In the past few months I've replaced spark plugs/wires, Fuel pump, fuel pressure regulator and the optispark. The reason is that I am trying to fix a hard start problem ( Takes 5 -7 Seconds for the engine to start).

Anyways, so my question is the following:

Today I noticed that If i try to start my car with the throttle wide open, it wont start. It will just keep cranking and cranking. So I began to try different combinations of throttle and see what effects it had on my hard start problems

0 - 20% Throttle - Hard Start 5 - 7 Seconds

25% - 70% - Car starts right up or after a one second crank

70% - 100% - Car doesnt start, regardless of how long, I tried up to 15 - 20 seconds.

This testing has me thinking that my Throttle Position sensor isnt working correctly. Can anyone shine some light on my scenario?

Also, Could someone with try to start their car with wide open throttle (GAS Pedal all the way down, not in gear) and tell me if it does start?

 

Opening the throttle wide open forces the PCM into "clear flood mode" which shuts off the injectors and inturn will cause a no start condition. You can check the tps using a voltmeter or a scanner it should have about .5 volts with the throttle closed and nearly 5 volts at idle. Voltage should increase smoothly as you increase throttle input.

 

I think you meant to say "nearly 5 volts at WOT".

The LT1 PCM will accept any closed throttle TPS voltage between 0.20-0.90V, and set that for the baseline as 0% throttle. WOT voltage is usually about 4V higher than closed throttle voltage.

 

.59 at Idle at 4.29 at WOT.

So then what else could it be? Ive replaced my fuel pump twice, optispark once, spark plugs and wires. The issue hasn't gotten any better or any worse. I have hard starts even when the engine is warm.

 

bump - Car isn't priming to 40 I need to prep the car several times on a cold start to get it going.

Does the LT1 engine store pressure in the lines when the car is off?

 

It will hold pressure for a while but will bleed down, you may have a bad fuelp pump/ check valve that may be why its not holding

 

well after two Treperformance pump replacements; im going to just insert a check valve before the the pump.

 

I'd like to know how you plan to do that...Perhaps you should refine your diagnostic methods instead of inventing unheard-of fixes. If pressure is bleeding down that quickly, then it could be one of only four possible causes.

-Leaking fuel pump check valve (integral to the PUMP)
-Leaking fuel pump flex pipe (inside the tank)
-Leaking fuel pressure regulator
-Leaking injector(s)

 

Get a different pump. I had a Treperformance that lasted a whole 20 minutes.