I’m having the infamous cold start issue.

I turn the ignition to ON. I listen to the fuel pump run for a couple seconds, when it stops, I crank her over. She doesn’t start like she’s suppose to. I believe she’s flooding. Messing around with the throttle (WOT- clear flood mode) I can eventually get her to start. But it takes a lot of fooling around.

After that initial start-up she is good all day. Whether she sits just a few minutes, 20 mins, 40 mins, 1 hour, or several hours, as long as she is mildly warm she starts back up fine. By mildly warm I mean the temp gauge is not even measuring heat at less than 100*F.

The TPS tests fine. 0.46 closed and 4.56 WOT.

The CTS tests fine.

Fuel pressure before cranking the engine is 38 PSI. Once started it stays there until warm then lowers to 35PSI.

I think the Cold Start Valve (injector) might be dumping too much fuel when open and causing flooding. Does this sound probable?

I don’t think it leaks under pressure. Or it would always flood, even when warm, Right?

What will happen if I just disconnect the cold start valve without getting the PROM reprogrammed?

 

I had this problem. A few of my injectors would leak when the motor was off.

 

But it only happens on the very first start of the day. She can sit for four hours and she'll start right up. If injectors were leaking I think four hours would be enough for them to leak down.

 

Starting the car with the gas pedal pressed prevents the injectors from fireing (i'm pretty sure). Doing this would also help me a lot because the motor was already flooded.

So if your car is starting better like that, you seem to have a flood condition. It has to be your injector[s], or maybe your fuel pressure regulator. If you pull the vaccum line off of your fuel pressure regulator, does it have gas in it? Or smell strong of gas?

 

I'll check that this weekend. I'll be testing a few more items before buying any parts.

Per the book, "How to Tune and Modify Chevrolet Fuel Injection", I'll be testing the cold start injector with a stethoscope, listening for a click. If I hear that,

Then on to the 'thermo-time switch'. I need to check the voltage on the tan wire. Where is this switch? Anyone have a pic?

Thanks,

 

oh , I would like to get that book . Can you give me the author and all the other stuff. I am gonna get it.

 

I would like to get a copy of that book also. I am having the same problem with cold start. I will try to check injectors & cold start sensor this week.

 

Title: How to Tune & Modify Chevrolet Fuel Injection
Author: Ben Watson
Publisher: Motorbooks Workshop
ISBN: 0-7603-0422-X

motorbooks.com

It's not TPI specific, but it's pretty good at explaining the types of electronics involved in EFI without getting too technical. It's good for getting a basic understanding of the sytem, and for trouble-shooting.

As far as the "modifying" part, I think it's lacking. But it did mention something that I never see discussed, that an H-pipe installed in the wrong spot will actuall hurt performance, it goes on on how to find the right spot. (one little tid-bit like this makes it worth it).

Now off to work on this problem

 

Isn't this the switch on the front of the intake manifold that turns off when the temperature gets high enough? There is this switch and a coolant temp sensor side-by-side in the front of the intake manifold. The CTS is the smaller of the two.

 

I've located the switch just left of the CTS.

Yes, the switch circuit is closed when cold, and provides ground for the Cold start injector.

It will heat and open the circuit by two methods:
1) The temp of the manifold base. Opens @ 95*
2) The hot wire for the CS injector also runs to the switch. The current heats the switch and will cause it to open (5-12 seconds).

 

I had the same problems with my car, It turned out to be the CTS connector was corroded

 

The CTS or the Cold Start Switch?

I'm leaning towards my problem being related to the cold start circuit as it only happens on the very first start of the day.

I've tested my CTS, and got the correct resistance for the outside temp.

Unfortunately, I did not get to finish my diagnostics this weekend. It will have to wait till next weekend.