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2014 Chevy Silverado
Platform: Truck, GMT 400, 800, & 900

Misfire and hard start.

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Old January 17th, 2011, 10:16 PM
  #21  
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I m sorry bro, you re losing me. I was a Ford guy, so SFI and CFI are terms I know. What is CSPI? This car has 2 injectors right? In the Carburetor? So it is CFI or TBI? MPFI was a GM term, Ford called it SFI(Sequential Fuel Injection). But that means an injector over every cylinder right in the intake manifold. What is CSPI? To us Ford guys, a spider only generally describes the lower intake manifold(the one with the 8 runners, hence "spider"). So how many injectors do you have?

I m not familiar with fuel injector jets clogging. They tend to leak over time, but I suppose they could clog or the fuel spray pattern could change.

And dont be fooled, many people "lose interest" in a car when they take something apart and cant figure out how to put it back together again. Some head bolts are located right in the middle of the valvetrain.

If the valve is seized shut, then you may have to use some Marvel Mystery Oil or Rust penetrant to soak through and hopefully free it up. Another thing to think about Goatie is that the Valve spring may have collaped, broken, jammed or just came undone.

The thing is that if the rocker arm isnt pushing the valve open then how are you getting fuel in that cylinder? And a situation like that will always keep the plug clean because its not burning nothing. And your compression ratio wont fail because the cylinder is taut.

We wont know until we look, let us know...
Old January 17th, 2011, 10:49 PM
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Originally Posted by RacerX
I m sorry bro, you re losing me. I was a Ford guy, so SFI and CFI are terms I know. What is CSPI? This car has 2 injectors right? In the Carburetor? So it is CFI or TBI? MPFI was a GM term, Ford called it SFI(Sequential Fuel Injection). But that means an injector over every cylinder right in the intake manifold. What is CSPI? To us Ford guys, a spider only generally describes the lower intake manifold(the one with the 8 runners, hence "spider"). So how many injectors do you have?

I m not familiar with fuel injector jets clogging. They tend to leak over time, but I suppose they could clog or the fuel spray pattern could change.

And dont be fooled, many people "lose interest" in a car when they take something apart and cant figure out how to put it back together again. Some head bolts are located right in the middle of the valvetrain.

If the valve is seized shut, then you may have to use some Marvel Mystery Oil or Rust penetrant to soak through and hopefully free it up. Another thing to think about Goatie is that the Valve spring may have collaped, broken, jammed or just came undone.

The thing is that if the rocker arm isnt pushing the valve open then how are you getting fuel in that cylinder? And a situation like that will always keep the plug clean because its not burning nothing. And your compression ratio wont fail because the cylinder is taut.

We wont know until we look, let us know...
CSPI is Central Sesquential Port Injection. There is a fuel injection 'spider' inside of the intake manifold. There is a main 'body' to the spider, which houses the 6 injectors, then there is 6 'legs' that connect the injectors to the poppets. The poppets are plugged into the manifold, 1 above each cylinder.

Very poor work with MS Paint, but maybe that will clear it up for ya. And it's not really the injectors that gum up, it's the poppets. There is a tiny ball in the tips of them that holds/releases the fuel, and dirty gas will cause them to hang in place, holding the fuel in. And I stupidly tried starting the engine, (quite a few times) with 6 year old gas in the tank. Eventually I caught on and pulled the tank to dump the fuel, but the damage was already done... or this is my theory anyway.

But yes, I will definitely look inside the valve covers. Just wondering how I will be able to see the valves move without a massive teardown? That is of course if I don't see something else out of place first...
Or will a siezed valve cause one of the rockers to not move?
Old January 18th, 2011, 7:34 AM
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When you take off the covers start the engine and you will see the rockers moving. If they all move look close at the studs (what the rocker arms are bolted to) if one is pulled it will be sticking up higher than the rest. If a valve was stuck and you ran the motor it would have either pulled a stud, bent a push rod, or flatten the lobe on the cam.
Old January 18th, 2011, 11:56 AM
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Originally Posted by wmiller1337
CSPI is Central Sesquential Port Injection. There is a fuel injection 'spider' inside of the intake manifold. There is a main 'body' to the spider, which houses the 6 injectors, then there is 6 'legs' that connect the injectors to the poppets. The poppets are plugged into the manifold, 1 above each cylinder.

Very poor work with MS Paint, but maybe that will clear it up for ya. And it's not really the injectors that gum up, it's the poppets. There is a tiny ball in the tips of them that holds/releases the fuel, and dirty gas will cause them to hang in place, holding the fuel in. And I stupidly tried starting the engine, (quite a few times) with 6 year old gas in the tank. Eventually I caught on and pulled the tank to dump the fuel, but the damage was already done... or this is my theory anyway.

But yes, I will definitely look inside the valve covers. Just wondering how I will be able to see the valves move without a massive teardown? That is of course if I don't see something else out of place first...
Or will a siezed valve cause one of the rockers to not move?
That was some freaky shhhhht bro, you showed me something new. Crazzzy! So are you getting fuel coming out of position #2?

If the valve doesnt move, it wont move. Nothing hard to see about it. Look at the other valves, they are moving, this one isnt. You just have to find out WHY it isnt moving. If that is your problem.

you can still use old fuel if it is in the tank, just have to add fresh fuel to it to reconstitute it. Of course you have to make sure you have gasoline in there and not water or diesel.
Old January 22nd, 2011, 5:12 PM
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It was the spider. Half the poppets were icky, and #2 was over half gummed over. Replaced it and it's running great.
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