Ok guys so heres the deal, i have a 305 TBI. In the past few weeks ive been noticeing its been getting harder and harder to get my car to start. I will turn the key on, and i can hear the pump prime for 2-3 seconds. Then i will try and crank car over but it wont fire. Then i will turn key off n back on, listen for pump to prime then crank and then i get ignition. In the past month and last couple of days here is what i have replaced:

Distributor Cap and Rotor
Spark Plugs
Spark Plug Wires
Ignition Coil
EGR Valve
02 Sensor
Fuel Filter

Fuel line going into back of TB from pump
various TB gaskets inside and outside of TB

I have plenty of spark and i have an open element as well. I have a recipt from 4-21-07 for a new AC Delco Fuel Pump that was replaced before i bought the car in Septemeber of 07'. I know i have fuel as well because when i replaced the incoming fuel line going to the TB, the line would leak as soon as i turned the key because the gasket/threads inside TB were bad. So i retapped the threads and installed a new gasket now there is no leak. I work at a GM Dealership and i have been planning on gettin car into the shop to see what the problem is, but im hoping someone on here will have had the same problem and know what is going on. Like i said it just started a month of so ago. I do get an exhaust lean code every once and awhile, even after i replaced the 02 and EGR valve. I have no catylatic converter if that helps or not. I would really like to figure this out. My valve seals are very bad and it smokes like crazy on start up, so im thinking possibly the oil from the seals is causing my long starts? I have an aftermarket volt gauge in my car and when i turn key to crank the gauge drops past or around 8 volts. But it has a fairly new Interestate battery in it. Thanks for reading and let me know what i can do/test to find my problem.

* Also i have my TIMING adjusted to *6+.

 

The number one check you should perform is a fuel pressure during cranking. It should be around 10 to 15 PSI for a healthy TBI system. Just because fuel leaks is no indication of correct fuel pressure.

//RF

 

yeah ive ben talking about it with a fellow co worker of min who deals in the fuel system area, and i keep trying to get him to bring my car in for a pressure check, but weve been very busyand from what i hear its also a P.I.T.A. I just read that having a bad nuetral safety switch could also be making it hard for my car to start. If i find the post on here ill post a link to it.

 

your timing could be off i believe 305 tpi are 6* btdc but i think tbi is around 8 btdc but im not sure

 

Have you checked the fuel pressure regulator?

 

i havent had a change to take a really good look at it, but when i had my TB apart when i was trying to install my pod spacer, i purchased a TB Rebuild kit, and i installed the new fuel pressure reg. gasket/o ring. But i noticed it comes with a new one so maybe i should tear it apart again and install it. I will take a pic of the kit and show you all what i have left from before and you all can tell me what i should and shouldnt put it. this is my first TB car so i have alot to learn about it still, but im slowly getting there.
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i know that stock TBI engines are *0 from the factory. And yes TPI engines are *6 from the factory. When i first checked my timing, it was at *12+ so i turned it down to *0 and it sounded all cammed out and the rpm's were all over the place. so i adjusted it to *4+ and then test drove it and still felt sluggish, so i bumped it *6 and it repsonded alot better.

 

You can check into functionality of O2 by measuring its voltage swing. On your car NBO should be on the driver side exhaust manifold next to oil filter. The wire harness is usually a single deep purple wire. Service, replacement O2 sensors may use different color wires!. ECM puts 450 mV DC bias voltage on this line while O2 sensor swings its output around it. For lean condition O2 sensor will pull voltage low to about 50 to 100 mV, while rich condition will be above 800 mV. In close loop ECM constantly alters fuel mixture by cycling it from rich to lean and back. This is tracked by a healthy NBO which feeds back to ECM were a control loop algorithm keeps system about prescribed fuel mixture range -14.7:1. It is however never stays at 14.7:1. Enough of theory.

In your case - get a DVM and measure voltage at NBO with engine not running, but ignition in run position. If you are getting 450 mV then harness is OK otherwise look for harness problem. 0 mV can indicate a dead short to ground or an open harness.
Start engine with DVM connected. If O2 is alive it should show 800mV or higher indicating rich mixture as it warms up to about 600 deg-F. You should bring the engine above 2000 rpm for about two minutes to warm the O2 sensor and try to get into closed loop. Closed loop operation is indicated by the sensor showing several cross counts per second (200 to 700 mV swings).

You are still getting 450 mV O2 is most likely open. Since in your case ECM tries to go into close loop it is indicative of a 'poisoned' NBO - which always reads high regardless of concentration of O2 in the exhaust stream. This happens when NBO gets contaminated by silicon or antifreeze.

So you have a bit of checking to do. Ignore AIR diverter valve for now. To keep ECM from going into close loop you can short ALDL connector pins A & B as this will force ECM to flash DTC codes and keep ECM out of the close loop.

//RF

 

ill try this but i noticed that when i hooked our snap on scanner up to my car, i let the car run to operating temp for about 5 mins till it got around 180* or so, and the ecm was still in closed loop. And with the scanner i can force the car to go into open loop of id like and when i tried the car would sputter for a second then go right back into closed loop. When i first checked for codes i had code 32 for egr and it said DO NOT DRIVE, then i had a code for lean exhaust. I disconnected the battery for about 5 minutes and then hooked it back up then i had none. But after driving it for a day after replacing the egr valve and 02, my SES light came back on then turned off 30 seconds later.