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No start saga continues...what is it???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 89GMCSuburban, Dec 4, 2002.

  1. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    Alright, once again, fuel pump is pumping, no fuel out injectors. I tried spraying PB in the TBI to start the engine, no start...just cranks. Here's what I've checked:
    Dist. Module in dist. = New, re-tested, it's ok
    Fuel flow out filtered end = Good
    Pressure regulator = brand new
    plug wires = good
    plugs = good
    cap/rotor = good
    coil = good
    oil pressure = 35 lbs
    Fuel pump = new
    Knock sensors = new
    O2 sensor = new

    What is it? It's obviously spark if it didn't start..is it a sensor preventing fuel from coming out of the injectors?
    This is pissing me off... /forums/images/graemlins/angryfire.gif /forums/images/graemlins/angryfire.gif /forums/images/graemlins/angryfire.gif /forums/images/graemlins/angryfire.gif /forums/images/graemlins/angryfire.gif
     
  2. Derf00

    Derf00 1/2 ton status

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    Did you check the fuse on the computer module? Just a thought.
     
  3. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    Yes, it's fine, it actually started this morning. Does anyone have any ideas before the P.O.S. does it again on me?
     
  4. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    Just a question on sensors on this thing...it seems to have 2 MAP sensors!!! There are two sensors with vacuum lines running to them...Also, there's a module or something that's a large square, it's very flat and mounted on a braket on the passenger side of the manifold. What is that?
     
  5. Thunder

    Thunder 3/4 ton status

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    No there are'nt 2 Map sensors
    1 is the MAP sensor
    The other the EGR solonoid. it is vacume controlled also.
    Map sensors usually wont cause starting problems.
    The square thing it the timing control module. They usually dont cause too many problems and will usually throw a code when they fail
    The magnetic pick up coil in the dist can cause problems like you have. It usually throws a code 42. If the ECM does not recieve a distributor reference signal it shuts off the fuel. Also a bad coolant Temp sensor (located by the thermostat) can cause starting problems when its cold.
     
  6. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    I wish I had a picture...I see the metal EGR solenoid on the manifold...do you mean that the sensor controls the EGR? Both the things that have vacuum lines going to them are plastic and have pluggs coming from them.
    I have no codes showing up...
     
  7. Thunder

    Thunder 3/4 ton status

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    Yes that little plastic box with the vacume line and 2(red and brown?) wires to it controlles the EGR. Basicly it just keeps the vacume to the EGR shut off till the engine warms up. The computer sends voltage to it and opens it up when the engine is at operating temp. If you trace the lines you will see a vac line to it from the front of the TB and a vac line going out of it to the EGR valve.
    The MAP sensor is the little unit with the vacume line coming from the back of the TB. I think it has 3 wires and a flat plug. The MAP sensor will most always throw a code when they go bad because they are part of the emission system..
    EGR will throw a code too but it is usually the code for the O2 sensor detecting a lean fuel mixture. or a code saying the solonoid is malfunctioning. dont rember the code numbers off hand.

    Just wondering. Do you have problems starting it just when its cold or do you have problems when it warms up also??
     
  8. Muley

    Muley 1/2 ton status

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    Since it is FI motor, does the motor have a crankshaft sensor?

    If the sensor is not reading the crankshaft position then the comp does not know what cylinder to send spark to and which one to send fuel to.

    Just a thought.
     
  9. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    It'll do it after being run for 6 hours on the highway or if it's sat cold for 2 days. It also does it at varying times. Sometimes it'll be good for a month, sometimes it'll do it the next day. Weird, huh?
     
  10. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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  11. k20

    k20 3/4 ton status

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    I had same prob, have you replaced your engine temperature sensor in the intake manifold? Mine was tellin the computer it was 201 deg's when it was 50 so it wouldnt send it any fuel. I think it was 21.36 at pepboys
     
  12. TopOff

    TopOff 1/2 ton status

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    "Ask" the computer what's wrong. It should have stored the code. Something like, crank sensor out of specifications or something.

    Good luck.
     
  13. Thunder

    Thunder 3/4 ton status

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    The TBI system uses neither Cam or Crank timing sensors so you can rule that out. The distributor provides all the info to the ECM reguarding engine timing.
    Its pretty hard to trouble shoot computer systems without a scanner. Let alone over the internet.
    But my best guess is as said. Either the Coolant temp sensor or the Magnetic pickup coil.

    With a scanner you can rule out many problems because you can see how the engine is runing and how all the sensors are operating. For instance : If the Coolant temp sensor was the problem the scanner would tell you what temp the computer was seeing. If the engine was cold but the computer was seeing 200 degrees from the coolant temp sensor. it would mean the sensor is bad. That saves a lot of needless replacment of parts.
    For around 140 bucks you can get a AutoXray easy link GM obd 1 scanner. I have one. It works great. It has paid for itself many times over. Many autoparts store carry them.
    Heres their web site:autoxray.com For more info
     
  14. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    I'll have to look into that... My temp sensor might be bad, I'm going to be putting a new engine in this thing, so I'll replace it anyway. Thanks guys! Nothing can beat this board for helpfulness....
     

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