andysfbird

OK guys/gals here is a good one for you:

This is my first time trying to start my 67 Firebird LS1 conversion. When I am in the "run" key position everything is fine but when I go to the "start' position the PCM looses power!!! As soon as I let go of the key it tries to start. It doesn't keep running i guess because of this strange scenario. The Battery is in the trunk, then goes to a distribution block under the hood which feeds both the PCM and the rest of the car (excluding the separate feed to the Starter). I could really use some help here.

ls1nova71

iTrader: (4)

You're not powering up your ignition relay with the right wire. Most accessories will loose power in crank, so you need to hook to one that doesn't, like the wire that originally went to your ignition coil.

S10xGN

iTrader: (11)

Same thing with my Maverick. Cars back then with points had a straight 12v supply to the coil for cranking but went thru a ballast resistor for run. You need to make a jumper so your PCM sees 12 volts in both crank and run.

andysfbird

Mavrick,

im not sure what to jumper. the pcm is getting its power directly from the battery. the switched power I would have to check.

bczee

iTrader: (12)

This is a common problem that many run into.

Take a Volt meter (or a test light) and find one of the Pink wire that is hot on Run and Start. Flip the key from Run to Start and back to Run. If the voltage doesn't drop, you can use that one. If you see it drop.. try another one.

I would then rout this to a Relay using Battery power and then to the PCM and other IGN Hot circuits that are needed to be hot on IGN only.

BC

andysfbird

BCZEE,
Thanks! ill let you know what I found out

ryeguy2006a

iTrader: (27)

If you are using a factory of factory style harness all of the Orange wires should be constant. Maybe put a test light to one of those wires to make sure that they aren't switched. Trial and error is the name of the game.

I had an issue originally with my fan relays, and once I finally figured it out I realized I never added the power wire to the relay... Sometimes it is something simple that gets overlooked. Let us know how you make out.

Ryan

Slo_240sx

iTrader: (17)

The Orange wire should be a constant. The pink IGN wires are powered with the key on. Disconnect the big purple starter wire, this will prevent cranking which in turn will draw voltage down to turn the engine over. With it disconnected, you can then turn the key to "crank" and see if those pink IGN wires have battery voltage while cranking.

andysfbird

OK guys/gas here is wht i found out:
First I looked at the switched power feed to fuse which then fed to all of the wires that require a keyed power to the PCM. i guess I had some forethought when I installed it because I used the distributor wire from the OER harness. I used a voltmeter and when I turned the key to "run" and got 8.5dc volts in the line side of the fuse and also 8.5dc volts on the load side. when I went to start there was no change. Hmmm, so I disconnected the five wires from the load side of the fuse and the voltmeter read 12.5 volts! Its been recommended to me to distribute the PCM keyed and hot wires to several fuses to allow the PCM to pull more power. I only had a 15A fuse! I wanted to get your opinions before I changed it. So any comments???

bczee

iTrader: (12)

When you used the Dist Wire.. did it have Ballist Resistor ?.. and a wire from the starter to the + side of the coil ?.. if so.. people using that wire seem to have this problem..

Since the older Elecitrical system might not be up to par with powering all of the new Electrical Circuits. .Yes, I would suggest adding some new Aux Fuse boxes and relays.. as your asking or referring to.

I usually take the keyed IGN powered wire, route it to a Battery powered Relay, that will active all of the new IGN powered fused circuits (PCM, INJ, Coil, Trans, etc)

Where you able to start the engine now ?

BC

andysfbird

Bczee,
Its just wire, nothing more, what type of relay should I use? heavy duty of som sort?

bczee

iTrader: (12)

Just a standard Bosch 30 or 40 amp SPST relay will work, depending on how much you drawing (coil, injector, o2, trans, PCM, etc).

I used a "Painless CirKit Boss®™ Auxiliary Fuse Block/7 Circuits"
http://www.painlesswiring.com/webcat...rchField=70107

but you could build this pertty simple with spare parts as well as find many other vendors make simular setups.

Just use that one IGN hot wire to activate the Relay (term #86)
Good Battery source (term #30).
Use Term #87 to the fuse block to power all IGN hot required wires (PCM, Inj, Coils, etc)
#85 is the ground for the Relay

BC

mantycarguy

In 67 the wire that ran to the coil was a resistor wire built right into the harness from the firewall bulkhead connection out to the coil. You can remove this wire and replace it with a standard 14 gauge wire and you will then have a full 12.6 volts to power up your pcm.The wire that you remove will usually have a braided covering on it and is white in most cases.