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98 GMC 1/2 Ton

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  • SpiderGearsMan
    replied
    the pump goes bad and stalls

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  • SSChevyManiac
    replied
    Thanks for the offer Charles. However being a work truck, everything is footed by the company thankfully.

    And of course, IT RUNS!!! POWERRRRRRRRR!!!

    Started the day running down to the parts store for the new injection system. Worked on installing that and getting everything buttoned up.


    That's the new parts which place actual injectors where the poppet valves used to be. Supposedly more power and MPG, it sure runs great now.

    However, when we first got it back together, we hit the key and got one turn and it stopped dead. I about evacuated the bowels then remembered we disconnected the upper rad hose. Well, over night the hose fell back into place and it seems leaked some water down the intake ports. Ok, pulled the plugs did the whole water fountain thing. Good.

    Try again, crank, crank, crank. No go. Work the fuel pump a few times, still nothin. Alright get the ether. It ran on starting fluid well enough for me. Next we scratch our heads and ponder the fuel pump. Run back down to the parts counter and talk with the boys. Brad at the store lends us his pressure gauge. Back at the truck, check the pressure, 0. Purge the gauge and the truck will push fuel through the gauge, but not build pressure. Hmm. Fuel pump time.



    Yank the pump.... Well it turns out that even though I personaly put 5 gallons in the truck in January, its gone. So in this instance, the hole in our floor and pulling the pump is a really effective gauge.

    We put gas in the pig and cranked the key. Holy Seafoam moment. The truck was sitting next to a shipping container that we store tools in, well that thing will NEVER rust. It was at that point I suggest we change the oil, because well, it was about 4 quarts over full and smelled like a Gulf station.

    After the oil change it was test and tune time. This thing has only 80 thousand miles on it and runs like a champ. The boss laid rubber in second and we bangshifted up and down the site road.

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  • BOOOGHAR
    replied
    I have a early 99 Yukon with that same set up, started to dive into and started pricing parts and then finding issues with the front suspension, interior was completely shot, all kinds of interior electrical issues and i said F that - if theres something engine wise you need intake wise lemmie know and I probably have it

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  • phitter67
    replied
    Yep, got one one order for my '98 yukon. New seals are available without needing to buy upper intake now.

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  • SSChevyManiac
    replied
    Well, finally got back to working on this truck today. Seeing the price for a fuel pump, we decided to try the regulator first. The regulator for these trucks is inside the intake. I don't enjoy the job, but fortunately I've done it on a 4.3 before. We removed the throttle body and started pulling intake bolts and generally moving things out of the way. Straight forward thus far.

    Now, the warm spring Pennsylvania sun shines on us and we see through the opening where the throttle body used to be, what do we see? The beloved spider legs. I am atypically the more experienced hand on this job. I explain how the system works to my fellow "mechanic" and carry on removing the upper plenum.

    We're studying the engine finding ways to remove the intake with what tools we have, turns out we really needed a deep well 10mm in 1/4 in drive, but had a shallow 3/8 that did the job with some tricks. Anyhow, my co worker says, "Hey, those spider thingies are about shot." I look again, and see that the lines are absolutely SHOT going to # 2 and 4.

    Called up the parts store, $3XX some dollars for the "conversion" part. Its the company site truck and they want it to run to I said I'd be in to pick it up. Apparently the new part essentially makes the system operate like a newer style injection with regular injectors. I'll grab a picture of that tomorrow when it goes in.

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  • DanStokes
    replied
    Eager to know what you find.

    Dan

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  • SSChevyManiac
    replied
    The gentleman at the parts store (a chain, but a real one, with books even!) said in his experience they are very sensitive to fuel pressure. This truck was run completely out of gas before I started working there. The problem started immediately after that happened. Yesterday all we were able to do was change the filter and try and diagnose some things. When it does run, it will idle smooth as silk on starting fluid carb cleaner or whatever you wish. Add fuel from the pump and it misses and carries on and backfires through the intake. I'm trying to get a scanner on site to pull codes. The backfiring through the intake makes me think lean, however the exhaust color and smell seems insanely rich. Working on this truck is also a downtime filler for us, I'll try and keep you all updated thanks for the ideas.

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  • DanStokes
    replied
    Dan and TC both know WAY more about this engine than I do. I'd just suggest that you check the Dorman catalog if you need the intake - they're making improved versions of some of these plastic manifolds for way less money than the dealer replacement.

    Dan

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  • TC
    replied
    Probably the fuel regulator or you have a really bad vacuum leak....... Check fuel pressure and for vacuum leaks......... The Upper Plenum on those intake manifolds were know to warp(they are plastic), and if you have to replace the spider, your going to need to get a new Upper plenum, it's the only way to get the gasket or at least that is how it used to be........
    Last edited by TC; January 4, 2013, 10:50 AM.

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  • Dan Barlow
    replied
    I'm guessing that this has the vortec 350. If it is like the 4.3 vortec with the tall 2 piece aluminum intake, after the fuel line go into the intake they turn to plastic. They eventually split.To check for this smell your oil. If it smells like gas, this is the problem.

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  • SSChevyManiac
    started a topic 98 GMC 1/2 Ton

    98 GMC 1/2 Ton

    Gentleman, truck stated in title. 305 with the spidery injection. Rough idle stalls on tip in. I'm open to any and all suggestions. This is a construction site truck, I've got limited tools and resources on site. Idles on carb cleaner.
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