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Help with 87 chevy half ton 2wd

Discussion in 'General Chevy & GM Tech Questions' started by realtree87, Dec 1, 2012.

  1. realtree87

    realtree87 New Member

    ok new to this site. I am going to try and explain clearly what is going on. I have a 87 chevy 350 tbi. stock with exhaust cut off before the cat. My truck idles fine but when i give it light - moderate throttle it cuts out and stalls for a second or two then goes and keeps doing this as long as I am in that range of throttle. I can run it WOT and it runs fine. Now about 3 months ago I put a new fuel pump in left tank, I dont use right tank bc PO said it didnt work. I also replaced the TPS at the same time. ran fine up until about a week ago then this problem came up. So I replaced the fuel filter. and back when I replaced the pump I actually had to add more hose to the fuel lines that run to the top of the tank. well it was leaking last week so I just replace those hoses and clamps with the good stuff. did this on thursday. started up and ran fine. And ran fine all day friday. I get in it today and drive for about an hour and it starts doing it again. monday I checked codes and it was throwing codes for abs thats it. today I ran codes and got code 13 o2 sensor. so I just replaced that and put a new tps on it and it still does the same thing. and now sometimes it completely dies. I dont know where to go from here so any help would be appreciated thanks.
  2. 87silver

    87silver Member 1 Year

    I had an issue with uneven throttle response in my 87 350 TBI. First, I changed out the fuel pump relay on the firewall. It seemed to help, but still wasn't running optimal. Changed the throttle body gasket and it smoothed out. Not saying that it's the problem with yours, but it worked for me.
  3. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Have you checked the vacuum lines and gaskets for leaks?
    Sounds like you've been concentrating on the fuel supply but could it be possible it's not advancing spark properly?
    If your sure its a fuel supply issue have you checked fuel pressures?

    87 is one of those weird years where GM knew they were changing to a new platform sometimes at change over points you get vehicles that have some of the old and some of the new on them, this makes them hard to repair at times.
  4. Pikey

    Pikey Moderator Staff Member 3 Years ROTM Winner 1000 Posts

    I don not know much about that year truck. Does it have an EGR valve? Have you checked it?
  5. 87silver

    87silver Member 1 Year

    Has an EGR. Not related to this post, but it also had a unique exhaust system (Last of the Rounded Line era, but with EFI)
  6. realtree87

    realtree87 New Member

    ok so update, after doin all that work i was working on it saturday night with it running and found that the vapor hose to the tank was putting fuel in the charcoal canister. So i plugged that line and switched caps since they are vented. I dont ever use the right tank, but now the problem is as follows:

    ok I have an 87 chevy 350 tbi. last week It was running like crap. I started replacing things, then finally after 3 days working on it i got it running and smelt fuel under the hood. got to looking and the charcoal canister was full. so I took it out and plugged the vapor vent hose to the tanks. and I switched gas caps bc I only use one tank. trucks running fine. my problem is yesterday as it sat running I noticed a leak on the passenger side and come to find out my right tank is full and coming out the filler neck. so idk if my left tnak had problems to start with or not. I still have the vapor line plugged. I need to know what the solutions are to fixing this, why its backing up into the right tank. Ive had the truck for about 4 months and never used the right tank and there was no fuel in it when I bought, the guy I bought it from said that tank didnt work. is there a way to eliminate that tank? is there a selector valve thats not working right? what? im lost any and all info would be great.
  7. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    First off the switch valve between the tanks is bad, its an anti siphoning style valve that should allow no fuel in, only out.

    If your left side tank is pressurizing its probably forcing fuel into the right side to relieve the pressure, and thats why you now have a full right side tank. It's also possible that the pressurization is why you have a full charcoal canister, very little liquid fuel should go through the canister it should be more fumes than anything.
    You need to check your tank vents for both left and right it sounds like and see why they arent venting properly.
  8. realtree87

    realtree87 New Member

    another update, i unplugged the vapor line to the canister and run in into a pan to catch it, and the right side tank is not pouring out the filler neck. now is there a way to bypass the selector valve where i can just run of the left tank at all times? if so how?
  9. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Just eliminate the line and switch valve to the right tank.
    Run your fuel supply from the left tank to the engine just like they do on single tank trucks.
  10. realtree87

    realtree87 New Member

    which would involve what? finding the supply line from the tank and the line to the tb and connecting them and thats it?

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