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Weird intermittent starting problem...


yoshisushi
02-21-2005, 04:52 PM
1998 1500 4.3 2WD Auto (Reg Cab)

Hello all,
I have an intermittent problem and Iím not sure where to begin troubleshooting. Basically on some days (it appears random) the truck will not start, most other days it starts fine.

I can hear the fuel pump run while Iím cranking the engine. Sometimes the engine will sputter a little bit but it doesnít start. The funny thing is it starts fine later that day or the next day. Usually the check engine light comes on the day following the truck not starting but goes away the day after that. I live in the North East and itís wintertime here and the thought of moisture being the problem is in my head. I do recall this problem happening once or twice in the summer when it rained heavily.

Iíve had the truck for about 6 months and havenít done any work to it yet. I donít know how old the wires and plugs are or the fuel filter. I just bought some AC-Delco wires, cap and a rotor but I havenít had a chance to replace them yet.

Has anyone seen this before or have any tips??

Thanks in advance!
Rick

Chevy-SS
02-22-2005, 01:02 PM
http://www.automotiveforums.com/vbulletin/showthread.php?t=336225&highlight=tamper

Go look at that thread that I started. I had this type of problem and it drove me nuts. I got all kinds of answers and opinions. I ended up fixing it myself for 99 cents. There's a good chance this is your problem too.

yoshisushi
02-22-2005, 03:33 PM
Chevy-SS,

Thanks for the response. I read your post. I went through that when I installed my remote starter. I found out that I dont have VATS on my truck. Thanks though.

Today is the day, it decided not to start again. I'm glad I have a beater car as a backup. Well I plan on doing a tuneup this weekend. Cap, rotor, wires, plugs and fuel and air filters. I guess I'll see how things go and post here.

Chevy-SS
02-22-2005, 04:58 PM
I suppose I could be wrong here, but I though all GM vehicles used 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 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.

Bottom line: your '98 truck 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 Diagram A. Hope this helps.

Good luck

Cadillakin'98
02-23-2005, 12:27 AM
I do believe Chevy-SS is correct about what he is saying about the VATS and Passlock systems. Bottom line is his bottom line is for sure correct. Your '98 has Passlock. Lokk at any wiring schematics for your truck......

yoshisushi
02-23-2005, 02:41 AM
Thanks Chevy-SS for the further clarification, I really appreciate it. However Iím worried that since our symptoms donít closely match that I could be chasing a bad lead but it sounds easy enough that itís worth a test. I will temporarily put in place the permanent bypass therefore eliminating the PASSLOCK system as the culprit or proving it culpable.

The reason Iím not sure if the PASSLOCK is the problem is because you said your truck would start 10 minutes after the problem occurred, I have to wait 6 Ė 8 hours, sometimes 24. Also, do you recall if your check engine light ever came on? Mine does and stays on for a day or so after the truck acting up but my ďsecurityĒ light never comes on.

I read in your post that you ran your resistor to an orange/brown wire, is that correct? Is that wire hard to find? The instructions you linked me to seem easy to follow for finding the resistance.


Rick

yoshisushi
02-23-2005, 03:00 AM
Found some instructions for the PASSLOCK bypass. Similar to what you did? This is from remote starter instructions for 1998 trucks and whatnot.

http://files.automotiveforums.com/gallery/watermark.php?file=/503/248112passlock.JPG

Chevy-SS
02-23-2005, 07:38 AM
yoshisushi, yes, that is the process for replacing the resistor circuit with a soldered in resistor.

I agree that our symptoms do sound a little different. If the vehicle goes into "Tamper" mode, then I think the wait time is around 8 minutes, for the computer to reset and then you will be able to start the vehicle. Although, it's possible that your resistor circuit is in worse shape than mine was, that is, it rarely produces the correct resistance now.

Your "check engine" light should stay on until it is cleared using the OBDII diagnostic. I don't understand how that could be intermittent. But then again, there's a lot I don't understand with all this electronic stuff.

J-Ri
02-23-2005, 08:20 AM
Some lights will stay on even with codes still present in the computer. I dunno why either, but it's not out of the ordinary to see that.

teamroperhdr
02-23-2005, 10:12 AM
Seems to me that if it was a passlock problem it would not "sputter" like he says. My best advice it to get the codes read. I had this same problem with my 97 1500 and the code read as failed O2 sensor. I know these are not in a loop until the engine is warmed up but I replaced it and have not had a problem since.

Chevy-SS
02-23-2005, 12:47 PM
Seems to me that if it was a passlock problem it would not "sputter" like he says. My best advice it to get the codes read. I had this same problem with my 97 1500 and the code read as failed O2 sensor. I know these are not in a loop until the engine is warmed up but I replaced it and have not had a problem since.

If it is the "Tamper" mode problem then the engine will start very briefly and then immediately die. It will do it this way every single time. About eight minutes later, it will re-set and it may (or may not) start properly.



:swear:

teamroperhdr
02-23-2005, 08:53 PM
If it is the "Tamper" mode problem then the engine will start very briefly and then immediately die. It will do it this way every single time. About eight minutes later, it will re-set and it may (or may not) start properly.



:swear:
Good to know, thanks for the info SS

cousincletus
02-26-2005, 08:50 AM
Yep. Worked on a Tahoe with a bad passlock and the truck would start and immediately die. I would do the tuneup first, get the code read and see what happens.

91imca
03-06-2005, 12:55 AM
I do not have remote start but sometimes truck cranks and runs fine but security light comes on, then other times it cranks and goes dead then wait 10 minutes it may crank and stay running or it may crank and go dead , when it cranks and goes dead it will do it every time i have tryed some of the methods mentioned here and none work, i may be doing it wrong or are their other problems with truck, it is a 1998 chevy .

Chevy-SS
03-06-2005, 08:08 AM
I do not have remote start but sometimes truck cranks and runs fine but security light comes on, then other times it cranks and goes dead then wait 10 minutes it may crank and stay running or it may crank and go dead , when it cranks and goes dead it will do it every time i have tryed some of the methods mentioned here and none work, i may be doing it wrong or are their other problems with truck, it is a 1998 chevy .

What exactly do you mean when you say "have tried some of the methods mentioned here"? Have you done the permanent security resistor wire bypass? That's where you cut the yellow wire, measure cranking resistance with ohm meter, and then install resistor of similar resistance. Did you do that yet? There is a link to web site explaining in my previous post in this thread, plus there is a small diagram in yoshisushi's post.

In my opinion, you should try the resistor wire bypass. It costs almost nothing to do it and it could solve your problem.

I had similar starting problems with my '98 truck and was getting told to replace fuel pump, computer and all kinds of stuff. I could easily have spent over a thousand dollars chasing this stupid problem, but I got lucky and found a guy at a local service station who had the same issue with his '98 truck. He correctly diagnosed the problem, but he chose to replace the wiring harness, which was a couple hundred bucks, plus a lot of work. I did a little more research based on his diagnosis and found the bypass trick listed on internet.

As I say, this is a very easy thing to do. It's very inexpensive also. I would make this your first task and see if it fixes you.


:iceslolan

yoshisushi
03-11-2005, 02:57 AM
Hi all,

OK, I did the tune up, new cap rotor wires and plugs, still happening. It's not a security Passlock problem because the symptoms don't match.

I had to drive around in a snow storm recently for about an hour and the truck died while I was driving (first time that's ever happened). I pulled over and made a call for a ride, 15 minutes later the truck started and I drove home fine. It kind of ran rough for the first 15 seconds but then ran fine.

My question right now is when I turn the key to ON and the fuel pump comes on, how loud should it be? Mine is LOUD! It's not bad sounding, not like a rock in a lawnmower sound but just loud like a vacuum cleaner is loud. Is that bad? People at work even notice it. I just thought that's how it's supposed to be.

Also, does it sound like a loss Spark problem or a loss of fuel pressure? Iím going to buy a fuel pressure gauge this weekend and when it will not start again Iím going to check the fuel pressure.

Thanks greatly for your help!!!

Rick

Chevy-SS
03-11-2005, 07:57 AM
My fuel pump is also very loud. My friends have commented on it. I can sometimes hear it while driving and it is a little annoying.

Have you put a code reader on this thing? That may help. Also, you said you were going to try the resistor bypass trick? Did you do that?

J-Ri
03-12-2005, 01:57 AM
It's not nescesarily bad because it loud. If you have access to an oscilliscope, look at the waveform of the fuel pump. It should be very even. The waves are where the brushes in the pump contact 1 or 2 contacts on the rotor. If the pattern is eratic, your fuel pump is bad.

yoshisushi
03-21-2005, 09:09 PM
It finally happened again and I was able to get the code pulled at AutoZone.

It's Troublecode ODBII (Alpha) P Code. P1351 IDM Input Circuit Malfunction.

About all I can find on the web is that IDM stands for Ignition Diagnostic Monitor Input Circuit.

marc_28269
10-10-2005, 10:03 AM
I suppose I could be wrong here, but I though all GM vehicles used 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 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.

Bottom line: your '98 truck 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 Diagram A. Hope this helps.

Good luck
Is there a diagram available without the automatic start involved?

Chevy-SS
10-10-2005, 12:02 PM
marc,

Just go to that page. At the bottom simply use Method A or B. I used (and recommend) Method A, which is a permanent bypass of the security code wire. You should be able to do the whole job in about an hour. You need something to measure resistance (an ohm meter), then you just need to go to Radio Shack and buy resistors to match (+/- 4%) the reading that you take. Solder the resistor in place as per instructions and you will have no more starting problems.

Of course, this bypasses an important security feature, but I'd rather be able to start my car, LOL.

:iceslolan

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