Hello. Let me preface this by saying I’ve done lots of research in terms of ground wires, +12V supply, harnesses and I just can’t put my finger on what’s missing. I’ve googled and searched this board up and down and now I turn to you folks for some help. I’ve searched “no crank LS swap” and cant find anyone with my same situation.

Bottom line: Everything is hooked up and I got no power or life in car. What am I missing?

Car: Originally a 1987 TPI 5.0

Parts: LS 5.3 out of an Envoy, LS6 intake, “LS1 Accessory Drive”, 4L60E.

PCM and harness: Are 4th gen F Body. Pocket built me a beautiful harness to mate the stock LS1 F body harness to plug into the 1987 bulkhead C100.

Power and Grounds: New 4th gen battery power cable: Running to Pos + side of battery to starter and alternator. Also a line to a fusible link (4th gen style) that powers the cluster of red power wires coming off of Pockets harness. Neg – side of batter goes to chassis and a line to the passenger side head. Also from head is a 4 ga. line to the strut tower bolt. On the driverside head, I got a small cluster of small ground wires coming off of the main LS1 harness and also ran a line 4 ga to the drivers side strut tower. I tested this grounding points and they are solid.

I see no clear ground wires missing. Nothing obvious standing out. Everything is plugged in from what I can see. Now there are incomplete systems like the MAF and intake bellow is off the car, the O2s are not plumbed into the exhaust, the steam line isn’t plummed either but I should be at least getting some power in the cabin and at least be able to crank the car, hear a fuel pump hum or something?

I ran a jumper to the starter solenoid and the starter cranks over. So that’s good.

Any thoughts would be great. Thanks in advance…

 

Do you have power inside the car?

 

No power inside the car. It’s as if the battery isn’t hooked up.

I just found a thread about a TPI Motor swap where this guy forgot to hook up a few +12 wires back to the starter. He hooked up only the feed from the battery. Sounded like a TPI to TPI install. These wires power the C100 the guy said.

Now I have no original TPI harness left in car, but that makes me think. While I was down there I’m not certain if I have wires that need to feed off the starter +12 wire. I got a line coming from the battery to the starter and that’s it. I got a group of wires that drop down from the “LS1 Harness” and in that are the crank position sensor wire (if I recall) but not sure what else. I need to go back and see if there is any additional wires that feed off the power from the starter.

 

All power for the original fuse box is supplied by two red 12 gauge wires that go thru C100 connector. Find those two wires somewhere in the engine bay and you probably found your problem.

 

I “thought” that in Pockets harness, those wires are plumbed in. In his harness he has about 4 or 5 smaller gauge wires that have the fish eyes that are labeled “power source/disb block”, which I have plumbed into a block right off the battery. His harness goes inside the cabin and integrates the C100 and into the stock LS1 harness.

There are no obvious wires sticking out anywhere – but it makes sense what you describe. I just figured those wires are what we are talking about AND they are getting power.

I’ll attach a picture.

 

Sounds like the C100 is not pinned properly so those fusable links are not actually powering anything inside the car

 

Probably time to disconnect battery and start ringing out some circuits to see what is what. The link below will take you to post #187 of my build thread where I show C100 pinouts for 1988 Firebird (from GM shop manual). It's not a 1987 but it is the closest I have found.

https://www.thirdgen.org/forums/ltx-...ml#post5825637

 

Damn. Sounds like I got a little bit of work to do. Thanks for pointing me in the right direction.

I found this specific to 1987, so that will help.

http://berlinetta.info/media/shopman...Firebird87.jpg

Thanks for the great help. I’ll report back with any new developments.

 

You may have found the issue right there.

 

Youre sure the c100 plug is fully seated and screwed down ?

 

Ok, I don't know who you are 88Greg from Canada, but that's what it was! OMG. That was the first thing I checked out when I got home. I owe you a big thanks!

Now I remember when we got all the harnesses loosely installed, I think we only put the screw finger tight. Fast forward to actually buttonin' up everything else I may have over looked that. Tighten it up and sure enough lots of hums and clicks as the car came back online. What a feeling.

So great to see the car show some life after about 5 years. Interior lights, dash lights, headlights, car will crank with the key now. Man I miss that "ding / chime" sound.

On to the next obstacle. This thread is now solved/closed.

So it will now crank like a dream but didn't start. I'll move onto the checking the fuel pressure, etc. I'll need a tune as I have an stock PCM from a 2000 Camaro. I know the VATS will be an issue.

At least I feel we've accomplished something here getting to this point.

Thanks again for all the help! You all are the best.

 

Nice to see that you are nearing completion!

 

Glad it was something simple

With VATS, the car should fire for 1-2 sec and die. No fire means something else
Check fuel pressure and check for the tach to move while cranking
FP issues are common as well as damaged wires to the crank sensor for 4th gen harnesses. No crank input, no fire ever. The PCM drives the tach based on crank input, so if you see it move, rule it out

 

Regarding fuel:

So now that I got signs of life, I can hear a nice firm click/clunk from the rear of the car when the key is turned on and I’m getting signs that the fuel pump is powered, but I’m afraid the fuel pump may be dead. I have nothing at the fuel rail when I press in the shreider valve. So time to dive into that. Plus car has been sitting for about 5 years. There was little gas in the tank back the car originally went down. Yesterday, I grabbed my gas can and put in two gallons. Still nothing. Lots of clicking an noises front and back but still not firing and no signs of fuel/PSI under hood. Ugh.

With regard to the ignition:

I don’t trust the tachometer needle because I was stupid and messed with them a while back by attempting to swap them out (rice, I know). I have an extra dash/gauge cluster I’m going to swap out. It’s a matching “140 MPH” and is all original untouched and will be an even swap. Perhaps then I’ll have accurate gauge readings.

Wires leading into the CPS look good. Tight around the starter, but look good. Once I get past this fuel issue, I’ll tackle that.

Thanks for all the feedback. I’ll continue trouble shooting and keep everyone posted.

PS. Does anyone in Southern California have a hook up with a tune? A start up tune? I was looking into HP Tuners and all that and wow, its expensive. Ugh.

 

Pull a plug wire off and do the screwdriver spark gap thing, See if it sparks while cranking. That will be a good sign.

 

Can't really screw up replacing the tach needle, it has a stop in the mechanism, so when it is not powered it is in the "park" position, as long as you didn't turn the needle when replacing it, it should be fine.
That being said, the factory gauges aren't necessarily the most accurate to begin with

 

The FP should prime the system when you cycle the key. If you dont hear it hum, then something is up

 

Ahh. Right. Thanks. I have the stock TPI "fuel pump". It sounds like that may or may not work or may not work for long.

I'm at a toss up - I see there has been some success in using a Typhoon/Syclone Fuel Pump in TPI applications. What about in LS1 Swap applications? I'm running the Vette FPR under the hood.


Side note: Pocket -

How can I jump the relay for the fuel pump? My buddy said to do a jumper and try to get confirmation that the fuel pump is working. I’ve got full electrical and seems like I hear clicks and clunks toward back of the car, yet zero PSI at the fuel rail under the hood. I need to test the fuel pump and make sure it’s working. I put a meter on the ecu/fuel pump “fuse” if that’s what its called and its got 12V. Guess I’m just trying to rule things out. I still need to pull a wire and test to see if I got spark.

Honestly, its only about 6 years old but the car has been

Any tips or insight would be great. Thank you!!

Eventually, I'll do a hotwire kit for the fuel pump.

 

A cheap pump that fits the bill would be 96-98 CK1500 5.0/5.7. Externally the same and IIRC, has the same connector too. Its a walbro 190

To jump any relay, first ID which one it is. Wire size/colors going in will decide
12ga red or orn is 12v batt input
12ga tan/wht or gry is 12 to pump
18ga DK grn/wht is PCM enable
18ga blk/wht grd

Take a short length of wire, bend it into a U shape and bridge the two 12ga terminals in the relays socket. With the battery connected and the pump plugged in, the pump will come on if it is functional. If it is dead or disconnected, you wont hear anything

Honestly, if the car has been sitting for 6 years with fuel in the tank, then the pump is likely shot and theres a high chance the gas turned, ruining the tank/sender

 

Slight Update:

Thank you Pocket. I was able to jump the fuel pump relay and I can definitely hear a "thump" in the back of the car when I tap the jumper in/out. However, I heard a nice his when I hit the shreader valve at the fuel rail, but no fuel. So I'm confident I got power back there and the fuel pump is toast.

Time for operation fuel pump! Thank you for the recommendation. I have a "4th gen" pump/sender unit from a friend. BUT don't want to take it apart just for the pump - plus the age and mileage of that pump are unknown. Thanks for the fuel pump recommendation. I'll check it out.

Side note - I could not get any "thump" sound when I put the relay back in the slot. Key on and all. So now I'm worried that something is still awry? Of course once I actually get to a new fuel pump in and fuel squirting at the rail, we'll cross that bridge then.

 

What's this census on one of these gems? Is the walbro-knock off I keep hearing about?

Perhaps not this model, but this brand. I have it saved on my cell phone / ebay app, but cannot pull up the same on a desk top computer.

https://www.ebay.com/itm/KEMSO-340LP...NYX4uA&vxp=mtr