94 s-10 4.3 still won't start

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Thread: 94 s-10 4.3 still won't start

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    Unhappy 94 s-10 4.3 still won't start

    Hi all, I posted a little while ago about this, and still can't get it running. A little history, Truck was running rough for some time, tuned it up, but no help. A few weeks ago It would not start, have spark , seems like it wants to start but wont. Took upper intake off, and tell tale sign of a bad spider, one side clean and gas puddles in there. Well replaced the spider with a rebuilt one, and same thing. It will run a little if I pour gas into the intake, then die, other than that, it wont start. Played with the timing but no good. new fuel pump and relay. Just seems like its gas starved for some reason. Don't know the psi on the fuel rail, but it seems like there is pressure in there, press the valve and gas shoots out, maybe not enough though, dont know. I found a plastic box underneath the dash by the fuse box that has a circut board in it and is plugged into a wire harness, dont know what it is. I'll try bypassing the fuel filter under the veh., maybe its clogged looks like the original. Any help would be great, I'm about ready to junk it if nothing works.

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    2.4 Liter SIDI ECOTEC Flynbyu's Avatar
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    Re: 94 s-10 4.3 still won't start

    For anything to run, you need gas, air, and spark.

    Are there any lights on the dash on?

    ~Brian

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    Re: 94 s-10 4.3 still won't start

    Got spark and air flow, dont know about how good my fuel delivery is though. Will replace fuel filter tomorrow.

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    Re: 94 s-10 4.3 still won't start

    Quote Originally Posted by loid58 View Post
    Got spark and air flow, dont know about how good my fuel delivery is though. Will replace fuel filter tomorrow.
    Remove a sparkplug, crank it, do you have these clouds of gas shooting out? You'll smell it

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    Re: 94 s-10 4.3 still won't start

    Well, replaced the fuel filter, It was really clogged. After a while, got the truck started, and seems to run fine at idle. When I give it some gas, it bogs down and stalls, then its real hard to start up again. I had to put gas into the intake to start it a few times. When its idling, it runs fine and even goes into drive no problem, but as soon as I hit the gas, it sputters and stalls. I tried disconnecting a few of the sensors on the intake, but the only thing that did anything was the MAP and a little round plug on the drivers side right next to the air intake, stalled as soon as I disconnected either of them. This is driving me nuts because the truck was running fine, a little rough though until it wouldn't start one day. The spider was definitely bad, I'm running out of ideas. Have good gas pressure, new fuel pump, spider and fuel filter. Any suggestions? Thanks

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    Re: 94 s-10 4.3 still won't start

    you need to get it running and let it sit and idle for a bit, it will take a bit of time for the computer to see it acting normal. it needs to relearn fuel trims and other data to figure out which block it will run in. try to disconnect the battery, remove both cables, then touch both cables together. it will drain any voltage out of the electrical system. then reconnect your cables to the battery, and see if it fires up. it will probably run a bit rough at first, but like i said, it needs a few minutes to relearn everything.

    hard telling what it could be really, those older cpi engines are a handful when they dont run good.
    There are no stupid questions, just stupid people.

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    Re: 94 s-10 4.3 still won't start

    Quote Originally Posted by Triple-X08 View Post
    you need to get it running and let it sit and idle for a bit, it will take a bit of time for the computer to see it acting normal. it needs to relearn fuel trims and other data to figure out which block it will run in. try to disconnect the battery, remove both cables, then touch both cables together. it will drain any voltage out of the electrical system. then reconnect your cables to the battery, and see if it fires up. it will probably run a bit rough at first, but like i said, it needs a few minutes to relearn everything.
    I was thinking the exact same thing! Woohoo I am a smarty....hope it works!

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    Re: 94 s-10 4.3 still won't start

    I had it idling for about a half an hour, and no change. I will try the disconnecting the battery thing, maybe thats the problem ( I hope). Its very weird because it was running fine, although a little rough, but started up fine every day. I'll keep you guys posted, Its rainy and nasty here in N.Y.C, so I will not be working on it for a few days. But Thanks again for the advice.

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    Question Re: 94 s-10 4.3 still won't start

    Oh, forgot to ask, do I disconnect the battery cable while its running, or shut it down then disconnect them?

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    4.4 Liter Supercharged Northstar bouda's Avatar
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    Re: 94 s-10 4.3 still won't start

    You played with the timing, yes? There is a wire you have to disconnect to adjust timing. You adjust it to 0 I believe.

    If your '94 4.3 S-10 is the same as mine was and I can only assume it is the wire is on a wire harness behind the glove box. It's taped to the outside if the bundle of wires, it's light brown.


    If you already knew this sorry for wasting your time lol.

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    Re: 94 s-10 4.3 still won't start

    Quote Originally Posted by bouda View Post
    You played with the timing, yes? There is a wire you have to disconnect to adjust timing. You adjust it to 0 I believe.

    If your '94 4.3 S-10 is the same as mine was and I can only assume it is the wire is on a wire harness behind the glove box. It's taped to the outside if the bundle of wires, it's light brown.


    If you already knew this sorry for wasting your time lol.
    i believe the item you are talking about is for the older engines, like say a early 90's silverado, to disable pcm timing. when you disconnect it, you can base time an engine. this vehicle should have it if it is old enough. i cant tell you if it does or doesnt. bouda, you seem to know where its located, maybe you can give him a heads up and description on everything he needs to do. i cant describe to you exactly where it is or what to do. ive only played with a couple of these style engines.

    this is true. i didnt even think about that until you brought it up. it may just be old enough that it may have the wire connector to disable it.
    also about the battery cable thing, you want to have the vehicle off. not running, just completely off. disconnect the battery, take both the positive wire and the negative wire, off the battery completely. then after you have both of them disconnected from the battery, touch them together, and hold them together for like 5 - 10 seconds or so. what this does is drain all power from all modules and basically the pcm is going to act like it has just been installed in the vehicle. this will allow it to relearn all the items it needs to adjust for fuel trims, slight timing changes, and will zero out the old information it learned. i say this because you have had to start it with fuel in the intake. what this is doing is falsifying the sensors, and cheating the system basically. it needs to relearn quickly to start correctly and run properly.
    Last edited by Triple-X08; 12-13-2008 at 05:22 PM.
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    Thumbs down Re: 94 s-10 4.3 still won't start

    Trip X, Got it started and let it idle for about 1/2 hr. shut it off and did the battery cable thing. Had to put gas in the intake to start it again, but got it going. Let it idle about another 45 min, and no help, as soon as I gave it gas, it stalled. (It's extremely hard to get it started without putting some gas into the intake). I found the timing disconnect that Bouda mentioned. When I disconnected it, the car imeadtially stalled. I'm at a loss, maybe it's the computer thats shot and caused the whole problem to begin with? Well at least with all the exploring I did, I found that the spider was bad anyway, which was causing the rough idling for the last 6 mos. I have a mechanic friend with all those cool diagnostic machines that plug in under the dash, I'll give him a call. I'm going to watch the hockey game and drink beer now, sick of this car stuff for today. If you can think of anything I may be overlooking, let me know. Thanks for all the help

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    Re: 94 s-10 4.3 still won't start

    Quote Originally Posted by loid58 View Post
    Trip X, Got it started and let it idle for about 1/2 hr. shut it off and did the battery cable thing. Had to put gas in the intake to start it again, but got it going. Let it idle about another 45 min, and no help, as soon as I gave it gas, it stalled. (It's extremely hard to get it started without putting some gas into the intake). I found the timing disconnect that Bouda mentioned. When I disconnected it, the car imeadtially stalled. I'm at a loss, maybe it's the computer thats shot and caused the whole problem to begin with? Well at least with all the exploring I did, I found that the spider was bad anyway, which was causing the rough idling for the last 6 mos. I have a mechanic friend with all those cool diagnostic machines that plug in under the dash, I'll give him a call. I'm going to watch the hockey game and drink beer now, sick of this car stuff for today. If you can think of anything I may be overlooking, let me know. Thanks for all the help
    Your truck is OBD-I you don't need a computer to hook up to it, a paper clip works just fine and it will flash the codes at you. Don't expect it to tell you much. How to do this is posted about a zillion times on the net, so I'll let you google it.

    I don't know what else to tell you. I'd have the mechanic friend take a look. If it idles ok, but bogs at higher RPM, it's usually a spark timing issue. Do you have a timing light? SOme mechanics these days have all their fancy computers, but don't know how to use a timing light...I'd check that, assuming the truck is cap and rotor style. I had a '93 and it was.

    And it is as simple as air, fuel and spark. You're not getting enough of of one or the other at the right time when you hit the gas. It's rarely an air problem, but how's your air filter?
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    Thumbs down Re: 94 s-10 4.3 still won't start

    It's not the timing, It was timed perfect before all this happened, and I played with the timing and nothing helped so I put it back to where it originally was, ( using a timing light). Air filter is good, and again it's the same with or without the air filter connected.

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    Re: 94 s-10 4.3 still won't start

    I had a '94 S10 4.3L with the cpi. When I rebuilt the engine I had to set the timing of course. I unplugged the wire, set the timing to 0 then plugged the wire back in.
    You have to put it to 0 or when the comp try's to adjust timing it will be way out of whack.
    I don't remember if I had to unplug the wire with the engine on or key on.

    I prolly found my info in the chilton's manual I had at the time.

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