locke577

Hey guys. I'm right now finishing up my Berlinetta LT1 swap.

I've just got a couple problems, some big some small.


Big problem #1: It won't start. I've got it cranking, and there's fuel going to the rails, but the injectors aren't sparking, and neither are the spark plug wires. I'm using an engine-only harness from a '96, and a pcm from a '97. I did not have the pcm reprogrammed, so if vats is an issue, then I need to address it. I also have a 93 harness and pcm I can put on instead, or one from a 95 caprice, but the 95 would still use the 97's pcm.

Big problem #2: I'm having a lot of trouble with the original harness, and I'm confused about a few things about mating it to the new one.


Here's what I want to know:


What should I troubleshoot for the engine starting?

Do I need to have the pcm flashed, and if so, where can I have that done quickly and soon?

What can be removed from the old harness? (2.8 LC1 V6 carb)

What do the wires from the old harness that go under the passenger side fender go to? How do I get to them? Will I have to remove my fender?




Thanks, guys.

keeslinger31

Vats is the issue. You must get it programmed out of the pcm. I used pcmforless. As for wiring there is a few threads around about what to splice in.

locke577

Did you notice any gains with PCMforless? Also, what's the process I have to go through when dealing with them?

keeslinger31

Well I could never know because I had to get vats tuned out for it to start so I had them add all my other mods. But I recently did a cam and ported my heads and I can say the car wouldn't even stay running until I had them send me another pcm tuned for it.
Easy to deal with just get ahold of bryan at pcmforless.com You can either send yours in and they tune it or send the money for a core and they will ship it out which is probably faster, Just fill out an ordersheet and send them paypal. They are usually quick with emails so you can go that route before deciding. Iv'e heard good things about madz28's tuning also. But no personal experience.
Btw the wiring for these is a bit tricky once your started best way is to do one wire at a time and don't just cut the bulkhead off then you'll have trouble finding out what is what trust me.
I think there are ways to trick the pcm into thinking its there like finding a key with the right amount of resistance and wiring it up for it but I didn't want to go through all that bs.

locke577

Also, I know this might be a hugely stupid question, but how will the car know the new engine is running alright, so the check engine light goes away?

And where do I run the bloody ALDL? I'd like to do OBDII so I can check what's wrong, if anything, but I'll run OBDI if I have to.

locke577

Alright, now how about the passenger side fender wires?

There's a huge chunk of them that go down under that fender to what looks like the old computer and light module (I've got a berlinetta, so it's got this huge light module that might as well be it's own computer for those who don't know.


How do I remove that so I can do a proper splice job of the two harnesses?

vetteoz

iTrader: (13)

https://www.thirdgen.org/forums/ltx-...rt-finish.html

vetteoz

iTrader: (13)

Self diagnosis
If the engine is running " right" , you wont have any codes so no SES.
On the other hand ........

You don't have a choice; if using 96/97 ECM you have OBDII and all the problems that come with it
Most swap to the OBDI 94/95 ECM for easy of install or modify the OBDII ECM to run OBDI

keeslinger31

check this one out too
https://www.thirdgen.org/forums/ltx-...g-dummies.html

I did obd-2 and it works fine. I did however take out my bulb because I have a few remaining codes that are always there, and now the code for no bulb. lol

locke577

Perhaps I'm not being clear. I'm using a standalone engine harness that doesn't attach to the body at all.

The only wires I know I need to hook up to the bulkhead C100 connector are speedo, tach, oil, coolant, ignition, and lights.

What I'm asking is how does the dash know the engine is working? What lets it know?

keeslinger31

A wire from the pcm to the dash light

locke577

Ah, thank you.

vetteoz

iTrader: (13)

Dash is run by all the original wiring that went to the engine sensors in old engine
Your standalone harness has no connection to the factory dash wiring except for the tacho signal
Your new harness should have provision for the SES light which you would connect to the old light in dash and the ALDL plug.

locke577

I'm splicing right now.

When I pulled the harness, I had trouble getting the oil level sensor plug out, so I yanked on it. The wires came out. What I need to know is looking at the top of the plug, which wire goes in the left side and which goes in the right? Options are brown and black with white stripe.

Thanks, guys.

locke577

Nevermind. Black on right, brown on left.

locke577

I just picked up lt1 corvette accessories and brackets because I decided I really want A/C.

Will all my plugs fit after a little bit of relocation, or do they have different plugs?

Also, the guy I bought it all from threw in a new MSD Blaster ignition coil for 10$. It was a 93 lt1 corvette and had the old style computer. Will the new coil work or should I craigslist it?

keeslinger31

Plugs? Spark plugs?
On the coil it depends on the connector atop of the coil if its the two plug it wont work the 95? and up have a single plugin. There may be a way to adapt it but iv'e heard of some msd parts like coils and the 6al setup melting opti caps because of the added spark heat. not 100% though.

locke577

I meant the wiring harness connection plugs. They all worked like a charm.

And as far as the coil goes, I've got an msd ignition coil. It has the gray and black plugs that connect to each other. Three connections in total, two on the black, and one on the gray.


Which brings us to a problem. I'm getting zero spark. I checked the plugs, and they're not getting a connection either. I believe I've got everything plugged in properly and the harness grounds are grounded.

The engine has never been started since the swap, and the computer just got back from pcmforless today.

Any ideas on what I should do to troubleshoot?

locke577

I should probably also mention that I don't have any of the "C___" plugs plunged in.

locke577

Which I just realized is half of my problem.

I was really wanting to avoid doing a proper mating job, but I guess that's what I'm going to have to do tomorrow.

Can anybody tell me how to remove the whole third gen harness? I can get the C100 off no problem, but I'm really confused about the wires that go under the passenger side fender. What do I have to do to get those out?

locke577

http://www.youtube.com/watch?v=F8z1umJ_2hA

There's a video of me attempting to start, pre-epiphany about the C___ plugs.

locke577

Hey guys. Having a lot of trouble here, and I've searched the boards already, and can't find it.


I don't know how to remove that bit of the third gen harness that goes under the passenger side fender. How do I get that out so I can start prepping my harness for mating with the lt1 harness?

John in RI

iTrader: (167)

You will need to remove a couple of the plastic push pins that hold the plastic fender liner in place so you can access the harness.

Behind the pass side kick panel there's a body hole that the ECM harness runs thru. Unplug the original ECM, remove the large plasitc "C" clip from the top of the wire pack at the body hole, push the tab at the top of the wire pack then push the whole pack thru the hole, pull harness into pass fender well, & then pull harness from the fender well into engine bay.

The wire pack WILL fit thru the gap in the side of the engine bay,..... it just needs to be positioned correctly in order to fit thru !

P.S. I'm not SURE - but If the PCM still has VATS 'enabled' - I don't think you will ever get spark.

locke577

Hey John. I actually just had it reprogrammed by PCMforLess, and they removed VATS.

I think my problem actually comes from my PCM not getting power.

I thought that it got power from the big purple wire in the same loom as the RH O2 and knock sensor on the LT1 harness, but I'm now thinking that it gets power from the C210 plug's orange wire (C). Can anybody tell me if this is correct or not?

locke577

Right now, this is what I think I need to do for wiring.


LT1 C100 Plug:
A to C207 B (injector fuse)
B A/C relay
C A/C Compressor Clutch
D unused
E unused
F unused
G IGN +12v
H not using because I'm using manual fan switch
J ^^^^^same^^^^^^^^^same^^^^^^^^
K unused

C105
A unused
B Power feed from engine sensors
C unused
D unused
E Serial Data, which I'm pretty sure goes to one of the ALDL wires?
F unused
G unused
H unused


C210
A to Starter Solenoid
B Ground
C Power to PCM
D Feed from fuel pump and fuel pump relay to prime connector??????? What do I do with this? Can I use it as a positive to my fuel pump?


C220
A Alternator feed to instrument cluster
B Oil pressure feed
C Oil level feed
D unused
E Power feed from injector fuse #13? (What do I need to do with all these injector fuses?
F unused
G VSS signal feed to instrument cluster
H unused
J unused
K Coolant Temperature feed to instrument cluster


C230
A unused
B MIL
C Diagnostic Request - I'm going to run this to C207 wire "E"
D Tachometer signal
E unused
F A/C request - What do I do with this?
G unused
H TCC (C207 Tan/Blk Wire "H")
J Park/Neutral
K unused


If anyone can help correct me if I'm wrong about any of these, or if I need to do anything else, I'd greatly appreciate it.


I have a 97 camaro engine, 96 firebird harness, and the car is an 84 camaro V6 carbureted. Originally had manual fan, so I have no fan relays.


Thanks, guys.

locke577

Alright, so, yesterday and the day before, I went ahead and started doing my LT1 harness according to Pocket's guide.


It still won't start up, but I'm thinking that might be something to do with the power distribution, since now my dash isn't lighting up. Hopefully, I didn't blow it. If I did, I'm going to be one unhappy camper.

locke577

Honestly considering just carbureting it at this point.

WhiteBlaze

iTrader: (1)

Check all of your grounds.

locke577

What I'm actually going to do, since I have it already, is I'm going to take one of my other lt1 harnesses (I've got about five, give or take), and do the process over again with it.


I regret cutting certain commons the first time round. This time, I'm going to leave them intact. If I can get it to start up using this harness, then I'll take the other one, de-loom it, and wire for wire copy it as the new one is. After that, I'll sell one of them as a pre-made harness ready for mating to a third gen.


Sound like a good plan?

WhiteBlaze

iTrader: (1)

I actually cut out the commons AFTER I got it running and wanted to clean it up a bit. Its a lot of work, but you'll probably have a better outcome. Its a shame you're not closer, I'd give you a hand with it.

locke577

Mate, poconos, PA is a daytrip for me. If you could help me out, I'd pay you for your time. Just tell me what you'd need me to bring.

89rs454

Let's see here, your not getting power to the pcm is that correct? I can't get to technical right now but follow the diagrams for your model and splice into the red,pink and purple wires and you should have power to the pcm, and spark. 12v switched to the fuel injectors and she should fire right up.

I got your private message today sorry for no reply for so long, i have been very busy away for 2 weeks, and today i'm relaxed drinking a few beers. Tomorrow i will give you wire for wire and have your car patched up in no time.

89rs454

This is for an 89Rs and a 95 lt1 but you will get the point.
c100
PIN A-Power feed from injector fuse 9 going to a switched 12v source
PIN G-Power feed from ignition fuse 11 to a switched 12v source
PIN K-Power feed from injector fuse 10 to a switched 12v source

c105
Power feed from Fuse #10
(injectors 1995/eng sensor 96-97)

c210
PIN A-Starter 12v source to B4 C100 Starter wire(purple)


C220
PIN J-Fuel Pump Relay Control to G4 of c100 Fuel Control gray wire


C230
PIN G-Power feed from ecm ign fuse 5 to switched 12v



http://shbox.com/1/harness_connector_faces.htm

At the bottom of the page you can click on the c100, c105 ect and match it right up.

http://shbox.com/1/harness.htm

Here is 1995 harness and plugs.

locke577

What does a 12v switched power source mean? What's the difference between that, and a regular 12v power source?

WhiteBlaze

iTrader: (1)

Switched 12 volt means that its supplying 12 volts when the key is turned to start or run.

locke577

Okay. Now there are some brown commons. IIRC, they're on the O2 sensors, and maybe one or two more things. Do they need ground or power?

89rs454

Maybe you should go carb, i gave you everything you need to get it started but unless you can comprehend wiring you have no chance. I don't mean to be harsh but by now a light bulb should go off and you understand everything i told you.

WhiteBlaze

iTrader: (1)

Or look at sending your harness out. Ic emissions is an issue, you can't use a carb.

oramac91

iTrader: (5)

lt1 is the problem.Reason there where only made for a few years .You did not blow your water pump did you? the ing, systems in LT are very funny.Know a guy that replaced 3 before it ran right (where all new too)hope that not the case.

89rs454

The LT1 had a five year lifespan there was plenty made iron head Buick Roadmaster,caprice,Impala SS, Aluminum headed Camaro, and corvette. The optispark was fixed in 1995 with the vented style and there is a way to mod the later versions so don't go spouting off false information . There still a force to be reckoned with.

The LT1 was a prototype for GM to get the LS1 out the door. Notice GM dominated the 90s with the LT1 and went on to dominate with the LS1 against the almighty Ford Mustang.

oramac91

iTrader: (5)

dont get mad lt are junk compared to ls that alll.Lt to many problems that s all.

oramac91

iTrader: (5)

Why would you tell someone to go carb?

locke577

Duplicate post. Sorry. I'm more than a bit drunk tonight, mates.

locke577

I had an option of either going LS1 or going LT1.

I chose LT1 because of the iron block. In my opinion, iron blocks have a throatier exhaust sound, and they're stronger/cheaper to find parts for.


And I've figured out the wiring issue. I just haven't had a chance to work on it. I've had bronchitis. Relax, 89RS454, I've got your info written down and plan to put it to use tomorrow. I'll let you know how it goes. If it won't work, because of something else, I've got an alternate harness pre made ready to go on. I was just hoping to be able to handle it myself, which I believe I will be able to.

oramac91

iTrader: (5)

OO NOOO ls1 is much better and easy to work on.And if your water pump ges up it wont cost you 500$And how hope you get the lt running right.No going back now? gl I hate wireing,Youll get it right.

WhiteBlaze

iTrader: (1)

Where are you getting $500 for a water pump? Is it gold plated? Some of us like our "junk" LT1's, so please, enough with the bashing.

oramac91

iTrader: (5)

When the water kills the ignition.Ok not junk, but not a good disign.That iginiton is just behond me.Friend has a speed shop.Alot more problems with lt than ls.But for the ppl with LT1.there not junk.Sorry for bashing lt1s all

cprmn14

iTrader: (3)

You could get an LTCC coil pack conversionthat eliminates the opti. And its just as much as a new GM opti and only requires minor wiring modification. Poor spot for the opti, yes. Poorly designed motor, id say not.

locke577

Give me the LT1 for the sound any day of the week.

http://www.youtube.com/watch?v=TOlZwxap6MM

WhiteBlaze

iTrader: (1)

You can even use the LS1 PCM to run it if you want. Then there is no opti to worry about at all.