Help! Engine runs till warm up then dies won't restart till it cools down

[corvetteguy1993]

;help I own a 93 Ruby with 38,000 miles - I took it out maybe four times last year but very little time out. I have a problem when starting the car it runs great around 1200 rpm - volts are around 14.0 - oil press is good - I tried to pull codes - It gives me the SYS - no luck the standard code 12 - when the car warms up for ten minutes it falls on it butt then doesn't start. Can't be opti - tow truck driver said can't be battery since we used his jump box and would not restart - when car cools down - it starts runs fine then falls on its butt again. Any help?

 

[LT4man]

The things that pop out at me are heat related items.

The ignition module which sits under the ignition coil can act weird when hot. Same goes for the ignition coil.

This is a very difficult problem to diagnose. Anything that is intermittent is hard to find.

SAVE THE

 

[corvetteguy1993]

Yeah I thought of that too but it runs only 20 minutes then drops off. Can you take it in to have it checked? I know where it is and I did check the connections. I would think it would give you a code at least..... LOL

 

[LT4man]

That's the problem. Those two items will not set a code.

I believe Autozone CAN check the module. I believe there is no test for the coil except for a scope of the ignition system. But the engine has to be running.

Also, be sure there is a film of heat sink compound under the module. The compound can turn solid with time and lose its cooling properties.

SAVE THE

 

[corvetteguy1993]

Thanks for the information LT4 I will remove it this weekend and Plus I do have a chevy dealer less than a mile away and order the OEM hopefully. I have worked diligantly to keep the car stock as it came from the showroom when I purcased it.

 

[gmjunkie]

That's the problem. Those two items will not set a code.

I believe Autozone CAN check the module. I believe there is no test for the coil except for a scope of the ignition system. But the engine has to be running.

Also, be sure there is a film of heat sink compound under the module. The compound can turn solid with time and lose its cooling properties.

SAVE THE

lt4man has hit on most things that it can be!!But put a fuel pressure gage on it and see what the Fuel pressure does first!!!I've had a fuel pump act like that before on 2-3 C4's!!

 

[corvetteguy1993]

I thought of that too but I have rev-d up the motor during the start up up to 3000 RPM's and did doesn't hesitate nor no lack of power. Would you think that would be a problem? I will put one on it - what's the pressure usually at? This is a off the wall guess - 20 PSI?

 

[gmjunkie]

I thought of that too but I have rev-d up the motor during the start up up to 3000 RPM's and did doesn't hesitate nor no lack of power. Would you think that would be a problem? I will put one on it - what's the pressure usually at? This is a off the wall guess - 20 PSI?

WAG's won't work!! You need a gage,92-96 needs 41-47 Lb's to run properly,much below that and they will run Poorly,30-35 some won't even Fart!!:ugh As far as revving to 3000 with out a load on it it could hit the rev limiter with out a problem!!:WWhat I'm talking about I've seen them run for 10-45 min. and the fuel pump just shut down!!I've had it happen to a few Corvettes through the years,but I've ran into it allot on Chevrolet and GMC trucks!!

 

[LT4man]

gmjunkie is correct, as always!

Fuel, air, spark. You need all three.

Fuel pump pressure is easy to check. Install a pressure gauge on the schrader valve located on the rear of the fuel rail.

Wide open throttle without a load don't mean squat!

SAVE THE

 

[WhalePirot]

Is the engine stumbling or idling unevenly before it quits?

Check for fuel pressure rise when you just turn the key on. Surely it is as the car starts, but note the number. It will drop some when the car starts/idles when some FP is relieved from the engine's use and low fuel requirement. When you blip the throttle, the lower vacuum pulls less on the internal diaphragm, allowing higher pressure for more power. FP is set (not on stock cars) with the vacuum line off.

Watch for pressure changes as the car dies; which happens first?It there is a vacuum loss, the regulator will richen the fuel mixture. I would also watch for it 'loading up'; too rich. Depending on the local temperature, the time frame you mention might be when the car goes into 'closed loop', bringing all the sensor inputs into the ECM. I still use a vacuum gauge as those indications are as valid today as ever.

I am now, not quite sure why I paid all that dough for an adjustable FP regulator, as my chip is 'cut' for stock FP. Just $$ up in fumes! Lesson learned. I know some tuners like to mess with it, but............

You may have a sensor failing, IF it quits as closed loop happens.

This is an interesting read: http://www.fuelinjection.com/portinj.html

 

[gmjunkie]

Is the engine stumbling or idling unevenly before it quits?

Check for fuel pressure rise when you just turn the key on. Surely it is as the car starts, but note the number. It will drop some when the car starts/idles when some FP is relieved from the engine's use and low fuel requirement. When you blip the throttle, the lower vacuum pulls less on the internal diaphragm, allowing higher pressure for more power. FP is set (not on stock cars) with the vacuum line off.

Watch for pressure changes as the car dies; which happens first?It there is a vacuum loss, the regulator will richen the fuel mixture. I would also watch for it 'loading up'; too rich. Depending on the local temperature, the time frame you mention might be when the car goes into 'closed loop', bringing all the sensor inputs into the ECM. I still use a vacuum gauge as those indications are as valid today as ever.

I am now, not quite sure why I paid all that dough for an adjustable FP regulator, as my chip is 'cut' for stock FP. Just $$ up in fumes! Lesson learned. I know some tuners like to mess with it, but............

You may have a sensor failing, IF it quits as closed loop happens.

This is an interesting read: http://www.fuelinjection.com/portinj.html

I Agree!!

 

[WhalePirot]

I Agree!!

Man, I am relieved. I think I understand the car fairly well, but am always nervous knowing the Junk is near and watching...otfl

Thank you.

Now, to get MINE to idle when hot. I just got it together again, yesterday, and think the valves are a bit loose and I need to check all the usual electric aspects for a TPI.

 

[G Winter]

Now, to get MINE to idle when hot. I just got it together again, yesterday, and think the valves are a bit loose and I need to check all the usual electric aspects for a TPI.

Valves set to tight will let it idle when cold but will hold them open just enough to cause bad idle when hot.
Have also seen issues with valve guides being to tight, same effect when hot. You can even have the engine hot and take a compression check and it won't show up because the valves will still close at low crank speed.

Glenn

 

[corvetteguy1993]

I Agree!!

OK its been awhile sorry for the slow response time - I have changed the ignition coil no luck - changed the ignition module - again no luck - car is running rich and it freakin cold out - when its warm out around 55 degree's it runs less than two minutes and quits - seams to be running rich - I guess I better pull out the old pressure gauge and hook it up?

 

[Hib Halverson]

;help I own a 93 Ruby with 38,000 miles - I took it out maybe four times last year but very little time out. I have a problem when starting the car it runs great around 1200 rpm - volts are around 14.0 - oil press is good - I tried to pull codes - It gives me the SYS - no luck the standard code 12 - when the car warms up for ten minutes it falls on it butt then doesn't start. Can't be opti - tow truck driver said can't be battery since we used his jump box and would not restart - when car cools down - it starts runs fine then falls on its butt again. Any help?

First thing to do is find out why the SYS is flashing on the IP. It might be because there are codes set in controllers other than the ECM. Virtually all consumer code readers and scan testers do not support CCM, ABS or SIR.

The factory service manual has instructions on how to get the IP display (currently flashing "SYS") to display codes from all the on-board computers.

Another thing to do is run the fuel pressure tests listed in the Service Manual.

Lastly, "Service Manual" means the factory data, not a Haynes or Chilton book.

 

[Fast Freddie]

also, don't rule out the Engine Coolant Temp sensor. i had a car that would run great for 15 minutes or so and then die. it would start right back up after a bit of cooling down time. plugged a scan tool up to it and the ECT was telling the computer that the coolant temp was like +450 degrees. $10 and 15 minutes of work and the car ran like a champ for several more years.

 

[corvetteguy1993]

Wouldn't the gauges the mechanical and digtal would be incorrect with each other? Just a thought....

also, don't rule out the Engine Coolant Temp sensor. i had a car that would run great for 15 minutes or so and then die. it would start right back up after a bit of cooling down time. plugged a scan tool up to it and the ECT was telling the computer that the coolant temp was like +450 degrees. $10 and 15 minutes of work and the car ran like a champ for several more years.

 

[corvetteguy1993]

I do have the service manual and I will check it this week and look for on how to extract the information - My volts from the alternator are reading 14.9 volts - battery is fully charged but I still am having issues with the display flickering every so slightly.

 

[Fast Freddie]

the ECT sensor and the temp gauge sending unit are independent of each other.

 

[corvetteguy1993]

the ECT sensor and the temp gauge sending unit are independent of each other.

Leave to GM to give you something else to scream at!! LOL Where is that located? On the thermostat?hnoes