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Gary, Chevy Technician
Category: Chevy
Satisfied Customers: 16242
Experience:  15 years GM master tech
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1989 camaro: start...Anti Theft system (VATS..crank..injectors to fire

Resolved Question:

1989 camaro 350, Z28, TPI.
My problem is it will run and drive as long as it's not turned off from the initial start.
When it is turned off it will not start immediately but after waiting 5
minutes it will start again and run as long as it's not turned off. My
understanding of the Anti Theft System (VATS) is that it not only causes the
engine not to crank over but it also sends a signal to the Theft Deterrent
Module (TDM) that gives a signal for the injectors to fire. If I squirt
fuel in the TPI It will start and run as long as I keep this up. So I know
it is not getting fuel. I assume the pump is doing its job as it checks out
fine 40 psi. Replaced the module in the distributor and the same results.
Something is not giving the TDM or the CPU the signal it needs to start it a
second time after initial starting. I hope this describes my problem so you
can get a better idea of what is going on.
Submitted: 5 years ago.
Category: Chevy
Expert:  Gary replied 5 years ago.
so if you spray in fuel you have to keep spraying in fuel for it to run?its not like you spray in fuel then it starts right up and will run correct ? do you have a test light ?
Customer: replied 5 years ago.
need to keep spraying fuel. Have a test light.
Expert:  Gary replied 5 years ago.
ok the most common problems for this exact problem you are having is the grounds on the back of the cylinder heads being loose or dirty and if those are clean and tight the problem is going to be a fuel injector pulling the circuit down.any fuel injector under 10 OHM's is bad.those injectors under 10 OHM's will pull the signal down the way they wired these injectors one or 2 bad one will cause this problem
Customer: replied 5 years ago.
I have had the same problem before with the injectors, and because of the low voltage the car would not start. When i puled one of the injector wires to test it with my noid the car would start that's when I tested all of them and found the problem. Why will it start and run fine? If it had a bad ground wouldn't it not start to begin with? If the injectors were so bad the car would'n start at all correct. Just asking.
Expert:  Gary replied 5 years ago.
the ground is just a common problem engough i wanted to be sure you checked that.most of the time those act up when warm.if you ohm them cold when it will start then ohm them hot when it will not start i think you will find they or some are under 10 OHM's when it will not start hot
Customer: replied 5 years ago.
So below 10 OHM'S is not acceptable. This is what it seems like to me and I'm not questioning your ability, Why will the ECM pulse the injectors on the initial start and let the car run for as long as I want it to, and then not pulse them when I try to start it again. If I wait a while it starts and runs just fine with no problems. This is what stumps me. Is there a way to by pass the ECM to have the injectors pulse when the engine is cranking and to keep it running? I have check all the grounds. changed the oil pressure switch. checked all the connections for good contact. set the timing. And as stated before by passes the key resister. What does the theft deterrent module do?
Expert:  Gary replied 5 years ago.
hard to tell why.put if you get this car not to start hot if you unplug one injector on one bank and put the test light across those 2 terminals on the harness connector for that fuel injector which means the clip end of the test light to one terminal and the point of the test light to the other terminal crank it over and see if the test light flashes.then plug that one back ina nd go to the other bank and do the same thing.i think you will find when hot you will get no pulse.and its usually caused by injectors out of spec. but under 10 OHM'S is bad injector
Customer: replied 5 years ago.
OK. Thanks for the info. I'm sure we will figure this out. Did the test you suggested with a NOID and they were no pulses. I forgot to tell you that even if I start it and let it run for 30 seconds, the same problem. It will not start,(wait 4-5 min.and it starts just fine) so it is not a heating issue. You might be right about the injectors. But even cold it does the same thing. I'v been working on this car to help out a friend. Have an OBD 1&2-- read out says that its the ECM. One of his friends replaced that but put back the same prom and added a jet performance chip(stage 1). But the problem existed before all this was done. I would really like to get this thing out of my shop. Hope this helps.
Expert:  Gary replied 5 years ago.
i would stick to the diagnosis on this car.check those 2 grounds if they are good and clean and tight replace the fuel injectors or at least the ones that fail being under 10 OHM'S
Customer: replied 5 years ago.
If I accept this will I be able to ask more Questions and not get charged if this does not work?
Expert:  Gary replied 5 years ago.
you can reach me anytime threw this post.either before or after accept.i will reply back as soon as i can like tomorrow i know i will be hard to reach from 8:00 am to 4:00pm due to meetings at work all day.but i will not leave you hanging !
Customer: replied 5 years ago.
To replace the injectors will take a least 2 days. will have to be ordered and flown in from Calif. Not is stock in Hawaii. Will keep this post open till then. Appreciate your help. Hope this is OK with you. Await your reply.
Expert:  Gary replied 5 years ago.
ok let me know how you make out
Customer: replied 5 years ago.
Just to let you know I ordered the injectors from my local parts house. They will not be here till April 4th (next Wed). I don't want you to think I'm avoiding you. OHMED them again and found only 3 in spec. (16.2)The rest were below 10 ohms. Since I need to take it apart will change all of them. Will get back to you with the results on Wednesday or Thursday. Thanks again for the help.
Expert:  Gary replied 5 years ago.
any time let me know
Customer: replied 4 years ago.
Haven't had a chance to change the injectors yet. Had a emergency ( 1955 Chevy Bel Air ) needed to fly to Maui on Thursday and just got home. Will work on the camaro on Monday. Let you know what happens when done.
Expert:  Gary replied 4 years ago.
no problem
Customer: replied 4 years ago.
Changed all the injectors yesterday. All seems fine. The car went home yesterday and haven't heard from the owner yet so I guess the problem is solved. Thanks for all your help. I understand the voltage drop but I still would like to know why it would'n start after the initial start. Could it be that when in open loop it did not recognize the problem and when in closed loop then the computer knew that there was a problem with the injectors? Need to understand why this happens.
Expert:  Gary replied 4 years ago.
any time im glad my answer was acceptable.usually when those injectors temp greatly changed the resistance would be too great and one injector would have so much resistance it would not complete the path threw the banks circuit as they wires these in or cooler they would run but as it warmed up and resitance changed it would start to lean out the engine and then have so much resistance it would kill most or all the injectors
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