Problem starting 1993 C/K 1500 5.0 V8

Discussion in 'Chevy C/K Truck Forum' started by gmund, Dec 12, 2011.

  1. gmund

    gmund New Member

    Hello, I'm new to this site and was hoping someone can help out.

    My 1993 has a 5.0 V8 and when it's been sitting all night and you go to start it, I used to just turn the key and it would start. Now, you have to hold the pedal to the floor for it to start.

    I changed plugs, rotor, and cap.

    Once the truck is warmed up, I can turn it on with no problem by just turning the key or using the remote starter.

    I only use 93 octane and use a fuel cleaner every oil change.

    Any ideas what could be the issue? It does seem to happen more in the cold winters.

    Thanks in advance! ​

     
  2. dipstick

    dipstick Member 2 Years 100 Posts

    Holding to floor should not help any .. unless tps is in flood mode. If doing in colder weather maybe water in line somewhere.
    Check fuel filter ... fuel pressure 9 to 14 psi.. will not hold this tbi does not hold pressure like newer vortec ect.
    Look at the injectors when cranking first thing .. see if they are pulsing.
     
  3. gmund

    gmund New Member

    Holding down the pedal is the only way it will start when this occurs. I can keep turning the key and it will not start. Happened this morning, held key in cranking position for about 15 second, stepped down on pedal to the floor and it started up after being off all night outside in 30 degree weather.
     
  4. dipstick

    dipstick Member 2 Years 100 Posts

    Are you getting a check engine light? Sounds like a bad throttle position sensor. Or coolant temp sensor.. located beside thermostat housing.
    Throttle sensor on passenger side of tbi. Can check with a meter closed throttle .045... wot/wide open throttle 4.50 volts.
    Cts ten bucks change it get it out of the equation . Sounds like getting flooded have to hold throttle down to start.
     
  5. gmund

    gmund New Member

    No check engine light, once it starts up it runs fine. Hardly ever happens in the summer mornings.

    Winter, it's almost every morning. It doesn't hesitate once I start it. Revs high as expected when cold and then levels out as expected. It's just the actual starting that requires the pedal to the floor.

    I'll check those two items you mentioned.

    Thanks!
     
  6. Ethan

    Ethan Rockstar 100 Posts

    OBD I doesn't have the flood mode, so holding the pedal to the floor does nothing but inject the maximum amount of fuel possible. From what I gathered from my 94 doing a fuel pressure test, it'll run around 15 psi with engine running, and when you turn it off, it'll drop to about 2-5 psi and hold.

    I would look at the injectors as you crank it, they might be leaking. Also, you should replace your coolant temp sensor, cold weather could make it think it's warmer than it is and cause it to not inject enough fuel to start.

    It could also be your TP sensor, if it's out of adjustment or bad it could cause the PCM to think you have no command, so it injects no fuel, when it should be adjusted to have at least 5% command at idle(I don't know the exact percentage, but it needs some kind of command).
     
  7. dipstick

    dipstick Member 2 Years 100 Posts

    If tps get out of voltage reading 4.50 volts ecu will think it is at wot cut fuel off. have to hold pedal to floor . to start. A tbi system does not hold any pressure.
    Tp voltage at idle should be in .45 to .65 range.. wot range 4.50 volts.
     
  8. Ethan

    Ethan Rockstar 100 Posts

    Like I said, OBD I does not have a flood mode, so holding it to the floor will create a super rich start, and some other issues you might not like. And a TBI system does hold fuel pressure, just not much. What's the point of an anti drain back valve in the fuel pump and a fuel regulator if it doesn't hold pressure? And if it didn't hold pressure, you would get extended cranking.
     
  9. dipstick

    dipstick Member 2 Years 100 Posts

    Last edited: Dec 24, 2011
  10. timhall1787

    timhall1787 New Member

    i took my 89 305 to mi from tx for a few months and had the same exact problem. i threw parts at it bc it had no codes. fuel pump filter rebuilt tbi cap rotor sensors... it ended up being the ignition coil. check it before you go any farther.
     

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