Expert: Roland Finston - 11/17/2011

Question
QUESTION: Roland,
I have a starting problem with my 98 3.0l caravan.  Cranked for long time then tried to fire when key was returned to run position.  It finally started but would not tach to rev limiter.  After trying to retrieve codes (none shown) and about 20 mins. run time the cat was very red.  It has not started since although it sometimes tries when the key is returned to the run position.  The fuel pump and filter were replaced, it has spark and the ignition timing appears to be close enough to fire (5-10 while cranking) and the cam timing is good (physically checked all three timing marks)  Changed the crankshaft sensor.  Still no fire.  Any help would be appreciated.
Tim

ANSWER: That ignition timing is supposed to be 12 BTDC at curb idle but I am not certain whether you can rotate the distributor to change that in a '98, it might be non-adjustable. But the hot cat suggests that could be the problem. However the hot cat also could mean the the honeycomb has come loose and is obstructing the outflow of exhaust. The code retrieval unfortunately doesn't work on the '98 model by using the ignition key. So only a plug-in reader will give you any codes.
The starting when the key returned to 'run' position suggests to me that the battery voltage is being dragged down by the starter too low for a good spark. Try a jump start or charging the battery would be a good thing to do.
Roland

---------- FOLLOW-UP ----------

QUESTION: Roland,
The ecm was read with a code reader and the battery has a full charge.  the engine tries to fire sometimes when the key is released to run position and may "bump" three or four times but doesn,t continue to run.  The last time the engine ran (last Sat.)I checked the tail pipe and the exhaust seemed to have proper flow at idle However that may not allow higher RPM's.  Would burnt o2 sensors prevent starting?
Thank you
Tim

Answer
Hi Tim,
No the O2 sensors don't come into play until the engine is warmed up.
How about gas in the tank?
Any history of earlier issues just before this began?
If the spark is strong and you are sure the fuel pump is running when you are cranking it, then it is either mixture (faulty sensor but not so bad as to set a code, such as the MAP sensor which can do that, or compression for some reason is low.
Did you touch any of the spark plug wiring related to the distributor? I ask because that is not in same order arounn the cap as the actual firing order on that distributor.
Maybe the distributor cap is cracked so that it might not give you a good spark on all 6 cylinders or the rotor is opening up and giving an inconsistent spark?
All those are possible. Good luck and please let me know how it goes.
Those