Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

ECM/TBI Help

Discussion in 'The Garage' started by eblick, Jul 15, 2006.

  1. eblick

    eblick 1/2 ton status

    Joined:
    Nov 7, 2004
    Posts:
    218
    Likes Received:
    0
    Location:
    Jacksonville
    OK I have searched and searched on here and found some info but nothing I have done yet seems to work. My truck was running fine yesterday and then it quit. I thought it was out of gas so put 5 gallons in to get it back running. It wont start. I am not getting the check engine light when I initially turn the key on. At first I thought it was a fuel problem but know I am thinking it is electrical somewhere. Fuel pump works if connected to 12V. I also pulled the ECM out and put it in my other truck and the check engine light came on like normal start up so its not the ECM either. I checked all the grounds and they seem good too. I also checked the fuse block and they all look good. Any thing else I can check? Its an 87 350 TBI Suburban.
     
  2. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

    Joined:
    Jun 13, 2003
    Posts:
    29,623
    Likes Received:
    1,379
    Location:
    Jersey Shore
    Is the pump coming on when you turn on the key? sounds like the pump relay....
     
  3. eblick

    eblick 1/2 ton status

    Joined:
    Nov 7, 2004
    Posts:
    218
    Likes Received:
    0
    Location:
    Jacksonville
    No its not. But it does if I connect it to 12V power. Will that cause the check engine light to not come on? It acts like there is no computer installed.
     
  4. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

    Joined:
    Jun 13, 2003
    Posts:
    29,623
    Likes Received:
    1,379
    Location:
    Jersey Shore
    It's the pump relay... Little black box on your firewall above the passenger side valve cover....

    I always keep a spare in my console...
     
  5. diesel4me

    diesel4me 1 ton status Premium Member

    Joined:
    Jul 24, 2003
    Posts:
    17,553
    Likes Received:
    939
    Location:
    Massachussetts
    Truck has several "spares"!!..


    I recently learned from a friend that most vehicles that use relays on the electric fuel pumps share the same # relay as the one for A/C or power door locks,etc,and you can swap them around in a pinch,to limp home if one fails!...I got a lady that stalled out on a hiway exit ramp going again by swapping a different relay in place of the fuel pump one on her Ford Crown Vic by using this trick...she was VERY appreciative!:wink1: ....
     
  6. eblick

    eblick 1/2 ton status

    Joined:
    Nov 7, 2004
    Posts:
    218
    Likes Received:
    0
    Location:
    Jacksonville
    I just swapped out relays and it still wont start. Is there a way to see if the computer is powered up? I am still not getting the check engine light like a normal start up.
     
  7. sweetk30

    sweetk30 professional hooker Premium Member

    Joined:
    Nov 1, 2004
    Posts:
    25,539
    Likes Received:
    539
    Location:
    horseheads , ny 14845
    even with a bad relay at fuel pump cerkit you should still have check engine light. the lack of the light not cycling is the first place you should look.
     
  8. eblick

    eblick 1/2 ton status

    Joined:
    Nov 7, 2004
    Posts:
    218
    Likes Received:
    0
    Location:
    Jacksonville
    Ok I just pulled out the plugs to the computer and there is power to the computer at pins A6, B1 and C16. Where do I look next? I am getting very frustrated.
     
    Last edited: Jul 16, 2006
  9. sarasotausmc

    sarasotausmc 1/2 ton status GMOTM Winner

    Joined:
    Dec 16, 2003
    Posts:
    769
    Likes Received:
    0
    Location:
    Jacksonville NC
    Try the fuel filter. My truck sat for nearly a month with the same problem. If it's not the problem, it cost you $2.50 and 5 mins of work.
     
  10. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

    Joined:
    Jun 13, 2003
    Posts:
    29,623
    Likes Received:
    1,379
    Location:
    Jersey Shore
    Well, if the fuel pump isn't coming on when the key is turned on, your problem lies there... You need to check power to that relay.. IIRC the only 2 things that will prevent power to that are the fuse (have you checked the ECM 1 or b fuses?) and the low oil pressure switch... If Dorian chimes in, he will remember...
     
  11. eblick

    eblick 1/2 ton status

    Joined:
    Nov 7, 2004
    Posts:
    218
    Likes Received:
    0
    Location:
    Jacksonville
    Both fuses are good and there is power to the computer at the ECM. Going to go back oout there with my girl so I have an extra set of hands to trace wires.
     
  12. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

    Joined:
    Jun 13, 2003
    Posts:
    29,623
    Likes Received:
    1,379
    Location:
    Jersey Shore
    Pull that pump relay out and put a test light to the feed for it...
     
  13. eblick

    eblick 1/2 ton status

    Joined:
    Nov 7, 2004
    Posts:
    218
    Likes Received:
    0
    Location:
    Jacksonville
    OK just checked for power at the pump relay and there is no power when turning the key on. Does anyone know the whole electrical sequence? I changed computers thinking that would fix it and still no luck. There is power going to the computer. What am I missing?
     
  14. sweetk30

    sweetk30 professional hooker Premium Member

    Joined:
    Nov 1, 2004
    Posts:
    25,539
    Likes Received:
    539
    Location:
    horseheads , ny 14845
    sorry but what does a bad fuel filter have to do with no power to the pump or no check engine light cyclying?
     
  15. eblick

    eblick 1/2 ton status

    Joined:
    Nov 7, 2004
    Posts:
    218
    Likes Received:
    0
    Location:
    Jacksonville
    If the oil pressure switch is bad would that cause the check engine light to not come on as well as not turn on the fuel pump relay? I am not sure of the whole sequence but from the diagram the oil pressure switch looks like it connects to B2 or fuel pump in on the ECM. It seems I am not getting any voltage at this connection. Does B2 power A1 the fuel pump relay control?

    Thanks for all the help so far.
     
  16. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

    Joined:
    Jun 13, 2003
    Posts:
    29,623
    Likes Received:
    1,379
    Location:
    Jersey Shore
    yup
     
  17. eblick

    eblick 1/2 ton status

    Joined:
    Nov 7, 2004
    Posts:
    218
    Likes Received:
    0
    Location:
    Jacksonville
    Is there a way to test the oil pressure switch? This problem is driving me crazy!
     
  18. sarasotausmc

    sarasotausmc 1/2 ton status GMOTM Winner

    Joined:
    Dec 16, 2003
    Posts:
    769
    Likes Received:
    0
    Location:
    Jacksonville NC
    SweetK30, I posted prior to the above. I thought I had checked everything when I was having problems with mine including the pump, relays, ECM and senosrs, etc... and I didn't, or didn't do it correctly. I also ended up spending more money that I had to. In the end, it ended up being my filter. I overthought the problem I had and offered a suggestion to something. What I ended up doing worked for me. I'd say I'm sorry if you don't like the suggestion I made, but I'm not.
     
  19. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

    Joined:
    Jun 13, 2003
    Posts:
    29,623
    Likes Received:
    1,379
    Location:
    Jersey Shore
    This is just guessing on my part, but, most oil pressure switches are a variable ground switch..

    Don't think their is any specifac test for those switches... But I would hook a test light to the positive battery post and touch the sending stud, while off, then cranking...

    Hopefully Dorian will chime in here for you because I know he remembers this stuff... I don't have firsthand experience with how that system relates to the pump relay...
     
  20. eblick

    eblick 1/2 ton status

    Joined:
    Nov 7, 2004
    Posts:
    218
    Likes Received:
    0
    Location:
    Jacksonville
    I disconnected the oil pressure switch on both trucks the parts truck shows around 8 volts at pin B2 while the problem truck is only showing .35 volts or so. I am going to keep back tracking to see where I am losing the power. Also do the injectors go into this sequence at all and if so how? It doesnt look like the are firing either?
     

Share This Page