99 vortec 454 random hard start

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Bowtie89

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Hey all ive read a bunch on forums and found some info but not a situation quite like mine. I've got a 99 k2500 pickup with the 454. It has a random hard start issue. Sometimes it will crank for a second then backfire through the intake and stall the starter out. Try cranking on it again and it will take 5 to 10 seconds to get it to fire then it will run like it dropped a cylinder for 15 to 60 seconds then it runs fine. It only does this after its been sitting for a long period of time (in the morning, after work). It only does it occasionally, every other day or every couple days. Only once in the morning. All the other times it starts in half a second and runs fine. I replaced plugs, wires, cap, rotor, distributor, upper and lower intake manifold gaskets, fuel pressure regulator, fuel pump, MAP sensor, and ECT sensor about 6k miles ago. Just did the crank sensor. I was wondering if the fuel injectors were leaking if it would cause it to backfire and lock up the starter?
 

Christian Steffen

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Sounds like it's try to fire too soon, indicating a timing issue. But you replaced the main components of the ignition.

Have you checked what your cam position is at? I know that should throw a code but it would be nice to know it's not an issue. strange it only happens after sitting for awhile.
 

Bowtie89

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Sounds like it's try to fire too soon, indicating a timing issue. But you replaced the main components of the ignition.

Have you checked what your cam position is at? I know that should throw a code but it would be nice to know it's not an issue. strange it only happens after sitting for awhile.
As in checking the rotor or the valves? My next step is to check the cap and rotor and see if they are cracked or something. Yeah its strange that it does it after sitting for a while. Also that its intermittent, some days it won't do it at all. It has the leaky injector symptoms, takes 5 seconds of cranking after its been driven and sits for 20+ minutes. Its done that for a while, its a shame I didnt have the cash to do the injectors when I did the gaskets.
 

454cid

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It has the leaky injector symptoms, takes 5 seconds of cranking after its been driven and sits for 20+ minutes. Its done that for a while, its a shame I didnt have the cash to do the injectors when I did the gaskets.

So the intake gasket leaking was what prompted the work 6000 miles ago?

I thought my injectors were getting really bad, but since I recently put in a new fuel pump it starts a lot better. What did you put in for a new pump? I've heard that sometimes they check valves don't work, or go bad, so even if the injectors aren't leaking, the gas still drains out the other end.

If you do take the cap off, you might as well pull the ICM too, and take it to Autozone to get tested. The backfiring kind of reminds me of what my engine will do when it's gone bad (shakes and kind of coughs).... although mine won't start until I put a new ICM in.
 

Bowtie89

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So the intake gasket leaking was what prompted the work 6000 miles ago?

I thought my injectors were getting really bad, but since I recently put in a new fuel pump it starts a lot better. What did you put in for a new pump? I've heard that sometimes they check valves don't work, or go bad, so even if the injectors aren't leaking, the gas still drains out the other end.

If you do take the cap off, you might as well pull the ICM too, and take it to Autozone to get tested. The backfiring kind of reminds me of what my engine will do when it's gone bad (shakes and kind of coughs).... although mine won't start until I put a new ICM in.
Yeah the lower intake gasket was leaking coolant horribly so I did both gaskets, o rings, and the FPR since I had it apart. The fuel pump a reputable shop did, it was low on fuel pressure. Not sure what brand. Everything else I did. The cap rotor plugs and wires I did because mine were mud soaked and baked and had about 50k on them so I figured I would do it all at once. I put my fuel pressure guage on it today but I think my bleeder block thing is no good.. I could get a reading with just the gauge on it but I'm not sure if its accurate without bleeding the air out of the line. Couldn't get it to read anything with the bleeder connected. Quality performance tool part... I didn't know they could test the ICM.
 

454cid

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...I put my fuel pressure guage on it today but I think my bleeder block thing is no good.. I could get a reading with just the gauge on it but I'm not sure if its accurate without bleeding the air out of the line. Couldn't get it to read anything with the bleeder connected. Quality performance tool part... I didn't know they could test the ICM.

I don't have a bleeder or pressure release on mine. I don;t think it matters, except for convenience. Mine is from Harbor Freight. I just pull the fuel pump relay while the engine is running to relieve most of the pressure... it dies at about 10 lbs.

Yes, both Autozone and Orielly have machines that will do it. My local Orielly doesn't have a plug for it so we had to use alligator clips to connect it. Autozone could just plug it in. I don't know if Advance can do it, but they probably can. They are the biggest US parts store chain.
 

Bowtie89

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I don't have a bleeder or pressure release on mine. I don;t think it matters, except for convenience. Mine is from Harbor Freight. I just pull the fuel pump relay while the engine is running to relieve most of the pressure... it dies at about 10 lbs.

Yes, both Autozone and Orielly have machines that will do it. My local Orielly doesn't have a plug for it so we had to use alligator clips to connect it. Autozone could just plug it in. I don't know if Advance can do it, but they probably can. They are the biggest US parts store chain.
Hmm ill check the pressure again tomorrow without the bleeder. Ill try having the ICM checked. Could fuel leaking into the intake cause it to backfire and stall the starter out?
 
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