01 supercrew 4.6. Have had intermittent no start. The first few times it did start with a jump. Cranks fine but I thought the battery was weak. Replaced battery, same issue. 40 psi gas pressure at the fuel rail with analog gage. Theft light blinks with battery inserted. Theft light not illuminated while cranking. Battery light flashes while cranking. Battery is brand-new and charged. Opened and closed inertia switch several times to check. Ideas? Thank you.

 

When you first turn the ignition key to run the CEL should illuminate.


When you turn the ignition key further to crank, does the CEL turn off while its cranking?

 

Your not making sense on some things.
What do you mean the battery light flashes during cranking?
It will normally be lighted until the motor starts because the alternator is not turning fast enough to output for the regulator to put the light out.
.
If you see fuel pressure at 40 psi the Inertia switch is not the problem or the pump would not run at all.
.
Be clear what the Theft light does.
If it flashes at anytime the motor will not start as was designed to happen.
Good luck.

 

CEL light goes out when cranking. Theft light blinks with key inserted, but goes out once cranking. Got it to start. Not sure how what did it, just checked connections, etc. It stalled but restarted. It has stalled 2 times in the last week, never before. Ordered a scan tool last week. Thanks for the replies.

 

The CEL, Theft, dash, interior, charge lamps will all go out because there is a loss of power from the battery due to a poor connection.
Most all the voltage is dropped across the poor connection leaving none for the rest of the system.
A Scan tool is of no value for power issues.
Power cannot be monitored by the PCM that uses the same power source.
The starter tries to draw near 100 amps. Any small resistance drops a large amount of the 12 volts available from the battery..
Check the fire wall connection area.
Good luck.

 

I am having the same problem as the OP and have yet to find what is wrong. I have discovered that when there is a no-start situation I can quickly turn the key from off to run to off quickly and after 10 - 15 times the door locks will unlock and then it will start.

Any ideas? Can anyone direct me to a diagram that shows where the inertia switch and/or starter relay are located?

 

Inertia switch is in the passenger kick panel.
Starter relay is on the firewall on the passenger side originally under a plastic cover. Lift off that cover by pulling at the bottom of it toward you and up. The relay will be in that wiring mess.

 

Still had intermittent hard starts (cranks but no start) for the last couple weeks. Fuel pressure still good. Couldn't find any loose or suspect connections. Tested the crank position sensor. It sent pulses, but seemed low ~ 200 mV AC. Finally got a code after a hard start and some rough running - P0320 - crank position sensor. Picking one up today, plan to replace tomorrow. I will post again after replacing.

If anyone has replaced their crank position sensor, do I have to evacuate the refrigerant out of the AC compressor, or can it be moved enough to replace the sensor without opening the system? Thank you.

 

The compressor can be unbolted and nudged out of the way to get to the crank sensor on most of these modular motors.

Section JD in the PCED has the diagnostic procedure for the CKP sensor. In addition to the CKP sensor itself, low output (amplitude) from the sensor may also be caused by wiring concerns. You may want to follow that procedure to accurately diagnose the fault.

 

Thank you for the reply projectSHO89. I did have the harness connected when I ran that test so I will isolate the sensor and retry. I see the procedure in section JD, thank you. I will follow that before taking anything apart.. I have read that there is a low failure rate for these sensors, but I have also replaced a bunch of them on gas turbines in the power industry.

 

That sensor was a really common failure on the 89-95 V6 SHO engines, usually due to a weeping water pump. Replaced more than my fair share of them back in those days.

 

Thank you for the replies. I lucked out. It went from intermittent to no start at all. I started troubleshooting at the crankshaft position sensor. It read open with my meter. The new sensor reads 312 ohms. The hardest part was moving the a/c compressor, packed in pretty tight. Took about 1.5 hours. Truck running better than it has in a long time.

 

Good job tracking it down, hope that fixes it permanently.

Merry Christmas!