Extended crank time and A/C question

[upper_tanker]

Hey all. I just got a 2000 K2500 454 from my dad with 160k on it. Truck is in great shape. Ever since he's owned it (probably 8+ years now), it takes a long time to start when it's warmed up. If it's cold, it cranks right up. If you let it warm up, turn it off, and try to start it, it probably takes 8-10 seconds of cranking before it starts. It does always start though. I guess I'm really hoping that this is an easy-to-replace sensor, but I'm sure it's not, with my luck. Fuel pump was replaced about 3-4 years ago.


My A/C issue is that air (and heat, for that matter), will blow out of the defrost AND vent if I put it on vent. I know this is a big issue with these trucks, but I'm not sure if it's the blend door or the actuator. Is there a way to tell? All of the modes work fine besides this. If I put the air flow on defrost, it will ONLY blow out of defrost. It's just the "vent" that has an issue. If this is a blend door/actuator, how hard are they to replace? I measure difficult-ness in "tools thrown" usually.

 

[someotherguy]

Problem #1 pretty common symptom on the Vortec 7.4's. Usual suspects - regulator (and vacuum line to it), and injectors. The OEM injectors leak; Five-O Motorsports sells a better set of Bosch units to replace them.

Problem #2 also somewhat common; check the linkages on the vent position actuator, the one towards the far left of the HVAC box, just above the driver side of the transmission hump. Sometimes the sliding pieces of metal get gummed up; you can clean 'em carefully with some shots of WD40 and then spray a little white lithium grease to help them slide. Unfortunately, from 95-up the flaps seem to be more prone to breakage for some reason and they can snap where they pivot in the box, which can be a pain to fix. Check the linkages first. Also the controls aren't the greatest from 95-up and can be the problem as well, especially if the radio has been out and the truck operated that way - the antenna lead often falls down on the unprotected A/C control circuit board and shorts it. FYI that particular actuator rarely goes bad. The one for fresh air/recirculate (far right near the blower motor) is #1 to fail, and the temperature mix actuator in the middle is a distant #2 to fail.

Richard

 

[df2x4]

Unfortunately, from 95-up the flaps seem to be more prone to breakage for some reason and they can snap where they pivot in the box, which can be a pain to fix.

Yup, unfortunately. My red truck has broken one, my Suburban has broken two now. It's still blowing through the defrost vents a little bit at all times because paying my mechanic to pull the dash again hasn't made it to the top of my priority list yet. And I'm kind of halfway looking for a replacement gray dash before that point... In my experience when the blend doors fail they behave in this exact way though.

Pro tip, fold up a towel and lay it over the defrost vent. If/when you need the defrost vent, pull the towel off.

 

[east302]

My A/C issue is that air (and heat, for that matter), will blow out of the defrost AND vent if I put it on vent. I know this is a big issue with these trucks, but I'm not sure if it's the blend door or the actuator. Is there a way to tell? All of the modes work fine besides this. If I put the air flow on defrost, it will ONLY blow out of defrost. It's just the "vent" that has an issue. If this is a blend door/actuator, how hard are they to replace? I measure difficult-ness in "tools thrown" usually.

If the linkages check out and the actuator’s position indicator dial (silver with notch) rotates smoothly, then I’d say you might be seeing normal operation.

For a 98, at least, it is normal for some air to come out of the defrost and side dash circular vents at all times. Here’s a top view picture of the air box out of one. The defrost port damper is on the left, the dash (panel) damper on the right. The floor damper is not shown, but it’s in a housing that attaches at the bottom.

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See the small square opening on the lower left? That connects to the defrost channel in the ductwork. The defrost damper does not extend to it, so a small amount of air is always going to go through it and out the defrost. Here’s a view from the bottom.

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You can get air leakage if the rubber edge of the defrost damper is damaged, but even then you may not notice the increase in air flow.

To me, it’s a dumb design considering that I want to eek out as many CFMs from the panel vents as humanly possible.

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On my two 98s, it was the floor damper that went bad, causing air to leak through the floor vents when the panel was selected. If you’re seeing that, you can pop the center floor vent and see if the thin rubber perimeter seal is torn off.

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Edge seal is torn, air will leak out onto the floor.

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Compare to new damper:

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[df2x4]

@east302 Thanks for the pictures and the explanation. I had no idea about that little opening that always feeds the defrost vents. I'll have to compare my '97s now to see if the Suburban is actually pushing much more air to the defrost vents than my red truck is.

I wonder if there would be any negative effects from blocking that small opening in the box? I agree that it seems like a poor design choice.

 

[east302]

I doubt it would hurt since air would go to the defrost when the damper was opened. A quick check would be to cover up the defrost vents and see if it made a difference.

 

[upper_tanker]

Thank you all for your replies. Busy day at work yesterday and I didn't have time to respond.

Just a few more questions of course... haha

1. For the starting issue, I'm guessing I should start with the FP regulator and inspect the vacuum hoses first as the easy fix? regulator is only 65ish on RockAuto for a Delco one. I'm sure this isn't the issue, as my issues usually never have an easy fix LOL. As far as the injectors, I'm going to save that website. I'd eventually like to get the injectors, as I plan on rebuilding this motor down the road when I get time.

2. If I DON'T get this fixed, what's the worst that will happen? Will I just start to get a misfire, surging, etc? Will it just suddenly not run? I will probably only put 2-3k miles/year on this thing. I'd like to get the body work done first on it before it gets too bad, but engine is next after that.

3. For the air flow thing.. I'll check the linkages first. If these are good, and I understood df2x4 right... the dash has to come out for this blend door replacement? If so, I guess this is something that I could live with. lol

 

[someotherguy]

Depends on what you consider "easy" - the regulator and its vacuum line are at the rear of the fuel rail. The fuel rail is buried under the upper intake, so the regulator is pretty much inaccessible with the upper intake in place. This shot probably is the best example I have; you can see the new regulator (gold cad-plated color) peeking out near the distributor rotor. Now take a look at your engine, assembled, and see if you can imagine getting the snap ring out so you can remove the regulator with the intake in the way. At best, *maybe* you can replace the vacuum line if you work with a mirror and patience? I dunno.

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Worst that can happen if you just leave it be? Annoyance with it not wanting to start.. poor fuel mileage, crummy driveability. This pic of the lower intake should give you an idea of just how badly the stock injectors were handling fuel delivery..

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Richard

 

[upper_tanker]

Depends on what you consider "easy" - the regulator and its vacuum line are at the rear of the fuel rail. The fuel rail is buried under the upper intake, so the regulator is pretty much inaccessible with the upper intake in place. This shot probably is the best example I have; you can see the new regulator (gold cad-plated color) peeking out near the distributor rotor. Now take a look at your engine, assembled, and see if you can imagine getting the snap ring out so you can remove the regulator with the intake in the way. At best, *maybe* you can replace the vacuum line if you work with a mirror and patience? I dunno.

You must be registered for see images attach

Worst that can happen if you just leave it be? Annoyance with it not wanting to start.. poor fuel mileage, crummy driveability. This pic of the lower intake should give you an idea of just how badly the stock injectors were handling fuel delivery..

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Richard

Thanks for your pics and info. I guess you're right, not easy by any means. I guess I'd be better off just trying to wait until I rebuild the motor to do all of this instead of having to touch it twice. Other than the hard warm start, the truck runs great, has tons of power, and doesn't act up. I'm guess I'm in the beginning stages of these injector issues. Hopefully the hard start is the only thing that I have to deal with until I get it fixed.

 

[df2x4]

3. For the air flow thing.. I'll check the linkages first. If these are good, and I understood df2x4 right... the dash has to come out for this blend door replacement? If so, I guess this is something that I could live with. lol

If it is the blend door then yes, dash has to be pulled.