: Hard Starting Warm - if not Pedal to the Metal



MachoDemon
06-25-13, 12:43 PM
1993 northstar Engine is rebuilt except bottom part.

New Fuel Pressure Regulator.

Everything fine until after a few weeks when the car
after sitting warm an hour or two didn't start after
two Three trials. Then I pushed the accelerator which
made it start - this has been common after sitting warm
except for very short time

Any ideas?

Ranger
06-25-13, 12:56 PM
"Pedal to the metal" during cranking is the "Clear Flood Mode". That disables the injectors. Hard hot starts are usually attributed to a leak FPR, but you said it was replaced. Assuming it was done correctly and the O rings are not leaking, I'd suspect a leaky fuel injector.

Manic Mechanic
06-25-13, 03:27 PM
Most common is a defunct or disconnected ECT (engine coolant temperature) Sensor. If the PCM sees the coolant temp as really low, as in -32*, it floods on crank. Putting the pedal down clears it as Ranger stated. If one injector was leaking it would cause a long crank immediate short term misfire on start-up. If one injector was stuck open you'd be luck to get it to start and run at all. The sensor is on the rear head or just below it in the block, drivers side. Look for a two wire connector below the electronic EGR valve on top and above the trans-axle bell-housing down low. The wire harness also grounds just behind it on. It's up in there, take a light and a mirror just in case.

Vernon

Ranger
06-25-13, 04:24 PM
Vern, Correct me if I'm wrong, but isn't the ECT sensor monitored and shouldn't it set a DTC and trip the MIL if it failed?

MachoDemon
06-26-13, 01:28 AM
Ho to check if leaking injector or pressure regulator?
(car is 1993 allante - where the Engine was taken out
and partly rebuilt (including heads) because of the
infamous northsar oil manifold leak)

Ranger
06-26-13, 11:25 AM
See the Tech Tips section.

Manic Mechanic
06-26-13, 11:46 AM
What I've seen <in general> on the ECT sensor and code setting is that on the newer stuff it will set the code immediately if the signal suddenly makes a drastic change with the key on, it knows you can't go from 200* to -32* instantly. The engine will still flood and die at that moment. But if something happens when the PCM is shut down, as in this case it seems where it ran fine but then wouldn't re-start, there may not be a code until the engine has ran long enough to establish that the ECT should be higher. So say the system is down and the sensor or circuit develops an issue (due to thermal expansion, corrosion, physical, or whatever) and then the system is powered back up it hasn't been keeping time and assumes that it's a fresh restart at -32* when it's anything but. Fuel trim is maxxed out and it floods. Now if you can get it started and run it long enough usually a timer induced code will set a ECT code or thermostat code.

Vernon