FireDemonSiC

I have a 1985 Z28 with a 305 TPI and it seems to have recently developed a starting bug.

The issue is with cold starts. like when I come out of work to go home and the car has been sitting all day, or when I come out first thing in the morning and turn the key, the engine cranks and cranks and cranks but will not turn over. I usually have to crank it 2 - 3 times with 7 second crank intervals before it will start on It's own. However, if during the struggle I hold the gas pedal down about 1/4 or 1/2 of the way, it will fire right up. 99% of the time on a warm start like when I make a 7-11 run, it will start right up with only the slightest hint of a struggle or none at all.

Usually when it is about to start right up with no problems, you can tell because when the fuel pump primes it sounds faster and more agressive than a prime on a struggling start.

Here are two videos of a cold start and a warm start you be the judge.

This is the first winter I've owned the vehicle so I'm not sure if It's a real problem or if the car just doesn't like the cold.

FireDemonSiC

Here is the cold start video. I will upload the warm start once my camera finishes charging.

http://www.youtube.com/watch?v=ogLdcBoPLEY

FireDemonSiC

Here is the warm start video.

http://www.youtube.com/watch?v=py5JJ1RDKrc

irocuroc

cold start valve is no good commonly called the 9th injector. Take it out and put current to it and activate the solenoid. Use a blow gun with a rubber end, blow air into the valve while current is added. if air comes through remove the current and air stops the valve is good. if no air comes through it the valve is no good. This car does not have a cold start enrichment program in the ecu like thd newer ones. The ecu senses cold via the CTS and turns on the valve until the ecu senses rotation above 200 rpm then shuts off. If the valve checks good look at the cold start switch and make sure you are getting 12vlts to the cold start valve during cold cranks. hey your keys are very noisy. Looks like a nice car.. go fix it

FireDemonSiC

I actually thought it might be the CSV, but the part that puzzled me was the gas pedal thing.

I didn't think pressing the pedal in a fuel injected car made a bit of difference nor did I think that the earlier TPI computers fire the other injectors while cranking



What is the proper way to bleed the fuel system so you can safely remove the CSV?

irocuroc

just push the schraeder valve on the rail to relieve the pressure, use a rag it only takes a sec to relieve it. then take out the bolt that holds it in the manifold and remove the fitting on the back of the rail that the tube is connected to. remove the valve with the tube. Then lift the tab up to unlock the valve and unscrew. then test it

FireDemonSiC

Is there a way to test the Thermo Time Switch without actually removing it?

I'm not sure which I'd prefer to be bad.

If It's the switch, I gotta pull the alternator and drain the block. If It's the valve, I gotta pull the drivers side plenum to disconnect it from the fuel rail.

What exactly was the purpose of the cold start valve anyways if GM switched to all 8 injectors 4 years later???

rgarcia63

Pressing the pedal to the metal so to speak turns of the signal to the fuel injectors, it's used to clear a flood condition. Maybe the CSV is adding too much fuel which is why the "clear flood" helps. You can test this theory by removing the "Crank Fuse" before cranking, the fuse powers the CSV circuit.
The CSV just adds fuel when it's cold. The CSV Thermo-timer switch is a stand alone circuit it's activated once for every start cycle. As temperature increase the timer shortens it's on time until it doesn't come on at all. If the ECM controlled it there would be no need for the thermo-timer, so why use an extra injector when you already have 8? probably because there was no room in the EPROM for more hind-sight programming.

I deleted it as well using the '89 programming.