intermittant starting issue
Thread Starter
Heel & Toe
Joined: Jun 2010
Posts: 23
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intermittant starting issue
Hi - my C4 has a warm starting issue. I bought a scanner and it flashes 12 but no other code. According to the service manual it could be an ECM. The symptom is it will not re-start once it reaches 110 degrees - so I can drive it to and from work, but if I turned it off in the driveway or parking garage it will not start. Have you ever encountered an issue like this? Does this sound like an ecm issue
Kind Regards
Kind Regards
Race Director
Joined: Jun 1999
Posts: 14,924
Likes: 9
From: Merritt Ils Fl
First, it would be nice if we had a clue what year the car is and what has been done to it. That said: No you do not have an ECM issue. Code 12 is the ECM checking itself and reporting for duty. Second: No start when hot is chronic in Small Block Chebbys. Problem is in the contacts in the starter solenoid. With age and use they become burned and will not carry the required current to turn the engine. Most common fix is to replace the starter. A less expensive fix is replace the solenoid, an even cheaper fix is to replace the contacts in the solenoid or simply clean the contacts. A short while ago jfb wrote an excellent piece on this problem, explained it in detail. Worth a read if you can find it.
Drifting
Joined: Jan 2007
Posts: 1,908
Likes: 3
From: Supreme Soviet Peace-Loving Pipple's Kollektive of Seattle Wa
"not start" can mean a couple of things. The starter can fail to turn the engine over and thus "not start". The starter CAN turn the engine over and the engine "not start". Which condition do you have? A starter circuit issue, or an air/fuel/ignition issue?
Drifting
Joined: Jan 2007
Posts: 1,908
Likes: 3
From: Supreme Soviet Peace-Loving Pipple's Kollektive of Seattle Wa
As replied earlier here, people will gladly try to help-but the questions you never answered is the YEAR of your car and are the fuel/ignition systems stock? Just like walking into a parts store-to get help, you've got to supply information...
Racer
Joined: Jun 2010
Posts: 264
Likes: 1
From: San Antonio Texas
I looked back at one of his previous posts on a fuel sending unit, and he stated that he has an 89 Vette.
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Team Owner
Joined: Mar 2001
Posts: 54,124
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From: Cincinnati, Oh USA
Another warm starting cause is the spark module which provides weak spark when hot but work ok cold. When it won't start is the time to do some diagnosis to find out the cause. Engines require hot spark, spark at the right time, fuel and air and in the correct ratio and cylinder compression in order to start and continue running. Pull a plug wire and bring a grounded wire near the boot while someone cranks. You should have a snappy at least 1/2" spark. Use a timing light to see if it is correct. Measure the fuel pressure, it should be 35-42 psi and it should hold up at least 1/2 hr after the ign is off or you have leaky injectors or defective fuel pressure regulator check valve. Use a noid light (available at parts stores) or make one with an LED (light emitting diode) and a series 680 ohm resistor and check an injector on both banks during cranking to see if the injectors are being pulsed. Homemade noid light must be connected with the correct polarity to work. Use some starter spray to see if it will start hot, if so, you have a fuel delivery problem. Last, measure cylinder compression.
Thread Starter
Heel & Toe
Joined: Jun 2010
Posts: 23
Likes: 0
Ok fellas here is the 411 - it is an 89 automatic with no mods 115k miles, runs real well at speed idles roughly when the issue evolves - by that I mean when i start it cold I can re-start it until the cold idle goes to normal at which point it idles just a bit roughly and if I turn it off at that point which is above 110 degrees it will turn over and not start. Things recently replaced after the issue evolved are the sending unit and pump(didn't display properly so I replaced them both), the control module in the distibutor because of a thread I read about them malfunctioning when they get hot. JFB I appreciate your candor sir but I am mechanically inclined and I have done all of that except the noid tests so I'll go get one of those. It does get spark and it will start with the help of ether and run. One other anomoly with the car is the temperature display occasionally blinks irradically. Lastly if I disconnect the MAF sensor I should get a code - no code just code 12. your take ?
Team Owner
Joined: Jan 2009
Posts: 73,568
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From: Somewhere in Mo
St. Jude Donor '09-'10, '14
If it starts with ether you're getting spark. Could be wrong but it still points to fuel but you said the FP was fine right?Do you have a FSM? I'll look in mine and see what it says.
It sure seems like this sounds familiar. Someone else just had this problem but I don't recall what the fix was.
It sure seems like this sounds familiar. Someone else just had this problem but I don't recall what the fix was.
Last edited by RetiredSFC 97; Jul 14, 2010 at 07:46 PM.
Team Owner
Joined: Jan 2009
Posts: 73,568
Likes: 33
From: Somewhere in Mo
St. Jude Donor '09-'10, '14
Team Owner
Joined: Jan 2009
Posts: 73,568
Likes: 33
From: Somewhere in Mo
St. Jude Donor '09-'10, '14
If it starts with ether you're getting spark. Could be wrong but it still points to fuel but you said the FP was fine right?Do you have a FSM? I'll look in mine and see what it says.
It sure seems like this sounds familiar. Someone else just had this problem but I don't recall what the fix was.
It sure seems like this sounds familiar. Someone else just had this problem but I don't recall what the fix was.
Team Owner
Joined: Jan 2009
Posts: 73,568
Likes: 33
From: Somewhere in Mo
St. Jude Donor '09-'10, '14
Yeah it's telling you to check the entire injector system and if that's not it, it's the ecm. That's what I wondered about when you shot ether in it and it started.
I did some more research but people are good about asking for help but few are good about coming back and saying what the fix is.
i know in the past when people had the warm start issue it turned out to be fuel related quite a bit.
I would give jon, at FIC, a call and see what he thinks. he can probably tell you if it could be the injectors.
He's a vendor here and you should be able to find him on the list on the left side of the page.
Also post this on the tech side. Some guys hang out there that are more savvy with these things than I.
I did some more research but people are good about asking for help but few are good about coming back and saying what the fix is.
i know in the past when people had the warm start issue it turned out to be fuel related quite a bit.
I would give jon, at FIC, a call and see what he thinks. he can probably tell you if it could be the injectors.
He's a vendor here and you should be able to find him on the list on the left side of the page.
Also post this on the tech side. Some guys hang out there that are more savvy with these things than I.
Team Owner
Joined: Jan 2009
Posts: 73,568
Likes: 33
From: Somewhere in Mo
St. Jude Donor '09-'10, '14
Here's his sticky on fuel injectors. If you click his name you will see a place to go to his web page. Pull it up and give him a call.
http://forums.corvetteforum.com/c4-t...questions.html
Just thinking out loud but I wonder about the coolant temp sensor?
http://forums.corvetteforum.com/c4-t...questions.html
Just thinking out loud but I wonder about the coolant temp sensor?
If your vehicle starts using more fuel than usual, starts having trouble starting when the engine reaches normal operating temperature or you notice black smoke coming out from the exhaust tail pipe, it is very likely that these symptoms are related to a bad coolant temperature sensor
Last edited by RetiredSFC 97; Jul 15, 2010 at 08:12 PM.
Thread Starter
Heel & Toe
Joined: Jun 2010
Posts: 23
Likes: 0
Thanks much for taking the time I sure do appreciate it! I ordered a fuel pressure gauge to test it myself - the place that did the test didn't do the full 30 minute thing "if it is leaking down it is probably ok" so he said. Anyhow I agree it is fuel - almost like a fuel pressure regulation of some sort. I'll replace the temp unit and I will communicate the progress I make - again thanks.
Team Owner
Joined: Jan 2009
Posts: 73,568
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From: Somewhere in Mo
St. Jude Donor '09-'10, '14
The fuel pressure should reach at least 42 PSI. Then after about 30 minutes or so it should still read in the 35 to 39 range. Also when you get the gauge, tape it to your winshield and go for a drive, considering it starts of course, and watch what the pressure does as it warms up.
I'm not the smartest mech on the forum by far but my common sense meter tells me fuel first, a sensor second, and a spark issue third. Spark as in bad ground, coil, or ecm issue. The starting with ether is why I would rule out fuel first.
When my FPR was bad the pressure would drop like a rock when I turned the car off.
I was thinking of putting together a simple no nonsense hookup to run fuel pressure tests but Haven't done it yet. To do a complete thorough test you need to pinch off lines, and I thought of a couple valves with shut offs to hook to the fuel line and then the return line to make it easier to do the check. I'll have to get on that!
Good luck and let us know when you get it figured out. I'm trying to fugure out a closed loop idle stumbe myself.
I'm not the smartest mech on the forum by far but my common sense meter tells me fuel first, a sensor second, and a spark issue third. Spark as in bad ground, coil, or ecm issue. The starting with ether is why I would rule out fuel first.
When my FPR was bad the pressure would drop like a rock when I turned the car off.
I was thinking of putting together a simple no nonsense hookup to run fuel pressure tests but Haven't done it yet. To do a complete thorough test you need to pinch off lines, and I thought of a couple valves with shut offs to hook to the fuel line and then the return line to make it easier to do the check. I'll have to get on that!
Good luck and let us know when you get it figured out. I'm trying to fugure out a closed loop idle stumbe myself.