98 Chevy dies once in a while

98Chevyguy · 08-26-2007, 10:30 AM

I am wondering if anyone can help me out. I have a 98 Chevy 4x4 with 350 vortec that has 71,000 miles. I take excellent care of this truck and it rarely has been off road. A few months ago I had Flowmaster exhaust installed. The truck completely died while driving 30 mph. shortly after. Replaced fuel pump with GM fuel pump (500.00 for pump alone) Truck still died sporadically. Finally did get a service engine soon light. Checked OBDII and replaced 02 sensor. Truck died again. Replaced fuel pump relay fuse. Out of frustration, had a tune up done. Truck still dies once in a while.
I live 5 miles from work. I notice that when I first start the truck, the amp gauge is reading slightly above 14. By the time I get to work, it is reading between 13-13.5. The alternator is only a year and a half old. It is an autolite supreme. I also notice when I park in my driveway after driving home from work, the amp gauge will dip lower when I put in park and leave lights on and turn on turn signal. Even without this, the amp gauge varies and I think it is the belt tensioner which I am going to replace next. Does anyone have any ideas. Appreciate the site.

PeckerWood · 08-26-2007, 01:36 PM

Welcome to techsupportforum.

'98Chevyguy' I am
new here too.Seems to be a nice forum.

Well,I had the same problem and it was the alternator.

Does it do this when you leave the A/C off ?
Then you turn on the A/C and problems begin again.

If so,it's the alternator.

98Chevyguy · 08-27-2007, 02:31 AM

Thanks peckerwood. (good one) I haven't run the AC except once this summer. (live in the northwest - rain) It is not a consistent issue and that is why I am struggling pinpointing it. I think that I am going to replace the alternator and belt tensioning assembly to see if this works before I throw in the towel and take the truck to dealership and have their mechanics take a look. The alternator, although fairly new, makes sense and is about the only thing I haven't replaced. I will try this tomorrow on my day off and let you know. Thanks for the response!

**qldit** · 08-27-2007, 03:10 AM

Good Evening 98Chevyguy, that ammeter reading does sound odd, I would suggest getting a meter and actually monitoring the voltage under different circumstances.
Cranking voltage should never drop below 9 volts even after thirty seconds cranking.
Voltage when running at a stiff idle should approach 14 volts (possibly as high as14.4 volts) after a few minutes.

Your description and PeckerWoods idea sounds pretty accurate, or the battery may have a shorted cell and is not topping out with it's charge.

I like to fit voltmeters on vehicles that do any work, they are well worth the effort and show so more clearly what is happening.

Cheers, qldit.

98Chevyguy · 08-27-2007, 04:05 AM

Thanks qldit, The gauge reads 14+ when the truck is first started. After driving a few miles, the gauge starts dipping and eventually will be below 14. I have talked with a lot of mechanics about this. The only troubling thing is that when it dies, the gauge is still reading 13-14. When parked and truck is idling, the gauge is varying. If you turn the headlights on and turn on a turn signal, the gauge really starts to dip and the headlights dim each time the turn signal blinks. This seems odd and the truck has never done this before. Even without turn signal on, the truck in park with headlights on, the gauge is bouncing. I watched the belt tensioner and can see that it is bouncing. At the same time it does this, the engine starts to slow which would coincide with gauge.
Just out of desperation and process of elimination, I would like to try and replace alternator and belt tensionser assembly. If not that, I can only try new battery cables and ground. I don't feel it is those because I do not have any issues starting truck. Also when truck dies, lights and radio stay on. I have an Optima battery that is only 1.5 yrs. old. Supposedly one of the best batteries you can buy. I am going to have some tests done today. Thanks for your help. Let me know what you think.

**qldit** · 08-27-2007, 04:56 AM

Good Evening 98Chevyguy, a bouncing belt could be simply a damaged belt, or possibly the tensioner but that kind of thing can also be caused by an alternator which is having intermittent load effect, or has an internal problem.
Intermittent load effect can also be caused by the actual wire from the alternator to the battery having a problem. (bad lug kinds of end fittings) The negative lead may also be involved with this kind of thing but is not all that common.

This kind of thing sometimes happens when the actual connection on the alternator has a high resistance connection and causes internal local heating throught the terminal bolt into the internal regulator area, but the wire at the alternator post usually would be "cooked" and easily apparent.
It just makes intermittent better connection.

You sound like you are right onto the problem there.

The reading shouldn't really go below 14 volts at all unless there is significantly great current draw once the motor has been running for a few minutes. The thing should just float on approximately 14V.
That dropping figure points to a definite charging problem for whatever reason.

Don't miss the fact that it may simply be a bad belt, I imagine it is a serpentine type.

Check the tensioner bearing with the belt removed for slop, (should be none!) and the spring tension.

Check the battery for correct fluid level.

By the way, make sure you draw a description of the belt routing on a piece of paper if you remove it, some of these belts can be a major job how to replace and refit them. (lol !!)

Cheers, qldit.

PeckerWood · 08-27-2007, 05:38 AM

Quote:

Originally Posted by 98Chevyguy

Thanks peckerwood. (good one) I haven't run the AC except once this summer. (live in the northwest - rain) It is not a consistent issue and that is why I am struggling pinpointing it. I think that I am going to replace the alternator and belt tensioning assembly to see if this works before I throw in the towel and take the truck to dealership and have their mechanics take a look. The alternator, although fairly new, makes sense and is about the only thing I haven't replaced. I will try this tomorrow on my day off and let you know. Thanks for the response!

Well,when you are running the defrost for window defogging during rainy
periods,you still activate the A/C compressor.

08-26-2007, 10:30 AM	#1 (permalink)
98Chevyguy Registered User Join Date: Aug 2007 Posts: 3 OS: XP	98 Chevy dies once in a while I am wondering if anyone can help me out. I have a 98 Chevy 4x4 with 350 vortec that has 71,000 miles. I take excellent care of this truck and it rarely has been off road. A few months ago I had Flowmaster exhaust installed. The truck completely died while driving 30 mph. shortly after. Replaced fuel pump with GM fuel pump (500.00 for pump alone) Truck still died sporadically. Finally did get a service engine soon light. Checked OBDII and replaced 02 sensor. Truck died again. Replaced fuel pump relay fuse. Out of frustration, had a tune up done. Truck still dies once in a while. I live 5 miles from work. I notice that when I first start the truck, the amp gauge is reading slightly above 14. By the time I get to work, it is reading between 13-13.5. The alternator is only a year and a half old. It is an autolite supreme. I also notice when I park in my driveway after driving home from work, the amp gauge will dip lower when I put in park and leave lights on and turn on turn signal. Even without this, the amp gauge varies and I think it is the belt tensioner which I am going to replace next. Does anyone have any ideas. Appreciate the site.

08-26-2007, 01:36 PM	#2 (permalink)
PeckerWood Registered User Join Date: Aug 2007 Location: USA Georgia Posts: 26 OS: Windows XP	Re: 98 Chevy dies once in a while Welcome to techsupportforum.'98Chevyguy' I am new here too.Seems to be a nice forum. Well,I had the same problem and it was the alternator. Does it do this when you leave the A/C off ? Then you turn on the A/C and problems begin again. If so,it's the alternator. __________________ Where Do You Folks Keep The Liverscuits?LOL!! Last edited by PeckerWood; 08-26-2007 at 01:46 PM.

08-27-2007, 02:31 AM	#3 (permalink)
98Chevyguy Registered User Join Date: Aug 2007 Posts: 3 OS: XP	Re: 98 Chevy dies once in a while Thanks peckerwood. (good one) I haven't run the AC except once this summer. (live in the northwest - rain) It is not a consistent issue and that is why I am struggling pinpointing it. I think that I am going to replace the alternator and belt tensioning assembly to see if this works before I throw in the towel and take the truck to dealership and have their mechanics take a look. The alternator, although fairly new, makes sense and is about the only thing I haven't replaced. I will try this tomorrow on my day off and let you know. Thanks for the response!

08-27-2007, 03:10 AM	#4 (permalink)
qldit TSF Gearhead Join Date: Mar 2007 Location: Brisbane Australia. Posts: 592 OS: All Systems, mainly Linux	Re: 98 Chevy dies once in a while Good Evening 98Chevyguy, that ammeter reading does sound odd, I would suggest getting a meter and actually monitoring the voltage under different circumstances. Cranking voltage should never drop below 9 volts even after thirty seconds cranking. Voltage when running at a stiff idle should approach 14 volts (possibly as high as14.4 volts) after a few minutes. Your description and PeckerWoods idea sounds pretty accurate, or the battery may have a shorted cell and is not topping out with it's charge. I like to fit voltmeters on vehicles that do any work, they are well worth the effort and show so more clearly what is happening. Cheers, qldit.

08-27-2007, 04:05 AM	#5 (permalink)
98Chevyguy Registered User Join Date: Aug 2007 Posts: 3 OS: XP	Re: 98 Chevy dies once in a while Thanks qldit, The gauge reads 14+ when the truck is first started. After driving a few miles, the gauge starts dipping and eventually will be below 14. I have talked with a lot of mechanics about this. The only troubling thing is that when it dies, the gauge is still reading 13-14. When parked and truck is idling, the gauge is varying. If you turn the headlights on and turn on a turn signal, the gauge really starts to dip and the headlights dim each time the turn signal blinks. This seems odd and the truck has never done this before. Even without turn signal on, the truck in park with headlights on, the gauge is bouncing. I watched the belt tensioner and can see that it is bouncing. At the same time it does this, the engine starts to slow which would coincide with gauge. Just out of desperation and process of elimination, I would like to try and replace alternator and belt tensionser assembly. If not that, I can only try new battery cables and ground. I don't feel it is those because I do not have any issues starting truck. Also when truck dies, lights and radio stay on. I have an Optima battery that is only 1.5 yrs. old. Supposedly one of the best batteries you can buy. I am going to have some tests done today. Thanks for your help. Let me know what you think.

08-27-2007, 04:56 AM	#6 (permalink)
qldit TSF Gearhead Join Date: Mar 2007 Location: Brisbane Australia. Posts: 592 OS: All Systems, mainly Linux	Re: 98 Chevy dies once in a while Good Evening 98Chevyguy, a bouncing belt could be simply a damaged belt, or possibly the tensioner but that kind of thing can also be caused by an alternator which is having intermittent load effect, or has an internal problem. Intermittent load effect can also be caused by the actual wire from the alternator to the battery having a problem. (bad lug kinds of end fittings) The negative lead may also be involved with this kind of thing but is not all that common. This kind of thing sometimes happens when the actual connection on the alternator has a high resistance connection and causes internal local heating throught the terminal bolt into the internal regulator area, but the wire at the alternator post usually would be "cooked" and easily apparent. It just makes intermittent better connection. You sound like you are right onto the problem there. The reading shouldn't really go below 14 volts at all unless there is significantly great current draw once the motor has been running for a few minutes. The thing should just float on approximately 14V. That dropping figure points to a definite charging problem for whatever reason. Don't miss the fact that it may simply be a bad belt, I imagine it is a serpentine type. Check the tensioner bearing with the belt removed for slop, (should be none!) and the spring tension. Check the battery for correct fluid level. By the way, make sure you draw a description of the belt routing on a piece of paper if you remove it, some of these belts can be a major job how to replace and refit them. (lol !!) Cheers, qldit. Last edited by qldit; 08-27-2007 at 05:04 AM.