87 Starting Issues

[Stace the Ace]

I have an 87 Coupe that has begun to die after starting. It does not want to idle at first. It shows black smoke in the exhaust indicating an over rich condition and will die within a couple of seconds of starting. If I rev the engine for 20 seconds or so, the car will run a little rough then idle and continues to run just fine. I am thinking that the start enrichment device (terminology ?) may be sticking, but I am a novice to this fuel injection and could use some clarification and enlightenment. Thanks in advance for any ideas you may offer. PS. I am an experienced mechanic and car builder but a novice Corvette owner.

 

[vigman]

Cold start injector...

Ok the real deal

The 9th injector is controlled by the following.

The CRANK line provides power to a cold start switch ( Located on the front of the intake manifold with a Purple & Tan wire 2 pin BIG connector.)

There are a few sensors up there make sure you have the correct one.

This switch open's & closes based on engine temp & current flow.

So when the car is COLD the injector stays OPEN for 8 seconds @ -4 F

As the car is warmer ( So Cal 60-100 degrees ambient ) the duration is shorter.
More like 2 seconds.. but it is NOT pulsed.. it's like a spray paint can...PSSSTTTTTTTTTTT just DUMPING raw fuel into the intake.


( the idea was )
This supplies a prime spray to help richen the mix for start.

The COLD START VALVE/SENSOR is NO WAY controlled by the ECM


..... real world

Your injectors are leaking anyway (over 75K)... so if you trigger the 9th you've flooded the engine (Typically).

I unplugged mine last week and she starts better.... and I do not get the WAFT of Chevron unburnt supreem anymore.


FYI

Vig!

 

[Stace the Ace]

thanks vigman for the insite. That seems to fit perfectly with my symptoms and my intuition. Does the sensor sense the temperature on its own or does it recieve input from another source. If you are correct, my sensor must think that it is colder outside than it really is because at 65 degrees F. it must be on for 6-8 seconds. Will replacing the sensor fix this issue?

 

[HallenTi]

I just happened on this thread while looking at something else, and saw that you had a question that didn't appear ro have been answered (way back in 2003). There is a sensor that is dedicated to this cold-start injector, which has a timer circuit in it. I have not seen this sensor, but have seen it noted in a fuel injection book, and it appears just as Vigman said, that it knows the temperature and adjusts the timer accordingly. I am not sure where this is located on the engine (I have a 1990 which doesn't have this injector) but I am sure it is there... somewhere. Tim