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Please help

Discussion in 'Chevy Trucks' started by bnc services 2, Sep 9, 2005.

  1. bnc services 2

    bnc services 2 Member
    Messages: 66

    Anyone know what controls the fuel pump and injectors on a 90 blazer with a 350cid. i have no power to either one the pump is good. i cant find any relays or anything!!!!! please help
  2. The Boss

    The Boss 2000 Club Member
    Messages: 2,099

    Have you checked for any codes? Maybe a wire is cut somewhere also. :confused:
  3. bnc services 2

    bnc services 2 Member
    Messages: 66

    normally codes wont show with truck not runing. the truck did run and then one day it stoped so i thought it was the fuel pump that was the only thing that has not been changed. so i did that tonite and when it still did not start i ck injector pulse and nothing..... :eek: and now its really starting to piss me off!!!! it should somewher have a relay or fuse but i cant find one yet.... what ever it is controls both at the same time i know that much.......... got anymore ideas :cry:
  4. Mebes

    Mebes Senior Member
    Messages: 451

    If I remember correctly.
    The fuel pump is run off a relay, and low oil pressure will cut it out.
    The injectors are fired off by the computer using the signal from the distributor (ignition module).

    Did you check for spark?
    The ignition module sets up the injector pulse and the signal to the ignition coil for spark.

    If you have no fuel, no injector signal, and no spark then I would look for a fuse (ECM) or an ECM relay.

    The pump should cycle with the check engine light for about 3 seconds when you turn the key to run, then stop.
    It turns back on (the fuel pump) when it sees oil pressure (while cranking).

    If you have spark then try pouring some gas into the throttle body (about 2 tablespoons) and crank the engine.
    If it starts and stalls then you have a fuel delivery problem (fuel pump, Injector, filter, etc.)

    If you don't have spark then you have a fuse, computer (ECM), relay, distributor, or (most likely) an ignition module failure.
  5. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    Mebes is correct.

    Also, I have had a similar problem with my own truck. The wire running from the fuse box area to the tank is going bad INSIDE the insulation and needs to be replaced. I keep patching it but proper replacement is the only solution...
  6. bnc services 2

    bnc services 2 Member
    Messages: 66

    the truck runs when you put gas it the TBI it has spark and oil psi i cant find a relay for the fuel pump anywhere . some keep telling me ign. module i will try that on tuesday..... and all the wiring is good i traced it . im thinking it and ECM :cry:
  7. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    Doesn't make sense to be an ignition module if it runs when you put gas down the TBI. Fuel wiring problem.

    On my truck (the wiring was taken from an '87 R30 dually) the relay is one of two that are bolted to a small bracket on the passenger side of the firewall above the heater core (near the hoses that go to the engine and rad). They don't look like a standard small cube-style relay, they are longer (maybe 3"?), like a rectangular block with the corners cut off (ovalish-shape if looking from the top).

    They are about $10 new from GM, I bought one for testing purposes. I put my old one back on because it still worked.

    I assume you checked the ground between the fuel tank and the frame of the truck, right? Very Important!
  8. Mebes

    Mebes Senior Member
    Messages: 451

    If it runs when you pour the gas in then it's probably not the ignition module.

    The ECM probably uses a different oil pressure sender than the one that sends to your gage on the dash.

    Call the auto part store and find out if you truck has 1 or 2 senders for oil pressure.

    Does the check engine light turn on for 3 seconds when you turn the key to run?

    Do you have a tap on the fuel rail to check fuel pressure? (looks like a tire valve but smaller)

    You said you checked the injector for injector pulse.
    How did you do that? (what tool)

    By the way I have installed fuel pumps before that were bad right out of the box.
    Check for voltage at the connector at the fuel tank.
    Or jump power to it (fuel pump) to see if it runs.
    Maybe you have a bad ground back there.
  9. bnc services 2

    bnc services 2 Member
    Messages: 66

    I cked the injectors two ways one with a noid lite and two with a test lite no power as for the fuel psi valve there is non like that on TBI models. i cked ground and made a new ground no good. the pump is good i used a jumper and it runs, But with no pulse it will not run. i will ck the fire wall pass. side for the relays first thing in the a.m. thanks guys keep the ideas coming
  10. mikes plowing

    mikes plowing Member
    from cent pa
    Messages: 77

    Best thing to do is go to the parts store and look for the haynes book that covers the tbi. Looking at the book I have hear it should be book# 10220. See if that helps you.
  11. schnitz

    schnitz Member
    Messages: 98

    Kinda long, but bear with it....

    About 2 months back, I got a call from a guy to check out an '87 C-20 van. It had a 350 TBI. Probably just like the TBI on yours. I checked every last trace that I could. Did the noid light deal. After a week of trying to track it down, I sat down with the guy, and showed him the noid light test as a way to show him the reason why I was giving up. He was going to take it in. Plain and simple. I got injector pulse on both sides of the TBI when I showed him. I rehooked the injectors, and it ran. Until the end of the driveway. The tech that got it running for him said it was the main computer. It runs like a champ now. I hate to ruin your day, but that sounds like it's the problem for you too.

    In a while, Chet.
  12. Mebes

    Mebes Senior Member
    Messages: 451

    It's starting to sound like ECM relay, or bad computer to me.
    Does the check engine light come on when you turn the key?
  13. bnc services 2

    bnc services 2 Member
    Messages: 66

    OK, thanks for all your guys help! :nod: i greatly appreciate it, after talking to the idiot i bought the truck from he said his tech. told him it was a fuel pump, no big deal whe i got it home i put a fuel pump in the truck and as you all know it didnt run. I cked everything you all helped with and then some :dizzy: , just to find out this guys TECH :angry: pulled out the ECMB fuse which controls the TBI and INJECTOR pulse. YEP A $.20 FUSE IS ALL IT WAS !!!! :gunsfiring: THANKS ANGAIN
  14. tccortes1

    tccortes1 Junior Member
    Messages: 25

    Have you ever check you camshaft position sensor, or crankshaft position sensor?. one of those sensor triggers the injector and the fuel pump. if i'm
    not mistaken, It would be the crankshaft position sensor. But to be sure,
    Get it scanned and hopefully get a code out of it.