| Re: LT4 Starts and stalls |
Subject: Re: LT4 Starts and stalls by Pcolt94 on 2008/6/11 12:02:41 I have encountered this phenomena my self. Sometimes I turn the key and it instantly starts and other times it might spin for a few seconds. Generally less than 5 seconds but always starts. First thing I did was to hang a fuel pressure gauge on it. When I turn the key it hits 40+ lbs of pressure instantly. When I ran it all was normal. Fuel pressure would respond to throttle/ vacuum response. Had even checked return flow at one time at tank. Played with this for a few days and found nothing. Have considered check valve in pump but since pressure is there instantly, I didnt feel it was a factor. It does hold pressure for a good while but have never seen a spec on or what the norm is for how long it should. Not even thinking about injectors being bad. No symptoms of any kind, and even if one was so what. 6 or 7 cylinders working should pop right off anyway. And besides the injectors of the 94 vintage are much more reliable than the earlier C4s of the 80s. And yes they all measure 12 ohms not that that really means much in regard to a leaking injector. Ignition system seems to be in good shape and opti just a few years old. But my gut feeling is that it might be fuel related, point being injector pulse width. After driving around with a Tech 1 for awhile I have seen things happen not as advertised in any book. I believe the code or software in the PCM in the way it works (runs) and thinks in that all information is not know about it, and Im not talking about tuning. If you read the FSM on starting it takes various inputs from the CHT, MAF, TPS and several others and comes up with a pulse width for a cold start on that day. Perhaps the correct pulse width is not selected and some days its just way off, other days right on. There is no cold start valve so the PCM decides how much fuel to give it. Anyway this is just my theory as to what might me going on. Right or wrong Im willing to go in either direction. Just something to think about since the symptom seems to come and go. Open to any questions or ideas. |
