Hard to start VS V8

[vombil]

yeah wouldve been an easier job than the pump! got a CTS on order. at least i can hear the pump prime now so can cross that one off :/

 

[vombil]

Update: havent changed any parts yet but can report:
Blocked fuel return in the event the reg was playing up. No change.
Bridged 5 & 6: No codes
Will not fire unless I apply accel pedal so maybe it's TPS related?
no accel and it just turns over.

 

[losh1971]

Could be wrong but i would have thought TPS would have more affect on acceleration and gear changes rather than prevent the engine from actually starting.

 

[losh1971]

Does your car have a MAF sensor?

 

[VR38]

I would be doing a complete fuel pressure system test and testing the temp sensor.
Also wouldn't hurt to check the IAC valve.

 

[BlackVXGTS]

Refer to the description below, which is an excerpt taken from the Holden VS Service Manual - V8 Fuel Control System section (I have included the complete section as a PDF for those interested in improving their knowledge of the system and all of it's modes).

The symptoms being experienced by the OP seem to indicate that the engine is flooded when it's cold. The OP mentions that the accelerator has to be used to start the engine - in other words, initiating Clear Flood Mode as described below. I recall other posts in the past referring to injectors that don't close off completely, and allow fuel to "dribble" into the engine when cold, resulting in a flooded engine situation. Not sure if this could be an answer to the OP's problem.

MODES OF OPERATION (partial)
The ECM/PCM looks at voltage signals from several sensors to determine how much fuel to give the engine, and when to operate in the open-loop or closed-loop modes. The fuel is controlled in one of several possible modes. All the modes are controlled by the ECM/PCM, and are described in the following paragraphs.

Starting Mode
When the ignition key is first turned "ON," the ECM/PCM will energise the fuel pump relay, and the fuel pump will build up pressure to the fuel rail. The ECM/PCM then checks the engine coolant temperature sensor and determines the proper injector pulse width for starting the engine.

When cranking begins, the ECM/PCM will operate in the Starting Mode until engine RPM is more than about 400 -or- the "Clear Flood" mode is enabled. Pulse width during the Starting Mode is between approximately 4 - 26 milliseconds, depending upon engine coolant temperature.

Clear Flood Mode
If the engine floods, it can be started by pushing the accelerator pedal down all the way to the floor while cranking the engine. The ECM/PCM then pulses the injectors with only a four millisecond pulse width, which should "clear" a flooded engine. The ECM/PCM holds this pulse width as long as the throttle position sensor input indicates the throttle is nearly wide open, and RPM is below 400.

If the throttle is held wide-open while attempting to make a normal start with a non-flooded engine, the engine may not start. A 4 millisecond pulse width may not be enough fuel to start a non-flooded engine, especially if it is cold.

Run Open Loop Mode
After the engine is running (RPM more than 400), the ECM/PCM will operate the fuel control system in the Open Loop mode. In open loop, the ECM/PCM ignores the signal from the Oxygen Sensor, and calculates the air/fuel ratio injector pulse width based on inputs from the crankshaft reference signal (RPM input) and these sensors: MAP, IAT, ECT, and TP sensor. The system will stay in the Open Loop mode until all the following conditions have been met:

1. The oxygen sensor has a varying voltage output, indicating that it is hot enough to operate properly. This is described fully in the previous section on ECM/PCM and sensor operation.
2. The engine coolant temperature is more than 44 degrees C.
3. Not at idle. Refer Idle Mode.

In open loop, the calculated pulse width may give an air/fuel ratio other than 14.7 to 1. An example of this would be when the engine is cold, because a richer mixture is needed to ensure good driveability.

Run Closed Loop Mode
In Closed Loop mode, the ECM/PCM initially calculates injector pulse width based on the same sensors used in open loop. The difference is that in closed loop, the ECM/PCM uses the Exhaust Gas Oxygen Sensor signal to modify and precisely fine tune the fuel pulse width calculations in order to precisely maintain the 14.7 to 1 air/fuel ratio that allows the catalytic converter to operate at it's maximum conversion efficiency.

 

[Immortality]

flooring the throttle during start makes the PCM think it's flooded....

But BlackVXGTS has beat me to it with another very comprehesive post.

 

[vombil]

definitely not flooring the throttle guys. just a slight amount of pedal to let some air in and it starts to fire. if i turn the key with no throttle it just cranks.*** yes the plugs stink and are 'wet' with fuel when i checked at stone cold engine.*** I'd imagine if the injectors were leaking then i should be able to smell some fuel in the oil? thats trickled down past the rings? when it first gets going it smells rich but once its warm exhaust fumes smell normal.

I've been told that any fuel problems will not throw a code. Ie dirty fuel, fuel pump, pressure issues; injectors leaking... I have no codes.

I agree it's not symptomatic of TPS. Wet plugs on a stone cold motor will not be explained by IAC, TPS or CTS i can't imagine. Hell! Looks like the rail is coming out

 

[Immortality]

Check the fuel pressure regulator. Sometimes when these fail they leak internally straight into the intake manifold via the manifold vacuum reference tube. Pull the tube off and see if you can see/smell fuel coming from it when you prime the fuel system.

 

[EYY]

The pcm doesn’t control spark on cranking - there’s an additional circuit for that. I have a feeling that touching the throttle means the pcm takes over.

Had issues with mine a while back. Change of wiring loom, ignition module and pcm fixed the issue. Not sure what it was in the end.