Question about 1999 Chevrolet Silverado 1500

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Just changed the ECM and now the truck dies.

I have a 1999.5 Chevy Silverado 1500 5.3L. I just changed the ECM because the die getting on the freeway and then after restart it would only stay on for 30 seconds.

After changing the ECM the truck will run but as soon as I step on the gas to move it dies.

What could this be?

Posted by on

  • bryan372 Jun 19, 2009

    After replacing the ECM I ran it for 30 mintues before trying to drive it. Once I try to drive it it died. Before replacing the ECM I checked the fuel pump and it was working fine.



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Are you having any error lights coming on the dashboard? If yes then you will need a computerised diagnostics to find the exact fault.Else it will take you forever to find this fault..I Also you need to allow the vehicle without battery for 24 hours if you change an ECM which I assume stands for electronic computer management, right? Stop me if I am wrong..Keep an eye on your temperature gauge and if it going for more than 1/2 then it may be drastic to the engine.Hope this helps.

Posted on Jun 19, 2009

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Initially, the airbag light should not stop the fuel pump from working. We would first check the fuel pump relay then check to see if the new fuel pump is faulty. Also, be aware that some Chevy trucks around 1997 had bad ignition switches

Check for fuel pressure as it sounds like your fuel pump has failed.

Test for fuel pump pressure. Running out of gas is not a good idea for more than one reason. When a fuel pump runs with no gas in the vehicle it can damage the pump beyond repair.

: We would look at the fuel pressure regulator. It may have developed a pinhole leak in the diaphragm allowing raw gas to be drawn into the engine.

Your no start problem may be the fuel pump. Fuel pumps normally fail to start after they are shut off. It is very rare for them to fail while they are running. Before you charge into replacing the fuel pump, determine if your car does not start because of lack of fuel or lack of spark. If it is getting fuel, the fuel pump is obviously not your problem.
Check for water in the distributor, especially the bottom side of the distributor cap. Also, check the plug wires and shorting out.

It sounds like your choke may be hanging up. A choke releases two ways, as the engine gets warm. One way is by a small electric heater in the choke housing. Another way is that it pulls warm air off the exhaust manifold. Verify that the choke releases as the engine warms up.

You may have a fuel injector that is bad. Check the resistance of each injector. The alternator may be giving AC (alternating current) spikes into your electrical system. Try temporarily removing the belt from the alternator and see how the engine runs.

Check the Engine Coolant Temperature sensor located by thermostat housing. Ohm check at 68 deg. should have 3520 ohms of resistence.

check for an intake manifold leak. the gaskets were prone to leaking and have been redesigned. if you have access to a scanner, compare "MAF" with "Desired IAC airflow" - should be pretty close to each other. you can also look at fuel trim - but its not always obvious. sounds like your problem - once truck enters closed loop it can easily compensate.

this applies to silverados with 4800 and 5300 - not older c/k with 5.7 - made both in 1999

Is your system CSI or SFI? if SFI engine running diaconnect vacuum line is vacuum present? does fuel pressure increase 4 to 10 psi

CSI just says if fuel pressure high check for kink in line low and pump good replace regulator.System should hold pressure after engine off for quite some time. your regulator is mechanical preset at factory so if it does not close all fulr pressure would be returned to tank.

Have no data fromGm on flow rate only pressure did find out a test for regulator. Run engine normal temp open throttle quickly pressure should increase to 66psi. if not replace regulator. Go with OEM

Posted on Jun 19, 2009

  • 2 more comments 
  • mohammed marika thambi
    mohammed marika thambi Jun 19, 2009

    Disconnect a sparkplug wire or 2 and ground it to the engine
    -have helper crank engine over-do you have a snapping blue spark? If
    so-you have a fuel related problem, check the fuel pressure to rule out
    the fuel filter/fuel pump/pressure regulator and listen to the
    injector/s are they pulsing or hook up a noid light. No snapping blue
    spark continue to troubleshoot the ignition system-power input to the
    coil/coil packs,cap and rotor /distributor pick-up coil, ignition
    control module, ECM,Ignitor cam and crank sensors- Note: If it doesn't
    apply disregard it

    Start off by checking your battery connections.
    They should be tight and free of any corrosion. The original batteries
    are known for problems of acid leaking from the positive terminal. Make
    sure it's not leaking. If all checks good, have it scanned for trouble codes

    HAS the check engine light come on? It sounds
    like an ignition module problem. Also, I realize you replaced the fuel
    pump. What is the pressure you are getting from it?

    Check the fuel pressure and also for injection pulses
    It is a diesel and all new lines and they were
    bleed.This is the fourth fuel pump put on it and it run for a day good
    with each pump, but then starts missing so bad it won't run

    Check the catalytic converter its plugged and not letting enough air
    out of the engine. I am sure its plugged something broke and plugged up
    pipe, and if thats not the problem you should be showing a engine code
    light, throttle postion sensor could be bad but you would think that
    you would get and code. also check your fuel for water. But it sounds
    like not enough air geting into and out of the engine, try those out .

  • mohammed marika thambi
    mohammed marika thambi Jun 19, 2009

    It is probably the fuel pump. Test it by checking
    the fuel pressure. Also, check the fuel pick-up that is inside the gas tank.

    First off it is injected there is no choke. Second do you have a way to check the fuel pressure? It must be a tester for fuel injection as the fuel pressure
    need to be 55-65 to start and 55 to run. Also how old is the fuel
    filter? Just for your info don't use regular carb cleaner on this use
    throttle body cleaner ok

    If you have the tester, most likely you know how to use it. Here is a how to video if you need help.

  • mohammed marika thambi
    mohammed marika thambi Jun 19, 2009

    If you have the tester, most likely you know how to use it. Here is a how to video if you need help.

    you might clean the throttle-body, check fuel pressure. Go from here.

  • mohammed marika thambi
    mohammed marika thambi Jun 19, 2009

    I think I may have found the problem, after
    replacing the IAC along with everything else I have mentioned before.
    The other day it started up just fine. Idle was fine left it running
    for about 30min then when I went to put it in gear it shut off again.
    Started right up again then tried putting it in gear again and shut
    off. After about the third try it would not start up, it just would
    crank but not turn over. I was curious to see if I was getting any
    spark to the plugs so I pulled one of the wires and had someone crank
    it while I checked for spark. Nothing no spark present, I tried a
    different wire and still no spark. Finally it donned on me It must be
    the IC ignition control module. So I went out and replaced it and it
    started right up. Still a little weary of it maybe shutting down on my
    I was reluctant to test drive it. So I let it warm up for about 20 min
    or so then got the courage to take it around the block and hope it
    didn't shut off on me. The only question I have now at this point is
    when I put my truck in gear what should the rpm be at? when it's in
    park it's around 1000k but when I shift it into gear it drops down to
    like 250-300rpm. And if I turn my steering wheel at that moment it
    sounds like it wants to shut off. I'm wondering if my idle in gear is
    set too low. Maybe when I put the new TPS I didn't set it right. Is
    that even possible? and if so If i adjust the TPS a little will that do
    the trick I wonder. If you can tell me what the rpm should be at when
    the truck is in gear that would help me out. And if you think that by
    adjusting the TPS will do the trick

    Set it at 600 RPM- for the throttle position sensor voltage at closed throttle should be 1.25volts or less.
    If the TPS checks out OK, then check the ignition control module and the coolant temperature sensor. Just replacing these items is probably a good move -- considering you have 228000 miles on the truck.

    The ground for the fuel pump commonly corrodes -- check it out also.



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