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  1. #1
    Jr. Apprentice
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    Nov 2010
    Location
    San Tan Valley az
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    Question Questioning myself on this fuel problem.

    Taking a butt kicking here. I have a 1987 3/4 ton Pickup since it had 12k on it and only have 69k on it now. It is a 454 tbi with a turbo 400 and the towing package. My grandparents special ordered it new.

    I have had fuel problems for a while. a few months back i moved the bed back and replaced both fuel pumps with the strainers. I also replaced the rocker switch for choosing the tank. the right tank was not working i was getting bad readings on the fuel gauge, and it was jumping. I have not added a second ground to the tank to make sure that is tight. the reason for that is years ago i would change the pump by dropping the tank and i wonder if i stretched the wire on inside the shield and possibly that is why the gauge was not working.

    So the other day i decide i want to look at the right side. i flip the rocker switch to the right side then crawled under the truck to test the voltage. I asked for a meter and was smelling a burning smell, when my son came over to give me the meter he told me that the truck was smoking inside. When i got in i did not see any smoke but i could smell it.

    Well guess what? the truck now would not start at all. I did test the pumps for noise using the test line on the fuel pump relay, and could hear both of them. I did find a bad ecm B fuse and a second one. but either one of them burning should not have created the smell. I did remove the dash bezel and dash and have been through the wiring and was not able to find any wires that look like they have heated up.
    When turn the key on i can hear the pump running, but when i got under it tonight i was easily able to use my finger to try to feel any flow and there was very little. I did not put a gauge on it to check for the 9 psi but there seem to be very little flow. I did disconnect the line at the TBI and did not get any flow there. I thought that the new filter i had replace may have been bad, i removed it and it was fine, with no restrictions.

    So not i am wondering if it is possible that the diverter valve may be causing some type of problem, and possibly the rocker switch was causing the smoke. I did not pull it yet.
    Any ideas would be helpful.
    thanks

  2. #2
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    stephan's Avatar
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    Far West, Oregon USA,
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    Welcome to the GM truck club Aficio. Since your son saw smoke in the truck & you could smell it when you got in, you have to find the burnt wires before you go any farther. You talk about checking the wires at the dash bezel, but did you check them at the switch? If the switch wiring or the "switch itself" is burned out, that may be why the valve is not working & it could be stuck inbetween because it didn't get switched all the way before the electrical burn/malfunction. The diverter valve is easy enough to check just by disconnecting it, but I believe your first problem to address is your burnt wiring. Also need more info on this ground wire that was questionable from the fix from months ago??

    BTW, I believe your TBI needs 12 psi not 9psi
    Last edited by stephan; 11-23-2010 at 11:10 PM.
    1988 Chevy C-3500 2wd (no pic)
    350 c.i. 5.7 L Stock Block, 4 Bolt Mains
    L-31 Vortec Heads, Edelbrock Cam & Intake,
    Holley 650, Flowtech Headers, Magnaflow exh.
    Jet Trans 700R4, B&M Ratchet, 4:10 gears,
    3" susp. lift kit "shadetree"
    No rev limiter, No speed limiter lol


  3. #3
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    mfleetwood's Avatar
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    Jul 2010
    Location
    Denver, CO
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    Welcome!!!


    Mike (Denver, CO) - 2008 Sierra 1500 Z71 SLE 5.3L 4WD

    SUSPENSION: Rancho 4" Suspension Lift; Rancho RS9000XL Shocks; Rancho Skid Plates; Rancho MyRide Wireless Shock Controller;
    TIRES:
    BFG All Terrain KO 315/70/17
    DRIVE TRAIN: 4.56 Gears; Detroit TrueTrac Differential; True Cool 40k Transmission Cooler
    PERFORMANCE: DiableSport Predator Tuner; Custom Tuned by Diablew; Magnaflow Exhaust; AFE Cold Air Intake
    ELECTRONICS: Kenwood DNX6180 Touchscreen; Subthump box w/10" Kicker; Driver Information Center (DIC); Rear View Camera
    ACCESSORIES: Westin Brush/Grill Gaurd; Westin Nerf Bars; Truxedo Tonneau; 20% Tint; Tow Mirrors w/Heat & Signals

  4. #4
    Jr. Apprentice
    Join Date
    Nov 2010
    Location
    San Tan Valley az
    Posts
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    Default

    I will double check the switch in the tomorrow after work. With everything apart it will pretty easy to pull. Thanks

  5. #5

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    Welcome to the club.

  6. #6
    Jr. Apprentice
    Join Date
    Nov 2010
    Location
    San Tan Valley az
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    Still taking a butt whipping here.
    Well I wish it was the switch, Changed it out and no difference, did need to replace a blown guage and ecm b fuse.
    And After i thought about it i pulled and replaced the fuel selector valve and bought a kit and took the time to replace the harness for it, i use solder on the joints and shrink wrap to keep it sealed. Tested it on the left tank and it started up and ran fine. The only problem is when i turned the ignition switch off the truck keep running, not dieseling but running, it did change rpm i think because of the computer, but i could give it gas and it was smooth, the accessories like the ac would not work unless i had the key on but the motor ran fine. HELP and ideas??

  7. #7
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    Hey Aficio,
    It seems like this new problem started after your son saw smoke coming from the dash & you could smell something burning. You need to find out what was burning because I think it is what is causing your "new" problem with the engine running after you turn it off. It is maybe burnt wires giving power, or could be a burnt relay that is burned in "closed" position & supplying power.
    It is not the ignition switch, because if it was staying on, the AC would have worked, & since the accessories were not working when you turned the ign. off, this indicates switch is working. You must find out what was burning that caused all the smoke. I think this is where your problem is.
    1988 Chevy C-3500 2wd (no pic)
    350 c.i. 5.7 L Stock Block, 4 Bolt Mains
    L-31 Vortec Heads, Edelbrock Cam & Intake,
    Holley 650, Flowtech Headers, Magnaflow exh.
    Jet Trans 700R4, B&M Ratchet, 4:10 gears,
    3" susp. lift kit "shadetree"
    No rev limiter, No speed limiter lol


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