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1998 K1500 Vortec 350 starts and dies

This is a discussion on 1998 K1500 Vortec 350 starts and dies within the Technical / Maintenance forums, part of the General Discussion category; Seven wires? My '98 C3500 only has four. Power and ground for the pump, power and ground for the sender. ...

  1. #21
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    Re: 1998 K1500 Vortec 350 starts and dies


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    Seven wires? My '98 C3500 only has four. Power and ground for the pump, power and ground for the sender. Do you see two different modules on top of the tank, possibly a pressure sensor too (part of the evap/emissions system)? Mine doesn't have it, but has a spot for it. Been a while since I've seen one so I can't remember how many wires go to it or what their colors are.

    Richard

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    Re: 1998 K1500 Vortec 350 starts and dies

    Two different plugs go into the top of the pump. One is as you describe. Could be the other one is for the evap system.

    Interesting you bring up the sending unit. When the ignition switch is turned to ON, the fuel gauge oscillates rapidly. Reading is accurate, but it just vibrates at that reading, neighbor says it had been doing that awhile before the truck died.

    Which color is the pump, which the gauge? I noted that the gauge did not change reading when I unplugged the plugs at the fuel pump.

    Our worry is that, even with a new pump, it will still have the underlying condition. Pump starts at inital pressurization, shuts off, will not restart for RUN sequence.
    Last edited by jswordy; 11-02-2009 at 09:36 AM.

  3. #23
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    Re: 1998 K1500 Vortec 350 starts and dies

    Not 100% sure since I did this hack a week+ ago now, but the four colors I've got on my '98 are two black, one purple, one gray. The black that grounds to the frame right by the sender should be the ground for the pump, though it's probably bundled into the harness so it won't be readily apparent which is which. Some quick work with a meter set on continuity will show you which one. Then throw the meter over to DC volts and you'll see which wire is power to the pump, as it will only come on momentarily with the key on to prime the fuel rail then will shut off.

    Richard

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    Re: 1998 K1500 Vortec 350 starts and dies

    Here again is a recap of the basic conditions: 1998 K1500 4WD pickup. Key to ON, pump runs for initial prime. Key to START, pump does not run for RUN segment. The engine would start for a second, use up available fuel from the prime, and die.

    When we first started working on it months ago, pump would prime to 65 psi and hold that pressure. It now will prime to just 10 psi.

    We now have a steady SECURITY light. Never shuts off.

    I also noted last night something I had not seen before, and this happens repeatedly. Key ON, pump primes and shuts off. Key turned from ON to OFF, pump runs again and shuts off. Is that correct? Owner says it has always done this; I never noticed it prior to last night. Bad ignition switch, maybe?


    -----

    OK, last night's test results, using the Shrader valve test port at the plenum (which is straight off the fuel line):

    1.) Key to ON, pump runs and shuts off. 10 psi. Falls slowly.

    2.) R line pinched off at pump, key to ON: 10 psi, falls slowly.

    3.) Gray wire tapped, direct wired to battery, pump runs constantly: 10 psi.

    4.) Electrical test, gray wire to black wire on a digital meter, key ON: 11.34 initial volts, falling back to 0.

    5.) Electrical test, brown wire w/white stripe to black wire (this should be the fuel sending unit): 5.34 steady volts.

    If you are thinking fuel filter, it was replaced when we first started working on the truck. I think the fuel pump is toast, or maybe the screen is plugged. As mentioned before, the fuel gauge needle oscillates slightly at its reading point, and owner says it has done so since pump was replaced about 3 years ago. He only got abbout a year and a half out of new AC/Delco pump before this trouble.

    Now, on to the security system. The only test performed that may have coded it was several months ago, when a certified GM tech at a dealership gave me a test ignition switch/harness and told me to plug it in to the connector and use a screwdriver to operate it, as a test to see if the switch in the truck had burned up. That could have been read as a theft attempt.

    But there are many reasons the SECURITY light could stay on, including broken wires in the column at the tumbler. I want to check all that out before giving it up to the dealer.

    It would appear that our next action is to replace the fuel pump, then start worrying about the other issues. What do you think?

    I've been working on cars and trucks for 32 years, and this thing is the most wacked FI/security system I have seen. Thanks!
    Last edited by jswordy; 11-04-2009 at 07:34 AM.

  5. #25
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    Re: 1998 K1500 Vortec 350 starts and dies

    First you have to get the security light to go out.Try a relearn first.

    The following procedure allows for anyone to reprogram the EVO/Passlock™ module learned data code with any tools, other than the scan tool, when any of the following parts are replaced:

    - The EVO/Passlock™ module
    - The passlock™ sensor
    - The VCM/PCM



    The following is the Auto Learn Procedure:

    1) Insure the ignition key is in the ON position.

    2) Clear all EVO/passlock™ module and VCM/PCM DTCs. Record and refer any VCM/PCM DTCs to:
    - For 5.0/5.7L engines, refer to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls - 5.0/5.7L

    3) Momentarily rotate the ignition key to the CRANK position (Do NOT start the vehicle), then release it to the RUN position (Do NOT key OFF in the process).

    4) Wait 10 minutes. Observe the SECURITY indicator. Refer to the following list for the appropriate responses:
    - If the passlock™ sensor was replaced the SECURITY indicator will flash for the 10 minutes duration.
    - If the EVO/passlock™ module was replaced, the SECURITY indicator will flash for a few seconds and then remain ON for the remainder of the 10 minutes duration.
    - If the VCM/PCM was replaced with a new programmed VCM/PCM and connected to the vehicle for the first time, the vehicle will start and this procedure may not be necessary.
    - If the replacement VCM/PCM was connected to any vehicle at any other time, even momentarily, the SECURITY indicator will flash for a few seconds and then remain ON for the 10 minutes duration.

    5) The SECURITY indicator will transition from flashing to ON briefly to OFF after 10 minutes if remaining in the ignition ON position.

    6) Turn the ignition switch to the OFF position and wait for 10 seconds.
    Repeat steps 3-6 two more times. The new security code is ready to be communicated among the Passlock sensor, EVO/Passlock module and VCM/PCM.

    7) The new password is learned on the next ignition lock cylinder cycle from OFF to CRANK to ON (start attempt).
    04 K1500 Silverado EXT 3:73 gears, 5.3L 265/75-16,Pace Edwards tonneau,

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    Re: 1998 K1500 Vortec 350 starts and dies

    Man, I know there is a lot of text to all this because it is a long and complicated problem, so you may not have read it all.

    I did the relearn. The SECURITY light does not go out. EVER. So I did it on a timed basis. Tried it twice. No change.

    The SECURITY light can stay on constantly if there is a break in the wires from the tumbler to the module somewhere. We intend to trace those to make sure. Most common break area is right at the tumbler. That will all be checked soon.

    BUT...

    I want to attack the fuel pressure problem first, so I can get back to 65 psi on initial prime, which is what we had 5 months ago before it was just let sit. Then we will be back to the original problems we had when we started on it.

    Others at other sites say the Passlock system does NOT cut off the RUN cycle of the fuel pump, but rather shuts off the injector commands. In that case, the pump not running on RUN would not be caused by Passlock, but by some other fault.

    Here is my other thread going on this. Maybe you'll get an idea from it:

    http://www.automotiveforums.com/vbul...14#post6059614

    Willing to test or try anything before we start spending money on it. But it is very close to time to start putting in new parts. It has to get off the dime somehow so we can move forward in the diagnostic progression, and 10 psi prime ain't gonna get it.

    Thanks for all suggestions.

  7. #27
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    Re: 1998 K1500 Vortec 350 starts and dies

    The SECURITY light stays on solid in my '98 and the truck starts fine, been like that ever since I've owned it - several years - and to be honest, I don't care to mess with it! I'm just glad it still starts. It doesn't have the original column (has an airbag column/wheel in a 1 ton non-airbag truck) so I'm guessing someone has hacked the tumbler wiring or done something else to get past the issue of the tumbler resistor and the code in the BCM/TDM not matching.

    Richard
    Last edited by someotherguy; 11-04-2009 at 08:54 AM.

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    Re: 1998 K1500 Vortec 350 starts and dies

    There is a procedure to disable the security system to fail/safe mode by using a toggle switch in the yellow wire, or cutting it completely. The toggle switch is preferred, because then you can re-enable the system if you ever need to (like after replacing a battery, which in some cases will not allow it to start with the system disabled, but in others will).

    Likewise, a solid security light can mean one or more of the leads from the tumbler have become disconnected, pinched or have bad plug-in connectors...all of which changes the resistance reading. That is what we are going to explore in the column down to the firewall. The tumbler resistance inside may also be off through wear, etc.

    You can also bypass by measuring resistance at the tumbler and insert the requirted number of resistors between the tumbler security wires after disconnecting them, so it will "read" the correct resistance every time. The security light usually goes out using this system, though.

    I know a bunch about these systems now but not enough to fix this one! LOL.

    I have another interesting theory I dreamed up for the low pressure reading that has to do with the fuel pump/sender being hung up somehow. It's the oscillating fuel gauge needle that puzzles me. I will check that, too, since we obviously have to pull the pump now.

    What I really think it needs for starters is an ignition switch and a fuel pump. Maybe a relay, as well. I'll likely start with the pump, run the wires at the tumbler for faults, then try the switch next. I do not think it is correct for the pump to run again after the switch is shut off.
    Last edited by jswordy; 11-04-2009 at 12:08 PM.

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    Re: 1998 K1500 Vortec 350 starts and dies

    The hummingbird gauge needle is a somewhat common problem in the later OBS trucks. It's got nothing to do with the pump. You'd expect that the sending unit is faulty but I've seen some claims that even after a replacement, it continues.

    Richard

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    Re: 1998 K1500 Vortec 350 starts and dies

    Throw a new sender/fuel pump module in there. Test it dry first if you'd like. (If its not the problem, take it back.)

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    Re: 1998 K1500 Vortec 350 starts and dies

    Quote Originally Posted by LS1GMCTruck View Post
    Throw a new sender/fuel pump module in there. Test it dry first if you'd like. (If its not the problem, take it back.)
    That's what we're going to do. I did not know it was possible to test it dry without burning up the pump. On other makes, they specifically warn against that. I donlt think it will fix everything. But it seems this clearly is the place to start!

  12. #32
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    Re: 1998 K1500 Vortec 350 starts and dies

    I havent read all the posts in this thread, sorry if I miss anything. ut here is some input.

    Once the pump has primed, it will shut off after 2 seconds, then once you crank the engine over the pump will only run so long as the crank position sensor is sending out signals. Once they stop, meaning the engine has stalled, teh pump wont run anymore. This is a feature so that if the fuel ine is ruptured during an accident, the pump wont continue to pump fuel onto the accident scene.
    I have tested this myself on my 97. If I leave teh key on in the run position, crawl under the truck, garb teh harmonic balancer and proceed to turn teh engine over. As the crank is slowly turning all of a sudden the fuel pump will prime. If I keep turning the crank another 180º the fuel pump will prime again. It will prime twice for every full 360º revolution.

    IIRC VATS only kills the injectors while allowing the pump to operate normally.

    Your pump seems to be operating normally. Try leaving the key on and turn the engine over by hand, if the pump cycles the fuel pump/relay can be ruled out.

    After starting tehtruck, VATS will allow it to run for about 4 seconds, then it will kill the injectors.

    Maybe I'm not comprehending your problem properly, but it sounds to me like you have a VATS issue. That is disabling your injectors after you got the engien started. Once the injectors are disabled they wont fire again for 30 minutes or some certain amount of time.
    After you have gotten the engine to run for its few seconds, you can pull off the air intake and dump some fuel into the throttle body. If the engine starts and runs for a few seconds again, that would almost guarentee its a VATS issue that is disabling the injectors.

    I just read that it will only prime to 10 psi. The pump will prime for a PCM controlled 2 seconds. Something is going on there. Pressure is bleeding somewhere. FPR, poppet valves.


    peace
    PAuly
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    Re: 1998 K1500 Vortec 350 starts and dies

    Quote Originally Posted by Pauly View Post
    I havent read all the posts in this thread, sorry if I miss anything. ut here is some input.

    Once the pump has primed, it will shut off after 2 seconds, then once you crank the engine over the pump will only run so long as the crank position sensor is sending out signals. Once they stop, meaning the engine has stalled, teh pump wont run anymore. This is a feature so that if the fuel ine is ruptured during an accident, the pump wont continue to pump fuel onto the accident scene.
    I have tested this myself on my 97. If I leave teh key on in the run position, crawl under the truck, garb teh harmonic balancer and proceed to turn teh engine over. As the crank is slowly turning all of a sudden the fuel pump will prime. If I keep turning the crank another 180º the fuel pump will prime again. It will prime twice for every full 360º revolution.

    IIRC VATS only kills the injectors while allowing the pump to operate normally.

    Your pump seems to be operating normally. Try leaving the key on and turn the engine over by hand, if the pump cycles the fuel pump/relay can be ruled out.

    After starting tehtruck, VATS will allow it to run for about 4 seconds, then it will kill the injectors.

    Maybe I'm not comprehending your problem properly, but it sounds to me like you have a VATS issue. That is disabling your injectors after you got the engien started. Once the injectors are disabled they wont fire again for 30 minutes or some certain amount of time.
    After you have gotten the engine to run for its few seconds, you can pull off the air intake and dump some fuel into the throttle body. If the engine starts and runs for a few seconds again, that would almost guarentee its a VATS issue that is disabling the injectors.

    I just read that it will only prime to 10 psi. The pump will prime for a PCM controlled 2 seconds. Something is going on there. Pressure is bleeding somewhere. FPR, poppet valves.


    peace
    PAuly
    You have both problems well in hand, Pauly. I would just clarify that the pump runs in PRIME, but never, ever runs in RUN. The engine starts the test gauge shows it uses up the primed pressure, and dies due to fuel starvation. That is the essential problem, and AFAIK, that is independent of any Passlock issues.

    Here is what we have done, then a question or two.

    Pulled the fuel pump last night. There is some black debris and water in the tank. It looks like the filter pad is contaminated. When the last new pump was installed, I have been told they never dropped and cleaned the tank! Tonight, we will pull the tank to clean it, drain fuel line, and install a new fuel pump. That hopefully should restore 65 psi prime. Then I have a couple other things to do that will take me away from it. Sometime this weekend, we should know where we stand. There are still mechanic friends saying replacing the pump will fix it all. I doubt it -- but wouldn't that be nice?

    From what you say, Pauly, the crank position sensor could be bad, and that could be stopping the pump from running in the RUN portion of the cycle. My understanding of the cycle is that the prime phase is a timed deal that's semi-independent of the system used for the run phase. So a bad or iffy crank sensor could result in prime but no run? Am I correct in this?

    If so, that is another thing we could explore. Crank sensor has been brought up before, but I took that to be an ignition thing only. There are three terminals on the sensor. Is there a way to test it with a VOM?

    Thanks for the input! I AM GOING TO WIN ON THIS THING, no matter what!
    Last edited by jswordy; 11-05-2009 at 08:26 AM.

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    Re: 1998 K1500 Vortec 350 starts and dies

    Pulled the fuel tank last night, cleaned it, installed new fuel pump, rewired harness to an updated fuel pump plug included with new pump, reinstalled tank, removed fuel filter, drained lines, replaced with new filter, and ran out of time.

    Looking around for a crank position sensor today, as we had trouble locating one yesterday. This weekend, we will plug up the fuel lines and harness, add gas, test pump. Then run through CPS wiring harness and install new CPS if we are back to full prime but no-run condition.

    I think once that has all been done, if condition persists, next would be to inspect passlock wiring in the steering column to firewall.

    I'll keep you posted on what we find, how it goes. Any other suggestions, they are appreciated.
    Last edited by jswordy; 11-06-2009 at 07:09 AM.

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    Re: 1998 K1500 Vortec 350 starts and dies

    Well, after this weekend we are extremely disheartened.

    1. We do have 60-65 psi fuel pressure now.

    2. The new pump does run.

    3. The truck just starts and dies.

    4. It runs great on carb cleaner. We ran it quite awhile on it.

    5. It did not set any engine codes while running.

    6. All lights go out on the dash while running (Check Engine, etc.) EXCEPT THE SECURITY LIGHT, which stays on constantly.

    We removed the bottom clamshell from the column. The wires running to the tumbler for passlock all seem OK, none were loose.

    We have no access to an engine/body capable scanner other than hauling it to a dealer.

    We CANNOT do the relearn process as it has been described because the SECURITY light NEVER GOES OUT. It is necessary for it to go out in the relearn process, but you can let the truck sit in ON for 30+ minutes, and still have a solid security light. I know, cuz we did! We also tried disconnecting the battery, which some have said reset their passlock, no luck.

    I just don't know what else to do but tell my neighbor to save up to pay the freight to have a dealer fix it now. The problem is clearly in the security system, and without the right level scanner, we are shooting in the dark. Judging by the symptoms, I think it most likely is a bad lock tumbler assembly, but I'm just guessing without a code.

    Man, this stinks. Any other ideas?

    How do I remove the lock tumbler from the upper column clamshell, so I can remove the clamshell and see up top?

  16. #36
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    Re: 1998 K1500 Vortec 350 starts and dies

    You gently pry the plastic bezel off the tumbler first; I like to use the "soft fork" style of door panel tool. Then carefully lift the top part of the column shroud off, while taking care not to strain the hazard button (they break very easily.)

    Look at the aluminum casting around the tumbler and you'll see a small hole in the top. Disconnect the battery, turn the key to the start position, and you'll see a tab appear in that hole. Press the tab with a thin pick and you can pull the tumbler out.

    Richard

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    Re: 1998 K1500 Vortec 350 starts and dies

    Quote Originally Posted by someotherguy View Post
    You gently pry the plastic bezel off the tumbler first; I like to use the "soft fork" style of door panel tool. Then carefully lift the top part of the column shroud off, while taking care not to strain the hazard button (they break very easily.)

    Look at the aluminum casting around the tumbler and you'll see a small hole in the top. Disconnect the battery, turn the key to the start position, and you'll see a tab appear in that hole. Press the tab with a thin pick and you can pull the tumbler out.

    Richard
    Thanks. I dunno what it will do to look at it, since I am officially stumped, but at least I know how to get it all out of there now.

    Jim

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    Re: 1998 K1500 Vortec 350 starts and dies

    Just talked to a mechanic. He says he has dealt with passlock on other vehicles. Says the SECURITY light is on constantly because the lock tumbler (he used a $50 term for it) is bad, not reading the resistance. Tells me to replace it and the ignition switch, try relearn. If it does not relearn after replacement, bring it to his shop and he has a guy who will clear the codes to get it to work.

    Sounds right to me, how about you?

  19. #39
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    Re: 1998 K1500 Vortec 350 starts and dies

    Beats me man. It's a complicated enough system, best thing any of us can do from a distance is guess. And as you've already noticed, guessing gets expensive!

    The downfalls of the Passkey system do seem to be: worn tumbler, bad connection at tumbler, bad connection to BCM/TDM, not sure what else.

    Richard

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    Re: 1998 K1500 Vortec 350 starts and dies

    Quote Originally Posted by someotherguy View Post
    Beats me man. It's a complicated enough system, best thing any of us can do from a distance is guess. And as you've already noticed, guessing gets expensive!

    The downfalls of the Passkey system do seem to be: worn tumbler, bad connection at tumbler, bad connection to BCM/TDM, not sure what else.

    Richard
    Well, I appreciate the help so far. This is the Passlock system, not Passkey. The resistor is built into the ignition lock, rather than in the key.

    If I can get a reading, I may try bypassing it with a resistor of similar value. I can't see what I have to lose by trying that option. But the lock assembly is probably too worn out to get a reading, in which case a new assembly will be required. I can hope for now, anyway.

    Thanks again, and when it does run, I will post what was found and done.

 

 
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