I have a 1996 Chrysler Concorde 3.3L That once it is warmed up if you let it sit for a half hour or longer won't start unless you hold the key down let it crank for a while and press the gas pedal. It starts fine cold. I have replaced the plugs and wires and cleaned the throttle body and Idle Air Control Valve. Any help would be appreciate. I checked for codes and there are none so not sure where to go from here.

Replace the Engine Coolant Temperature (ECT) Sensor, which affects fuel injector pulse width. The ECT Sensor is a temperature dependent resistor (thermistor), whose resistance decreases as the engine coolant temperature increases. It provides a richer mixture when cold, leaner mixture when hot. They become corroded, due to not changing the coolant frequently enough, flood the engine, and waste a tremendous amount of fuel.

I replaced the ECT Sensor and the problem is still there. It starts a little better but you still have to push down the gas pedal while the car is cranking to get it to start. After replacing the sensor I disconnected the battery to let everything reset. What else do you think could be causing the problem. Could it be the crank sensor or maybe the Idle Air Control Valve. Your help would be appreciated again.

Did you install only the exact Champion spark plugs that originally came in the car? If you did, I would focus on the Crankshaft Position Sensor. You might try removing and cleaning the sensor with WD-40, prior to installing a new one. If the problem persists, you may need to replace the IACV--cleaning sometimes does not really work well at all.

Yes I was sure to put in the Champion plugs and made sure they were gapped correctly before putting them in. Could the MAP sensor be causing this as well? The car runs great once it starts only has 47,000 miles on it! I will try cleaning the crank sensor and let you know how that works. Thanks again for the help!

Yes, the MAP Sensor could be the culprit. It controls timing (similar to the old vacuum advance on distributors) and air/fuel mixture, depending upon manifold pressure changes. Like any transducer, it converts energy from one form to another. Here, it converts throttle body vacuum pressure changes into fluctuating electrical current signals to the ECM.

MAP Sensors, however, are very reliable components. Prior to replacement, ensure it's not leaking manifold pressure. To test-> locate test chart "SU8" in Wells test manual at AutoZone.

It's too bad a code was not thrown to provide some direction.

So far I have replaced the following items with no luck fixing the problem.
Plugs
Plug Wires
Coolant Temperature Sensor
Crank Sensor
MAP Sensor
Intake Air Temp Sensor
Idle Air Control Valve

Any idea what else it could be?? There isn't much left to replace.

Thoughts:

. Test the Throttle Position Sensor (TPS).

. Coil pack may be breaking down under heat.

Throttle position sensor tested out OK replaced the coil pack hoping to solve the problem. Replacing the coil did not fix the problem. I also ran some Mopar Combustion Chamber cleaner through it thinking maybe there was some carbon build up and the problem still exists. Any other things you can think of I should try??

Have you:

. Checked for any codes, even though the CEL may not be on?

. Replaced the fuel filter in the last 30,000 miles?

. Checked the fuel pressure?

. Checked the fuel injector pressure regulator?

Replaced the fuel filter because it needed to be done. Turns out the problem was the fuel pressure regulator. Thanks for all of the help and I'm glad it is fixed.

Thanks for the update. I don't believe, in the four years that I have been at AMHD, that I've seen a bad fuel pressure regulator. Nice work.