Fuel system help.... maybe

[crammit442]

Charles, Thanks for the update! Because of the "clutter" and no ability to easily and correctly search these forums it may be better to stay on this thead. Only start a new one if you resolve problem and create a sticky or Troubleshooting help post.

From what I have seen on VATS, the dash light flashing on momentarily and going out is the correct operation if theft is not active. Light would stay on if active. A Tech2 or similar hi end scanner would verify a theft shutdown or correct operation with the corresponding codes. Where do you live? several members here have Tech2's willing to help.

There is little info available for the internal workings of this system and UTube wont likely post "How to steal a Chevy".
There are 10+ posts here unsolved on no start similar to you.
I recommend you do some more diagnostics to "prove" this is your issue. Unplug the big connector on top of intake for F/I harness and verify pin connections were good/deep. Also noid light tests here- you can use a 194 bulb for a noid lite. The VATS injector shutdown shuts off the ground inside computer. So a bad engine/computer ground could be your cause, with some grounds under dash.
The factory manual is a big help here. Go here- you have to join to download-GMT400 CK Manual Project - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Keep us updated! We are here to help.

I appreciate the link. I've been looking at the different manuals and I'm a little confused about which one applies to the . On another note, I found a module (New Rockies) that claims to permanently fix all VATS issues. It uses a universal module with adjustable dip switches and different installation instructions for specific vehicles. The website looks a little like an "as seen on TV ad", but I was able to find several installation videos on YouTube with lots of positive comments. They claim to have a 30 return policy with a lifetime replacement warranty. It's $300, but could be money well spent if it permanently fixes it.

Charles

VATS Passkey Passlock PERMANENT Bypass | NEWROCKIES

GM Passlock FULL PERMANENT bypass fix: stop security-caused stalling for good with the NEWROCKIES PRO Module.

newrockies.com

 

[iamdub]

This is all still pretty confusing to me. I'd never even heard of VATS before your post Monday. I think you're right that all the versions of VATS are sort of under the same umbrella. Even though my system (Passlock) doesn't use a chip or resistor key like PK/2,3, if I'm understanding it correctly, the system shuts off the fuel injectors until the ignition switch tells the system it's been turned has been turned by a real key. I saw that the system could be turned off in a tune. I don't actually need it tuned for what I do, but who are some recommended tuners and what does it typically cost? I guess before I look into that option I want to be sure my ignition switch is sending good key information to the rest of the system. Thankfully I don't have to drive it right now so I can afford to take a step back and do more testing before waste more money on things that may not be the problem. I really appreciate all the suggestions and feedback.
Charles

Tuning prices vary, particularly by what all is done. It's usually around $150 at a minimum. Using HP Tuners as an example, most vehicles of this type require two credits to tune at $50 each, so $100 in credits. If a tuner is just making basic changes and not really tuning for power, etc., they might tack on something like $50 for their labor, totaling $150. I had mine tuned to disable AFM, delete the rear O2 sensors (for future plans of catless headers), remove the speed limiter and maybe some other small things for $150. For an actual power tune where they use their knowledge and experience to read and modify the fuel, timing and shifting tables, it would be a few hundred more, as it very well should be. It's not for the inexperienced.

For your purposes, I'd just find a local reputable tuner, explain what you're doing and go from there. It shouldn't cost much. They might even suggest a few small extras or tweaks they'd include as freebies since most of all they're doing is checking or unchecking boxes.

 

[crammit442]

Tuning prices vary, particularly by what all is done. It's usually around $150 at a minimum. Using HP Tuners as an example, most vehicles of this type require two credits to tune at $50 each, so $100 in credits. If a tuner is just making basic changes and not really tuning for power, etc., they might tack on something like $50 for their labor, totaling $150. I had mine tuned to disable AFM, delete the rear O2 sensors (for future plans of catless headers), remove the speed limiter and maybe some other small things for $150. For an actual power tune where they use their knowledge and experience to read and modify the fuel, timing and shifting tables, it would be a few hundred more, as it very well should be. It's not for the inexperienced.

For your purposes, I'd just find a local reputable tuner, explain what you're doing and go from there. It shouldn't cost much. They might even suggest a few small extras or tweaks they'd include as freebies since most of all they're doing is checking or unchecking boxes.

After more research I've decided to go this route. I saw a shop recommended on another forum and talked with them this morning. He thinks the VATS disable should work. It's $150 and I should have the PCM back by the end of next week. I'll link the thread where I read about this below. It's a later vehicle, but it's still the best thing I've found about how VATS/Passlock/Passkey works. I appreciate all the help and I'll keep this updated.
Charles

PassLock Ignition Switch Disassembly & Modifying

www.355nation.net

 

[exp500]

Charles- Ref posts15, 20- You should have a chip key for your year!
I would at least pull the codes with a tech2 or similar before investing in proposed mod. That would pay for your very own vcx nano with beer money left over!

 

[crammit442]

Charles- Ref posts15, 20- You should have a chip key for your year!
I would at least pull the codes with a tech2 or similar before investing in proposed mod. That would pay for your very own vcx nano with beer money left over!

I thought the same thing too until I looked at the VATS relearn guide below and compared my key. When I talked to my buddy that owns the car audio shop he said the same thing because they have to bypass the key/switch to install remote start systems. I've actually solved (at least temporarily) the problem. It's a long story and I'll put it in a separate post after this. Thanks again for the help.
Charles

GM Security Relearn Procedure - Module Experts

Complete GM security relearn procedure guide covering VATS, Passkey, Passkey II, Passlock, and Passkey III, plus the Crankshaft Position Sensor relearn.

moduleexperts.com

 

[crammit442]

Well, the Tahoe is alive again. Time for the walk of shame. I've managed to squeeze 6 days of pain and misery out of a 45 minute/5 cent repair. I may make try to make a new thread for future reference if what I've learned can help anyone else avoid the same thing. An accurate fuel pressure test might have sent me in a different direction, but I'm not sure. The truck has been hard starting for a couple of years, but was always fine after the first start of the day. A couple of weeks ago it would still start, but I couldn't get it to run more than about 3-4 seconds. I still had compression and spark so I assumed the fuel pump had finally quit. Last Saturday I dropped the tank and replaced the pump and figured everything would be good. I couldn't believe it would still only run for a few seconds. I spent Saturday night and Sunday searching this forum, YouTube, and everywhere else before starting this thread. I'd never even heard of VATS until iamdub said my issue sounded like an anti theft problem. If he hadn't mentioned it I probably wouldn't have ever figured it out. Even though the symptoms were right I didn't have a flashing or steady security warning light. When searching for VATS problems I saw how many other people had similar unresolved problems. Passkey, II, III/Passlock all turn off the fuel injectors if a "good key" signal isn't sent from the ignition switch to the BCM. Some of the keys are plain, some have resistors, and some have a transponder. Totally confusing. Every potential solution seems to just add more variables and don't end up working for most people. There are a bunch of videos on bypassing the Passlock version using a resistor, but I couldn't get a consistent resistance valve from my switch so I didn't try it. I found a place that rebuilds Theft Deterrent Modules (TDM), but he said it probably wouldn't fix my problem because the warning light wasn't on. Tuners can disable VATS, but I haven't been able to get firm answer on whether it'll fix a system that has already quit. After reading everyone's suggestions I decided to try the resistor bypass before spending any more money. I called my buddy at the car audio shop this afternoon and he left me a bag of assorted resistors that could be wired in series to get any value needed. I still got wonky readings from my switch, but decided to start with a 3k ohm resistor. After temporarily installing it I turned on the ignition switch and the flashing security light finally came on. I followed the Passlock relearning process and it worked exactly like it was supposed to. During the 10 minute relearn sessions, the flashing light worked down to the second on my timer. This was a big circular process, but it would have been a lot worse without everyone's suggestions and feedback here. Putting everything in writing and rereading everything really helped. Hopefully the fix will stick long term. If it doesn't I think I'll be way ahead going forward. I'll keep this updated either way. Sorry for the long story, but it's been a LONG week. Thanks again!

Charles

 

[crammit442]

Double post.

 

[exp500]

No walk of shame due! Congratulations on the repair !
I had a ford with this system beat me up pretty bad till I modified the relearn cycle thru the scanner to learn new keys, 3-4 hrs to fix after diagnostics. I was the 3rd to try and fix, ford dealer had it 2 weeks. Failed at the last step repeatedly. It's still on the road.
I'm still curious about your repair resistor placement as I'm running 12 work trucks and 20+ years is a long time for electronics to last. Private Message (PM) me. so its not public.

 

[willxfs]

Glad you got this sorted out and thanks for keeping us updated!

 

[crammit442]

No walk of shame due! Congratulations on the repair !
I had a ford with this system beat me up pretty bad till I modified the relearn cycle thru the scanner to learn new keys, 3-4 hrs to fix after diagnostics. I was the 3rd to try and fix, ford dealer had it 2 weeks. Failed at the last step repeatedly. It's still on the road.
I'm still curious about your repair resistor placement as I'm running 12 work trucks and 20+ years is a long time for electronics to last. Private Message (PM) me. so its not public.

Please send me a PM. I can't seem to send one to you.

 

[Matthew Jeschke]

Long thread, maybe somebody already said these things or you already got a pressure gauge...

My 2 cents... Don't take advice on it's face. Everybody is well intentioned on forums but if you can, measure & validate theories before you replace. Otherwise you'll chase phantoms and play parts darts. The parts on these trucks are VERY HIGH QUALITY (aside form body). I've torn down most of my 2001 and rebuilt it. Many of the parts are Denso (Japanese - high quality). All of which are still on the truck with 250k miles and working like new. They can easily run hundreds of thousands of miles. I've seen lots of good pumps thrown away.

Moral I'm getting at. Find yourself a fuel pressure gauge. Many parts stores rent them. Make sure your pressure is in spec (60PSI on rail? Not sure PM me if you need exact spec and I'll look it up). The gauge screws on like a bicycle pump to the fuel rail. They're SUPER easy to use and you know if fuel is a problem in seconds. Since you replaced the pump, the regulator would be next item if you have bad pressure.

I don't know exact behavior of each pump, some prime / pressurize then turn off... others no? So that it turned off doesn't necessarily mean much.

If your pressure is bad, then it could be issue with pressure regulator on side of rail. Otherwise if pressure is good... Could be injectors and or spark.

Once it starts is it running rough or smooth? (maybe an injector or spark problem otherwise).
Sounds like it is only hard to start on first attempt?
How is power when you drive it? Smooth or kind of hesitating? Stumbling?
Do you have any more details to offer up?


As good measure run fuel cleaner through system. 5,000 miles I run a tank with injector cleaner such as seafoam or gumout. You Might also try to run the seafoam through the intake, they make a spraycan for this. Not saying intake cleaning will help but maybe varnish on injectors???

Also get yourself a good test light I have the one below and LOVE it. It lives in my emergency tool bag. Injectors are easy to test electrically, as well as the pump with a test light like that.

29050 Digital Circuit Tester 3-30V

360° Visibility of Polarity. Operating Range 3-30 volts DC to Work on Most Vehicle Electrical Systems.

www.lislecorp.com

Lastly, don't fret! It's something simple and CHEAP. Feel free to ask me anything as you work on it. You'll have it running like a top in no time. 4runners are awesome trucks, these are a bit different animal, a little more heavy duty / utilitarian.

 

[robhotdog]

I'm a retired GM Tech. I've owned and worked on a ton of these vortec 350s. I suggest you make sure your fuel system is correct. I hope you put in a delphi pump. It was a good idea after 100k. Pressure test and make sure it holds pressure key off. Pull the hose off the fuel pressure regulator and see if fuel is in it! Bad regulator if there is. There were just a couple of things that NEED to be done on those engines..Replace the injector assembly! Updated design works much better. 2 intake manifold gaskets! Had a problem leaking coolant into the oil..Felpro gaskets 1 and done. Do not overtighten! The security system isnt a problem if the dash light goes off!! I believe your problem is still fuel related. Stick with OE parts ! Too much junk out there. Last note. Look in owners manual. 100k service due...all the fluids need changed. Sounds like you got a nice truck.

 

[crammit442]

I definitely took the circular route to find the problem. I should have started with a fuel pressure test. I put in a new Delphi pump, although I have questions about a fuel pump with a 100k life expectancy. I do have a lot of confidence in Denso parts. The fuel pressure test kit came in today and it reads 62 psi and holds it. I haven't checked the pressure regulator electrically, but the vacuum line does not leak fuel. I don't have a noid light, but I do use a test light as well as a multimeter. My truck should have given me a flashing or solid security light, but didn't. Thankfully iamdub mentioned it or I would have never known about the problems with the VATS system. It would start immediately and ran well for 3-4 seconds. I guess a high end scan tool might have caught the anti theft codes and I could have started there and saved a bunch of time. I pulled the lawn trailer with the truck today and knock on wood, it's running perfectly with no check engine or other lights. I suppose these trucks are like everything else where you have to get familiar with their particular quirks. Thanks again for all the help.
Charles

 

[crammit442]

Just a quick update. The truck is still starting every time and running well. I'll keep this updated as time goes on. Thanks again for all the help.
Charles

 

[crammit442]

It's been a couple of months and the Tahoe still fires right up every time. Thanks again for all the help.
CH