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  1. #1
    Sr. Apprentice Tagerman's Avatar
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    Default 1987 TBI 5.7l fuel delivery problems

    Okay,

    I am a mechanic but i don't know a whole lot about these old trucks so before I do a lot of work for nothing I thought i'd see what you guys thought. I have a 1987 R10 [COLOR=blue ! important][COLOR=blue ! important]Silverado[/COLOR][/COLOR] with the 5.7l TBI motor. I have not had a problem with the truck everything was working as it should. Yesterday I was driving and the motor just cutoff, no warning signs or anything it just stopped right after a fill up at the gas station. I got a buddy to tow it back to the house and I have found out that I am not getting any fuel out of the injectors. Now for the questions. I let the truck get lower than I ever have before it was at an eighth tank when I filled it is it possible by letting it get that low that I have clogged the fuel strainer? Or maybe my fuel pump has just given up. Any suggestions would be nice! Oh and I also noticed my oil pressure gauge seems to be stuck would that sensor going bad cause the fuel to shutoff?

    Thanks,
    Trent

    1993 K1500 Suburban
    2008 Subaru Outback Sport
    1987 Chevrolet R10 Silverado (Sold)
    2012 Hyundai Santa Fe

  2. #2

    Default

    Pull the fuel filter (easiest thing to check). You can also see if the fuel pump is getting gas that far while you have it off. You will need someone that can turn the ignition on/off real quick for a test.
    Jason
    College Station, Texas
    1994 GMC Sierra 1/2 ton 5.7L V8

  3. #3

    Default

    I would check and see if the injectors are getting any voltage. Fuel filter could be the culprit.

  4. #4
    Sr. Apprentice Tagerman's Avatar
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    Default

    the only thing that makes me think it isn't the fuel filter is that it happened suddenly I replaced the fuel relay tonight and my gas tank was about to rust through so I'm putting a new one in, see if i can't get the truck running this weekend, really hope its not the oil pressure switch that thing is not going to be fun to get to

  5. #5
    Sr. Apprentice
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    Default

    Hi Tagger I have the same truck. Mine is two tone red and creme! Same engine and TBI.

    First check is always the filter. Proper fuel line pressure should be between 9-13 PSI.
    I had two issues that caused a similar effect.
    First one was caused by the power wire to the fuel pump getting pinched between the bed and the truck frame.
    Second one was when the fuel tank switch failed. I have dual tanks on my truck.

    The Chevy OEM troubleshooting manual I have states to do the following.
    FIrst Apply 12v to the fuel pump test terminal and listen for the in tank fuel pump. Test terminal is on the fire wall and on mine is clearly labled if yours is not let me know and I can copy a photo of it here for you.
    Does it run If No then the issue is a open circuit #120 (TAN/WHT wire coming out of the relay)or #150 to the fuel pump or a faulty relay. Check these and fix the appropriate one. Remember mine was circuit 150 to the fuel pump and was pinched by the bed on the frame.
    If the pump runs with 12v applied to test terminal then:
    Remove 12v from test terminal
    Ignition off for + 10 secs
    Ingition on listen for in tank fuel pump, pump should run for 2 secs after ignition is turn on. Does it?
    If it runs then NP
    If it does not run then:
    Disconnect fuel pump relay
    Ingnition on, engine off
    Probe relay harness connector terminal ckt 440 with a test light to ground. 440 is the orange wire from the battery fuse link to the relay.
    If light does not come on then repair open ckt 440
    If light lights up then:
    Let me know and I will keep typing the rest of this manual for you ! lol

    OH BTW if you go to http://www.helminc.com/
    and search on your truck like I did mine you will find Chevrolet 1987 Light Duty Fuel, Driveability and Emissions Service Manual ST-376-87
    Here is the link to the whole list of service manuals on our trucks.
    http://www.helminc.com/helm/product2...87K&itemtype=K

    I bought the full set for $120 and it was the best investment I ever made. I gives step by step troubleshooting guides with full size wireing diagrams, cut away drawings, parts assembly drawings, specialty tool lists, etc...

  6. #6
    Sr. Apprentice Tagerman's Avatar
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    Default

    well I have completely refurbished the fuel system under investigation it was in really bad shape. Now I have another problem it will run for about 45 seconds then the truck blows the ECM B 10A fuse according to my wiring diagram book this fuse doesn't exist but somehow it is keeping the fuel pump from pumping, without a wiring diagram i'm not sure how to go about diagnosing it. Any help would be greatly appreciated.

  7. #7
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    The manual I mentioned above has a diagram of the fuel pump relay circuit on page 3-26 that shows this issue perfectly. You have a 12v battery feed to one side of the ECM B fuse and the 440 (orn) circuit runs from the fuse to the power side of the fuel pump relay a tee in the line before the relay allows it to also feed through the oil pressure switch. Not sure but sounds like you have a fuel pump relay that is going out.

    I was able to photo the page and attach it to this thread.
    Attached Thumbnails Attached Thumbnails photo.jpg  

  8. #8
    Sr. Apprentice Tagerman's Avatar
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    Default

    thanks for the help i got it running. There was to much resistance in the ground wire causing the pump to pull to many amps. She's running like a top now. My local GM dealer also recommended that I upgrade the fuse to a 15 amp from a 10 amp after installing an aftermarket pump because they said the aftermarket pump pulls more amperage than the factory pump which would also cause the fuse to blow.

  9. #9
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    Default

    Thats great news congradulations!!!

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