Tracing cold start issue

[dantye]

If you have good spark, I might suggest, if you have not done so, cleaning and re-connecting ALL grounds on the car. Time consuming, but can change everything. It only takes one or two good grounds to get a good spark, but many other ground connections can affect other voltage levels.

[burlybryan]

Thanks for the reminder Dante. One of the first things I did when I got the car was brighten up all the grounds (that i could find). Today i shined up the cluster grounds on the inner fenders as well as the ground at the firewall and the one next to the coil. It actually cranks a little quicker, but still about 4.6v at the cold start injector.

Is there a summary of ground locations? I'll go thru the wiring diagrams as well. It sure does seem like i have a wiring or ground issue. Maybe one of the PO's kludged something.

Thanks.
Bryan

[dantye]

I know of no guide to the physical locations of grounding points. I just had to track them down using the Artigue and other wiring diagrams. Good luck!

[wizard124]

Try cleaning the plug contacts at the ECU.

[burlyb]

Using the Mirafiori wiring faqs and diagrams, I've spent the last few evenings going over every ground and making them shiny brite (sanding, dremel where accessible and contact cleaner), cleaning connections to the alt and starter, ecu pins, added a second ground strap from intake to firewall, did the brown wire fix. All this gained .2v - so now the CSI reads 4.8 (with some fluctuation) instead of the previous 4.6v. Still need to check the bell housing ground, but I cleaned that one up last winter when I rebuilt the drive shaft (cold start problem has been around since I got the car 4 years ago).

So, there's still a voltage drop somewhere, but I have no idea where to look next. I think I'll try to decipher what circuits are energized when cranking. I should measure voltage at the injectors too. I also need to trace the wiring of the previous owner installed stereo to see if it's messing with anything (probably is). I suppose then the only thing left is to remake every f'in terminal connection...

Bryan

[wizard124]

I've had a cold start issue since I got this car last year and am working through troubleshooting. Jumpering the cold start injector indicates it works, but its not getting a signal. I pulled the thermo time switch plug and checked for voltage at the harness pins when cranking and there is nothing. From what I've read, the ECU should be sending power to the TSS which then signals the cold start injector to operate. Do I look to the ECU (or chase a wire break) next or would it make sense to start at the ignition wiring?

Thanks for any insight.

It actually cranks a little quicker, but still about 4.6v at the cold start injector.
Bryan

Bryan:
I have looked into my manuals, reading up on the operating descriptions and viewing the wiring diagrams. Your understanding of this system is not correct.

Cold Start Valve and Thermo Time Switch:
The current flows from pin 86 of the dual relay via a white wire to the CSV. In "Start", current flows thru 50 of the ignition switch to 86a of the dual relay. The CSV only operates in "Start".

The ground comes thru the Thermo Time Switch. The contact should be closed below 35C/95F. There should be zero resistance between a known ground point and terminal 46 of the TTS/CSV.

During "Start", voltage is spliced off the hot side of the CSV to the TTS. This voltage heats an internal coil which breaks the ground within 10 seconds regardless of coolant temperature. "This prevents an overly rich mixture during an extended period of engine cranking."

In any event, there is conductivity between the harness pins on the TTS and the Cold start injector. Also, the injector harness shows about 5 volts when cranking - which I assume should be 12v (?). Maybe it's lower due to association with the TTS - and the fact that it's about 62º in the garage. At rest, measuring the TTS to ground reads 35 ohms.

My speculation (assuming a cold engine). The 35 ohms mentioned above is probably the resistance of the internal heater coil. Check the resistance of both TTS prongs (plug removed) to the engine block. One side should be the resistance through the heater coil. The other should read 0 or infinite. That side is the contact (closed when cold and open when hot). If it is open, then the TTS is faulty, the cold start valve will not ever be grounded and will not squirt!

Since you read 4.6V at the CSV plug, I think the problem is on the hot side. Check the voltage behind Ignition Switch 50 then Relay 86a, then 86, then the hot side of the TTS, then the hot side of the CSV. This will determine where the voltage drop occurs and/or alert you to PO wiring and spice errors.

[kacperix]

Dear all,
I have a problem with a cold start, I have to push the accelerator to start the engine, after it start it not keep the idle speed and gous out... only if I keep the accelerator pushed it will be running until it goes to operating temp. They everything is fine.
does anyone know how long the cold start valve is spraying the fuel?
I demount it and start to cranking it's spray only for a 1-2 sec. when I crank again it doesn't spray, only if I take out the ignition key and put it again it's spray also for 1-2 sec... without the pushing accelerator it will not start.
I check other topic and see that can be the problem with the AFM, but i would like to also check TTS,
do You know maybe value of the ohms on the cold and hot?
hot to check the TTS?

Thanks for support.

[skykng]

How often do Thermal Time switches go bad? Is it a common or high failure rate item? My 1982 2000 is 33 years old -- been around a long time, overdue to quit???? tnx

kacperix -- the csv only works during start, so it sounds like it is operating OK. Is your Throttle Position Sensor set correctly?
It may be off a little so you need to compensate on start???

[kacperix]

I think I have screwed-up AAV,
I am looking for the replacement, but it's hard to find the same part number.

[kacperix]

problem was with the AAR and small air leak on the air tube, now its work fine.
Thanks

[skykng]

excellent - especially since you fixed the problem yourself!

[burlyb]

Ancient thread, but thought I should note what finally fixed my cold start problem. Since it was never really a problem in summer, I didn't bother renewing the quest until last fall. I realized that when replacing various sensors/parts, I replaced the original thermo time switch with a used one (because new was so expensive). Well, last fall I finally decided to bite the bullet and get a new one and it solved the problem. I don't recall my electrical testing techniques and why I couldn't electrically determine it's malfunction, but I'm impatient and more of a "parts thrower" than a tester.

Today I got the car out of storage and it fired up on the third crank!