Help! Hard Cold Start on my '89

[slowhand]

My '89 starts every time (even when cold) but takes a long time cranking to start when it's cold. Once started, it will start instantly throughout the day, as long as I don't let it sit for more than 4 hours. After that it takes a long time cranking to start it again. I just had to replace the battery because the long cranking (with only short driving time) twice a day killed it.

I have a new fuel pump in it and the pressure is at specs.

Someone told me that there is a specific sequence of turning on the ignition without cranking for a certain number of seconds, off, on etc. after which a C4 will start right away (as if warm already) and if anyone knows about that I'd certainly like to try it. Otherwise I'd sure like some suggestions for what might be the problem. I've had it two years now and it's always been like that.:eyerole

FYI..I'm a fair back yard mechanic but by no means a Corvette expert so please keep your responses at my novice level...Thanks

 

[boomdriver]

This can be the result of a bad coolant temp sensor, or cold start switch/sensor (if yours is equiped) .
This ECM knows to add fuel if below a specified temp, so if the sensor is faulty the ECM does not know it is cranking a stone cold engine.
Another phenomonon is the Bosch-III injector upgrade. Many folks have done this for whatever reason and 99.999% give rave reviews of the engines performance once running...however, there is a large percentage that has this cold start problem that did not exist with the old, dirty, shorted injectors. The conclusion is that the B-III inj is causing the hard start even on systems that utilize a 9th injector just for cold start,. and there is no good answer so far. I have seen the question a thousand times and a doz theories...but none have been proven.
So, go thru your temp sensor plugs and wiring at the front of the intake. I think your ECM just enrichens the 8 inj and does not have the 9th like some do. Make certain that the distributor connections are clean and tight, because the ECM uses the dist as reference to know that the engine is running on its own and to send fuel inj signals. If that dist signal is corrupted the ECM may not be getting the correct signals. Since the control functions are all measured on sensitive resistance values or low voltage reference signals, harness connections and grounds are critical for decent performance. More than one engine has been misdiagnosed over a bad ground or loose elec connection somewhere.

The key sequence that you refer to comes from the B-III issues....some cars do better if the key is turned ON for 2 seconds to allow the fuel pump to do its 2 second prime, to charge the fuel rails with pressure, then Key OFF and then Key ON to crank. Some do ok by cranking for 2 seconds then key OFF, then another crank and it fires off faster than just holding the key to crank for 5 seconds, which is very hard on starters and battery life. Kinda gives you the Cold Cranking Cramps...

Hope this helps

 

[slowhand]

Hard cold start

Thanks for the info. I will apply my limited expertise and see what happens.

 

[WRECKER88]

I had the same problem with my 1989 coupe with a code 14. I had to change the ecu. It thought the coolant temp was 252 degrees all the time. I got a reman Ecu from GM and now my car starts right up.

 

[boomdriver]

I forgot to mention that you really need to get a FSM so you will know what the shop is doing and if its needed or not..

 

[TedC]

My '89 starts every time (even when cold) but takes a long time cranking to start when it's cold. Once started, it will start instantly throughout the day, as long as I don't let it sit for more than 4 hours. After that it takes a long time cranking to start it again. I just had to replace the battery because the long cranking (with only short driving time) twice a day killed it.

I have a new fuel pump in it and the pressure is at specs.

Someone told me that there is a specific sequence of turning on the ignition without cranking for a certain number of seconds, off, on etc. after which a C4 will start right away (as if warm already) and if anyone knows about that I'd certainly like to try it. Otherwise I'd sure like some suggestions for what might be the problem. I've had it two years now and it's always been like that.:eyerole

FYI..I'm a fair back yard mechanic but by no means a Corvette expert so please keep your responses at my novice level...Thanks

Starting in 1989 GM reprogrammed the ECM EPROM to delay the firing of the injectors during cold starts. The intent is to build up oil pressure before the engine starts. At one time I owned a 1988 and cold starting was instant. Not so on my 1989. This delayed starting will occur with any type of injector (stock, Bosch III ...). Try this... Turn key to run, hear the pump run for a few seconds, then turn key to start for only a quick second, then wait three seconds, and start again. It should fire up right away. When you engage "start" for the first time, this signals the ECM to start the timing process.

Additional info: With one long crank it takes about 4 seconds of cranking to start.

 

[slowhand]

Hard cold start

Thanks all you guys for the tips. I'm going to try everything you guys suggested...especially getting the FSM.

 

[slowhand]

Hard cold start

You guys are awesome...I tried that starting sequence and it starts instantly....when cold as a dead fish. Thanks guys!

 

[geekinavette]

Slowhand...how long was it cranking when cold before starting up?

Kinda gives you the Cold Cranking Cramps...

:L Ok that was a good one.

 

[slowhand]

Hard cold start

It varied but at least 15 seconds and sometimes until the starter started slowing down. (Like the precursor to a dead battery)

 

[TedC]

It varied but at least 15 seconds and sometimes until the starter started slowing down. (Like the precursor to a dead battery)

GM programmed in a long crank when cold, but not that long. More link 4 seconds. Time to get a FSM and run some tests.