No Start! (on 96 V6)

[Aeroman]

Drove my car to work, started a bit funny but ran O.K. ( although engine died for 2 secs while cruising). Came out from work, engine cranks well but NO sign of firing, completely no combustion. Seems to be spark related but no chance to check anything yet. Battery is good, plugs, wires, etc are new, as is fuel filter. Any thoughts? It has normal compression. I can hear the fuel pump prime up.
I've heard coil pack problems but surely not all 3 of them? maybe the CKP sensor has failed? It does not have an alarm system.

 

[wmburns]

Check battery and terminals

Engine quitting while crusing sounds like a bad/weak battery (classic symptom). The alternator has to have a stong battery to power the alternator field coil. A weak battery can also cause a difficult restart condition (PCM needs good voltage to work).

Check all connections to/from the battery and alternator. Ensure they are clean and tight.

I have seen myself Mustangs apparently turning over fast enough to start but don't. As soon as the battery is replaced (or jumpped), the engine fires right up. Bottom line. Today's cars will not run right without a solid battery. The days of jump starting a car with a totally dead battery are over.

This is NOT a PATS issue. PATS will not turn the engine off while underway. Besides, it will flash an error code on the theft light.

Reminder: For the 96-98 MY, PATS disables the starter. For the 99-04 MY, PATS disables the fuel/spark.

A bad Crank shaft position sensor can cause a no-start. To test, monitor the RPM's with an ODB2 scanner. If no RPM's, the Crank shaft position sensor is bad or the wiring to/from is bad.

A bad IAC can cause a no-start. It could also cause it to die when letting off the throttle. Try this, crack the throttle halfway. If it starts right up, suspect a bad IAC.

To rule out a fuel pressure leak down, cycle the key on/off several times (do not start). If the engine fires up, suspect a weak fuel pump, leaky injectors, or bad FP check valve.

To rule out a bad MAF: disconnect the electrical connection to the MAF. If the problem improves, suspect a bad MAF.

This could be the coil packs as will as the PCM itself. Diagnose the ignition system as usual. Verify spark and go from there. OBTW, if the problem was in the low voltage side of the circuit, it could easily affect all of the coils. Also not a bad idea to check all fuses.

 

[4tun8]

Good info and good troubleshooting techniques!!! Good luck to OP!

 

[Aeroman]

Thats a lot of good troubleshooting info right there!

So this morning I had about 15 mins to go over the car (By myself)
The coil pack is O.K. & there is b+ voltage to the coil pack. I charged the battery overnight & it reads 12.4v after 20 mins (charger disconnected) so is almost fully charged. I could not verify spark yet since I cant do a visual yet. I will do that next. I do have a scan tool so I may be able to read crank speed before the engine starts (pip). The fuses are O.K.

There is NO fuel smell but the fuel pump does prime & hold pressure.
I/m guessing CKP sensor at this point!

I'll keep updating,

Cheers, Aeroman

 

[wmburns]

Verify good CKP before replacing coil packs

Note: if you do have a bad CKP, then there will be NO SPARK. Without a good CKP signal, the PCM will not know when to fire the injectors (no fuel smell) or when the fire the spark.

So, it is vital to verify a good CKP signal before replacing a coil pack for an apparent lack of spark.

A zero RPM signal during cranking will confirm the diagnosis.

 

[Aeroman]

Success!

So the 96 Mustang lives on!
Thanks for the help, Mr Burns.

Last night me & my Son did some troubleshooting. We tested the HT from the coil packs & found a no spark condition on all coils. I already tested the Primary coil winding voltage B+ terminal & knew it was good. Next we removed the CKP sensor & found that almost nothing could be detected with a multimeter set on AC volts (reading was less than 15 mV). Furthermore there was no reading directly across the sensor terminals during an static Ohm test. Voltage from the PCM to the CKP sensor at the plug was 1.5Vdc with Key on engine off. Taking into account that the injectors were not firing I decided we have a problem with the CKP sensor. We bought a new sensor & measured the resistance across the sensor terminals & this gave 625 Ohms. At this point I knew the old sensor was bad.
We fitted the new sensor, cranked the engine & she fired right up!
$40 fix ..... my son was pleased & he had his car back!
http://www.aa1car.com/library/crank_sensors.htm
Once again thanks for the inspiration.

ATB Aeroman.

 

[wmburns]

Good work on closing the diagnosis and repair.

From the post, its apparent that you have a good grasp of how the CKP works and how to use the VOM to troubleshoot. You even understood that the CKP generates it's own AC signal.

All to often when asked to Ohm out a sensor, the only reply I hear is the sound of crickets chirping......

I personally use these "opportunities" to try and teach my Son some basic auto trouble shoot tips/tricks. Working on today's cars needs a lot more electrical skills than ever before.

Time to get an adult beverage with the $$ you just saved.