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cant figure out the problem with my 87 :(

Discussion in 'General Chevy & GM Tech Questions' started by 77gmc, Oct 24, 2010.

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  1. 77gmc

    77gmc New Member

    alright so i have a 87 chevy 1/2 ton truck with a tbi 350 but the motor is not the original motor it has a older motor in it that somebody swapped all the tbi stuff back onto now when i go to start it when you turn the key over the fuel pump in the tank is constantly running never shuts off then when you go to crank it it will sit and crank forever then you turn the key off and turn it back on then it will crank and crank and crank then it will fire right up anyone know what the deal is??? it also has two tanks that apparnetly the switch or the solenoid tht is inbetween the tanks went out and someone jerry rigged the thing to get it to only use the one tank instead of fixing it right looks like the cut a few lines and idk its just a mess if anyone has has some expierence with this problem i could use all the input i can get! also has a new fuel filter on it from what i can tell

    this is a picture of the solenoid that connects the two tanks dont know if this is how it is suppose to look from the factory so if anyone else has some pictures of how it should look that would be awesome!
    [​IMG]

    ---------- Post added at 09:55 PM ---------- Previous post was at 08:09 PM ----------

    i just figured out the fuel problem with my truck there is a fuse in the fuse block for a ecm2 and there was no fuse in there so i put a fuse in and two cranks she fired right up!!!! i tried it 4 times just to make sure and sure enough thats the problem so now the problem is that when the fuse is in there when you shut the key off the truck stays running but if you pull the fuse it shuts off so the only way i can see to fix it is to run a kill switch to this fuse
    this is the fuse that was missing
    [​IMG]
  2. 77gmc

    77gmc New Member

    anythoughts???
  3. stephan

    stephan New Member 1000 Posts 100 Posts

    Probably not what you wanted to hear, but the fuel switching valve is expensive, & even if you replaced it, the dash switch might also be bad & it is just more $$ so most everybody always just bypassed the valve & ran both tanks together. Besides saving money it also gives you the benefit of drawing on both tanks together so the fuel in the alternate tank never goes stale.
  4. 77gmc

    77gmc New Member

    i foiund that the solenoid on lmc is only 99 dollars and thew switch is only a couple bucks
  5. stephan

    stephan New Member 1000 Posts 100 Posts

    ha ha, ok, the price has gone up 100% since my dad decided not to replace his. If I remember right it was around $50. back then.
  6. 77gmc

    77gmc New Member

    dang lol well that still doesnt solve my problem of my truck not shutting off when i turn the key off with that fuse in :(
  7. stephan

    stephan New Member 1000 Posts 100 Posts

    Sorry, I have no clue what the electrical part of your problem could be. Since this engine was swapped before you got it, it is most likely something that was done to make this older engine work with the newer wireing harness. Can you contact the owner that you bought it from & ask him?
  8. randomsandwhich

    randomsandwhich New Member 100 Posts

    I think the ecmb fuse goes to the fuel pump, so my guess would be the fuel pump not shutting off. maybe a bad relay somewhere? start testing wires for continuity and double check connections. Only things I can think of, haven't touched a tbi in a couple years.
  9. dualdj1

    dualdj1 New Member 100 Posts

    well i'm guessing the fuse was out, because they had a wiring problem causing the truck to not shut off. This type of problem just takes some time and wire tracing, but you should be able to do it. On that year, you should have an ignition switch somewhere on the steering column, with a hot all the time going to it, and a switched off the key coming out. usually red/yellow wires, one should be hot, one switched (don't remember right off which is which). if you've got juice all the time on all wires with key on or off, then you need a new ignition switch, and that's your problem. if the switch is working properly, then somewhere in their transplant, they hooked the switched ignition feed to battery +12v. Do some tracing with a good multimeter, and see what's hot and what's not with key on and off.
  10. 77gmc

    77gmc New Member

    now see shouldnt these year trucks shouldnt you be able to turn the key backwards to get the radio to come on? cause that tumbler will not turn back what so ever idk if this has anything to do with it

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