She won't fire up. Please help me! I"m at a complete loss!

[BR3W CITY]

Dude here is a WICKEDLY awesome thread on the wiring on some of the LAN stuff. Its a long thread and jumps around between the model years, but it may contain some of the stuff you'll need to start straightening it out.

http://www.performancetrucks.net/for...-494579/page4/

[Hart_Rod]

Looks like you are getting closer.

[jorgensensc]

Thanks guys! And thank you for the links! This goes to show that the #1 rule of doing an LS swap should be........Get it all from the same vehicle!!!

[68GMCCustom]

If you're going to have to run a '11 ecm then I would sure have them(someone) check to see if there are differences in the '08 vs '11 wiring.

my harness was built on '09 specs only to find out my '07 ecm wanted things plugged in a little differently, which meant pin out changes. just saying ....now that you've corrected things to this point... don't be surprised if your in for more pin changes with the '11 ecm swap.

[jorgensensc]

Thank you for that input. I just got off the phone with Jon from PSI. Really nice guy and he is making things right for me. Him and I discussed the pin out issues and he is going to verify those pin outs for me.

[68GMCCustom]

good to hear

[jorgensensc]

Hey guys. So I've gotten a little progress. I can drive it now, though I've only got one gear. Pretty sure I'm in limp mode due to the TCM and ECM not communicating correctly. The tranny not going into gear was my fault. I didn't have enough tranny fluid in it. I've also got a nasty vacuum leak that is causing a squeeling chirp. Very limited power brakes. Sometimes none at all. I'm guessing it's the brake booster, but when I pull the hose from the engine to the booster after turning the engine off I get a very good whoosh like the booster is retaining vacuum. Never had a problem before the swap. I've sprayed carb cleaner and starter fluid every where, but can't get it to idle up. Although in park and neutral it is at like 1400 rpm. Drops to 700 rpms in drive and reverse. Guess I need to hunt down this leak!
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[68GMCCustom]

thought I had a vacuum leak on mine. was fine when carb'd....but after efi upgrade the power brakes didn't work right. after lots of looking and parts swapping.... it turned out to be in the tune.

[jorgensensc]

Hmmmm. Was their a crazy squeeking noise with it. I've got a pig squeel that is minimal at idle, but gets crazy loud as driving. Really loud when I push the gas from a stop, even before moving. I almost thought it was a wheel bearing at first. Or a pulley. If has a cyclical sound , kinda like a wheel bearing or pulley would.
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[BR3W CITY]

cracked intake manifold?

[jorgensensc]

Gosh I hope not! That's the last thing I need at this point. The original intake manifold was broken, so they had to get me a new one. That would suck if that happened again!
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[BR3W CITY]

I've seen so many cracked plastic intakes on those older 3100's all the time, and they would develop strange vacuum leaks. A fracture in the poly might not actually leak until the manifold pulls enough vacuum to suck past the crack.

[68GMCCustom]

how much vacuum does it have at idle?
I've heard that a good tuner can see a motor has a vacuum leak by the fuel trims, or some other way...not sure how. my tuner was surprised when I told him I was chasing a vacuum leak...saying he hadn't seen indications. Sure enough after replacing the intake with a brand new one w/new gaskets, swapping TB's with the one of the LS2 in my TBSS, and I forget what else...I came to the conclusion my low vacuum was in the tune. Told my tuner and he said he could help some, gave it another inch or two...but still not where it was with the carb. Then another tuner tells me my motor will never make as much vacuum efi as it did carb'd. I ws like.......huh?

[Custom 68]

Originally Posted by jorgensensc

Hmmmm. Was their a crazy squeeking noise with it. I've got a pig squeel that is minimal at idle, but gets crazy loud as driving. Really loud when I push the gas from a stop, even before moving. I almost thought it was a wheel bearing at first. Or a pulley. If has a cyclical sound , kinda like a wheel bearing or pulley would.
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If it gets really loud when you push the gas I don't think it will be vacuum leak as it should not have vacuum at that point. I would look more for your belts or pulley. Your brake thing is odd that does sound like a vacuum problem.
Good luck
Dave

[jorgensensc]

I think you are right. I was looking up the infamous GM belt squeel and it sounds dead on for what it probably is. I didn't hear the squeel initially on start ups before going to the exhaust shop. But of coarse I had open exhaust. When I got to the exhaust shop and turned the truck off I spewed radiator fluid everywhere (I forgot to tighten the a heater hose ). I cleaned it up pretty good, but I'm thinking that the radiator fluid is still on some things. I sprayed belt dressing aon the hose and it made it 10 times worse. I then sprayed some carb cleaner on it and it stopped while I was spraying it on the belt. As soon as I stopped spraying it the squeel came back. I'm going to take the belt off and clean it and the pulleys really well.
As for the crappy brakes all of the sudden and the high idle, I don't know. I'll have them check the tune when I get the new computer.
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[Hart_Rod]

Unplug the booster and cap it. See if that makes a difference. Maybe your computer and engine had hydro boost???
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[jorgensensc]

Good point. I'll try that. The hose was on the both manifolds when I got them. But I will check. I did pull the hose before with it running and put my thumb over it and there was no difference, but I don't know if the computer would let it fix that quickly.
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[BR3W CITY]

Originally Posted by Hart_Rod

Unplug the booster and cap it. See if that makes a difference. Maybe your computer and engine had hydro boost???
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Does this matter? I switched to hydroboost but never changed anything in the computer?

[Hart_Rod]

Originally Posted by BR3W CITY

Does this matter? I switched to hydroboost but never changed anything in the computer?

I'm not sure. I'm was trying to eliminate a bad booster, plus I've heard of crazier things happening with computers,
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[rcrahn]

Very interested in seeing what this turns out to be. Keep plugging away....

[truckdude239]

If you used belt dressing on a serpentine belt the belt is doneand need to be replaced that stuff sucks and is a pain to get off the pullies
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[jorgensensc]

Ok guys small update. Still waiting on new ECM to get here. But, figured a few things out.
The squeel is definitely the belt. I sprayed it and the pulleys down really good with carb cleaner, then tightened the belt more (manual tensioner). Almost got the squeek to go away, but I need to get a little smaller belt as I'm about to hit the other side of the belt running above the tensioner. So one problem mostly solved.
The brake thing was my mistake. I didn't realize it but when I was pushing down on the brake pedal it was hitting the accelerator pedal bracket I fabbed up. Just on the edge. So it felt like I was bottomed out, but wasn't stopping. I made the adjustment and now they work great!
Added a 120 ohm resistor on the datalink wires right before the datalink connector, per the information in one of the links provided
Then rechecked the tranny. Found a major issue that I didn't realize was happening. The connector wasn't actually plugging in to the tranny! The connector is round with a thumb turn lock ring that cinches the plug into the tranny. The plug was going into the hole and the lock ring was cinching down, so I thought it was plugged in. But it was turning the plug as it locked down. I thought that was very odd. I couldn't figure out how that could work. So I messed with the connector a bit and the lock ring popped off. I lined up the correct pins with the plug and connector and shoved them in. Suddenly I had datalink communication!! Turns out the lock ring had slid down on the connector and wasn't pushing it in deep enough into the hole to engage the pins. So I fixed the lock ring and plugged it in properly! Now my tranny temp gauge registers also! Somehow this cured my idle problem too. Now she idles perfect! Very well mannered.
So now (oddly enough) I have first gear and no other forward gears. I jave reverse and nuetral and park. Before when it wasn't plugged in correctly I had 3rd gear and no other forward gears. But now I can't get out of first. My understanding is that is because the computer tells it when to shift and that info is not being delivered to the TCM because of the incompatibility of the engine ECM and tranny TCM.
I can't wait to get the new computer. Just in first alone the throttle response off the line is a beast! Can't wait to see what it will do when I get more gears!
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[oldman3]

Been following this since you first started, glad you have most everything corrected...Jim

[rcrahn]

Wow! that's some great troubleshooting....I have that same connector on my 4L80E....and will be very watchful when I connect it now.... thanks for covering that..

[Custom 68]

recheck your tranny fluid.
That is great news you found all those little issues.
I didn't mention this earlier because I dont know much about these new new engines but my gen 3 had a 4l60E however I bought an aftermarket harness and it had provisions for both a 60 and an 80 tranny well I grabbed the wrong plug in my excitement and hooked up part of the 80 harness to my 60 and I only had one gear I believe first. I know the 4l80 tranny has an input and an output where the 4l60 only has an output or something like that (it has been a while since I set mine up) Anyway after getting all the right plugs things worked like a champ. That said double check all your wiring to your tranny.