Good Morning!

I have a 1998 Silverado C1500 with a 5.0L V8. Since last Sunday, I've had two occasions (both first start of the day) where the engine will fire but not run. It turns over, sounds like it's started but immediately dies.

Possibilities???

1) The fuel pump does engage but I lifted the breather off and can't smell or feel any gas in the throttle body. Maybe fuel pressure? It's not all the time though.

2) I checked all relative relays and fuses in the engine compartment...they appear good.

3) After pulling and reinserting the fuses, I filled the bowl up with gas manually and it eventually started..after 15-20 minutes of off-and-on attempts. It doesn't die after it starts and then restarts just fine for a couple of days.

4) I filled up the tank last Saturday and did not have this problem prior to then..could it be bad gas? I have not used any injector cleaner or additive yet.

What could this be????

Thanks!

http://www.automotiveforums.com/vbu...ighlight=tamper

Go look at that thread that I started. I had this exact type of intermittent problem (start and immediately die) and it drove me nuts for almost six months. I got all kinds of answers and opinions. If I had listened to everyone, I would have spent a thousand or more dollars and still not be fixed. I ended up fixing it myself for 99 cents. There's a good chance this is your problem too.

GM vehicles use VATS or PASSLOCK. Introduced in 1996, GM has changed the VATS anti theft system to Pass-Lock system. This is a similar device to the VATS system, in that there is a resistor present during the start cycle. However, in the PASSLOCK system, the resistor has been placed inside the ignition switch, instead of the key. This is why you no longer see the resistor actually in the key itself. This is still a theft-deterrent device.

To remotely start a car (in your case, I don't know if this is remote-start related) with this feature, you must bypass the PASSLOCK system. There are two methods of doing so.. The first, is to permanently bypass this system. This is the easiest method for accomplishing your task and this is what I did. The second way, is to temporarily bypass the PASSLOCK, by introducing relays into the system, which retain all of the features of the system, while allowing your remotes start module to bypass it automatically during a remote start cycle.

Also, even if you have no remote starter, you will have the same starting issues if this resistor circuit starts to go bad. The truck will enter "Tamper" mode and then you need to wait about 8 minutes, and then the truck computer will re-set and it may (or may not) start and run properly. It's a very random problem and cannot be located with a OBDII code reader.

Your '98 truck (like mine) uses PASSLOCK with the built-in resistor circuit, therefore you could certainly be having the problem that I was. After you get stuck a few more times, if you can't fix it, then do as I did and measure the cranking resistance, buy or make your own resistor of matching ohms and solder in place.

http://www.e-z.net/~iei/vatts.htm

There's a page with instructions. Go to the bottom and use Method A. Hope this helps.

You would need to remove the dash panel below the steering wheel and then carefully access the wiring harness under the steering column. The job is not very hard, so long as you are somewhat adept at repairs. You need an ohm meter and soldering gun. Once you measure cranking resistance, you can go to Radio Shack and buy a resistor that closely matches. If they can't get with 5%, then you may need to make one. The Radio Shack folks can tell you how to come up with the proper resistor. I would estimate total time for this repair at about an hour. Cost of resistor(s) will be only a few dollars.

Of course, this will permanently dis-able the resistor wire anti-theft feature, but if a crook wants your truck, he'll take it.

Good luck

Good Morning!

I have a 1998 Silverado C1500 with a 5.0L V8. Since last Sunday, I've had two occasions (both first start of the day) where the engine will fire but not run. It turns over, sounds like it's started but immediately dies.

Possibilities???

1) The fuel pump does engage but I lifted the breather off and can't smell or feel any gas in the throttle body. Maybe fuel pressure? It's not all the time though.

2) I checked all relative relays and fuses in the engine compartment...they appear good.

3) After pulling and reinserting the fuses, I filled the bowl up with gas manually and it eventually started..after 15-20 minutes of off-and-on attempts. It doesn't die after it starts and then restarts just fine for a couple of days.

4) I filled up the tank last Saturday and did not have this problem prior to then..could it be bad gas? I have not used any injector cleaner or additive yet.

What could this be????

Thanks!

You may be having the dreaded CTS disease as well. Your truck and most every vehicle made since the mid 1980's has been equipped with a coolant temperature sensor. The function of this sensor is to tell the ECM(computer) how much fuel and air mixture to advance based upon engine temperature readings. The ECM in turn increases the a/f mixture to satisfy the demands of the engine load, temps, etc.
I know it sounds silly to many people that a cheap little sensor can cause so many problems, but in cold start issues or stalling/stumbling issues, I have found that 4 out of 5 times this is the case. For $6 or $7 dollars you can't go wrong if you don't have access to the DTC's or someone who can obtain them for you.
The coolant temperature sensor is located very near or in the thermostat housing and is usually just a single wire, or 2 wire component. At any rate, if the Check Engine light has been on, make sure to reset the ECM after installing any new information sensors.
Good luck and please post your results.

I forgot to say that my "check engine" light was NOT on. Typically, if it's a sensor, such as suggested in the post after mine, then the "check engine" light would come on and you could read the codes to find out what's wrong.

I was, however, having the "security" light coming on and off at various times. My '98 Silverado truck has been 100% perfect since I did the resistotr wire by-pass.

Thanks so Much to both of you for your help! But Chevy-SS, I believe you have the answer! My security light just started coming on and off recently...about the same time that this starting problem cropped up. I am an electronics tech by trade and work for a company that sells resistors so I'm going to give this a try this weekend!

Again, thank you so very much for the assistance and also to automotive forums for presenting a forum to speak to folks like you.