1986 Coupe 80k on the clock.

I have an intermitent cold start problem. Sometimes it will start right up no problem. Other times no matter how long you crank it will just sputter and not start. I usually just let it sit a while and try again, but this makes me use it less reliably of course.

I wanted to know how common it is that the cold start switch fails?
It acts like it is not getting enough fuel.

 

We were just having a discussion about the COld Start Circuit over on another thread.

Here's a copy of my last 'book' over there.

Dan and the rest of you guys are EXACTLY RIGHT.

The Cold Start Injector has NO association with the ECM.
There is NO ASSOCIATION of this circuit whatsoever with the ECM.

Just as you guys said and particularly AGENT86.

This is a REALLY SIMPLE circuit and should be SUPER EASY to troubleshoot.

The Cold Start Sensor out on the front of the manifold is more of a 'time controlled switch' than a sensor.

Here's how it works in plain language:

A "Bi-Metal" switch is constructed a lot like those little 'clickers' we played with as children. Those little click-click things we agravated all the adults with.
The bi-metal is heat activated instead of activated with your finger, LOL.
The bimetal switch uses two different types of metal to cause the switch to 'click' or move and operate two switch contacts.

The Cold Start Sensor has a 'bi-metal' switch inside it that supplies GROUND for one side of the Cold Start Injector.
The Cold Start Injector is connected to the rear of the fuel rail so it has fuel 'available' all the time the fuel rail is pressurized.

During the 'Start Sequence' +12 volts is applied to the other side or terminal of the Cold Start Injector.

The COld Start Injector bi-metal switch will be CLOSED (or connected) when the temperature of the sensor is below 95* F.
When the switched is turned to start and the temp is below 95* F the bi-metal switch will be closed and the Cold Start Injector will be activated.
This will enrich the fuel mixture during starting when and only when the temp of the engine (actually the Cold Start Sensor) is below 95* F.

The Cold Start Sensor has a HEATING ELEMENT inside it. The heating element will heat the bi-metal switch and cause it to open after 8 seconds.
THis will cut off the Cold Start Injector after 8 seconds even if the starter is run for a longer time period.

There appears to be TWO maybe THREE failure modes for the COld Start Sensor.
1) The bi-metal switch could not make connection (bad contacts).
This means there will be NO cold start fuel enrichment. As per the design this should have NO EFFECT if the temperature of the engine (actually the COld Start Sensor) is above 95* F. The engine could exhibit hard starting when it is cold but would start and run great when warm.

2) The bi-metal switch contacts could stick (fused contacts).
This could cause the Cold Start Injector to be activated whenever the starter is engaged. Likely the fuel mixture would be enriched too much. THis could cause the engine to be very hard to start when cold. The engine would seem to be flooded and probably would blow balck smoke out the exhaust when it starts.

3) Note: If the Cold Start Injector has +12 volts applied all the time the car is in run mode the following would happen:
I couldn't tell definitively IF the +12 volt source is applied to the Cold Start Injector only when the starter is activated or at all times when the ignition is "ON" ..........

The heating element inside the sensor could be open. When the temp. is below 95* the Cold Start Injector would stay activated until the engine warmed up enough to cause the bi-metal switch to open.
This would cause the fuel mixture to be enriched beyond the design spec of 8 Seconds. The engine would be running VERY rich for quite a while until the bi-metal switch inside the Cold Start Sensor opened because of ambient engine heat.
The engine would likely be blowing black smoke out the exhaust or at least running very, very rich until, finally, the COld Start Sensor bi-metal opened and deactivated the Cold Start Injector.

That's about the only ways I can see the Cold Start Sensor could fail and cause problems.

That leaves just TWO other possibilities for trouble with this particular system.

1) The Cold Start Injector could fail.
a) The Cold Start Injector coil could fail and that would turn off the fule enrichment. There would be NO fuel enrichment when the engine is cold. Hard cold starts would be the results.
b) The Cold Start Injector could be clogged or stopped up. The results would be hard cold starting
c) The Cold Start Injector could fail in the 'Open Position'. THis would allow fuel enrichment at all times. The mixture would be very rich and the engine would struggle to run at lower speeds with all the excess fuel being squirted in by the defective Cold Start Injector.

2) The wiring that supplies +12 volts to the Cold Start Injector could fail
This will result in no cold start enrichment.
a) The wiring from the negative side of the Cold Start Injector could fail.
b)The failure could be an open from the injector to the Cold Start Sensor and this would disable cold start fuel enrichment.
c)The wiring could fail with a short to ground. This would activate the Cold Start Injector all the time that +12 volts is applied to the injector.
Rich fuel mixture would be the results.

That's about it. Seems GM would have used a couple of pins on the microprocessor to handle the Cold Start function. As is, the failure of any component of this system will not cause the ECM to flag the failure.

But it's a really simple circuit. Should be straight forward to troubleshoot.

The link posted by AGENT86 gives all the info necessary to understand how Cold Start Enrichment works.
THe hardest part of fixing some of these problems is tracing the wiring to make sure there are no problems with it.
A volt ohm meter is all one should need to check this circuit out.

Ok, hope I can remember this stuff for 'next time'.

 

Do you hear the pump run for a couple of seconds when you turn the key to run ??
Will it start easier if your foot is to the floor during cranking ??
Do you have access to a fuel pressure gauge ??
Any codes relating to the CTS ??
Here is some brain food
http://members.shaw.ca/corvette86/En...ButWontRun.pdf
http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf
http://members.shaw.ca/corvette86/Co...rt%20Valve.pdf
http://members.shaw.ca/corvette86/Code%2014.pdf
http://members.shaw.ca/corvette86/Code%2015.pdf

 

Hey AGENT SMART,

Man!! I like your FSM a LOT better than mine.
I can never find the right book. Can't even find the WRONG book sometimes.

 

Is there a way to read the ECM error codes without a Scan Tool? If not, is there a prevailing favorite ECM scan tool that forum members recommend for the Vette or Chevy in general?

 

To pull codes: http://www.troublecodes.net/GM/

Just follow the how-to on pulling the codes and report back what you get.

As for a scan tool, the best would be a laptop/cable and good scanning software. An autoxray 5000 works well, so I hear.

 

I just started using Moates TunePro RT and cable from them... Just starting to play, but seems great.... $30 for software lic (don't need it to run but help support Moates) and $60 for the cable...

 

http://members.shaw.ca/corvette86/No...it%20Check.pdf

 

VetNutJim, your description of how the CSV system works is very good. I will add some other facts as well.

1. The CSV system gets it's power supply from the starter solenoid.
2. The CSV system consist of a 5a fuse located behind the DIC and not on the passenger side fuel panel.
3. If you ohm test the CSV coil, you will find the resistance to be 4-6 ohms. The other 8 injectors are usually 16-17 ohms.

For any more info on how to troubleshoot the CSV system, do a advanced search for "CSV" in C4 Tech/Perf.

 

Great info. RRT Vette.
I should have ohmed out one of the CSV coils while I was out in the garage last night.
6 ohms @ 12 volts = 2 amps. So if that 5 amp fuse goes then there's a 'real' problem with the CSV OR the wiring.

I'm 'thinking' the +12 volt source for the CSV comes thru the contactor side of the starter solenoid. So the Cold Start Sensor can only activate the CSV when the key is in the 'starting' or 'starter run' position.

 

guys......guys........
you are flooding this poor individual with copious amounts of valuable information he doesn't need at this time.
Does it not sound like a bad fuel pump relay or fuel pump with an intermittant oil pressure switch?
Chris

 

Well, it could be anything. tdf suspects a fuel problem. A fuel pressure guage would help confirm or rule out a fuel problem. I would try and spray some starting fluid in the TB while trying to crank. If it starts and runs then yes, a possible fuel problem.

Waiting on if there is a code or not.

 

OK guys been following this thread as I am changing my intake so I decided to check cold start injector and other injectors for leaks .I hooked up cold start connectors and cranked engine over and no gas out of cold start injector .I also had a strange thing happening with hose going to my evap canister there was gas in the line when cranking engine any help would be appreciated . Thanks Steve

 

Is the Fuse CINJ/CLU only for the coldstart system ?
Can I pull it to disable the CINJ ?

 

This thread has been dormant for fifteen years. You may have better luck asking your question in a new thread.

 

I did..... not really succesfull