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Fuel pump - gone from bad to worse

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by OneInTheSun, Jul 30, 2001.

  1. OneInTheSun

    OneInTheSun 1/2 ton status

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    First of all - 85, 305, mechanical fuel pump
    Started to die out under accleration, so I figured the fuel pump wasn't putting out enough juice (new tank and sending unit two months ago, new fuel filter). Put in some aftermarket replacement pump and now things have really gone bad. When it's cold, it'll run for about a minute and then dies. Have to wait a couple of minutes before it'll fire up again and then dies out again. Repeat process - you get the idea. The lines are hooked up correctly and as far as I can tell, the fuel pump arm (or whatever it's called) is under the rod coming from the engine. The only thing I can figure is maybe the rod isn't sitting on the cam correctly. Can I adjust the fuel pressure somehow? Bad fuel pump possibly? Any thoughts are greatly appreciated. Thanks.

    <font color=blue>Rob
    85 K5</font color=blue>
    [​IMG] 24 beers in a case, 24 hours in a day - Coincidence?
     
  2. wayne

    wayne 3/4 ton status

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    Are you sure it is the pump and not the carb. Also if you have a Q-jet did you replace or clean the filter in it.

    <font color=blue>Wayne<font color=blue>
    <font color=blue>Happy Trails<font color=blue>
     
  3. Rockjunkies

    Rockjunkies 1/2 ton status

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    Believe it or not, some aftermarket or rebuilt pumps are of poor quality. They can go bad shortly after you put them on. Best to pull the pump off and cycle it by hand with a finger over the out port to see if any pressure is coming out. Then go from there.

    Keep it simple!
     
  4. OneInTheSun

    OneInTheSun 1/2 ton status

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    Yeah, the carb can definitely use a rebuild - that might be my original problem. For right now though, I'd just like to know what I screwed up on the new fuel pump.
    I'll probably end up redoing it tonight and if that doesn't solve something, I'll just go get a different pump.

    <font color=blue>Rob
    85 K5</font color=blue>
    [​IMG] 24 beers in a case, 24 hours in a day - Coincidence?
     
  5. newyorkin

    newyorkin 1 ton status

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    That sounds kinda wierd that you have to wait a minute to start it again. Are you sure it's not flooding it out? I haven't actually worked on carbs in a while, but flooding was the first thing I thought of when I read you have to wait a minute to re-start.

    Maybe a bad what's that thing? Needle valve? I'm rusty on the mechanical side...

    Ratch
    &lt;a target="_blank" href=http://k5.8m.com&gt;k5.8m.com&lt;/a&gt;
    **K5 - What more is there to life?**<P ID="edit"><FONT class="small">Edited by newyorkin on 07/30/01 01:23 PM.</FONT></P>
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    Try pulling the fuel outlet line off the carb, and seeing if when you crank it, fuel is actually being pumped. (disconnect the BATT lead at the dist. first)

    When my last fuel pump died, I was just sitting in traffic, and the truck died. No warning, just running, then dead. Tried starting while waiting for the light, nothing. Coasted down the hill to a parking lot, and tried to start it again. Started up fine. Got to work (maybe 5 miles) then parked it all day. Got in it to leave, about 200 feet, the truck died again, and that was it. No start until i replaced the fuel pump.

    Fuel pump lobe on the cams DO go flat, but if you aren't getting fuel, and you then test the pump off the motor, that would tell you if its pump or cam lobe. I will say though, that all the aftermarket chain store parts seem to be getting worse and worse in the quality department...

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</a>
    No anti-theft measures on your truck? No pity when its stolen
     
  7. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    I'm not really sure what's causing your problem- that said, the cam lobe that runs the mechanical pump on 305s are well know for wearing out.........Most of the problems I've heard about(including my PITA 6 month fuel-related puzzle) occur when the engine is hot, not cold. I would tear into the carb and take a look. Maybe there was some crap left in the new pump during the rebuild that got pushed into the filter or needle/seat.



    <font color=red>PHOTO ALBUM-</font color=red> <a target="_blank" href=http://albums.photopoint.com/j/AlbumList?u=1289798>http://albums.photopoint.com/j/AlbumList?u=1289798</a>.......<font color=blue>TRUCK & HIKING PICS</font color=blue>
     
  8. BlazerGuy

    BlazerGuy 3/4 ton status

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    I know this sounds dumb but I was having some of the same problems and turned out that the fuel line was kinked next to the water pump. Might wanna check it out

    <a target="_blank" href=http://www.k5.rockcrawler.com>Click here to see my K5</a>
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  9. OneInTheSun

    OneInTheSun 1/2 ton status

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    Thanks guys. I'll check everything that's been recommended again before I break out the 20 lb sledge. Just kidding about the hammer. Maybe. Anyways, this all started right after I got some exhaust work done (two new mufflers, slightly larger pipes out the back). Probably just coincidence but I'll check again to make sure those monkeys didn't crimp a fuel line or something. I'll post again whenever I solve this dilemma. Thanks again.

    <font color=blue>Rob
    85 K5</font color=blue>
    [​IMG] 24 beers in a case, 24 hours in a day - Coincidence?
     

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