once?
Returned new PCM, so I'm only out a few parts and some time. Got a scanner to boot.
Thanks for the suggestions...
JW